biomedical applications

Complimentary Contributor Copy


POLYMER SCIENCE AND TECHNOLOGY

BIOPOLYMERS AND NANOCOMPOSITES FOR BIOMEDICAL AND PHARMACEUTICAL APPLICATIONS

No part of this digital document may be reproduced, stored in a retrieval system or transmitted in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.


POLYMER SCIENCE AND TECHNOLOGY Additional books in this series can be found on Nova’s website under the Series tab.

Additional e-books in this series can be found on Nova’s website under the eBooks tab.

NANOTECHNOLOGY SCIENCE AND TECHNOLOGY Additional books in this series can be found on Nova’s website under the Series tab.

Additional e-books in this series can be found on Nova’s website under the eBooks tab.


POLYMER SCIENCE AND TECHNOLOGY

BIOPOLYMERS AND NANOCOMPOSITES FOR BIOMEDICAL AND PHARMACEUTICAL APPLICATIONS

ERAM SHARMIN AND

FAHMINA ZAFAR EDITORS


Copyright © 2017 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. We have partnered with Copyright Clearance Center to make it easy for you to obtain permissions to reuse content from this publication. Simply navigate to this publication’s page on Nova’s website and locate the “Get Permission” button below the title description. This button is linked directly to the title’s permission page on copyright.com. Alternatively, you can visit copyright.com and search by title, ISBN, or ISSN. For further questions about using the service on copyright.com, please contact: Copyright Clearance Center Phone: +1-(978) 750-8400 Fax: +1-(978) 750-4470 E-mail: [email protected].

NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Any parts of this book based on government reports are so indicated and copyright is claimed for those parts to the extent applicable to compilations of such works. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. Additional color graphics may be available in the e-book version of this book.

Library of Congress Cataloging-in-Publication Data Names: Sharmin, Eram, editor. | Zafar, Fahmina, editor. Title: Biopolymers and nanocomposites for biomedical and pharmaceutical applications / Eram Sharmin (Department of Pharmaceutical Chemistry, College of Pharmacy, Umm Al-Qura University, Makkah Al-Mukarramah, Saudi Arabia) and Fahmina Zafar. Description: Hauppauge, New York : Nova Science Publishers, Inc., [2017] | Series: Polymer science and technology | Series: Nanotechnology science and technology | Includes bibliographical references and index. Identifiers: LCCN 2016053697 (print) | LCCN 2017001749 (ebook) | ISBN 9781536106350 (hardcover) | ISBN 9781536106459 (ebook) | ISBN 9781536106459 H%RRN Subjects: LCSH: Polymers in medicine. | Nanocomposites (Materials) Classification: LCC R857.P6 B5675 2017 (print) | LCC R857.P6 (ebook) | DDC 610.28/4--dc23 LC record available at https://lccn.loc.gov/2016053697

Published by Nova Science Publishers, Inc. † New York


CONTENTS Preface Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

vii Polymers and Nanocomposites for Biomedical Applications Anujit Ghosal, Abhijeet Mishra and Shivani Tiwari Conducting Polymers and their Biomedical Applications Neha Kanwar Renewable Resource based Polyurethanes and their Biomedical Applications Shabnam Khan, Laxmi, Fahmina Zafar and Nahid Nishat Synthesis and Applications of Biopolymeric Nanoparticles Abhijeet Mishra and Anujit Ghosal Biopolymeric Nanoparticles as Drug Carriers for Intravenous Administrations Merari Tumin Chevalier, Monica Cristina García and Vera Alejandra Alvarez Poly (Lactic-co-Glycolic Acid) Nanoparticles: Current Advances in Tumor and Metastasis Targeted Therapies Merari Tumin Chevalier, Sergio Martin-Saldaña and Vera Alejandra Alvarez


1

17

33

51

63

93

vi Chapter 7

Contents Polymeric Nanocomposite Hydrogels as Emerging Biomaterials Arti Vashist, Rabia Kouser, Ajeet Kaushik, Atul Vashist, Rahul Dev Jayant, Sharif Ahmad, Y. K. Gupta and Madhavan Nair

Chapter 8

Biopolymer Nanocomposite as Biosensors Obaid ur Rahman

Chapter 9

Antifungal Effects and Future Perspectives of Curcuma longa (Turmeric) Rhizomes: A Natural Source for Developing a Novel Class of Antifungals Vaseem Raja, Sheikh Shreaz, W. A. Wani, L. T. Hun and W. A. Siddiqui

107

125

139

About the Editors

155

Index

157


PREFACE The persistent health and environmental hazards have caused an upward surge in the utilization of biopolymers in almost all facets of lives. Biopolymers are endowed with excellent attributes such as biodegradability, biocompatibility and functional versatility, which render them an edge over other polymers. Today, they find broad applications in the biomedical field and pharmaceutical world. Nanotechnology has offered tremendous opportunities to design and tailor make biopolymers augmenting their applications further. The book presents topical articles on the synthesis and applications of biopolymers, biopolymer nanoparticles and nanocomposites. The book includes chapters on vegetable oils, chitosan and cellulose based polyurethanes, conducting polymers, polymeric hydrogels, biopolymeric nanoparticles and nanocomposites and their applications as drug carriers, sensors, in cancer therapy and others. The target audience would include students, scholars, scientists (from polymer chemistry, materials chemistry, industrial chemistry, pharmaceutical sciences), interested particularly in the synthesis and biomedical and pharmaceutical applications of biopolymers and their nanocomposites. Ms Carra Feagaiga (Department of Acquisitions, Nova Publishers) is specially acknowledged for her timely responses. Mr. Abid Ali Khan (Department of Art Education, Jamia Millia Islamia, New Delhi, India) is appreciated and thanked for graphic designing of the cover page (front and back). Dr Fahmina Zafar is thankful to the Dept. of Science & Technology, New Delhi, India for the award of fellowship under the Women Scientists Scheme (WOS) for Research in Basic/Applied Sciences (Ref. No. SR/WOSA/CS-97/2016).


viii

Eram Sharmin and Fahmina Zafar

A heartfelt thanks to our family members for their great patience and tremendous support during the compilation of the book. Truly, no words of appreciation for all who endeavored to bring forward the book “Biopolymers and nanocomposites for biomedical and pharmaceutical applications”. Dr. Eram Sharmin, Ph.D. Department of Pharmaceutical Chemistry, College of Pharmacy, Umm Al-Qura University, P.O. Box 715, Postal Code 21955, Makkah Al-Mukarramah, Saudi Arabia and Dr. Fahmina Zafar, Ph.D. Inorganic Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025, India


In: Biopolymers and Nanocomposites … ISBN: 978-1-53610-635-0 Editors: E. Sharmin and F. Zafar © 2017 Nova Science Publishers, Inc.

Chapter 1

POLYMERS AND NANOCOMPOSITES FOR BIOMEDICAL APPLICATIONS Anujit Ghosal1,, Abhijeet Mishra2 and Shivani Tiwari1,3 1

Department of Chemistry, School of Basic and Applied Sciences, Galgotias University, Greater Noida, Gautam Buddh Nagar, Uttar Pradesh, India 2 Cancer Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India 3 Department of Zoology, Delhi University, New Delhi, India

ABSTRACT Polymers and nanocomposites can be derived from natural or synthetically obtained monomers or polymers and organic or inorganic nanoreinforcing agents or nano-fillers. They have found numerable uses in several fields, such as in electronics, optics, ionics, mechanics, environment, energy, medicine, paints, coatings, and others. The chapter briefly discusses their pharmaceutical and biomedical applications, along with the prime prerequisite characteristics that render them suitable for such applications.



Corresponding author: Anujit Ghosal, Assistant Professor, Department of Chemistry, School of Basic and Applied Sciences, Galgotias University, Greater Noida, Gautam Buddh Nagar, Uttar Pradesh, India. E mail: [email protected] (primary), [email protected].


2

Anujit Ghosal, Abhijeet Mishra and Shivani Tiwari

Keywords: polymers, nanocomposites, biomedical applications

INTRODUCTION Polymers have been an important research topic in academics and industrial development. Synthetic, natural, or hybrid polymers owing to their huge potential are used in everyday applications. They are considered to be creative alternatives in designing materials and composites for improved biomedical and pharmaceutical applications, during academic research in laboratories as well as for large scale industrial production. Defying classical physical laws, the nano sized particles produce unique optical, physical, chemical, mechanical and biological characteristics [1-4]. A nanocomposite can be developed by using different constituent materials that have significantly different physical or chemical properties. However, dimension of one component of the nanocomposite should be in nano range [3]. The nano sized component can be organic or inorganic in nature. The components can be mixed after separately synthesizing them or one of the components may be grown within the second component or polymeric material. The nature of interactions between these components decides the characteristic properties of the resulting material. On the basis of the type of interactions, polymer nanocomposites can be broadly classified in two classes:  First class: The composite materials only have physical interactions in between different components.  Second class: The composite materials have chemical bonds, hydrogen bonds or ionic interactions that combine different components [5]. These resulting composite materials have new and improved features, with promising applications due to synergetic properties of different components [1, 5-7]. Moreover, the electrical, optical, electrochemical, thermal, mechanical, chemical, and catalytic properties of the nanocomposites are remarkably different from their constituents. The properties of nanocomposites can be tuned by variation of certain parameters like: 1. 2. 3. 4.

composition of the individual components, shape and structure of components, nature of interactions between the components, and dimensions of the individual components.


Polymers and Nanocomposites for Biomedical Applications

3

Figure 1. Some examples of synthetic polymers used for preparation of nanocomposites for biomedical applications.

Literature revealed that polymer nanocomposites have been used in water purification, coating/painting materials for protection of the substrate from chemicals, atmospheric degradation, bio-corrosion, and others [4, 8-10]. The presence of nano structures inside the composite materials exceptionally improves their mechanical, chemical and thermal stability relative to the conventional polymer composites. The presence of high surface area, surface energy and difference in chemical reactivity of nanomaterials as compared to counter bulk materials alters the polymer chain mobility, toughness, crystallinity, hydrophobic nature and other properties of the resulting material. The reinforcing agents or fillers in the nanocomposites can be metal/metal oxide nanoparticles (zero dimensional), carbon nanotubes/fibres/wires (one dimensional) or exfoliated clay nanoparticles (there dimensional). Figure 1, Figure 2 and Figure 3 present some examples of synthetic polymers,


4


biopolymers and nanofillers for the preparation of polymer nanocomposite materials for biomedical applications. In past few decades, a huge surge in the use of biodegradable polymers (natural as well as synthetic) has been resulted to avoid generation of catastrophic conditions in near future [11]. These biodegradable polymers are derived from natural polymers like chitosan, guar gum, vegetable oils, animal oils, fats, lipids, carbohydrates, and others. However, their use in bulk for the replacement of synthetic or petro based polymer composite materials has been hindered due to inadequate mechanical strength of these polymers [12, 13]. The recent scientific reports have shown that the mechanical strength of the natural polymers can be improved by grafting, branching, blending, formation of nanocomposites by using nanofillers and other approaches [13-15]. All these modifications would lead to increase in viscosity, cross-linking density and ultimately toughness of the resulting polymeric composite materials. The ability of nanostructured materials to create surface roughness or air pockets on the resulting surface coat of polymeric nanocomposite has led to increase in hydrophobic or water repelling ability of the material [16]. Nanocomposites with water contact angle value higher then 90 are considered to be hydrophobic in nature and polymeric surfaces with water contact angle value more than 130 are considered to be super hydrophobic in nature. This property of higher contact angle value of water is utilised for development of anti-wet, self-cleaning, anti-fungal fabric and coating materials for biomedical applications [8, 10, 14].

POLYMERS AND NANOCOMPOSITES FOR BIOMEDICAL APPLICATIONS The physical and chemical properties of synthetic polymers can be modulated depending upon the units of monomers, polymerization reaction and copolymer formation. Some common examples of polymers in medical applications are polyolefins, poly(tetrafluoroethylene), silicones, methacrylates, polyesters, polyurethanes, with applications both within and outside the body, such as artificial joints, intraarticular implants, intraocular lenses, hemocompatible coatings, lubricant coatings, orthopaedic applications, vascular stents, suture materials, catheters, drugs and devices packaging, ampullas, syringes, compressible vials, hemodialysis membranes, wound dressings, tissue adhesives and sealants, surgical meshes, joint prostheses,



5

bone cements, ligament and tendon repair scaffolds, vascular stents, heart valves, cardiac assist devices, and others. They also find applications in plastic, cosmetic and reconstructive surgery, such as in chin and nose surgery for contour augmentation, facial augmentation, breast implants, and numerous other applications [17]. These applications are governed by stability, biodegradability, functional and responsive behavior of polymers. The carbon chemistry of polymers endows them with closer resemblance to biological tissues; however, often there are interferences caused by monomers, degradation products, additives, functional groups present, and others. The natural and synthetic biomedical polymers have to meet certain synthesis and design criteria in terms of their physical, chemical, biomechanical, biological, and degradation properties.

Figure 2. Some examples of biopolymers used for preparation of nanocomposites for biomedical applications.


6


Figure 3. Some examples of inorganic nanofillers used as functionalization or reinforcing agents in nanocomposites for biomedical applications.

The versatility of the polymer/nanocomposite materials for medicinal purposes depends on the compatibility and reactivity of the material with respect to biological aqueous system, selection of biopolymers and fillers. The components, individually or after the formation of final nanocomposite materials, should be biocompatible in nature. These materials should not leave any residue and should be gradually degraded, absorbed and eliminated by the biological processes. Biodegradable polymers stay in the body till their function is needed, and later break down or are excreted or resorbed, without the need of any surgical cision, such as in fixation in orthopaedics and augmentation of ligaments. The rate of degradation of polymers depends upon monomer structure and solubility, water diffusion, molecular weight, crystallinity, hydrophobicity, surface charge, their degradation and erosion mechanism, water adsorption tendency, and other characteristics. The hydrolytically degradable polymers bear bonds in their backbone that are susceptible to hydrolysis; these include polyesters [polyglycolide, polylactide, poly(lactide-co-glycolide), polyhydroxyalkanoates, polycaprolactone, poly(propylene fumarate)], polyanhydrides, polyacetals, polycarbonates, polyamides, polyurethanes and polyphosphates. Polyphosphazenes are hydrolytically unstable, while polyamides are hydrolytically very stable. The



7

enzymatically degradable polymers undergo degradation under physiological conditions. These include synthetic polyethers like poly(ethylene glycol) and poly(propylene glycol). Other biopolymers include proteins, collagen, fibrin, albumin, poly (amino acids), polysachcharides such as chitin, chitosan, alginate, and others that through several modifications have been rendered suitable for the purpose (Figure 1) [18-20]. Biodegradable polymer nanocomposites have shown promising pharmaceutical and biomedical applications, such as in the development of hydrophobic drug carriers, stabilizing agents, scaffold materials, in tissue engineering, bone reconstruction, and others. These materials can be derived from natural or synthetic biodegradable polymers, with the inclusion of organic/inorganic reinforcing agents or nano-fillers. There may arise concerns on the changes in the body caused by changes in material properties by degradation with time, or the response of the body to such changes. It is important to consider that such degradable polymers for medical applications should not cause, or be the cause, indirectly, of any inflammation, should not generate toxic degradation products, or those being difficult to be resorbed or excreted should have proportional degradation time in view of their function, with desirable mechanical properties, permeability and processability characteristics, for their proposed or intended end-use application. Optimal mechanical stability of these materials for a specific time duration till when they support the repairing of the body (tissue growth, scaffold, bone joints), within the body in aqueous, acidic and alkaline media has been a topic of research. A porous structure helps in improving the cells and growth factors, optimal mechanical stability in aqueous biological system and can produce favourable regenerative response or interaction with biological system. In applications such as drug release, the characteristics of swelling, water absorption, collapsing (of pores) of structures, in response to change in pH, temperature, or other stimuli responses, are needed. Mechanical reinforcement and functional response is also needed for several applications [17]. The production of bionanocomposites mimicking natural approaches and electrically conductive polymers has been another recent focus of researchers [21, 22]. The inspiration for architecture of biomimicking biomaterials can be taken from biomaterials; it stems from pre-existing natural structures like shark skin and lotus leaves (surface design) as they have been highly efficient, with sophisticated anisotropic flow characteristics and superhydrophobic properties in nature. The nanocomposites have great scope in biotechnologies such as tissue engineering, scaffold materials, hydrogels patches, bone replacement, remedification of joints, dental filling, and target drug delivery [23-25]. Some


8


of recent and important literature on polymer nanocomposites with their biomedical applications has been tabulated in Table 1. A potential scaffold and drug-delivery device for maturogenesis and regenerative endodontics has been proposed. The electrospun fibrous three-dimensional nanocomposite scaffold is made of polydioxanone (PDS II®) and halloysite nanotubes (HNTs). The porous structure of the composite material (PDS–HNTs), its biocompatibility and ability of nanotubes to encapsulate distinct bioactive molecules propagates the proliferation of human-derived pulp fibroblast cells [23]. In another prominent work, vascularized bone regeneration was achieved by Calcium Phosphate scaffolds with a novel graphene oxide-copper (GO-Cu) nanocomposite coating on it [26]. The GO-Cu nanocomposite upregulates the Hif-1α expression in stem cells which project the in-vivo application of nano metallic ions and graphene in regenerative medicine. The hemocompatibility of electrospun halloysite nanotubes (HNTs) along with carbon nanotubes (CNTs) and mechanical strength of nanofibre scaffold or cardiovascular or blood-contacting medical devices were synergistically improved by incorporating HNTs and CNTs within poly(lactic-co-glycolic acid) nanofibers [27]. A natural design has been used which mimics the depth-dependent properties of the native tissue, preparing a trilayered nanocomposite hydrogel (ferrogel) which was used as a scaffold material for cartilage tissue engineering [21]. Such materials find scope in tailoring site specific cartilage regeneration/replacement. By varying the density of magnetic nanoparticles, concentration of base hydrogel and number of cells, the modulation of properties of ferrogels or nanocomposite scaffolds can be accomplished.

CONCLUSION The use of polymers and nanocomposite materials for biomedical applications like tissue engineering, scaffold materials, drug delivery and biomimicking implants requires certain important integral properties. Today, with advanced techniques and computer-aided-technology, it has been made possible to design complex structures that can mimic their biological counterparts. The biomimicking property of developed polymeric material can be used for in vitro studies due to resemblance to in vivo interactions of drug/biomolecules. The progress still continues in the field with collaborative efforts of scientists, chemists, biologists, physicists, material chemists, and medical scientists.


9

Polymers and Nanocomposites for Biomedical Applications Table 1. Some examples of polymer nanocomposites used in different biomedical applications S. No. Polymer Nanocomposite

Polymer

1.

Hydroxyethyl MethacrylatePoly(acrylic/maleic) Acid Resin-Mesoporous Bioactive Glass Composite TiO2- Polyhydroxyethyl methacrylate Hydrogel Nanocomposite (nNiO-Multi-Walled Carbon Nanotubes) Nanocomposite

Hydroxyethyl methacrylate and Poly(acrylic/ maleic acid)

4

n-NiFe2O4-CH Nanocomposite

Chitosan

5

poly(ε-caprolactone) /graphene oxide and poly(ε-caprolactone)/Ag Composites Nanoparticle/polymer Composite System UCNP@P-Pt/RhB

poly(εcaprolactone) matrix

Graphene-Silver Hybrid Particles

Amphiphilic Triblock Copolymer, mPEG-b-PCL-bPLL Polyoxoborate Matrix Natural Cellulose

Oleic AcidCisplatin (IV) Stabilized UCNP Delivery and Nanoparticles Biomedical Imaging Gold Antibacterial Nanoparticles Activity Cu Nanoparticles Inhibition of a Multi-Drug Resistant Wound Pathogen NaAntibacterial Montmorillonite Activity and Nanoclay Cytotoxicity Silicate, Bioglass, Tissue Wollastonite, Engineering and Silicon-Doped Repair Calcium phosphate

2

3

6.

7. 8

9

10

Gold–Oxoborate Nanocomposites Copper-Based Cellulose Nanocomposites

Nanoclay-reinforced Electrospun Chitosan/pva Nanocomposite Poly(DL-lactic acid)Silicate Nanocomposite

Reinforcing Agent SiO2-CaO-P2O5 Glass

Application

Ref.

Photocurable Bioactive Bone Cement

[28]

Polyhydroxyethyl TiO2 methacrylate Nanoparticles

Ophthalmological [29]

Polydimethylsiloxane

Microfluidics Biosensor Platform

Poly(vinyl alcohol) Poly(DL-lactic acid)

Nickel Oxide Nanoparticles and Multiwalled Carbon Nanotubes Nickel Ferrite Nanoparticles

[30]

Improved [31] Conductivity, Fast Redox Properties and Antimicrobial Activity Cytocompatible [32] and Antibacterial


[33]

[34] [35]

[36]

[37]

10

Anujit Ghosal, Abhijeet Mishra and Shivani Tiwari Table 1. (Continued)

S. No. Polymer Nanocomposite

Polymer

11

Poly(methyl methacrylate)

12

13

14

15

16 17

18

19

20

Nanohydroxyapatite/poly (methyl methacrylate) Composite

Reinforcing Agent Nanohydroxyapatite

Application

Bone cements, Oriented growth of Rat Schwann cells Polyurethanes- modified Polyurethanes Modified Layered Stomach Acid Layered Silicates Silicates Reducing Nanocomposites Medicine Hyperbranched Hyperbranched Fe3O4 Shape Polyurethane/Fe3O4 Polyurethane Nanoparticles Memory Nanocomposites Materials Dicalcium Phosphate Poly (Lactic Acid) Calcium Fibrous Anhydrate/Poly (Lactic Phosphate Scaffolds for Acid) Nanocomposite Nanocrystals Hard Tissue Regeneration Functionalized Poly(Amino Acid) Hydrophobic Cell Hydrophobic Nanocrystals Nanocrystals of Luminescence with Poly(amino acid) NaYF4:Yb3+/Er3+ Imaging Nanocomposite @PSIOAm-COO− Gold/Amino Acid Amino Acid Gold Uric Acid Nanocomposites Nanoparticles Biosensor Graphene Oxide-Iron Polyethylene Glycol graphene oxide- Magnetically Oxide Nanocomposite iron oxide hybrid Targeted Drug Nanoparticles Delivery ZnS/poly-vinyl-2N,NZnS Artificial pyrrolidone/polydimethylacrylamide Nanoparticles Cornea dimethylacrylamide and N-vinyl-2Implants pyrrolidone Poly(ethylene glycol)-co- Poly(ethylene Poly(lactic-coTissue (l-lactic acid) composite glycol)-co-(l-lactic glycolic acid) Engineering acid) Hydrogels microspheres Scaffold Lipid–Polymer Biodegradable Lipid-Based Drug delivery Nanocomposites polymers Drug-Loaded Nanocarriers

Ref. [38, 39]

[40]

[41]

[42]

[43]

[44] [45]

[46]

[47]

[48]

REFERENCES [1]

Raman N, Sudharsan S, Pothiraj K. Synthesis and structural reactivity of inorganic–organic hybrid nanocomposites–A review. Journal of Saudi Chemical Society. 2012;16(4):339-52.


Polymers and Nanocomposites for Biomedical Applications [2]

11

Aimon NM, Choi HK, Sun XY, Kim DH, Ross CA. Templated Self‐Assembly of Functional Oxide Nanocomposites. Advanced Materials. 2014;26(19):3063-7. [3] Nicole L, Laberty-Robert C, Rozes L, Sanchez C. Hybrid materials science: a promised land for the integrative design of multifunctional materials. Nanoscale. 2014;6(12):6267-92. [4] Sharmin E, Akram D, Ghosal A, Rahman Ou, Zafar F, Ahmad S. Preparation and characterization of nanostructured biohybrid. Progress in Organic Coatings. 2011;72(3):469-72. [5] Sanchez C, Julian B, Belleville P, Popall M. Applications of hybrid organic–inorganic nanocomposites. Journal of Materials Chemistry. 2005;15(35-36):3559-92. [6] Das B, Renaud Al, Volosin AM, Yu L, Newman N, Seo D-K. Nanoporous Delafossite CuAlO2 from Inorganic/Polymer Double Gels: A Desirable High-Surface-Area p-Type Transparent Electrode Material. Inorganic chemistry. 2015, 54(3), 1100-1108. [7] Rahimi A, Shokrolahi P. Application of inorganic polymeric materials: I. Polysiloxanes. International Journal of Inorganic Materials. 2001;3(7): 843-7. [8] Ghosal A, Rahman OU, Ahmad S. High performance soya polyurethane networked silica hybrid nanocomposite coatings. Industrial and Engineering Chemistry Research. 2015; 54 (51):12770-12787. [9] Ghosal A, Shah J, Kotnala RK, Ahmad S. Facile green synthesis of nickel nanostructures using natural polyol and morphology dependent dye adsorption properties. Journal of Materials Chemistry A. 2013;1 (41):12868-78. [10] Nine MJ, Cole MA, Johnson L, Tran DN, Losic D. Robust Superhydrophobic Graphene-Based Composite Coatings with SelfCleaning and Corrosion Barrier Properties. ACS applied materials and interfaces. 2015;7(51):28482-93. [11] Dasari A, Yu Z-Z, Mai Y-W. Ecological Issues. Polymer Nanocomposites: Springer; 2016, 263-77, DOI. 10.1007/978-1-44716809-6_11. [12] Castro C, Zuluaga R, Rojas O, Filpponen I, Orelma H, Londoño M et al. Highly percolated poly (vinyl alcohol) and bacterial nanocellulose synthesized in situ by physical-crosslinking: exploiting polymer synergies for biomedical nanocomposites. RSC Advances. 2015;5(110): 90742-9.


12


[13] Sharmin E, Zafar F, Akram D, Alam M, Ahmad S. Recent advances in vegetable oils based environment friendly coatings: A review. Industrial Crops and Products. 2015;76:215-29. [14] Sharmin E, ur Rahman O, Zafar F, Akram D, Alam M, Ahmad S. Linseed oil polyol/ZnO bionanocomposite towards mechanically robust, thermally stable, hydrophobic coatings: a novel synergistic approach utilising a sustainable resource. RSC Advances. 2015;5(59):47928-44. [15] Zafar F, Sharmin E, Zafar H, Shah MY, Nishat N, Ahmad S. Facile microwave-assisted preparation of waterborne polyesteramide/OMMT clay bio-nanocomposites for protective coatings. Industrial Crops and Products. 2015;67:484-91. [16] Zhang X-F, Chen R-J, Liu Y-H, Hu J-M. Electrochemically generated sol–gel films as inhibitor containers of superhydrophobic surfaces for the active corrosion protection of metals. Journal of Materials Chemistry A. 2016;4(2):649-56. [17] Maitz MF. Applications of synthetic polymers in clinical medicine. Biosurface and Biotribology. 2015;1(3):161-76. [18] Nair LS, Laurencin CT. Biodegradable polymers as biomaterials. Progress in Polymer Science. 2007;32(8-9):762-98. [19] Ulery BD, Nair LS, Laurencin CT. Biomedical applications of biodegradable polymers. Journal of Polymer Science Part B: Polymer Physics. 2011;49(12):832-64. [20] Nair LS, Laurencin CT. Polymers as biomaterials for tissue engineering and controlled drug delivery. Advances in Biochemical Engineering/Biotechnology. 2006;102:47-90. [21] Carrow JK, Gaharwar AK. Bioinspired polymeric nanocomposites for regenerative medicine. Macromolecular Chemistry and Physics. 2015; 216(3):248-64. [22] Kaur G, Adhikari R, Cass P, Bown M, Gunatillake P. Electrically conductive polymers and composites for biomedical applications. RSC Advances. 2015;5(47):37553-67. [23] Bottino MC, Yassen GH, Platt JA, Labban N, Windsor LJ, Spolnik KJ et al. A novel three‐dimensional scaffold for regenerative endodontics: materials and biological characterizations. Journal of tissue engineering and regenerative medicine. 2015;9(11):E116-E23. [24] Vashist A, Ahmad S. Hydrogels in tissue engineering: scope and applications. Current pharmaceutical biotechnology. 2015;16(7):60620.



13

[25] Vashist A, Ghosal A, Gupta Y, Ahmad S, Nair M. Nanocomposite hydrgels for neuro drug delivery. Journal of neuroimmune pharmacology. Springer 233 Spring St., New York, NY 10013 US, 11, 2016, S48-S49. [26] Zhang W, Chang Q, Xu L, Li G, Yang G, Ding X et al. Bone Regeneration: Graphene Oxide‐Copper Nanocomposite‐Coated Porous CaP Scaffold for Vascularized Bone Regeneration via Activation of Hif‐1α. Advanced Healthcare Materials. 2016;5(11):1247-1375. [27] Zhao Y, Wang S, Guo Q, Shen M, Shi X. Hemocompatibility of electrospun halloysite nanotube‐and carbon nanotube‐doped composite poly (lactic‐co‐glycolic acid) nanofibers. Journal of Applied Polymer Science. 2013;127(6):4825-32. [28] Hesaraki S. Photocurable bioactive bone cement based on hydroxyethyl methacrylate-poly(acrylic/maleic) acid resin and mesoporous sol gelderived bioactive glass. Materials Science and Engineering: C. 2016; 63:535-45. [29] Reinhardt HM, Recktenwald D, Kim H-C, Hampp NA. High refractive index TiO2-PHEMA hydrogel for ophthalmological applications. Journal of Materials Science. 2016;51(22):9971-8. [30] Ali MA, Srivastava S, Solanki PR, Reddy V, Agrawal VV, Kim C et al. Highly efficient bienzyme functionalized nanocomposite-based microfluidics biosensor platform for biomedical application. Scientific reports. 2013;3. [31] Singh J, Roychoudhury A, Srivastava M, Chaudhary V, Prasanna R, Lee DW et al. Highly efficient bienzyme functionalized biocompatible nanostructured nickel ferrite–chitosan nanocomposite platform for biomedical application. The Journal of Physical Chemistry C. 2013;117 (16):8491-502. [32] Kumar S, Raj S, Jain S, Chatterjee K. Multifunctional biodegradable polymer nanocomposite incorporating graphene-silver hybrid for biomedical applications. Materials and Design. 2016;108:319-32. [33] Ma Pa, Xiao H, Li X, Li C, Dai Y, Cheng Z et al. Rational design of multifunctional upconversion nanocrystals/polymer nanocomposites for cisplatin (IV) delivery and biomedical imaging. Advanced Materials. 2013;25(35):4898-905. [34] Wybrańska K, Paczesny J, Serejko K, Sura K, Włodyga K, Dzięcielewski I et al. Gold–Oxoborate Nanocomposites and Their Biomedical Applications. ACS applied materials and interfaces. 2015;7 (7):3931-9.


14


[35] Cady NC, Behnke JL, Strickland AD. Copper‐Based Nanostructured Coatings on Natural Cellulose: Nanocomposites Exhibiting Rapid and Efficient Inhibition of a Multi‐Drug Resistant Wound Pathogen, A. baumannii, and Mammalian Cell Biocompatibility In Vitro. Advanced Functional Materials. 2011;21(13):2506-14. [36] Koosha M, Mirzadeh H, Shokrgozar MA, Farokhi M. Nanoclayreinforced electrospun chitosan/PVA nanocomposite nanofibers for biomedical applications. RSC Advances. 2015;5(14):10479-87. [37] Wu C-J, Gaharwar AK, Schexnailder PJ, Schmidt G. Development of biomedical polymer-silicate nanocomposites: a materials science perspective. Materials. 2010;3(5):2986-3005. [38] Quan C, Tang Y, Liu Z, Rao M, Zhang W, Liang P et al. Effect of modification degree of nanohydroxyapatite on biocompatibility and mechanical property of injectable poly (methyl methacrylate)‐based bone cement. Journal of Biomedical Materials Research Part B: Applied Biomaterials. 2016;104(3):576-84. [39] Xia H, Sun X, Liu D, Zhou Y, Zhong D. Oriented growth of rat Schwann cells on aligned electrospun poly (methyl methacrylate) nanofibers. Journal of the Neurological Sciences. 2016;369:88-95. [40] Xu R, Manias E, Snyder AJ, Runt J. New biomedical poly (urethane urea)-layered silicate nanocomposites. Macromolecules. 2001;34(2): 337-9. [41] Kalita H, Karak N. Bio‐based hyperbranched polyurethane/Fe3O4 nanocomposites as shape memory materials. Polymers for Advanced Technologies. 2013;24(9):819-23. [42] Chae T, Yang H, Ko F, Troczynski T. Bio‐inspired dicalcium phosphate anhydrate/poly (lactic acid) nanocomposite fibrous scaffolds for hard tissue regeneration: In situ synthesis and electrospinning. Journal of Biomedical Materials Research Part A. 2014;102(2):514-22. [43] Huang S, Bai M, Wang L. General and facile surface functionalization of hydrophobic nanocrystals with poly (amino acid) for cell luminescence imaging. Scientific reports. 2013;3. [44] Liu Y, Yuan M, Liu L, Guo R. A facile electrochemical uricase biosensor designed from gold/amino acid nanocomposites. Sensors and Actuators B: Chemical. 2013;176:592-7. [45] Ma X, Tao H, Yang K, Feng L, Cheng L, Shi X et al. A functionalized graphene oxide-iron oxide nanocomposite for magnetically targeted drug delivery, photothermal therapy, and magnetic resonance imaging. Nano Research. 2012;5(3):199-212.



15

[46] Zhang Q, Su K, Chan-Park MB, Wu H, Wang D, Xu R. Development of high refractive ZnS/PVP/PDMAA hydrogel nanocomposites for artificial cornea implants. Acta Biomaterialia. 2014;10(3):1167-76. [47] Jiang B, Akar B, Waller TM, Larson JC, Appel AA, Brey EM. Design of a composite biomaterial system for tissue engineering applications. Acta Biomaterialia. 2014;10(3):1177-86. [48] Raemdonck K, Braeckmans K, Demeester J, De Smedt SC. Merging the best of both worlds: hybrid lipid-enveloped matrix nanocomposites in drug delivery. Chemical Society Reviews. 2014;43(1):444-72.




Chapter 2

CONDUCTING POLYMERS AND THEIR BIOMEDICAL APPLICATIONS Neha Kanwar Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia – A Central University, New Delhi, India

ABSTRACT Conducting polymers have emerged as one of the most fascinating polymers in the field of material science and engineering. Their marvellous resourceful properties make them useful in every field of research. In biomedical arena, they find application in drug release, biosensors, tissue engineering, as well as stimuli responsive and bio mimetic polymeric materials. The chapter discusses briefly some electrically conducting polymers and their biomedical applications.

Keywords: conducting polymers, biomedical applications, drug delivery, biocompatibility



Corresponding Author: Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi, India. Email: [email protected].


18

Neha Kanwar

INTRODUCTION Conducting polymers (CPs) find vast applications in the field of fuel cells, computer displays, supercapacitors, corrosion resistant coatings and many other applications. CPs can be synthesised alone as polymers, interpenetrating polymer networks, composites, hybrids, and as nanostructured materials, with conferred biodegradability and biocompatibility. They are electroactive, exhibiting properties of biomaterials. They can bind to biologically significant molecules by functionalization methods, and thus their properties can be improved for further advanced applications. As they are conducting in nature, they can be utilised in drug release, biosensors, tissue engineering, stimuli responsive, biomimetic polymeric materials and other medical applications. CPs exhibit combination of properties possessed by metals and conventional polymers, showing potential to conduct charge, good electrical as well as optical properties, accompanying flexibility, ease in synthesis and processing. CPs attain high conductivity by the phenomenon of “doping” [1-4]. The family “polyheterocycles” contains the CPs of interest to researchers, e.g., polypyrrole, polyaniline [5, 6], polythiophene [7-10] and their derivatives. The classification of CPs is given in Figure 1 and some examples of CPs are given in Figure 2. Table 1 lists biomedical applications of some CPs [11-18]. This chapter is inspired by excellent reviews by Cartmell et al. and Kaur et al. [1, 2].

Figure 1. Classification of CPs.


Conducting Polymers and their Biomedical Applications

19

Figure 2. Examples of some CPs.

Figure 3. Various oxidation states of PANI.

One of the most investigated CPs is polyaniline (PANI) or aniline black [19], existing as pernigraniline base (fully oxidized), emeraldine base (halfoxidized) and leucoemeraldine base (fully reduced) [20] (Figure 3). PANI has emerged as the most versatile CP used in almost every field of research, yet it has some disadvantages such as low processability, non-biodegradability, poor cell compatibility and lack of flexibility which limits its application in biomedical arena, evident from many reports present, depicting chronic inflammation once implanted in human body [6, 21]. A recent study on skin


20

Neha Kanwar

irritation and sensitization tests of conducting and non-conducting PANI, performed in vivo, has shown good biocompatibility results, however, they exhibited considerable cytotoxicity which was found more in their conducting form (PANI hydrochloride) than non-conducting form (emeraldine base) [2]. PANI due to its promising properties was therefore envisioned to act as an emerging polymer in biomedical field. However, investigations have been carried out on the applications of PANI in the areas of biosensors, controlled drug delivery, neural probes, and tissue engineering. Polypyrrole (PPy) shows stimulus-responsive behavior, biocompatibility (both in vitro and in vivo), good chemical stability (in air, water), and high conductivity under physiological conditions. PPy can be fabricated with a large surface area, with different porosities, and can easily be altered making it useful for biomedical applications allowing successful incorporation of bioactive molecules [22] along its backbone. The pure PPy is crystalline, brittle, insoluble, and not suitable for biomedical applications, which is made possible only after certain modifications. For example, a carboxyethyl derivative of PPy is modified easily at N-position with biological moieties; this modification promotes tissue response and enhances the biomaterial-tissue interface. PPy nanoparticles demonstrated cytotoxic effects, at higher concentrations, in a recent in vitro study; however, at lower concentrations no negative effect was found on cell proliferation [2]. PPy is used in numerous applications [23, 24], such as biosensors [25], drug delivery systems, implants, scaffolds, neural probes, tissue engineering and others [26]. Polythiophene (PTh) is another interesting CP. The most interesting conjugated polymer is a derivative of polythiophene, poly(3,4ethylenedioxythiophene) generally known as (PEDOT). PEDOT is formed by the polymerization of the bicyclic monomer 3,4-ethylenedioxythiophene. PEDOT has a dioxyalkylene bridging group across the 3th and 4th positions respective to heterocyclic ring as compared to PTh (Figure 4). PEDOT has emerged as an aspiring new CP possessing additional properties in terms of stability (electrical, thermal, chemical as well as environmental) and high conductivity. It is used in biosensing and bioengineering applications, e.g., in neural electrodes, nerve grafts and heart patches. Another derivative of PTh used in biomedical applications is poly(3-hexylthiophene), which possesses good solubility in organic solvents, excellent environmental stability and electrical conductivity [27, 28].


Table 1. CPs and their properties including prominent works in biomedical field

Polymer

Abbreviation Family

Polyaniline

PANI

Amine

Polypyrrole

PPY

Hetro aromatic

Polythiophene

PTh

Poly(o-ansidine)

PoA

Hetro aromatic Amine

PEDOT Poly(3,4ethylenedioxythiophene)

Hetro aromatic

Conductivity Colour Advantages (in order) 102 green, cost effective, easy black synthesis, processibility 10-103 green, varying forms, cost blue effective, easy modification 102-103 brown, cost effective, biobrick degradable 102 dark easy synthesis, green processibility 102--103 yellow, highly conducting blue

Polyparavinylene

PPV

Amine

0.1-10

Polyfuran

PFu

Hetro aromatic

1-102

Short Comings less biodegradability

Biomedical application biosensors

health hazards, low hydrogels processibility high cost, nonbiodegradable less processible, bulky side group high cost, nonbiodegradable

Prominent work Shi et al. [11] Huang et al. [12, 13]

biocompatibility Yeow et al. [14] biosensors Davis et al. [15] bio-electronics Kesong et al. [16] brown, easy synthesis, easily fusible rings neural probes Zare et al. brick processibility [17] green small chains, easily small ring size, biodegradability Marta et al. fusible easy to modify [18]


22

Neha Kanwar

Figure 4. Various methods used for synthesis of CPs.

CPs can conduct charge contributed by the ease with which electrons jump within and between their chains[29]. The polymers possess a conjugated backbone. The latter is formed by a succession of alternating single and double bonds. The single and double bonds consist of a chemically strong, localized sigma-bond; double bonds also contain a less strongly localized pi-bond. The pi-orbitals in the series of p-bonds overlap each other hereby allowing further delocalisation of electrons (i.e., localized over a group of atoms and to move freely among the atoms) more conveniently. The polymer is synthesized in its oxidized, conducting form, and only in the presence of the dopant (negative/anion present), the backbone is stabilized and the charge is neutralized. The dopant presents a charge carrier into this system by removing or adding electrons from/to the polymer chain and relocalizing them as polarons or bipolarons. When an electrical potential is applied, the dopants start to move in or out of the polymer (depending on the polarity), disrupting the stable backbone and permitting the charge to pass through a polymer in the form of polarons and bipolarons. The conductivity is conferred by the p-type (bipolaron) conduction, the inter-chain jumping of electrons and the motion of anions or cations within the material. PPy and PTh can own a conductivity of up to the order of ~103 and 107 S/cm. The exact value depends on the charge transfer to adjacent molecules, the polaron, the chain and the conjugation



23

length, and can be controlled by using different types and quantities of dopants. The synthesis phenomenon of CPs comprises of two main methods: chemical and electrochemical polymerization (Figure 4). Out of the two, the most common method is electrochemical polymerization in which their monomers are polymerized at the electrode surface and electrolyte interface in the presence of a catalyst, (e.g., an oxidant such as FeCl3, oxides and inorganic chlorides). The key requirement for CP to conduct electricity is their oxidation/reduction phenomenon by ionizing their polymer backbone. This provides the extra ions commonly known as dopant ions, which can be introduced either during the synthesis reaction of CPs (insitu) or after it (exsitu). The doping process mainly occurs by either of the two approaches comprising simple mixing or chemical immobilization of these external ions, i.e., dopants on the backbone of the polymer. In biomedical field, doping has significant role, which can work by two modes, firstly when dopant is low molecular weight (small ion) and the non-covalent interactions are present, it leaches out of the CP matrix into the biological milieu resulting in reduction of conductivity of polymer. This phenomenon is used for CP-based drug delivery devices which are based on the principal of expulsion of the biologically active dopant from the material on electrical stimulation. Secondly, in case of high molecular weight dopants like dodecylbenzenesulfonic acid and when covalent bonds are present the polymer is known to function by self-doping process.

APPLICATIONS OF CPS IN BIOMEDICAL ARENA Hydrogels Some of the drawbacks of CPs such as their low mechanical strength can be overcome by the formation of their hydrogel blends. This approach helps in modulation and improvement of mechanical properties, and provides a platform for bioactive agents. CPs have been successfully encapsulated inside hydrogel networks either by polymerization or by dispersion. In one of the common methods of CPs based hydrogel formation, hydrogels are formed and dehydrated, and then made to re-swell in monomer of CPs. CP monomers are polymerised by electrical charges application or chemical oxidant exposure. The CP hydrogels have been found to attain improved mechanical and biological properties along with comparable electrical properties relative to CP alone. In another method, CP and hydrogel precursors are mixed together and


24

Neha Kanwar

simultaneous polymerisation of both CP and hydrogel occurs [30]. Thus, electroactive hydrogels are fabricated, with the redox changing capabilities of CPs and the fast ion mobility and elasticity/biocompatibility of hydrogels. These electroactive hydrogels can be produced with a number of properties, allowing them to bind bioactive molecules at their respective sites and mimic the extracellular matrix. These find applications in biosensors, drug release devices and brain stimulators. Hydrogels were produced by electrochemically growing PPy within poly(2-hydroxyethyl methacrylate) hydrogels and also by using a poly(2-methoxy-5-aniline sulfonic acid) dopant, thus, these hydrogels have high surface area and lower impedance relative to PPy film [31]. In another example, PPy and mucopolysaccharide hydrogels were produced that were non toxic, and employed for drug release, neural and tissue engineering [32].

DRUG DELIVERY The controlled delivery of chemical compounds has been a great challenge, but now the use of CPs has facilitated this requirement. CPs are suitable for drug release applications as they are porous and have delocalized charge carriers that aid in the diffusion of the bound molecules [33]. The cells or tissues cultured in them can be stimulated, and through the application of an electric signal, the bound drug is released. As an electric potential is applied, the bound molecules can be easily, rapidly and controllably expelled. In experiments, many therapeutic drugs, such as dopamine, naproxen, heparin, nerve growth factor and dexamethasone, have already been bound and successfully released from these polymers [34]. The dose adjustments are made possible by the application of external stimulus in drug delivery implants [35]. The advantage with conjugated polymers is that because of their reversible transition between their redox states, they are capable of immobilising and releasing ionic species. PEDOT has been used for the delivery of Ibuprofen (ionic form) [36]. There are certain drawbacks such as leaching of bound molecules, fatigue of CPs [37], swelling/deswelling [38], pits/decrements, delamination [39, 40], degradation of the polymer due to in and out movement of dopants [41-44].



25

BIOCOMPATIBLE POLYMERS Biomedical applications need a versatile cellular response for biological sites in molecules. Owing to their versatility, CPs (e.g., PPy, PANI, PTh and polyethyleneimine) have shown to support the growth of a great range of cell types. Moreover, biocompatibility of CPs, if not present accordingly can also be improved/introduced easily by bonding biocompatible molecules, segments and side chains onto the polymer chain (side or main). PPy has been found biocompatible in researches including in vitro growth and differentiation in all ranges of cell types such as bone, neural, endothelial, fibroblasts and stem cells. The good biocompatibility of PPy was evident from animal modelling studies. It showed that in vivo PPy has no significant long-term effect and showed only a minimal tissue response [45]. In another investigation, none of the emeraldine, penigraniline and leucoemeraldine forms of PANI were found to show any kind of inflammatory response in animal studies. PEDOT has shown good biocompatibility, with epithelial, neural and neuroblastoma cells; however, it has also shown slight cytotoxicity, and some other disadvantages, overcome by doping.

BIOMEDICAL COMPOSITES The most prominent method to decrease the existing shortcomings of a CP is to combine it with another polymer, incorporating the positive attributes of both the component polymer materials. To overcome the brittleness of PPy, it was deposited onto polyester and polyethylene terephthalate fabrics to be used in textiles. N-modified PPy-coated polyester fabrics were shown to be cytocompatible and support the growth of cells after an initial period of adhesion. CP-natural polymer composites achieved synergistic properties of both the components; poor processibility of CP was overcome by this approach and conductivity was introduced into an otherwise insulating matrix [2]. PPy was combined with poly(D,L-lactide)- either deposited onto its surface as a film or into its matrix as nanoparticles, yielding a flexible, biocompatible and biodegradable composite with improved conductivity compared to the PPy-coated polyester fabrics [46], causing only minor inflammation (when tested on rats). Another biodegradable composite was created through the polymerization of PPy with dextran [47], possessing high conductivity and antimicrobial behavior. Nanocellulose-PPy composites have


26

Neha Kanwar

excellent mechanical strength, flexibility and durability, high conductivity, high capacity and a fast ion exchange speed. PPy-cellulose nanofibres showed good electrical conductivity and no cytotoxicity, finding application as scaffolds in neural tissue engineering [48]. PPy-chitosan composites showed good electrical conductivity and radical scavenger activity, respectively, finding application as hydrogels, biosensors and controlled release of drugs [49-53]. PANI-collagen composites found application as scaffold materials [54]. PPy-hyaluronic acid composites found application in wound healing and tissue engineering [55]. PPy-carbon nanotubes composites are found to exhibit extra stability, conductivity and biocompatibility. PPy was combined with poly(2-methoxyaniline-5-sulfonate); this hydrophobic composite showed low electrical impedance, and supported the adhesion and proliferation of PC-12 nerve cells [45, 56]. PANI and polypropylene composites were developed for neurobiological applications. PANI and polycaprolactone composites were developed for cardiac tissue regeneration. PEDOT-based composites with multi walled carbon nanotubes produced high-performance neural electrodes [57, 58]. Research efforts are being focused on the development of CPs having further biocompatible and inherently biodegradable nature. PPy-PTh oligomers were effectively combined with ester linkages to generate new biodegradable polymer [59]. The degradation products of PPy-PTh produced oligomers consumable by macrophages, lowering the chance of any in vivo long-term contrary effect. Polylactide and aniline pentamer were combined to create a biodegradable and biocompatible copolymer [12]. Another interesting copolymer was formulated using PANI and its modification was accomplished to produce poly(aniline-co-ethyl-3-aminobenzoate)[60] and poly(aniline-co-3aminobenzoic acid). Many promising composite modified and co-polymer forms of PPy[26], [61], PANI and PEDOT exist, and are used in biomedical applications.

CONCLUSION Newly synthesized CPs show promising performance and applications, but more work is still necessary in this regard. One of the most important factors to be assessed for their application is to enhance their electrical conductivity, together with the ability to bind large quantities of molecules and release them in controllable mode, which would be complimentary for drug delivery applications as well as tissue engineering.



27

REFERENCES [1]

Balint R, Cassidy NJ, Cartmell SH. Conductive polymers: Towards a smart biomaterial for tissue engineering. Acta Biomaterialia. 2014;10(6):2341-53. [2] Kaur G, Adhikari R, Cass P, Bown M, Gunatillake P. Electrically conductive polymers and composites for biomedical applications. RSCAdvances. 2015;5(47):37553-67. [3] Shirakawa H. The discovery of polyacetylene film: The dawning of an era of conducting polymers. Synthetic Metals. 2001;125(1):3-10. [4] MacDiarmid AG. Synthetic metals: a novel role for organic polymers. Synthetic Metals. 2001;125(1):11-22. [5] Kinlen PJ, Silverman DC, Jeffreys CR. Corrosion protection using polyanujne coating formulations. Synthetic Metals. 1997;85(1-3):132732. [6] Long Y-Z, Li M-M, Gu C, Wan M, Duvail J-L, Liu Z, et al. Recent advances in synthesis, physical properties and applications of conducting polymer nanotubes and nanofibers. Progress in Polymer Science. 2011;36(10):1415-42. [7] Li X-G, Li J, Huang M-R. Facile Optimal Synthesis of Inherently Electroconductive Polythiophene Nanoparticles. Chemistry:A EuropeanJournal. 2009;15(26):6446-55. [8] Tierney S, Heeney M, McCulloch I. Microwave-assisted synthesis of polythiophenes via the Stille coupling. Synthetic Metals. 2005;148(2):195-8. [9] Yamamoto T. Molecular assembly and properties of polythiophenes. NPG Asia Mater. 2010;2:54-60. [10] Gök A, Omastová M, Yavuz AG. Synthesis and characterization of polythiophenes prepared in the presence of surfactants. Synthetic Metals. 2007;157(1):23-9. [11] Shi Y, Yu G. Designing Hierarchically Nanostructured Conductive Polymer Gels for Electrochemical Energy Storage and Conversion. Chemistry of Materials. 2016;28(8):2466-77. [12] Huang L, Zhuang X, Hu J, Lang L, Zhang P, Wang Y, et al. Synthesis of Biodegradable and Electroactive Multiblock Polylactide and Aniline Pentamer Copolymer for Tissue Engineering Applications. Biomacromolecules. 2008;9(3):850-8.


28

Neha Kanwar

[13] Huang Z-B, Yin G-F, Liao X-M, Gu J-W. Conducting polypyrrole in tissue engineering applications. Frontiers of Materials Science. 2014;8(1):39-45. [14] Nambiar S, Yeow JTW. Conductive polymer-based sensors for biomedical applications. Biosensors and Bioelectronics. 2011;26(5):1825-32. [15] Davis F, Higson SPJ. Structured thin films as functional components within biosensors. Biosensors and Bioelectronics. 2005;21(1):1-20. [16] Liu K, Tian Y, Jiang L. Bio-inspired superoleophobic and smart materials: Design, fabrication, and application. Progress in MaterialsScience. 2013;58(4):503-64. [17] Zare Y, Shabani I. Polymer/metal nanocomposites for biomedical applications. Materials Science and Engineering: C. 2016;60:195-203. [18] Lorenzo M, Zhu B, Srinivasan G. Intrinsically flexible electronic materials for smart device applications. Green Chemistry. 2016;18(12):3513-7. [19] Gospodinova N, Terlemezyan L. Conducting polymers prepared by oxidative polymerization: polyaniline. Progress in Polymer Science. 1998;23(8):1443-84. [20] Tran HD, Kaner RB. A general synthetic route to nanofibers of polyaniline derivatives. Chemical Communications. 2006(37):3915-7. [21] Gu H, Su Xd, Loh KP. Electrochemical Impedance Sensing of DNA Hybridization on Conducting Polymer Film-Modified Diamond. TheJournal of Physical Chemistry B. 2005;109(28):13611-8. [22] Zhang X, Zhang J, Song W, Liu Z. Controllable Synthesis of Conducting Polypyrrole Nanostructures. The Journal of PhysicalChemistry B. 2005;110(3):1158-65. [23] Lamaka SV, Zheludkevich ML, Yasakau KA, Montemor MF, Cecílio P, Ferreira MGS. TiOx self-assembled networks prepared by templating approach as nanostructured reservoirs for self-healing anticorrosion pretreatments. Electrochemistry Communications. 2006;8(3):421-8. [24] Tüken T, Yazıcı B, Erbil M. Polypyrrole/polythiophene coating for copper protection. Progress in Organic Coatings. 2005;53(1):38-45. [25] Lechna M, Holowacz I, Ulatowska A, Podbielska H. Optical properties of sol-gel coatings for fiberoptic sensors. Surface and CoatingsTechnology. 2002;151-152(0):299-302. [26] Lee JW, Serna F, Nickels J, Schmidt CE. Carboxylic acid-functionalized conductive polypyrrole as a bioactive platform for cell adhesion. Biomacromolecules. 2006;7(6):1692-5.



29

[27] Zhang Y, Steyrleuthner R, Bredas J-L. Charge Delocalization in Oligomers of Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b] thiophene) (PBTTT). The Journal of Physical Chemistry C. 2016. [28] Park DH, Kim BH, Jang MK, Bae KY, Lee SJ, Joo J. Synthesis and Characterization of Polythiophene and Poly(3-methylthiophene) Nanotubes and Nanowires. Synthetic Metals. 2005;153(1-3):341-4. [29] Bredas JL, Street GB. Polarons, bipolarons, and solitons in conducting polymers. Accounts of Chemical Research. 1985;18(10):309-15. [30] Rylie AGaSBaLAP-WaPJM. Conducting polymer-hydrogels for medical electrode applications. Science and Technology of Advanced Materials. 2010;11(1):014107. [31] Hodgson AJ, Gilmore K, Small C, Wallace GG, Mackenzie IL, Aoki T, et al. Reactive supramolecular assemblies of mucopolysaccharide, polypyrrole and protein as controllable biocomposites for a new generation of ‘intelligent biomaterials’. Supramolecular Science. 1994;1(2):77-83. [32] Guo Y, Li M, Mylonakis A, Han J, MacDiarmid AG, Chen X, et al. Electroactive Oligoaniline-Containing Self-Assembled Monolayers for Tissue Engineering Applications. Biomacromolecules. 2007;8(10):302534. [33] Sharma M, Svirskis D, Garg S. CHAPTER 11 Advances in Drugdelivery Systems Based on Intrinsically Conducting Polymers.Smart Materials for Drug Delivery: Volume 1. 1: The Royal Society ofChemistry; 2013. pp. 283-303. [34] Rawat NK, Ghosal A, Ahmad S. Influence of microwave irradiation on various properties of nanopolythiophene and their anticorrosive nanocomposite coatings. RSC Advances. 2014;4(92):50594-605. [35] Svirskis D, Travas-Sejdic J, Rodgers A, Garg S. Electrochemically controlled drug delivery based on intrinsically conducting polymers. Journal of Controlled Release. 2010;146(1):6-15. [36] Krukiewicz K, Zak JK. Conjugated polymers as robust carriers for controlled delivery of anti-inflammatory drugs. Journal of MaterialsScience. 2014;49(16):5738-45. [37] Rawat NK, Pathan S, Sinha AK, Ahmad S. Conducting poly(oanisidine) nanofibre dispersed epoxy-siloxane composite coatings: synthesis, characterization and corrosion protective performance. NewJournal of Chemistry. 2016;40(1):803-17. [38] Rawat NK, Sinha AK, Ahmad S. Conducting poly(o-anisidine-co-ophenyldiammine) nanorod dispersed epoxy composite coatings:


30

[39]

[40]

[41]

[42] [43]

[44] [45]

[46]

[47]

[48]

[49]

Neha Kanwar synthesis, characterization and corrosion protective performance. RSCAdvances. 2015;5(115):94933-48. Xu G, Li B, Wang X, Luo X. Electrochemical sensor for nitrobenzene based on carbon paste electrode modified with a poly(3,4ethylenedioxythiophene) and carbon nanotube nanocomposite. Microchimica Acta. 2014;181(3):463-9. Xu H, Qiu F, Wang Y, Wu W, Yang D, Guo Q. UV-curable waterborne polyurethane-acrylate: preparation, characterization and properties. Progress in Organic Coatings. 2012;73(1):47-53. Yang G, Kampstra KL, Abidian MR. High Performance Conducting Polymer Nanofiber Biosensors for Detection of Biomolecules. AdvancedMaterials. 2014;26(29):4954-60. Gerard M, Chaubey A, Malhotra BD. Application of conducting polymers to biosensors. Biosens Bioelectron. 2002;17(5):345-59. Kaushik A, Khan R, Solanki PR, Pandey P, Alam J, Ahmad S, et al. Iron oxide nanoparticles-chitosan composite based glucose biosensor. Biosensors and Bioelectronics. 2008;24(4):676-83. Solanki PR, Kaushik A, Agrawal VV, Malhotra BD. Nanostructured metal oxide-based biosensors. NPG Asia Materials. 2011;3(1):17-24. Kim S, Oh W-K, Jeong YS, Hong J-Y, Cho B-R, Hahn J-S, et al. Cytotoxicity of, and innate immune response to, size-controlled polypyrrole nanoparticles in mammalian cells. Biomaterials. 2011;32(9):2342-50. Nien P-C, Huang M-C, Chang F-Y, Ho K-C. Integrating an EnzymeEntrapped Conducting Polymer Electrode and a Prereactor in a Microfluidic System for Sensing Glucose. Electroanalysis. 2008;20(6):635-42. Liu M, Wen Y, Li D, He H, Xu J, Liu C, et al. Electrochemical immobilization of ascorbate oxidase in poly(3,4-ethylenedioxythio phene)/multiwalled carbon nanotubes composite films. Journal of Applied Polymer Science. 2011;122(2):1142-51. Thunberg J, Kalogeropoulos T, Kuzmenko V, Hägg D, Johannesson S, Westman G, et al. In situ synthesis of conductive polypyrrole on electrospun cellulose nanofibers: scaffold for neural tissue engineering. Cellulose. 2015;22(3):1459-67. Gülmen SST, Güvel EA, Kızılcan N. Preparation and Characterization of Chitosan/Polypyrrole/Sepiolite Nanocomposites. Procedia Socialand Behavioral Sciences. 2015;195:1623-32.



31

[50] Lee R-J, Temmer R, Tamm T, Aabloo A, Kiefer R. Renewable antioxidant properties of suspensible chitosan-polypyrrole composites. Reactive and Functional Polymers. 2013;73(8):1072-7. [51] Huang H, Wu J, Lin X, Li L, Shang S, Yuen MC-W, et al. Self-assembly of polypyrrole/chitosan composite hydrogels. Carbohydrate Polymers. 2013;95(1):72-6. [52] Li Y, Li G, Peng H, Chen K. Facile synthesis of electroactive polypyrrole-chitosan composite nanospheres with controllable diameters. Polymer International. 2011;60(4):647-51. [53] Sharma A, Kumar A. Study of structural and electro-catalytic behaviour of amperometric biosensor based on chitosan/polypyrrole nanotubesgold nanoparticles nanocomposites. Synthetic Metals. 2016;220:551-9. [54] Kim H-S, Hobbs HL, Wang L, Rutten MJ, Wamser CC. Biocompatible composites of polyaniline nanofibers and collagen. Synthetic Metals. 2009;159(13):1313-8. [55] Collier JH, Camp JP, Hudson TW, Schmidt CE. Synthesis and characterization of polypyrrole-hyaluronic acid composite biomaterials for tissue engineering applications. Journal of Biomedical Materials Research. 2000;50(4):574-84. [56] Fattahi P, Yang G, Kim G, Abidian MR. A Review of Organic and Inorganic Biomaterials for Neural Interfaces. Advanced Materials. 2014;26(12):1846-85. [57] Huang L, Sun Y, Yang T, Li L. Adsorption behavior of Ni (II) on lotus stalks derived active carbon by phosphoric acid activation. Desalination. 2011;268(1-3):12-9. [58] Du X-S, Zhou C-F, Mai Y-W. Facile Synthesis of Hierarchical Polyaniline Nanostructures with Dendritic Nanofibers as Scaffolds. TheJournal of Physical Chemistry C. 2008;112(50):19836-40. [59] Rivers TJ, Hudson TW, Schmidt CE. Synthesis of a Novel, Biodegradable Electrically Conducting Polymer for Biomedical Applications. Advanced Functional Materials. 2002;12(1):33-7. [60] Guo B, Finne-Wistrand A, Albertsson A-C. Molecular Architecture of Electroactive and Biodegradable Copolymers Composed of Polylactide and Carboxyl-Capped Aniline Trimer. Biomacromolecules. 2010;11(4):855-63. [61] Pekmez NÖ, Cınkıllı K, Zeybek B. The electrochemical copolymerization of pyrrole and bithiophene on stainless steel in the presence of SDS in aqueous medium and its anticorrosive performance. Progress in Organic Coatings. 2014;77(8):1277-87.




Chapter 3

RENEWABLE RESOURCE BASED POLYURETHANES AND THEIR BIOMEDICAL APPLICATIONS Shabnam Khan*, Laxmi, Fahmina Zafar and Nahid Nishat* Inorganic Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia – A Central University, New Delhi, India

ABSTRACT Polyurethanes (PUs) have emerged as a significant group of biomaterials owing to their distinctive and excellent mechanical properties and also their biocompatibility. The successful incorporation of biodegradable moieties, particularly renewable resources in the backbone of PUs can lead to an enhancement in the biodegradable characteristics of the same. Such biodegradable and biocompatible PUs obtained from renewable resources can find biomedical applications such as in drug delivery and tissue engineering. This chapter mainly highlights PUs based on renewable resources, particularly vegetable oils and polysaccharides and their biomedical applications.

*

Corresponding author: Inorganic Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi-110025, India. Email: [email protected]; [email protected].


34

Shabnam Khan, Laxmi, Fahmina Zafar and Nahid Nishat

Keywords: renewable resource, polyurethanes, biodegradable, biocompatible, biomedical applications

INTRODUCTION Polyurethanes (PUs) prepared by simple addition reaction between a polyol and an isocyanate, along with a chain extender, prove to be one of the most versatile and resourceful polymer in the field of materials science. PUs contain a significant number of urethane groups (-HN-COO-) as repeating units in the whole structure. In addition, other groups such as ether, ester, aromatic rings, amide, and urea groups are also present in PU backbone. The typical structure of linear PU derived from a diol (OH-R-OH) and a diisocyanate (OCN-R’-NCO) can be represented as shown in Figure1. PUs consist of alternating hard (rigid) and soft (flexible) segments. Hence, by the fine-tuned adjustment of composition and structure of the hard and soft segments, PUs with desirable properties can be achieved. The stabilization of hard domains due to the non-covalent hydrogen bonding interactions between hard segments provides strength and high elasticity to PUs. Another interesting aspect of PUs is flexibility, which is provided by the flexible ether linkages, ester linkages and long hydrocarbon chains comprising the soft domains of the structure.

Figure 1. Schematic representation of PU formation.


Renewable Resource based Polyurethanes …

35

In the past few decades, PUs emerged as a fascinating class of synthetic polymers with the ability to achieve a unique molecular design, specific for a particular application. PUs have proved to be the most efficiently utilized polymers for a range of products such as primers, adhesives, sealants, coatings, foams (flexible and rigid), elastomers, sports goods, medical devices and others [1-5]. PUs are widely employed in biomedical applications in accordance with their brilliant mechanical strength, better biocompatibility as well as high flexural endurance. The modifications in the properties of these materials through the introduction of biodegradable and non-biodegradable polymers are performed to achieve the desired performance characteristics [6-8]. The production of biodegradable PUs emerged to be a recent topic of interest in the field of PUs chemistry. PUs are widely utilized in various biomedical applications such as in vascular prosthesis, artificial skin, pericardial patches, soft tissue adhesives, drug delivery devices, and as scaffolds in tissue engineering [9-11]. For these applications, the biodegradable and biocompatible nature of PUs is an important aspect to be taken into consideration [11]. The polymers capable to undergo biodegradation can be obtained by the use of renewable resources, thereby, reducing the dependence on petrochemical-derived raw materials, that are often costly, toxic and non biodegradable, causing harm to the environment and health. Thus, there is an emerging interest in the development of cost-effective, abundantly available environmental-friendly polymers, with controlled life span. Thus, while designing the polymers, one must consider both physical and biodegradable characteristics of the same. A wide variety of materials are gifted to the mankind by nature including the resources from plants and animals such as vegetable oils, polysaccharides, wood and proteins.

VEGETABLE OIL (VO) BASED PUS VO are the most commonly used renewable resources used in the production of PUs due to their lower costs, domestic abundance, functional attributes and inherent biodegradability [12-14]. The production of polymeric biomaterials by the use of VO offers many advantages such as enhancement in flexibility, tuned mechanical strength, environmental compatibility, and improved biodegradation as well biocompatibility of the final product as derived from bio-origin [15,16].


36


The development of PUs by using VO based polyols started in the early 1950s, by the use of castor oil initially. VO emerged to be the promising route to renewable monomers and polymers [17]. VO are essential bio renewable resources derived from plants and are named according to their biological origin, such as castor oil (CO) and soybean oil (SO). VO are triglycerides of fatty acids formed between glycerol and fatty acids [18]. The physical state of VO is usually determined by the nature of fatty acids and its distribution. Most of the VO exist as liquids at room temperature. The most commonly used VO for the syntheses of PUs are CO, SO, linseed oil and others. Literature indicated a large number of publications on VO derived PUs as shown in the form of pie chart in Figure 2.

Figure 2. Pie chart representing the scientific publications on VO derived PUs in last 10 years searched by Scopus.

CO BASED PUS CO, a colorless to pale yellow liquid, is obtained from the seeds of castor oil plant, Ricinus communis. CO is natural polyol consisting of 90-95% ricinoleic acid, a monosaturated, 18-carbon fatty acid. The average composition of fatty acids present in CO is as follows (Table 1):



37

Table 1. Composition of CO S.No. 1. 2. 3. 4. 5. 6. 7. 8.

Fatty acid Ricinoleic acid Oleic acid Linoleic acid α-Linolenic acid Stearic acid Palmitic acid Dihydroxystearic acid Others

Average percentage range 85-95% 2–6% 1–5% 0.5–1% 0.5–1% 0.5–1% 0.3–0.5% 0.2–0.5%

Due to its hydroxyl containing fatty acid (i.e., ricinoleic acid) as a major constituent, CO can be employed as a potent raw material for the preparation of PUs [19, 20]. Because of the presence of the three available hydroxyl functional groups in CO, it can be used directly as a soft segment or chain extender without any further modification in the synthesis of PUs [21]. VO based PUs undergo low rate of degradation due to the inherent hydrophobicity of the same. Hence, to achieve biodegradability in PUs, several labile and hydrolysable moieties have been incorporated [22-25]. This goal is generally fulfilled by the application of polyols containing hydrolysable bonds as starting material for the PU preparation. Several reports have been published on the biomedical applications of CO based biodegradable PUs. Hamid Yeganeh et al. (26) synthesized a series of epoxy terminated polyurethanes (EPUs) based on CO and polyethylene glycol (PEG) with 1,6hexamethylene diamine used as curing agent, in various mass ratios. The results indicated better mechanical strength and degradation rate which can be modulated by controlling the ratio of PEG or CO based EPUs in the final product. The interactions of these developed polymeric films with L-929 fibroblast cells showed that the developed PUs were non toxic with good cytocompatibility. Namdev B. Shalke et al. [27] developed two types of PUs films based on CO, ethylene glycol, isophorone diisocyanate (IPDI) and CO, PEG (PEG-400 or 600), and IPDI. They also developed transdermal patches by the inclusion of varying amounts of indomethacin (IDM) drug, dibutylpthalate (DBP) and PEG as plasticizer and penetration enhancer, respectively. In vitro drug diffusion studies showed slow prolonged release of IDM attained in the absence of penetration enhancers.


38


Zhihong Dong et al. [28] developed porous nano-hydroxyapatite / PU scaffolds based on CO for application in bone tissue engineering with potential to be used as a repair or substitute of human menisci of the knee joint and articular cartilage. Gold nanotubes/nanowires (GNT / NW) mixed with CO-PEG based PU were fabricated to form PU-GNT/NW composites which were used as porous composite scaffolds for biomedical applications [29]. Stefan Oprea et al. [30] studied the changes in fungal biodegradation by dispersing different content of bonded cellulose in CO based PU matrix to form composites that showed high susceptibility to fungal attack. The study also revealed that the developed PU composites with high content of renewable raw material can be employed as an eco friendly biomaterial owing to its better biodegradability.

SO BASED PUS SO is extracted from the seeds of Glycine max. It is one of the most widely consumed oil mainly in cooking. The major unsaturated and saturated fatty acids present in SO triglycerides are as follows (Table 2): Table 2. Composition of SO S. No. 1. 2. 3. 5. 6.

Fatty acid Linoleic acid Oleic acid α-Linolenic acid Stearic acid Palmitic acid

Average percentage range 51% 23% 7–10% 4% 10%

Besides CO, SO emerged to be a useful oil for the preparation of PUs after the introduction of hydroxyl groups [31-33]. SO can be tailored to form soy based polyols by introducing hydroxyl groups by chemical reactions such as hydrogenation [34], epoxidation followed by oxirane opening [35], ozonolysis followed by hydrogenation [36], and microbial conversion [37]. These soy-based polyols can be employed for PU synthesis by proper selection of functional groups and side chains. S. Miao et al. [38] have used SO-based polyol that was obtained through ring-opening reaction of epoxidized monoglyceride with lactic acid for the



39

synthesis of biocompatible PUs. The synthesized PUs showed relatively high tensile strength and elongations. The biocompatibility of the synthesized PUs on mouse fibroblast cells (L-929) was confirmed by good adhesion and growth behavior of these cells on PUs surface, thus making it suitable for biomedical applications. H. Bakhshi et al. [39] synthesized PU coatings by the use of 1,2,3-triazolefunctionalized SO-based polyols. They also studied the effect of different (embedded) functional groups on their physical, mechanical, thermal and biological properties. The results showed good cell viability of up to 60-110% by studying the interaction of developed PUs on fibroblast cells. The developed polyols and PUs also showed moderate to high biocidal activity. In another work [40], bactericidal PU coatings were prepared by the introduction of quaternary ammonium salts, showing antibacterial activity, on to the backbone of SO. These PU coatings based on IPDI showed improved mechanical strength and adhesion characteristics for coating applications. PU was obtained by the use of methyl iodide as an alkylating agent of tertiary amine functional SO-based polyol and IPDI as diisocyanate monomer, for application as biocompatible and bactericidal surface coatings.

POLYSACCHARIDES BASED PUS Among all the renewable resources, polysaccharides (starch, cellulose and chitin) are one of the most abundant, naturally occurring, biodegradable polymers. In comparison to other polysaccharides, chitin and chitosan (CS) are considered as functionally blessed polysaccharides as they have antioxidant and haemostatic properties, solubility and different structural characteristics in different media [41-43]. Both chitin and CS find wide potential applications owing to their biocompatible, biodegradable, and environment friendly nature. All these resources undergo degradation readily in biologically active environment such as soil, sewage and marine locations in the presence of bacteria [44]. Chitin and CS are obtained commercially from waste products of the crustacean shells (such as crabs) and by-products of food industry [45]. Literature survey indicated that the introduction of labile moieties susceptible to hydrolytic degradation can lead to the formation of biodegradable PUs. The incorporation of a polysaccharide such as chitin as a chain extender/crosslinker in the main PU chain can usually enhance the degradation rate as these are readily biodegradable. The biomedical


40


applications of polysaccharide incorporated PUs have been reported as discussed below.

CHITIN BASED PUS Chitin [C8H13O5N]n is one of the most abundantly available natural polymer extensively distributed in nature, as crustacean shell wastes. It is found in various living organisms such as shrimps, crabs, tortoises and insects (46), internal structures of invertebrates, cell wall of fungi, and exoskeleton of arthropods. It is the second most abundant biopolymer after cellulose. Chitin has a cellulose like rigid structure composed of (1,4)–2-acetamido-2-deoxy-βD- glucose units with β-(1→4) covalent linkages. It is quite similar in structure to cellulose, but it is a modified amino polysaccharide with an acetamide group in place of hydroxyl group at C-2 position as shown in Figure 3. Due to the presence of acetamide group (NHCOCH3) in larger amount in the chain of chitin, it is more appropriate as a biomaterial for application in biomedical field. Chitin is basically protein in nature due to the presence of acetamide group which quite resembles the amide bond of protein present in the living tissue. Therefore, chitin is compatible to living tissues (human or animal), hence can be used in diverse applications such as wound healing and tissue engineering [47, 48]. The phenomenal property of chitin makes it appropriate for applications in biomedical field such as surgical sutures that are used in human body [49].

Figure 3. Structure of Chitin.



41

The fabrication of synthetic polymers such as PUs with natural ones, such as polysaccharides like chitin, became a suitable process for the development of biomaterials [50]. Chitin based PUs possess the flexibility in both mechanical and biological properties which turned to be an important parameter in wide range of applications [51]. Some of the latest work on the development of chitin based PUs for biomedical applications has been discussed here: A class of biodegradable PUs was synthesized by the reaction of poly(ϵcaprolactone) (PCL) and 4,4’-diphenyl methane diisocyanate with differing mass ratios of chitin and 1,4-butane diol. The incorporation of chitin in this PUs backbone increased its rigidity, strength and heat resistance making this biopolymer a suitable choice for heat-resistant elastomers in biomedical and industrial applications [44]. Another class of biocompatible chitin based PUs elastomers were developed by step growth polymerization using PCL with different diisocyanates, chitin and / or 1,4-butane diol as chain extenders. Results proved that with varying the diisocyanate from aliphatic to aromatic and using chitin as a chain extender, the mechanical properties tend to increase. In-vitro biocompatibility and non-toxicity tests demonstrated the application of these PUs in biomedical implants especially surgical threads [52]. K. Madhumathi et al. [53] synthesized chitin/nanosilver scaffolds with bactericidal activity against S.aureus and E.coli. These synthesized composites found use in wound healing applications due to the excellent blood clotting ability. This blood clotting ability is due to hemostatic nature of chitin which gets further enhanced on incorporating silver nanoparticles. In another study, CO based PU was prepared from CO polyol and hexamethylene diisocyanate, and incorporated with chitin nanocrystals. The modified PUs showed good in vitro cell response and shape memory behavior [54]. Chitin based water soluble hydrogels also serve as accelerators in wound healing, as tested on rats. Within seven days after creating the wound, complete re-epithelialization was observed; granular tissues were replaced by fibrosis and hair follicles [55].

CS BASED PUS CS (shown in Figure 4) is a polysaccharide, obtained by the deacetylation of chitin. Chitin can be transformed into CS having free amino groups that is highly beneficial in biomedical applications. In case of CS, a higher


42


percentage of amino groups usually imparts hemostatic characteristics to implanted devices [56]. The incorporation of CS into the PUs backbone resulted into a wide array of biomedical applications such as wound healing, separation membrane, tissue engineering scaffolds, stent coatings, sutures, sensors, and drug delivery systems. Lin et al. [57] prepared waterborne polyurethane (WPU) based CS blended films and found that on increasing the CS contents, tensile strength tend to increase with simultaneous decrease in elongation. The thermomechanical and water adsorption properties of WPU-CS films were evaluated to check their properties such as biocompatibility and mechanical strength. Biocompatibility test was done by using immortalized rat chondrocytes and revealed that WPU-CS films with higher percentage of CS content shows better mechanical properties and biocompatibility and can find potential use in cartilage repair.

Figure 4. Structure of CS and its applications.

Filiz Kara et al. [58] prepared PUs films from toluene diisocyanate and polypropylene ethylene glycol and then modifying the films with CS having antibacterial activity by covalent immobilization. These synthesized CS immobilized PUs films with antibacterial activity against S. aureus and P.



43

aeruginosa can be used for the production of medical devices as urinary catheters and can also inhibit pathogenic biofilm formation which is the common reason for the failure of medical equipments and materials. Blends of CS and PUs have been used to encapsulate water soluble antihypertensive drugs and cardiovascular drugs (isoxsuprinehydrochloride and calcium dobesilate) for controlled release [59]. CS shows good miscibility with several synthetic polymers. CS degrades faster, and it has lower mechanical strength than synthetic polymers. Thus, in CS blends with synthetic polymers, the mechanical strength and durability is offered by the latter while CS serves as biological functionality. CS-PCL nanoporous scaffolds showed balanced hydrophilicity and high structural integrity for application for nerve regeneration. CS-hydroxyapatite nanofibres found application in tissue engineering, fabricating bioactive scaffolds resembling extracellular matrix [60]. Chitin and CS based PUs have found numerous applications in biomedical field [61].

CELLULOSE BASED PUS Cellulose, a polysaccharide with the formula (C6H10O5)n, comprises a linear chain of repeating D-glucose units joined through β(1→4) glycosidic linkages [62]. Cellulose is the most abundant polymer that is mainly found in primary cell wall of green plants, various forms of algae and oomycetes [63]. The main advantages of biopolymers regarding availability, cost and others are fulfilled by the use of cellulose. Nowadays, there is an immense interest in the development of stiff nanometric particles from cellulose for reinforcing these with polymers and composites. The crystalline domains of cellulose are usually extracted by means of acid hydrolysis and are named as cellulose nanocrystals/whiskers/nanofibres/cellulose crystallites, due to their physical characteristics such as stiffness, length and thickness [64]. The properties of PUs can be tuned with cellulose fibres other than various fillers such as talc, mica, glass fibres, as reinforcement material. Pineapple leaf fibre (PALF) is an important example of natural fibre with high specific strength and stiffness that can be extracted into nanofibres that are thinner than bacterial cellulose fibres [65]. These cellulose nanofibres extracted from PALF have been used as reinforcement material with PUs showing enhanced strength and stiffness and can be used for application in medical implants [66]. Solanki et al. synthesized waterborne PUs crosslinked with cellulose and were loaded with felodipine drug to evaluate their drug release capacity. The


44


synthesized PUs find medical applications in fields such as vaginal and colon specific drug delivery [67].

CONCLUSION Among all the polymers used worldwide, PUs alone contribute more than 5% of the total world consumption due to their remarkable mechanical properties and biomedical applications. The use of renewable resources in PUs production adds towards biomedical applications owing to their increased biodegradability and biocompatibility properties. Hence, the combination of both PUs and renewable resources paved an attractive roadmap for advancements in the biomedical field. Much work has been reported regarding synthesis of PU membranes, foams, coatings, films and others, and their further applications ranging from antibacterial agents, wound dressings, medical implants, scaffolds for tissue engineering and much more. Thus, the researchers have investigated a lot on renewable resources based PUs and are continuously exploring the plausible uses of their exceptional properties to the fullest in multidisciplinary areas.

ACKNOWLEDGMENTS Author Shabnam Khan wishes to acknowledge University Grants Commission, New Delhi, India UGC for Maulana Azad National Fellowship, Ref#F1-17.1/2014-15/MANF-2014-15-MUS-UTT-36965/ (SA-III/Website). Dr. Fahmina Zafar is thankful to the Dept. of Science & Technology, New Delhi, India for the award of fellowship under the Women Scientists Scheme (WOS) for Research in Basic/Applied Sciences (Ref. No. SR/WOS-A/CS97/2016). Authors are also thankful to the Head, Dept. of Chemistry, Jamia Millia Islamia, for providing facilities to carry out the research work.

REFERENCES [1]

Li S, Vatanparast R, Lemmetyinen H. Cross-linking kinetics and swelling behavior of aliphatic polyurethane. Polymer. 2000; 41: 5571– 76.


Renewable Resource based Polyurethanes … [2]

[3]

[4]

[5] [6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

45

Kim BK, Seo JW, Jeong HM. Morphology and properties of waterborne polyurethane/clay nanocomposites. European Polymer Journal. 2003; 39: 85–91. Kim BS, Kim BK. Enhancement of hydrolytic stability and adhesion of waterborne polyurethanes. Journal of Applied Polymer Science. 2005; 97: 1961–69. Zia KM, Barikani M, Zuber M, Bhatti IA, Sheikh MA. Molecular engineering of chitin based polyurethane elastomers. Carbohydrate Polymers. 2008; 74: 149-58. Prisacariu C. Polyurethane elastomers from morphology to mechanical aspects: Wien/NewYork: Springer; 2011. Iannace S, DeLuca N, Nicolais L, Carfagna C, Huang SJ. Physical characterization of incompatible blends of polymethylmethacrylate and polycaprolactone. Journal of Applied Polymer Science. 1990; 41: 2691– 2704. Iannace S, Ambrosio L, Huang SJ, Nicolais L. Poly(3-hydroxybutyrate)co-(3-hydroxyvalerate)/poly-L-lactide blends: Thermal and mechanical properties. Journal of Applied Polymer Science. 1994; 54: 1525–35. Iannace S, Ambrosio L, Huang SJ, Nicolais L. Effect of degradation on the mechanical properties of multiphase polymer blends. PHBV/PLLA. Journal of Macromolecular Science Pure and Applied Chemistry–A. 1995; 32: 881-88. Das B, Chattopadhyay P, Mandal M, Voit B, Karak N. Bio-based biodegradable and biocompatible hyperbranched polyurethane: a scaffold for tissue engineering. Macromolecular Bioscience. 2013; 13: 126-139. Gisselfalt K, Edberg B, Flodin P. Synthesis and properties of degradable poly(urethaneurea)s to be used for ligament reconstructions. Biomacromolecules. 2002; 3: 951-58. Yeganeh H, Hojati-Talemi P. Preparation and properties of novel biodegradable polyurethane networks based on castor oil and poly(ethyleneglycol). Polymer Degradation and Stability. 2007; 92: 480-89. Uyama H, Kuwabara M, Tsujimoto T, Kobayashi S. Enzymatic synthesis and curing of biodegradable epoxide-containing polyesters from renewable resources. Biomacromolecules. 2003: 4: 211-15. Tsujimoto T, Uyama H, Kobayashi S. Synthesis and curing behaviors of cross-linkable polynaphthols from renewable resources: preparation of artificial urushi. Macromolecules. 2004; 37: 1777-82.


46


[14] Biermann U, Friedt W, Lang S, Luhs W, Machmuller G, Metzger JO, Klaas MR, Schafer HJ, Schneider MP. New syntheses with oils and fats as renewable raw materials for the chemical industry. Angewandte Chemie International Edition. 2000; 9: 2206-24. [15] Tabone MD, Cregg JJ, Beckman EJ, Landis AE. Sustainability metrics: life cycle assessment and green design in polymers. Environmental Science and Technology. 2010; 44: 8264-69. [16] Tanaka R, Hirose S, Hatakeyama H. Preparation and characterization of polyurethane foams using a palm oil-based polyol. Bioresource Technology. 2008; 99: 3810-16. [17] Xia Y, Larock RC. Vegetable oil-based polymeric materials: synthesis, properties, and applications. Green Chemistry. 2010; 12: 1893–1909. [18] Verh'e R. Renewable Bioresources: Scope and Modification for Nonfood Applications. In: Stevens CV, Verhé R, editor. John Wiley & Sons Ltd. West Sussex: England; 2004. p.208–250. [19] Silva MC, Takahashi JA, Chaussy D, Belgacem MN, Silva GG. Composites of rigid polyurethane foam and cellulose fiber residue. Journal of Applied Polymer Science. 2010a; 117: 3665–72. [20] Silva BBR, Santana RMC, Forte MMC. A solventless castor oil-based PU adhesive for wood and foam substrates. International Journal of Adhesion and Adhesives. 2010b; 30: 559–65. [21] Yeganeh H, Hojati-Talemi P. Preparation and properties of novel biodegradable polyurethane networks based on castor oil and poly(ethyleneglycol). Polymer Degradation and Stability. 2007; 92: 480–89. [22] Howard GT. Biodegradation of polyurethane: a review. International Biodeterioration and Biodegradation. 2002; 49: 245-52. [23] Okada M. Chemical syntheses of biodegradable polymers. Progress in Polymer Science. 2002; 27: 87-133. [24] Chandra R, Rustgi R. Biodegradable polymers. Progress in Polymer Science. 1998; 23: 1273-1335. [25] Pavlova M, Draganova M. Biocompatible and biodegradable polyurethane polymers. Biomaterials. 1993; 14: 1024-29. [26] Yeganeh H, Hojati-Talemi P. Preparation and properties of novel biodegradable polyurethane networks based on castor oil and poly(ethyleneglycol). Polymer Degradation and Stability. 2007; 92: 480-489.



47

[27] Shelke NB, Sairam M, Halligudi SB, Aminabhavi TM. Development of transdermal drug-delivery films with castor-oil-based polyurethanes. Journal of Applied Polymer Science. 2007; 103: 779–88. [28] Dong Z, Li Y, Zou Q. Degradation and biocompatibility of porous nanohydroxyapatite/polyurethane composite scaffold for bone tissue engineering. Applied Surface Science. 2009; 255: 6087–91. [29] Ganji Y, Kasra M, Kordestani SS, Hariri MB. Synthesis and characterization of gold nanotube/nanowire-polyurethane composite based on castor oil and polyethylene glycol. Materials Science and Engineering C. 2014; 42: 341–49. [30] Oprea S, Potolinca VO, Gradinariu P, Joga A, Oprea V. Synthesis, properties, and fungal degradation of castor-oil-based polyurethane composites with different cellulose contents. Cellulose. 2016; 23: 2515– 26. [31] Jalilian M, Yeganeh H, Haghighi MN. Preparation and characterization of polyurethane electrical insulating coatings derived from novel soybean oil-based polyol. Polymers for Advanced Technologies. 2009; 21: 118–127. [32] Jalilian M, Yeganeh H, Haghighi MN. Synthesis and properties of polyurethane networks derived from new soybean oil-based polyol and a bulky blocked polyisocyanate. Polymer International. 2008; 57: 1385– 94. [33] Lu Y, Larock RC. Soyabean-oil-based waterborne polyurethane dispersions: effects of polyol functionality and hard segment content on properties. Biomacromolecules. 2008; 9: 3332–40. [34] Lysenko Z, Morrison DL, Babb DA, Bunning DL, Derstine CW, Gilchrist JH. WO patent 2004096744 A2. 2004. [35] Petrovic ZS, Javni I, Guo A, Zhang W. Method of making natural oilbased polyols and polyurethanes therefrom. US patent 6, 433, 121. 2002. [36] Petrovic ZS, Zhang W, Javni I. Structure and properties of polyurethanes prepared from triglyceride polyols by ozonolysis. Biomacromolecules. 2005; 6: 713-719. [37] Hou CT. Microbial oxidation of unsaturated fatty acids: Advances in Applied Microbiology: In: Laskin AI, editor: Acad,. Press Orlando. 1995. Vol41. p.1-23. [38] Miao S, Sun L, Wang P, Liu R, Su Z, Zhang S. Soybean oil-based polyurethane networks as candidate biomaterials: Synthesis and biocompatibility. European Journal of Lipid Science and Technology. 2012; 114: 1165–74.


48


[39] Bakhshi H, Yeganeh H, Mehdipour-Ataei S, Shokrgozar MA, Yari A, Nasirodin Saeedi-Eslami S. Synthesis and characterization of antibacterial polyurethane coatings from quaternary ammonium salts functionalized soybean oil based polyols. Materials Science and Engineering C. 2013; 33: 153–64. [40] Bakhshi H, Yeganeh H, Mehdipour-Ataei S, Solouk A, Irani S. Polyurethane Coatings Derived from 1,2,3-Triazole-Functionalized Soybean Oil-Based Polyols: Studying their Physical, Mechanical, Thermal, and Biological Properties. Macromolecules. 2013; 46: 7777−88. [41] Peter MG, Domard A, Muzzarelli RAA. Advances in Chitin Science. Vol.4, Germany: University of Potsdam: 2000. [42] Larry LH. Biomaterials: A forecast for the future. Biomaterials. 1998; 19: 1419-1423. [43] Koide SS. Chitin-chitosan: Properties, benefits and risks. Nutrition Research. 1998; 18: 1091-101. [44] Zia KM, Barikani M, Bhatti IA, Zuber M, Bhatti HN. Synthesis and Characterization of Novel, Biodegradable, Thermally Stable ChitinBased Polyurethane Elastomers. Journal of Applied Polymer Science. 2008; 110: 769–776. [45] Prashanth KVH, Tharanathan RN. Chitin/chitosan: modifications and their unlimited application potential-an overview. Trends in Food Science and Technology. 2007; 18: 117–131. [46] Kumar MNVR. A review of chitin and chitosan applications. Reactive and Functional Polymers. 2000; 46: 1–27. [47] Yao KD, Tu H, Cheng F, Zhang JW, Lin J. pH-sensitivity of the swelling of a chitosan-pectin polyelectrolyte complex. Die Angewandte Makromolekulare Chemie/Applied Macromolecular Chemistry and Physics. 1997; 245: 63-72. [48] Wang H, Li W, Lu Y, Wang Z, Zhong W. Studies on chitosan and poly(acrylicacid) interpolymer complex. II. Solution behaviors of the mixture of water soluble chitosan and poly(acrylicacid). Journal of Applied Polymer Science. 1996; 61: 2221-24. [49] Khor E. Chitin: a biomaterial in waiting. Current Opinion in Solid State and Materials Science. 2002; 6: 313–17. [50] Yang JM, Yang SJ, Lin HT, Wu TH, Chen HJ. Chitosan containing PU/Poly(NIPAAm) thermosensitive membrane for wound dressing. Material Science and Engineering C. 2008; 28: 150-6.



49

[51] Werkmeister JA, Edwards GA, Casagranda F, White JF, Ramshaw JAM. Evaluation of a collagen-based biosynthetic material for the repair of abdominal wall defects. Journal of Biomedical Materials Research. 1998; 39: 429–36. [52] Zia KM, Zuber M, Bhatti IA, Barikani M, Sheikh MA. Evaluation of biocompatibility and mechanical behavior of chitin-based polyurethane elastomers. Part-II: Effect of diisocyanate structure. International Journal of Biological Macromolecules. 2009; 44: 23–28. [53] Madhumathi K, Sudheesh Kumar PT, Abhilash S, Sreeja V, Tamura H, Manzoor K, Nair SV, Jayakumar R. Development of novel chitin/nanosilver composite scaffolds for wound dressing applications. Journal of Materials Science: Materials in Medicine. 2010; 21: 807– 813. [54] Saralegi A, Fernandes SCM, Alonso-Varona A, Palomares T, Johan Foster E, Weder C, Eceiza A, Corcuera MA. Shape-Memory Bionanocomposites Based on Chitin Nanocrystals and Thermoplastic Polyurethane with a Highly Crystalline Soft Segment. Biomacromolecules. 2013; 14: 4475–82. [55] Jayakumar R, Prabaharan M, Sudheesh Kumar PT, Nair SV, Furuike T, Tamura H. Novel Chitin and Chitosan Materials in Wound Dressing, Biomedical Engineering, Trends in Materials Science, Ed: Anthony Laskovski: ISBN:978-953-307-513-6, InTech Publishers: 2011. [56] Prabaharan M. Chitosan derivatives as promising materials for controlled drug delivery. Journal of Biomaterials Applications. 2008; 23: 5–36. [57] Lin YH, Chou NK, Wu WJ, Hsu SH, Whu SW, Ho GH, Tsai CL, Wang SS, Chu SH, Hsieh KH. Physical properties of water-borne polyurethane blended with chitosan. Journal of Applied Polymer Science. 2007; 104: 2683-89. [58] Kara F, Aksoy EA, Yuksekdag Z, Hasirci N, Aksoy S. Synthesis and surface modification of polyurethanes with chitosan for antibacterial properties. Carbohydrate Polymers. 2014; 112: 39–47. [59] Sullad AG, Manjeshwar LS, Aminabhavi TM. Blend microspheres of chitosan and polyurethane for controlled release of water-soluble antihypertensitive drugs. Polymer Bulletin. 2015; 72: 265–80. [60] Mahoney C, McCullough MB, Sankar J, Bhattarai N. Nanofibrous structure of chitosan for biomedical applications. Journal of Nanomedicine and Biotherapeutic Discovery. 2012; 2:102. doi:10.4172/2155-983X.1000102.


50


[61] Usman A, Zia KM, Zuber M, Tabasum S, Rehman S, Zia F. Chitin and chitosan based polyurethanes: A review of recent advances and prospective biomedical applications. International Journal of Biological Macromolecules. 2016; 86, 630–645. [62] Updegraff DM. Semi microdetermination of cellulose in biological materials. Analytical Biochemistry. 1969; 32: 420–424. [63] Romeo T, editor. Bacterial biofilms. Berlin: Springer: 2008. p. 258–263. [64] De Souza Lima MM, Borsali R. Rod like cellulose microcrystals: Structure, properties, and applications. Macromolecular Rapid Communications. 2004; 25: 771–87. [65] Lopattananon N, Panawarangkul K, Sahakaro K, Ellis B. Performance of pineapple leaf fiber–natural rubber composites: The effect of fiber surface treatments. Journal of Applied Polymer Science. 2006; 102: 1974–84. [66] Cheriana BM, Leãoa AL, Ferreirade Souzab S, Costab LMM, Molina de Olyveira G, Kottaisamy M, Nagarajan ER, Thomas S. Cellulose nanocomposites with nanofibres isolated from pineapple leaf fibers for medical applications. Carbohydrate Polymers. 2011; 86: 1790–98. [67] Solanki A, Thakore S. Cellulose crosslinked pH-responsive polyurethanes for drug delivery: α-hydroxy acids as drug release modifiers. International Journal of Biological Macromolecules. 2015; 80: 683–91.



Chapter 4

SYNTHESIS AND APPLICATIONS OF BIOPOLYMERIC NANOPARTICLES Abhijeet Mishra1 and Anujit Ghosal2, 1

School of Life Sciences, Jawaharlal Nehru University, New Delhi, India 2 School of Basic Applied and Science, Department of Chemistry, Galgotias University, Greater Noida, Gautam Buddh Nagar, Uttar Pradesh, India

ABSTRACT Biopolymeric nanoparticles such as polysaccharides and proteins have attracted greater attention in therapeutic applications. Chitosan is the most famous polysaccharide, second in number in terms of abundance, first being cellulose. It is obtained by the deacetylation reaction of chitin. It is cost effective, biocompatible, environmentally benign, and biodegradable. Recently, nanoparticles of the biopolymer chitosan have drawn great attention for application in drug delivery agents due to their superior stability in aqueous solution, lower toxicity, and providing several routes of administration. Therefore, chitosan nanoparticles can be used as promising drug delivery vehicles in several diseases.

Keywords: chitosan, nanoparticles, drug delivery, polymers 

Corresponding author: Anujit Ghosal, address: Assistant professor, Department of Chemistry, School of Basic and Applied Sciences, Galgotias University, Greater Noida, Gautam Buddh Nagar, Uttar Pradesh, India, Email: [email protected].


52

Abhijeet Mishra and Anujit Ghosal

INTRODUCTION Nanotechnology is an interdisciplinary field in the science and technology area that deals with the use of materials with their dimensions equivalent to the one billionth part of a meter i.e., nanometer [1]. Due to their unique properties which are different from bulk counterparts, the synthesis of nanoparticles [NP] is a growing area of research [2]. NP have outstanding targeting (active/passive) properties due to which the drugs are conveyed to the specific target site. The blood circulation time and the property of targeting tumors by NP is governed by many factors such as the particle shape, size, molecular weight of the polymer forming the core, stiffness, surface modifications of NP and others. They can easily seep through the leaky vessel wall surrounding the tumor, and can be accumulated in higher concentrations (because of the pathophysiological differences between normal and abnormal tumor tissues referred as enhanced permeability and retention effect or EPR) in tumors for prolonged times [3]. NP can be modified by different entities and by various ways, for applications in different areas (Figure 1). Biopolymers are considered suitable for clinical applications. They are biocompatible, biodegradable and show low immunogenicity. Biopolymers such as proteins and polysaccharides are easily metabolized by specific enzymes, in contrast to the synthetic polymers that may often accumulate within our bodies and may degrade into toxic products. Among different NP, biopolymeric NP such as chitosan NP, which have superior stability properties than others, have been used as alternative drug carrier agents that overcome several problems. Chitosan is considered as an important polymer applied broadly in the medical field as well as in immobilization techniques. Chitosan holds scope for various chemical modifications through its reactive functional groups, improving the properties of chitosan and rendering it suitable for versatile pharmaceutical and biomedical applications. Chitosan is a linear polyaminosaccharide obtained by N-deacetylation of chitin. It is the second most abundant natural biopolymer, after cellulose. It occurs naturally such as in the cell walls of fungi and crustacean shells and it is, either fully or partially, deacetylated chitin (4). The chitosan polymer is composed of carbon (44%), hydrogen (6%) and nitrogen (7%) respectively. Chitosan is a natural polymer which is totally biocompatible and biodegradable, and further can be used as an antibacterial and antifungal agent [5]. In order to get different physico-chemical and biological properties, the degree of deacetylation along with the molecular weight of chitosan can be changed accordingly.


Synthesis and Applications of Biopolymeric Nanoparticles

53

Figure 1. Pictorial presentation of the use of NP for different applications.

PREPARATION OF CHITOSAN NP NP are defined as solid particles or particulate dispersions with a size in the range of 1–1000 nm. There are different methods available for the synthesis of chitosan NP such as the emulsion, ionic gelation, reverse micellar, and self-assembling methods. The reverse micellar and ionic gelation methods are popular and widely accepted for chitosan NP synthesis.

IONIC GELATION METHOD In ionic gelation method, chitosan NP can be synthesized by the attraction and interaction of oppositely charged macromolecules [6]. Tripolyphosphate (TPP) is extensively used in the preparation and assembling of the NP of chitosan. TPP has no or very less toxicity, multivalent and has ability to form


54


gels via ionic interactions. The interaction of oppositely charged molecules can be controlled by the charge density of chitosan and TPP by changing the pH of solution. Further, these interactions can be influenced by numerous factors, such as pH, method of mixing, and components’ ratio. Recently, very easy method to synthesize Fe3O4-chitosan NP (magnetic) by cross-linking with TPP, precipitation with NaOH and oxidation with O2 in aqueous HCl containing chitosan and Fe(OH)2 was reported [7]. Size of Fe3O4-chitosan NP (50-100 nm) was estimated using Transmission electron microscopy (TEM).

REVERSE MICELLAR METHOD Polymeric NP with controlled shape and size can be synthesized with this method [8]. In the preparation of reverse micelles, the surfactant was dissolved in an organic solvent. The solution of chitosan is added with constant shaking to escape any turbidity. The aqueous phase should be controlled in such a way to maintain the whole solution in an optically transparent microemulsion phase. To control the shape and size of chitosan NP, lowering the molar mass of chitosan would be advantageous due to either lowering in the viscosity of the internal aqueous phase or an increase in the separation of the polymer chains during the process.

MICROEMULSION METHOD Chitosan NP prepared by using microemulsion method was first introduced by Maitra et al. [9]. In this technique, the synthesis of chitosan NP was carried out in the aqueous core of reverse micellar droplets and successively cross-linked through glutaraldehyde. In this process, n-hexane was used to dissolve a surfactant. Then, glutaraldehyde and chitosan in acetic acid solution were mixed to surfactant/hexane solution under continuous shaking. To complete the crosslinking process, the whole system was agitated overnight at room temperature, which causes the chitosan free amine groups to be joined with glutaraldehyde. Next step is the removal of the organic solvent by evaporation under low pressure. The removal of excess of surfactant was done by precipitation with CaCl2. The precipitant was removed carefully by centrifugation process. The dialysis was carried out to get purified NP suspension before lyophilyzation. This technique offered a controlled size



55

distribution of particles which is less than hundred nm in diameter. In addition, the particle size can be controlled by changing the amount of cross-linking agent such as glutaraldehyde. Nonetheless, some disadvantages also exist with this technique for example time consuming preparation process, use of organic solvents, and difficulty in the washing step. Chitosan is an ideal candidate to create NP for medical applications due to its unique biological properties. In order to accomplish, the NP should have better system to enhance stability and longevity in the physiological environment [10]. The encouraging finding of the chitosan-TPP precipitation at pH 7.4 advocates that even if the colloidal system is not stable at this pH, the TPP appears to allow the maintenance of a chitosan-TPP complex at physiological condition. The kinetic behavior of this precipitation is solely determined by temperature and becomes unfavorable at higher temperature. In most cases, the chitosan-TPP NP synthesized and stored in saline solvents for further applications were stable up to one month with respect to particle compactness and changes in particle size. However, the zeta potential of the chitosan NP was generally higher in the absence of sodium chloride. The particles were less stable when stored in pure water. Interestingly, higher TPPto-chitosan ratios increased the compactness of the particles and reduced the zeta potential of the chitosan NP. Furthermore, higher concentration of chitosan leads to make larger particles [11].

APPLICATION IN DRUG DELIVERY Nanotechnology and polymers have gained a remarkable interest in different areas such as the biomedical science and therapeutics. Both natural and synthetic polymers can be used to form NP [12]. Among different polymer NP, chitosan NP are mostly used in biomedical applications. The haemostatic properties and accelerated wound healing efficiency of chitosan NP make them useful in wound healing, ulcer and burn treatments, while their biodegradable nature and cell affinity promote their application in tissue engineering [13] Chitosan NP are also employed in drug delivery especially in cancer (Figure 2) due to their biocompatibility, no toxicity, environment friendly, and cationic nature [14, 15]. On this note, it is supposed that the prepared chitosan NP can be employed for several biomedical applications for the research and development of new therapeutic drug release systems with enhanced biodistribution and better specificity and sensitivity, and lowered pharmacological toxicity. For non-invasive routes of drug administration such


56


as oral, nasal, ocular and pulmonary routes, chitosan NP have been found most suitable than others. Further, these applications are advantageous over other agents by the absorption-enhancing effect of chitosan [16]. In addition, chitosan NP have shown adjuvant effect in vaccines and also have been suggested for use as non-viral vectors in gene therapy [17]. Bioavailability and absorption of drug encapsulated into chitosan NP can be improved, so they can be used in different applications such as gene delivery, protein drugs and other compounds and can provide them protection effectively from enzyme degradation in vivo [18]. Tamoxifen (anticancer drug) loaded onto chitosan NP showed augmented chemotherapeutic efficiency. The drug and chitosan NP formed complexes; the system showed intelligently controlled pH responsive drug release from chitosan NP, as tested against MCF-7 breast cancer cells [13]. Camptothecin, an active anticancer hydrophobic drug, found limited clinical use in cancer treatment because of its poor water solubility and rapid hydrolysis of its lactone ring, under physiological conditions. The drawback could be overcome by the encapsulation of the drug by glycol chitosan NP (hydrophilic shell), chemically conjugated with cholanic acid (hydrophobic multicore). The hydrophobic core facilitated the efficient absorption, higher loading (80% drug loading efficiency) and controlled release of the hydrophobic drug. The inner hydrophobic cores of the conjugate preserved the lactone rings of the drug from hydrolysis under physiological conditions. Thus, compared to the free drug, chitosan NP conjugate encapsulated Camptothecin exhibited prolonged circulation time in blood, efficient tumor tissue targeting and substantially enhanced anticancer activity against breast cancer cells [19]. Similar glycol chitosan and bile acid conjugates have also been reported as drug carriers for anticancer drugs Cisplatin (80% drug loading efficiency) [20], Paclitaxel (drug loading efficiency as 80% and 97%, respectively) [21, 22], and others. The anticancer drug curcumin had low bioavailability which limited its use and its anticancer potential. This was overcome by the nanoencapsulation of curcumin by thiolated chitosan NP. Similarly, thiolated chitosan NP encapsulation of 5-fluorouracil augmented the antitumorogenic activity of the drug towards colon cancer [23]. Chitin and chitosan NP, membranes, hydrogels and films have also found applications in wound healing. Chitosan being a hemostat facilitates natural clotting of blood, and blocking nerve endings, it also reduces pain. It expedites wound healing and prevents scar formation. Chitosan films in combination with silver and zinc oxide NP have shown good antibacterial behavior against E. coli, S. aureus and B. subtilis [24]. Copper NP modified chitosan



57

nanocomposites demonstrated accelerated wound healing as tested on rats [25].

Figure 2. Schematic illustration of drug delivery by chitosan NP to targeted tumor.

Chitosan NP are used as an adjuvant for different vaccines such as hepatitis B, influenza, and piglet paratyphoid vaccine [26]. They are used as a vaccine for nasal delivery system. These NP have better antigen uptake by mucosal lymphoid tissues and lead to induction of strong immune responses against antigens. Chitosan has also been claimed as an antibacterial agent to prevent infection in wounds and hasten the wound-healing process by increasing the growth of skin cells [27]. It was also used for food preservative purposes during packaging foods [28].The chitosan NP have also been used as anti-aging skin agent and have shown the skin regenerative properties when materials were tested against skin cell fibroblasts and keratinocytes in the laboratory [29].


58


CONCLUSION The biodegradability, biocompatibility, and easy steps in processing of chitosan anticipate chitosan and their NP as one of the most prominent component for drug delivery purposes. Chitosan NP remain a tool of great potential, but nonetheless, further research must still be accomplished in order to allow more advanced medical applications.

REFERENCES [1]

[2]

[3]

[4]

[5]

[6]

[7]

Mishra A., Ahmad R., Sardar M., Biosynthesized Iron Oxide Nanoparticles Mimicking Peroxidase Activity: Application for Biocatalysis and Biosensing. Journal of Nanoengineering and Nanomanufacturing. 2015; 5(1):37-42. Ghosal A., Shah J., Kotnala R. K., Ahmad S. Facile green synthesis of Nickel nanostructures using natural polyol and morphology dependent dye adsorption properties. Journal of Materials Chemistry A. 2013; 1, 12868-12878. Jee J-P, Na J. H., Lee S., Kim S. H., Choi K., Yeo Y., et al. Cancer targeting strategies in nanomedicine: Design and application of chitosan nanoparticles. Current Opinion in Solid State and Materials Science. 2012; 16 (6):333-42. Kashyap M., Archana D., Semwal A., Dutta J., Dutta P. K. Chitosan: A Promising Substrate for Regenerative Medicine in Drug Formulation. In: Dutta KP, editor. Chitin and Chitosan for Regenerative Medicine. New Delhi: Springer India; 2016. p. 261-77. Ahmed T. A., Aljaeid B. M. Preparation, characterization, and potential application of chitosan, chitosan derivatives, and chitosan metal nanoparticles in pharmaceutical drug delivery. Drug Design, Development and Therapy. 2016; 10: 483-507. Fan W., Yan W., Xu Z., Ni H. Formation mechanism of monodisperse, low molecular weight chitosan nanoparticles by ionic gelation technique. Colloids and Surfaces B: Biointerfaces. 2012; 90: 21-7. Nicknejad E. T., Ghoreishi S. M., Habibi N. Electrospinning of CrossLinked Magnetic Chitosan Nanofibers for Protein Release. American Association of Pharmaceutical Scientists Pharmaceutical Science and Technology. 2015; 16 (6):1480-1486.


Synthesis and Applications of Biopolymeric Nanoparticles [8]

[9]

[10] [11]

[12] [13]

[14]

[15]

[16]

[17]

[18]

59

Kafshgari M. H., Khorram M., Mansouri M., Samimi A., Osfouri S. Preparation of alginate and chitosan nanoparticles using a new reverse micellar system. Iranian Polymer Journal. 2012; 21 (2):99-107. Banerjee T., Mitra S Fau - Kumar Singh A., Kumar Singh A. Fau Kumar Sharma R., Kumar Sharma R. Fau - Maitra A. Maitra A. Preparation, characterization and biodistribution of ultrafine chitosan nanoparticles. International Journal of Pharmaceutics. 2002; 243 (12):93-105. Croisier F., Jérôme C. Chitosan-based biomaterials for tissue engineering. European Polymer Journal. 2013; 49 (4):780-92. Vimal S., Abdul Majeed S., Taju G., Nambi KSN, Sundar Raj N., Madan N., et al. Chitosan tripolyphosphate (CS/TPP) nanoparticles: Preparation, characterization and application for gene delivery in shrimp. Acta Tropica. 2013; 128(3):486-93. Wong I. Y., Bhatia S. N, Toner M. Nanotechnology: emerging tools for biology and medicine. 2013; 27(22): 2397–2408. Vivek R., Nipun Babu V., Thangam R., Subramanian K. S., Kannan S. pH-responsive drug delivery of chitosan nanoparticles as Tamoxifen carriers for effective anti-tumor activity in breast cancer cells. Colloids and Surfaces B: Biointerfaces. 2013; 111:117-23. Mitra S., Gaur U., Ghosh P. C., Maitra A. N. Tumour targeted delivery of encapsulated dextran-doxorubicin conjugate using chitosan nanoparticles as carrier. Journal Control Release. 2001; 74(1-3):317-323. Prabaharan M. Chitosan-based nanoparticles for tumor-targeted drug delivery. International Journal of Biological Macromolecules. 2015; 72: 1313-22. Sayın B., Somavarapu S., Li X. W., Thanou M., Sesardic D., Alpar H. O., et al. Mono-N-carboxymethyl chitosan (MCC) and N-trimethyl chitosan (TMC) nanoparticles for non-invasive vaccine delivery. International Journal of Pharmaceutics. 2008; 363 (1–2):139-48. Mansouri S., Lavigne P., Corsi K., Benderdour M., Beaumont E., Fernandes J. C. Chitosan-DNA nanoparticles as non-viral vectors in gene therapy: strategies to improve transfection efficacy. European Journal of Pharmaceutics and Biopharmaceutics. 2004; 57 (1):1-8. Khdair A., Hamad I., Alkhatib H., Bustanji Y., Mohammad M., Tayem R., Aiedeh K. Modified-chitosan nanoparticles: Novel drug delivery systems improve oral bioavailability of doxorubicin. European Journal of Pharmaceutical Sciences 2016 Jul 26; 93: 38-44.


60


[19] Min K. H., Park K., Kim Y. S., Bae S. M., Lee S., Jo H. G., Park R. W., Kim I. S., Jeong S. Y., Kim K., Kwon I. C. Hydrophobically modified glycol chitosan nanoparticles-encapsulated camptothecin enhance the drug stability and tumor targeting in cancer therapy. Journal of Controlled Release. 2008; 127 (3):208-218. [20] Kim J. H., Kim Y. S., Park K., Park K., Lee S., Nam H. Y., Min K. H., Jo H. G., Park J. H., Choi K., Jeong S. Y., Park R. W., Kim I. S., Kim K., Kwon I. C. Antitumor efficacy of cisplatin-loaded glycol chitosan nanoparticles in tumor-bearing mice. Journal of Controlled Release. 2008; 127 (1): 41–49. [21] Kim J. H., Kim Y. S., Kim S., Park J. H., Kim K., Choi K., Chung H., Jeong S. Y., Park R. W., Kim I. S., Kwon I. C. Hydrophobically modified glycol chitosan nanoparticles as carriers for paclitaxel. Journal of Controlled Release. 2006; 111 (1–2): 228–234. [22] Saravanakumar G., Min K. H., Min D. S., Kim A. Y., Lee C. M., Cho Y. W., Lee S. C., Kim K., Jeong S. Y., Park K., Park J. H., Kwon I. C. Hydrotropic oligomer-conjugated glycol chitosan as a carrier of paclitaxel: synthesis, characterization, and in vivo biodistribution. Journal of Controlled Release. 2009; 140 (3): 210–217. [23] Anitha A., Deepa N., Chennazhi K. P., Lakshmanan V-K, Jayakumar R. Combinatorial anticancer effects of curcumin and 5-fluorouracil loaded thiolated chitosan nanoparticles towards colon cancer treatment. Biochimica et Biophysica Acta (BBA) - General Subjects. 2014; 1840 (9):2730-43. [24] Jayakumar R., Prabaharan M., Sudheesh Kumar P. T., Nair S. V., Tamura H. Biomaterials based on chitin and chitosan in wound dressing applications. Biotechnology Advances. 2011; 29(3):322-37. [25] Gopal A., Kant V., Gopalakrishnan A., Tandan S. K,. Kumar D. Chitosan-based copper nanocomposite accelerates healing in excision wound model in rats. European Journal of Pharmacology. 2014; 731:819. [26] Zhao F., Wu Y., Zhang X., Yu J., Gu W., Liu S., Zeng T., Zhang Y., Wang S. Enhanced immune response and protective efficacy of a Treponema pallidum Tp92 DNA vaccine vectored by chitosan nanoparticles and adjuvanted with IL-2. Human Vaccine. 2011; 7 (10):1083-1089. [27] Martin C., Low W. L., Amin MCIM, Radecka I., Raj P., Kenward K. Current trends in the development of wound dressings, biomaterials and devices. Pharmaceutical Patent Analyst. 2013; 2 (3):341-59.



61

[28] Dutta P. K., Tripathi S., Mehrotra G. K., Dutta J. Perspectives for chitosan based antimicrobial films in food applications. Food Chemistry. 2009; 114(4):1173-82. [29] Gupta S., Bansal R., Gupta S., Jindal N., Jindal A. Nanocarriers and nanoparticles for skin care and dermatological treatments. Indian Dermatology Online Journal. 2013; 4 (4):267-72.




Chapter 5

BIOPOLYMERIC NANOPARTICLES AS DRUG CARRIERS FOR INTRAVENOUS ADMINISTRATION Merari Tumin Chevalier1,,†, Monica Cristina García2,† and Vera Alejandra Alvarez1 1

Grupo de Materiales Compuestos de Matriz Polimérica (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Universidad Nacional de Mar del Plata (UNMdP), Mar del Plata, Argentina 2 Unidad de Investigación y Desarrollo en Tecnología Farmacéutica (UNITEFA), CONICET and Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. Ciudad Universitaria, 5000-Córdoba, Argentina

ABSTRACT Biopolymeric nanoparticles (BNPs) have proven to be one of the most valuable drug carriers used in nanomedicine. These submicron 

Corresponding author: M. T. Chevalier. Grupo de Materiales Compuestos de Matriz Polimérica (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Universidad Nacional de Mar del Plata (UNMdP), Mar del Plata, Argentina. E mail: [email protected], [email protected]. † Both authors contribute equally to this work.


64

M. Tumin Chevalier, M. Cristina García and V. Alejandra Alvarez entities can perform several key mechanisms to adequately introduce active ingredients in the human body and release them to their specific site of action in order to achieve improved therapeutic effect. Nanocarriers may be administered intravenously in several proposed new therapies, thus, it is essential to understand all the phenomena involved in this process. This chapter attempts to describe and report the most relevant facts regarding intravenous (IV) administration of BNPs.

Keywords: nanoparticles, biopolymers, drug, intravenous

INTRODUCTION Among all the drug delivery systems, Biopolymeric nanoparticles (BNPs) present great advantages, mainly related to their intrinsic features such as small particle size, large surface area and huge versatility to customize and personalize their surface. Over this past decade, BNPs made from different polymers have taken a leading role in the field of pharmaceutical sciences, mainly due to their high biocompatibility. Polymeric drug carriers are exceptionally valuable for biomedical applications because of their adaptability to achieve the most critical goals of drug delivery approaches. BNPs are able to carry a wide variety of drugs and protect them from degradation in the body before reaching the target site. They modulate drug release rate from the polymeric matrix to achieve the adequate pharmacological response and they present significant versatility regarding surface chemistry facilitating active targeting, long circulation and the stealth behavior [1]. The administration route is very relevant when determining BNPs transport kinetics and delivery efficiency. Systemic drug administration enables the active pharmaceutical ingredient distribution throughout the entire body, which is currently state-of-the-art to treat several serious diseases. Among different kinds of administration routes, IV injection is considered as the most common route used to deliver BNPs. After IV administration, these nanocarriers are circulating throughout the body and they escape the bloodstream to other tissues by endocytosis, shear forces, or passive diffusion through fenestrations in the capillary network [3, 4]. In this sense, numerous efforts have been dedicated to develop nanoparticulated therapeutics carriers, which are small enough for IV administration and possess a suitable bloodstream half-life [5]. In the following sections, the multiple factors affecting performance of BNPs after IV administration will be described as


Biopolymeric Nanoparticles as Drug Carriers …

65

well as the key biological and pharmacological phenomena that determine the fate of these submicronic entities in the human body. The chapter also reports the current research that involves the use of IV administrated BNPs towards the treatment of cancer.

BIODEGRADABLE POLYMERS USED AS DRUG CARRIERS Over the last twenty years, important findings took place in the development of biodegradable polymeric materials for biomedical applications. Biopolymers are considered as ideal materials for the development of biomedical devices with potential clinical application, such as drug delivery vehicles. This kind of application required specific physicochemical, biological, biomechanical and degradation properties in order to achieve efficient performance. In accordance with this both synthetic and natural polymers, that can undergo biodegradation by either hydrolytic or enzymatic route, are being studied considering the biomedical field needs. Biodegradable polymers can be derived from different sources. Several kinds of biodegradable polymers used in drug delivery are summarized in Figure 1. It has been observed that biodegradation of these materials involves hydrolytic or enzymatic cleavage of the polymeric bonds resulting in erosion [9, 10].

Figure 1. Classification of biopolymers used in drug delivery.


66

M. Tumin Chevalier, M. Cristina García and V. Alejandra Alvarez

Hydrolytically Degradable Polymers Polymers containing esters, orthoesters, anhydrides, carbonates, amides, urethanes, ureas, amongst others in their backbone are susceptible to suffer hydrolytical degradation through these labile chemical bonds [11]. Some of the most used hydrolytically degradable polymers are summarized in this section:

Poly(-Esters) Poly(α-ester)s are thermoplastic polymers. They bear hydrolytically labile aliphatic ester linkages in their backbone. Theoretically, all polyesters can be degraded by esterification which is a chemically reversible process. Nevertheless, for degradation to be accomplished in the desirable time frame as required for biomedical field, only those aliphatic polyesters that bear reasonably short aliphatic chains between ester bonds can degrade in this required span of time and thus are suitable for biomedical applications. This kind of polymers exhibited a wide diversity and synthetic versatility. They can be obtained from several monomers via ring opening and condensation polymerization routes depending on the monomeric units. In addition, bacterial bioprocess routes can be another strategy to prepare poly(α-ester)s. Poly α-hydroxy acids, which include polyglycolic acid (PGA) and the stereoisomeric forms of polylactic acid (PLA) (Figure 2), are the most extensively studied polymers.

1

2

Figure 2. Most common poly α-hydroxy acids. 1- Polyglycolic acid and 2- Polylactic acid.



67

An aliphatic ester of lactic acid, derived from renewable resources, such as corn starch or sugarcanes, polylactic acid (PLA), is a biodegradable polymer. It has received commercial interests due to its ease of manufacture [12]. The hydrolytic degradation of PLA is affected by several factors, such as:        

chemical composition, morphology (crystalline, amorphous), molecular weight and molecular weight distribution, water permeability and solubility, porosity, glass transition temperature, mechanism of hydrolysis (noncatalytic, autocatalytic, enzymatic), and several physico-chemical factors (ion exchange, ionic strength, pH), sterilization and site of action [13].

Poly (lactic-co-glycolic acid) (PLGA) is a biodegradable and biocompatible copolymer. Thus, it is used in several therapeutic devices approved by Food and Drug Administration (FDA). Amongst all the biomaterials, PLGA has shown immense potential as a drug delivery carrier and as scaffold for tissue engineering [14-16]. The success of this polymer resides in the fact that the hydrolysis of PLGA results in lactic acid and glycolic acid, metabolite monomers, both of which are endogenous and easily metabolized by the body via the Krebs cycle. Thus, the usage of PLGA in drug delivery and other biomedical applications is associated with a minimal systemic toxicity [17]. PLGA is approved by the US FDA and European Medicine Agency in various drug delivery systems in humans. Ring opening polymerization of cyclic lactones has developed into the most effective one pot polymerization route, to develop high molecular weight homo- and co-polyesters. During polymerization, definite initiator molecules (as hydroxyl containing molecules) are able to control the molecular weight of polymers. In addition, the rate of polymerization can be controlled by the application of a wide-range of biocompatible catalytic systems. Depending on the monomer, several homopolymers based on cyclic lactones can be obtained. For the synthesis of aliphatic polyesters for intended future biomedical applications, lactide, glycolide and caprolactone are the most extensively studied monomers, producing polylactide, polyglycolide and polycaprolactone (Figure 3). Several characteristics of these polymers are summarized on Table 1.


68


Among bacterial polyesters, which are naturally occurring biodegradable polyesters produced by many bacteria, the most common polymer among this class is poly(3-hydroxybutyrate) (PHB) (Figure 4). It is a semi-crystalline isotactic polymer that undergoes surface erosion by hydrolytic cleavage of the ester bonds. This polymer has a melting temperature in the range of 160180C and the glass transition temperature occurs between -5C and 10C. As a consequence of the hydrolytic degradation of PHB, D-3-hydroxy-butyric acid, a normal blood constituent, is formed. Nevertheless, the low degradation rate of PHB in the body could be related to its really high crystallinity. To increase the rate of degradation of this family of polymers, these are blended with more hydrophilic polymers or other low molecular weight additives, to increase water penetration and enhance the degradation [18]. Table 1. Characteristics of polylactide, polyglycolide and polycaprolactone

Polymer

Crystallinity (%)

Tg (C)

Tm (C)

E (GPa)

Polylactide Polyglycolide Polycaprolactone

37 45-55 50

60-65 35-40 -60

175 200 55-65

4.8 12.5 0.5

1

Strength Mass loss loss (months) (months) 1-2 12-16 1-2 6-12 6-12 24-36

2

Figure 3. Several lactone homopolymers. A- Polylactide and B- Polycaprolactone.



69

Figure 4. Structure of Polyhydroxybutyrate.

Enzymatically Degradable Polymers Proteins are the major structural components of many tissues. Protein based biomaterials are known to undergo naturally-controlled degradation processes [19]. Among them, the greatest important one is collagen, the most ample protein in the human body (Figure 5). The enzymatic degradation of collagen, by enzymes such as collagenases and metalloproteinases, within the body, yields corresponding amino acids. This material has been studied for several biomedical applications due to its enzymatic degradability, physicochemical, mechanical and biological properties. Several collagen-based gentamicin delivery vehicles are in use world-wide. Several composite systems of collagen and synthetic polymers are being investigated as drug delivery devices [20]. A considerable fact regarding the application of polymers as vehicles for drug delivery purposes is their biodegradation and adequate elimination. Considering systemic absorption of hydrophilic polymers such as chitosan, they need an adequate molecular weight for renal clearance. Chitosan may be degraded by enzymes which hydrolyze glucosamine–glucosamine, glucosamine–N-acetyl-glucosamine and N-acetyl-glucosamine–N-acetylglucosamine linkages. Alginic acid is a linear copolymer. It consists of homopolymeric blocks of (1-4)-linked β-D-mannuronate (M) and its C-5 epimer α-L-guluronate (G) residues, respectively. These are covalently linked together in different sequences or blocks (Figure 6).


70


Figure 5. Structure of Collagen.

Hyaluronic acid is a polymer of disaccharides (Figure 6), themselves composed of D-glucuronic acid and D-N-acetylglucosamine, linked via alternating β-1,4 and β-1,3 glycosidic bonds. Hyaluronic acid can be 25,000 disaccharide repeats in length. Polymers of hyaluronic acid can range in size from 5,000 to 20,000,000 Da in vivo.



71

A

B

C Figure 6. Structure of A- Alginic acid, B- Chitosan and C- Hyaluronic acid.

MOST CRITICAL BIOLOGICAL BARRIERS TO BNPS IN IV DRUG DELIVERY After IV administration, BNPs are exposed to several sequential hurdles that must be overcome in order to efficiently reach the site of action (Figure 7) [21, 22]:   

Opsonization and following sequestration by the Mononuclear Phagocytic System (MPS). Nonspecific distribution. Hemorheological/blood vessel flow.


72


1

2

3

4

Figure 7. Key events and strategies regarding intravenous administration of BNPs.

Moreover, once inside the organism, the particles have to overcome several limitations such as: pressure gradients, cellular internalization, escape from endosomal and lysosomal compartments, drug efflux pumps, among others. Being more specific, opsonization is the step by which a strange object once in the bloodstream is wrapped with opsonin proteins, enhancing aggregation and highlighting it for macrophages. In response to this call of attention, phagocytic cells (typically from the liver or Kupfer cells) are able to recognize the opsonins bound to the surface of the BNPs and as a result of this they engulf and dispose these «odd» particles from the bloodstream. More concisely, opsonins are key proteins in the blood serum that promote the elimination of vulnerable polymeric drug nanocarriers by marking them off for an immune response. The combination of these mentioned sequential processes leads to the main clearance mechanism for the removal of treacherous agents in the human body. The major part of opsonized BNPs is cleared by a receptor-mediated mechanism within seconds of IV



73

administration because of the intense presence of phagocytic cells in the liver and spleen, otherwise they are excreted [1]. The outcome of this whole phenomenon is a high accumulation of BNPs in organs, such as spleen and liver, contributing to the nonspecific distribution of nano-drug delivery systems to healthy organs. Considering normal flow conditions in the blood stream, it has been shown how the size and shape of BNPs impact on margination dynamics to vascular walls. Particularly, small spherical particles drift in a cell-free layer, at a considerable distance from endothelial surfaces, which could restrict both active targeting approaches and effective accumulation through passive targeting mechanisms, for example by enhanced permeability and retention (EPR) effect. Another important barrier to BNPs delivered to tumors is an increased pressure, as a result of the abnormal vasculature, a dense extracellular matrix, the aggressive nature of cellular growth, fibrosis, and impaired lymphatics. In consequence, cellular internalization and endosomal escape are challenging barriers. On the other hand, endosomal compartmentalization of internalized BNPs, exposed to a low pH environment and enzymes is really detrimental to drug load, mainly to genetic material. Last but not the least, upon entry into the cell, drug efflux pumps that confer therapy resistance expel chemotherapeutics from the cell [22].

BASIS OF NANOPARTICLE DESIGN FOR IV ADMINISTRATION In order to overcome the mentioned biological barriers that BNPs must face it is important to consider several design parameters that play a key role in the behavior of this kind of drug delivery system. The most relevant are listed and discussed below.

Size BNPs dimensions are probably the most critical parameter regarding BNPs for biomedical administration. After years of research it is possible to tailor size and size distribution of BNPs quite precisely in order to achieve a


74


convenient particle distribution in vivo. In general terms, BNPs larger than 6 nm suffer clearance from the liver and larger than 200 nm are trapped in the spleen; moreover BNPs less than 6 nm are largely cleared by the kidney [4]. In consequence, these are the key organs involved in the mononuclear phagocyte system (MPS), and the ability of BNPs to evade them often represents a higher time in the bloodstream. Long-circulating BNPs in the bloodstream allows selective delivery to a specific target or diseased tissue, thus improving therapeutic outcomes [4, 6, 7]. The size of BNPs used for biomedical applications, most commonly found between 10 nm and 200 nm, enhance their adequate biodistribution in the human body, whose behavior is considerably different compared to free small drug molecules [8]. In addition, BNPs present a vast surface area, easing surface functionalization. Decreasing the particle size to sub-micronic values allow greater drug loading, for this reason methods using biopolymers to obtain BNPs have been extensively studied achieving reproducibility and versatility. All these mentioned key demeanors are essential to gain an improved therapeutic effect in several fields where BNPs are involved [8]. Key behavior in biological media is driven by size ranges, such as: 

 

Particles 200 nm are retained by splenic filtration, due to the 200500 nm size range of inter-endothelial cell slits [24]. Particles in the micrometer range (2-5 µm) exhibit an easy and fast accumulation in lungs capillaries which could be a very crucial advantage to target one of the most hazardous metastatic locations. Additionally, liver, spleen and lungs macrophages involved a considerable particle uptake.

All in all, BNPs around 100 nm generally prove to be long-lasting in systemic circulation. Considering possible cancer treatment, long half-lives in blood increase the propensity of BNPs to accumulate in tumor vasculature, which range in size from 380-780 nm [21]. BNPs’ particular combination of known intermolecular forces and low density confers them stability in solution avoiding significant precipitation. This aspect makes these submicron drug delivery systems advantageous compared to larger drug carriers.



75

Figure 8. Several reported shaped BNPs: A- Nanosphere, B- Worm-like nanomicelle, C- Ellipsoidal nanoparticle, D- Nanorod, E- Disk-shaped nanoparticle.

Shape Pioneering research highlights how diverse nanoparticle shapes (Figure 8) perform an exclusive flow behavior in the bloodstream that considerably modifies biodistribution by affecting circulation lifetimes, cell membrane interactions and macrophage uptake. It has been reported that disc shaped BNPs promote vessel wall interaction more than spherical BNPs with great influence in endothelial adhesion and binding. Interestingly, controlling shape can also lead to achieving longer circulation half-life. Geng, Y. et al. have studied shape effects of filaments comparing them to spherical particles regarding flow and drug delivery, they found that filomicelles with extensions as long as 18 μm show circulation halflives of 5 days [24]. Discher et al. performed an outstanding study pointing out the persistent circulation of worm-like micelles of 1 week in mice; this value may be predicted as one month of circulation half-life in the human body. This phenomenon is attributed to the propensity of these kind of BNPs to align with blood flow [25]. Longer circulation half-life extends BNPs blood residence and optimizes their possibilities of reaching their specific site of action. Additionally, nanoparticle geometry has a great influence regarding macrophage uptake. In this particular field Mitragotri et al. carried out a seminal study proving that the architectural design parameter of curvature drives phagocytosis. By varying size and shape of polystyrene particles, phagocytosis by alveolar


76


macrophages was investigated concluding that particle shape, not size, plays a key role in phagocytosis. They could infer that particle shape precept whether macrophages simply spread on particles or effectively initiate phagocytosis and how this initiation is related with the complexity of the actin structure needed to promote this process, allowing the membrane to move over the particle [26]. Geometry-inhibited cellular uptake of BNPs was also observed. Zhang et al. changed polystyrene BNPs from three-dimensional spherical shape to twodimensional disk shape, promoting their cell surface binding with substantial reduction of cell internalization. This behavior represents a valuable potentiality for disk-shaped NPs as auspicious devices in biomedical applications such as imaging agents [27]. Furthermore, targeting BNPs using receptor-ligand systems is also governed by the shape. To maximize the specificity towards sites of interest, cancer cell targeting or vascular targeting strongly depends on the targeting effectiveness of BNPs. Compared to nanospheres, oblong-shaped BNPs are able to form a greater number of multivalent occurrences [28]. This is essential for targeting, especially in the case of vascular targets, since geometrically enhanced targeting can successfully offset hemodynamic forces that tend to disassemble the nanoparticle from the endothelium [29]. The strategy of modifying the surface of BNPs with poly(ethylene glycol) (PEG), is the most described aiming to evade the reticuloendothelial system (RES). This approach to achieve esteric modification of BNPs is also called “PEGylation” and involves the attachment of PEG chains to the surface of BNPs. Neutral PEG molecules form a corona over BNPs surface impeding particle agglomeration and protein absorption enhancing the avoidance of RES (Figure 9) [30].

Targeting (Active and Passive) The most relevant pharmacokinetic principle regarding the design of nanomedicines is the enhanced permeability and retention (EPR) effect proposed in 1986 by Matsumura and Maeda as a new concept of delivery of macromolecular drugs to tumors [31, 32]. This phenomenon describes the concept of passive targeting when considering nanoparticulated polymeric drug delivery systems.



77

Figure 9. 1- Injection of BNPs, 2- Opsonization, 3- Uptake of the marked nanoparticle by a phagocytic cell, 4- Surface modification of the nanoparticle to evade elimination by the MPS.

Thus, passive targeting consists in the transport of BNPs through leaky tumor fenestrated endothelial cells into the tumor and cells. Convection involves the movement of molecules within fluids. Convection must be the predominating transport mode for larger molecules across large pores. On the contrary, low molecular weight active principles are passively transported by diffusion without any energy cost to the cell [33]. On the other hand, in active targeting, BNPs surface can be functionalized with specific ligands for binding to appropriate receptors expressed on the target site. The ligand is chosen to bind to a receptor over expressed by tumor cells or tumor vasculature and not expressed by normal cells, in order to improve the selectivity of BNPs. Briefly, targeting ligands are either monoclonal antibodies and antibody fragments or no antibody ligands (peptide or not). The binding affinity of the ligands influences the tumor penetration because of the “binding-site barrier” [33].


78

M. Tumin Chevalier, M. Cristina García and V. Alejandra Alvarez Table 2. Behavior of neutral and charged BNPs [34-36] Neutral BNPs

Negatively charged BNPs

Are able to prolong circulation lifetime by reducing the absorption of serum proteins.

Minimize cellular interactions.

Less interaction with the negatively charged cell membrane.

Nonspecific interactions can also lead to BNPs binding to cell membranes

Lower levels of internalization as compared to the positively charged particles.

Can be obtained by coating the BNPs with neutral ligand such as PEG

It is believed that internalization may exist through nonspecific binding on cationic sites on the plasma membrane which are relatively scarcer than negatively charged domains.

Positively charged BNPs Best efficiency in cell membrane penetration and cellular internalization. It has been reported that they increase nonspecific uptake in most of the cells. Are able to translocate across the plasma membrane as result of binding with negative groups in the cell surface.

Surface Charge The surface charge of BNPs is another important factor to extend circulation half life in the bloodstream and also promotes selectivity and concentration of particles in a certain site of action. Table 2 lists behavior of some neutral and charged BNPs.

PHARMACOKINETICS AND BIODISTRIBUTION OF BNPS In the last ten years, significant advancement has been made in the development of novel nanotechnology platforms and the progression in the field of nano research has made possible to have access to numerous opportunities in pharmaceutical and medical sciences, mainly in the field of drug delivery [37].



79

In particular, through spatial-temporal drug controlled release, BNPs carriers for injectable administrations have the capability to improve the pharmacotherapy of different kinds of diseases, due to that the spatialtemporal control has important advantages. The spatial location of the drug release in specific target sites can reduce the overall dose in the bloodstream and injury that this drug would produce in different organs. The temporal control of drug release can also provide advantages, because the unwanted side effects would decrease, that otherwise could happen due to the circadian rhythms of drug levels throughout the entire body [38, 39]. The BNPs could improve tissue selectivity due to their uptake in particular tissues. These can be used to offer improved protection or decreased renal clearance for drugs with short half-life or easily degradable, such as nucleic acids and peptides, in order to provide a sustained pharmacological effect. The BNPs might also increase the drug release to unwanted tissues and therefore, produce undesired effects [40]. In this sense, it is quite relevant to study the pharmacokinetics (PK) and biodistribution of BNPs to understand and try to predict their efficacy and safety or side effects. Typically, the PK profile is mostly determined by the analysis of physicochemical properties of BNPs, such as size and shape, charge, and surface chemistry (Figure 10) [41]. The PK profiles of free drugs and drugs carried in BNPs are usually different. When hydrophobic drugs are intravenously administered, they are often transformed by liver metabolism into hydrophilic structures or excreted into the bile or eliminated into the urine. However, when the drugs are carried in the BNPs, it is possible to appreciate protection of the drug carried, from metabolizing liver enzymes, before they are released and also from renal clearance in accordance with their increased size [40]. In order to improve drug delivery devices, it is essential to consider that they be circulating in the bloodstream long enough to recognize its target or therapeutic site of action [39]. Typically the polymeric BNPs drug carriers are opsonized and removed from the bloodstream, and sequestered in one of the MPS, also known as the RES, which is a major problem to complete these aims [39]. This is because, when BNPs are intravenously administered, a diversity of serum proteins bind to the surface of these BNPs and they are recognized by the family of receptors present in the cell surfaces on the macrophages and internalized, leading to an important reduction of BNPs from the bloodstream [42]. It is important to stress that, in general terms, any blood serum component or serum proteins binding involve in the phagocytic recognition process by macrophages is called “opsonins.” The macrophages of the liver or Kupfer


80


cells cannot identify by themselves the BNPs in the bloodstream, but the presence of opsonins bound to the surface of these BNPs allow the macrophages to do the recognition [39]. Both opsonins and macrophages are implicated in the major loss of administered dose of drug carried in BNPs [40]. In case of unprotected or naked BNPs, or BNPs that have not been PEGylated, internalization in the MPS organs occurs quickly, in few seconds and is frequently concentrated in liver and spleen [39, 43, 44]. After an IV administration, RES have the ability to remove naked BNPs from the circulation within seconds, rendering them unsuccessful as spatialspecific drug release [44]. This is the reason why a variety of methods of camouflaging or masking BNPs have been developed in order to get a temporarily bypass recognition by the macrophages of the MPS and, in consequence, increase their half-life in bloodstream [39, 45]. In this context, diminishing protein binding is the key point to develop a long-term circulation BNPs as carrier systems. Moreover, the reduction of particle size allows increasing the drug dissolution rate, and consequently, leading to enhanced drug absorption and to improve the bioavailability. Many reports have shown that the size of BNPs plays a vital role in the final biodistribution and blood clearance of BNPs. In general terms, for molecules that have molecular weight less than 5000, they can be eliminated from the circulation via the renal clearance. For large molecules and BNPs that cannot be removed by this way, the reports have shown that particles with hydrodynamic radii of over 200 nm commonly present a more faster clearance rate than ones with radii under 200 nm, whether they are PEGylated or not [46]. The particle size also has impact in the final biodistribution. For example, PEGylated BNPs with a hydrodynamic radii smaller than 150 nm exhibit a larger uptake in the bone marrow of rabbits when compared to particles around 250 nm in diameter, which are mainly sequestered in the liver and spleen [47]. There are different hypothesis about the differences in the uptake and biodistribution of stealth BNPs indicating the presence of opsonins that are specific to only a particular type of phagocyte. Nevertheless, the precise reason for the size dependencies has not yet been completely clarified [39]. The PEGylation is a significant factor that impacts in the final biodistribution and clearance rate of BNPs, and therefore, surface properties of BNPs greatly influence their PK [40, 39]. The characteristics of this PEG cover, for instance its surface density, charge, thickness, functional groups, and conformation all impact the mode that the BNPs interact with opsonins. In this line, it has been described that the use of PEG polymers with larger



81

molecular weight led to longer bloodstream half-lives for the BNPs in vivo [48] and uncoated BNPs are concentrated mostly in the liver and the spleen [39]. Finally, it is important to mention that there are several different approaches available to study the PK parameters, final biodistribution and clearance rates of BNPs, both in vivo and in vitro which are widely reported in different scientific reports.

Figure 10. Summary of BNPs biodistribution considering size, shape and charge. 1Green bar: BNPs >150 nm, Grey bar: BNPs between 20 and 150 nm, Red bar: BNPs