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Synthesis of Silver Nanoparticles using Cinnamomum zeylanicum Bark Extract and its Antioxidant Activity Munnaluri Gauthami1, Nivedita Srinivasan1, Neelam M. Goud1, Kasilingam Boopalan2 and Kavitha Thirumurugan1,* 1
Lab 206, Structural Biology Lab, Centre for Biomedical Research, School of Bio Sciences and Technology, VIT University, Vellore-632 014, India; 2Materials Chemistry Division, School of Advanced Sciences, VIT University, Vellore-632 014, India Abstract: In this study, we report the synthesis of silver nanoparticles from cinnamon bark extract. The physical charactrization of these silver nanoparticles was verified using UV-visible spectroscopy, scanning electron microscopy, and powder X-ray diffraction. Size distribution of nanoparticles was in the range of 30 to 150 nm. The zeta potential was -32 mV, indicating dispersion ability. Superoxide anion radical scavenging assay showed 82% activity for silver nanoparticles derived from cinnamon bark extract.
Keywords: Cinnamon, silver nanoparticle, SOD, UV-Vis, XRD, zeta potential. 1. INTRODUCTION Chemical based synthesis of nanoparticles for biomedical applications proves to be hazardous as they may interfere with metabolic processes [1]. With the increasing demand for safer nanoparticles there is a need to synthesize and characterize biobased nanoparticles. Green synthesis of nanoparticles in the form of nanorods, nanotubes and nanofibres using different chemical formulations extracted from plants, algae, fungi and bacteria is the welcome challenge [2]. Basic formulation of the nanoparticle is selected based on need and area of application [3]. There are different formulations of nanoparticles bearing copper, silver, titanium, zinc and manganese encapsulated with plant extracts having medicinal properties [4, 5]. Silver in different forms, nitrate and oxide forms are widely used in biomedical applications [6, 7]. Silver nanoparticles are now used in drug delivery systems, gene delivery, artificial implants and diagnostic agents in imaging diseases at different stages [8-10].
*Address correspondence to this author at the Lab 206, Structural Biology Lab, Centre for Biomedical Research, School of Bio Sciences and Technology, VIT University, Vellore - 632 014, India; Tel: 914162202873. E-mails:
[email protected];
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Miri et al. [11] reported on plant-mediated biosynthesis of silver nanoparticles using Prosopis farcta extract and its antibacterial properties. In the synthesis and characterization of nanosilver with antibacterial properties using Pinus densiflora young cone extract, it was shown that phytochemicals present in the cone extract were acting as reducing agent [12]. In the study by Kaviya et al. [13], Citrus sinensis peel extract was used in the synthesis of silver nanoparticles. Prathna et al. [14] had shown biomimetic synthesis of silver nanoparticles by Citrus limon (lemon) aqueous extract at room temperature and theoretical prediction of particle size. Silver nanoparticles were formed when 20mM silver nitrate solution was mixed for 4 hrs with lemon juice (2% citric acid concentration and 0.5% ascorbic acid concentration) in the ratio of 1:4 (vol:vol). Nasrollahzadeh et al. [15] synthesized silver nanoparticles with E. helioscopia leaf extract as a reducing and stabilizing agent. In our study, we discuss the biosynthesis of silver nanoparticles using the natural spice Cinnamon zeylanicum bark. The bark has high antioxidant activity. Sathishkumar et al. [16] reported the differences in the biosynthesis of silver nanoparticles using C. zeylanicum bark powder (CBP) and extract (CBPE). The bark © 2015 Bentham Science Publishers
Synthesis of Silver Nanoparticles using Cinnamomum zeylanicum
Nanoscience & Nanotechnology-Asia, 2015, Vol. 5, No. 1
extract produced more silver nanoparticles than the powder.
Advance model with Cu K (k = 1.542 Å) radiation. Scanning electron microscopy (SEM) (Hitachi- S3400N) was used to observe the morphology of silver nanoparticles. Particle size and zeta potential of silver nanoparticles were measured using Zetasizer nano-series (Malvern).
2. MATERIALS AND METHODS 2.1. Preparation of C. zeylanicum Bark Powder (CBP) and Extract (CBPE) Clean, dry bark of C. zeylanicum was cut into small pieces, powdered and sieved using a 20mesh sieve. To produce the extract, 2.5 g of this powder was added to 100 ml sterile distilled water and boiled for 5 min. 2.2. Synthesis of Silver Nanoparticles For the silver nanoparticle synthesis from CBP, two stabilising agents sodium citrate and sodium dodecyl sulphate (SDS) were used. SDS (0.5 g) and sodium citrate (0.0294 g) were added to 50ml of 1mM AgNO3 solution. This solution initially appeared colourless and upon reduction it changed to pale yellow colour as sodium citrate acts as a reducing agent. To 25ml of this solution, 0.02 g of cinnamon powder was added and kept for incubation in a rotary shaker at 160 rpm in the dark at 25°C for eight days and absorbance was measured at every 24 hrs. This solution initially appeared brown in colour and changed to dark brown after 8 days of incubation. For CBPE, 1 ml of extract was added to 50 ml of 1mM AgNO3 solution. Initially this solution was brown in colour and after incubation it changed to dark brown indicating reduction of nitrate form of silver to free reduced form. 2.3. Synthesis of Silver Nanoparticles by Exposing to UV Cinnamon extract was added with stabilisers, treated with 1 mM AgNO3 and this solution was kept under UV light at 250 nm for 10 hrs. Absorbance was measured at 1 hr time interval and the change in colour was observed gradually as it turned dark brown at the end of 10 hrs of exposure to UV radiation. 2.4. Characterization of Silver Nanoparticles The synthesis of silver nanoparticles was observed periodically in a UV-visible spectrophotometer (Evolution 260 Bio Thermo Scientific) in the scan range wavelength of 300700 nm at resolution of 1 nm. Powder X-ray diffraction (XRD) patterns of the synthesized silver nanoparticles were collected on Bruker D8
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2.5. Total Antioxidant Assay Different concentrations of nanoparticles were treated with 6µl of 1mM ascorbic acid, then with 10µl of reagent solution which included 0.6M H2SO4, 4mM ammonium molybdate and 4mM sodium phosphate in 1:1:1 ratio. These aliquots were incubated in boiling water bath at 95°C for 90 min. After incubation, absorbance of each aliquot was measured at 695 nm following Prieto et al. method [17] with minor modifications and the same procedure was followed for crude cinnamon extract as a control and absorbance was measured. Ascorbic acid was taken as a standard. 2.6. Superoxide Anion Radical Scavenging Assay We followed the method of Jing & Zhao [18] with slight modifications. Tris-HCl buffer (1.9ml of 50mM) was added to 40µl of 45mM pyrogallol and this solution was incubated at 25ºC for 3min for the auto-oxidation of pyrogallol. Different treatments were made with varying concentrations of ascorbic acid and cinnamon nanoparticles. Absorbance was measured at 420nm. Extent of superoxide anion scavenging ability can be calculated by the formula A0-(A1-A2) / A0 x 100 Where A0 is absorbance of sample+ascorbic acid A1 is absorbance of sample A2 is absorbance of ascorbic acid only 3. RESULTS & DISCUSSION In the present study, we adopted a simple procedure to synthesize silver nanoparticles from cinnamon bark extract. Initially, we used crude plant extract as a reducing agent along with stabilisers sodium citrate and sodium dodecyl sulphate to convert silver from Ag+ to Ag0. This has been observed by change in colour of the solution from brown to yellow after 2 hrs and it became dark brown over the time. The solution was stable even after 8 days of incubation. In the
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Fig. (1). UV-Vis spectrum of cinnamon extract added with stabilisers and treated with 1mM AgNO3 shows distinct peak at 425nm after 8 days of incubation.
Fig. (2). UV-VIS spectrum of cinnamon extract with stabilisers exposed to UV for 9 hrs and absorbance was taken at intervals of 1hr.
UV-Vis spectrum, there is a visible peak at 425 nm after 7th and 8th day of incubation as shown in Fig. (1). Cinnamon extract with stabilisers was exposed to UV for 9 hrs and absorbance was taken at intervals of 1hr as shown in Fig. (2). Distinct peak was observed at 405nm which is an indication of reduction of silver. This indicates that by UV method, silver gets reduced in a faster way than the conventional method. Powder diffraction (XRD) profile for this sample was shown in Fig. (3). XRD profile shows intense
peaks of silver at 2θ values of 27.7º, 32º, 38º, 46º, 54.7º respectively corresponding to presence of silver. SEM analysis was done for this treatment and it is as shown in Fig. (4). Overall distribution and size of particles were in the range of 222nm, 241nm, 316nm, 318nm and 404nm. Zeta potential is the physical property of the particles in colloidal solution. Fig. (5). shows cinnamon silver nanoparticles with average zeta potential of -31.7. Magnitude of zeta potential gives an indication of potential stability of
Synthesis of Silver Nanoparticles using Cinnamomum zeylanicum
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Fig. (3). XRD profile of cinnamon extract treated with AgNO3 along with stabilisers. This profile shows intense peaks of silver at 2θ values of 27º, 33º, 38º, 47º, 55º respectively corresponding to presence of silver specifically.
colloidal system. If the particles have high negative or high positive potential they tend to repel and there will be no tendency of the particles
to be together in a system. If the particles have low zeta potential values there will be no force to prevent them to come together and flocculate. Particles with zeta potential in the range +30mv to -30mv are considered to be stable. To verify and confirm the range of particle size, sample is subjected to nanosizer which gives the average size of particles. Fig. (6) shows average size of particles around 118nm. This analysis is done to know the range of size and distribution of particles in the suspension.
Fig. (4). Scanning electron micrograph of cinnamon extract treated with AgNO3 along with stabilisers.
In the total antioxidant assay, cinnamon nanoparticle had shown higher absorbance than crude cinnamon extract. Superoxide anion radical scavenging assay was carried out to find out the percentage of superoxide anion scavenging ability of the nanoparticles. Radical scavenging activity was 82% in case of ascorbic acid with cinnamon nanoparticle and 23% scavenging activity was observed in the case of ascorbic acid with crude cinnamon extract. Silver nanoparticles from Cinnamomum zeylanicum are potent antioxidants [19].
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Fig. (5). Zeta potential of cinnamon silver nanoparticle.
Fig. (6). Size distribution of cinnamon silver nanoparticle.
CONCLUSION
ACKNOWLEDGEMENTS
An attempt has been made to synthesize silver nanoparticles from cinnamon bark extract. These particles have shown characteristic absorbance wavelength in UV-Vis spectrum, matching 2θ values in XRD, high zeta potential and nanosize range. Cinnamon nanoparticles showed better superoxide anion scavenging activity than cinnamon crude extract.
The authors of this paper would like to thank the technical support provided by Malvern co., for Zeta potential, Nanosizer and Pondicherry University for SEM.
CONFLICT OF INTEREST The authors confirm that this article content has no conflict of interest.
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Received: October 24, 2014
Revised: May 29, 2015
Accepted: May 30, 2015
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