View Article Online / Journal Homepage / Table of Contents for this issue
ChemComm
Dynamic Article Links
Cite this: Chem. Commun., 2011, 47, 7719–7721
Published on 07 June 2011. Downloaded by Imperial College London Library on 27/02/2015 19:04:57.
www.rsc.org/chemcomm
COMMUNICATION
b-Cyclodextrin conjugated magnetic nanoparticles for diazepam removal from bloodw Kaiyong Cai,* Jinghua Li, Zhong Luo, Yan Hu, Yanhua Hou and Xingwei Ding Received 1st April 2011, Accepted 18th May 2011 DOI: 10.1039/c1cc11855b b-CD conjugated magnetic nanoparticles that serve as a hemoadsorbent for diazepam removal are fabricated. The diazepam is arrested by the conjugated b-CD and then the adsorbed diazepam is efficiently removed by an external magnetic field. These particles have potential applications in hemoperfusion or separation of other toxins and drugs. Drug abuse or overdose in accidents is a serious social issue. Diazepam, a lipophilic benzodiazepine derivative drug, is widely used for treating various types of epilepsy, insomnia, anxiety, alcohol and benzodiazepine withdrawal.1 However, abuse of diazepam can have serious consequences, even causing death when taken in overdose.2 Diazepam is one of the specific drugs for drug-related suicide attempts. Hemoperfusion is a common rescue method to remove the diazepam with adsorbents, i.e. resins and activated carbon, by binding the ingested toxins in the blood.3 However, traditional adsorbents have limited blood compatibility since the corpuscles are easily fragmented to form platelet thrombosis. Development of novel materials for toxins removal has attracted much attention. Mesoporous carbide-derived carbon was prepared for cytokine removal from blood plasma.4 Antibody functionalized beads were used to remove uremic toxin.5 Core–shell structured mesoporous silica was employed for microcystins removal.6 Magnetic nanoparticles (MNPs) and multifunctional magneticmesoporous Janus particles were widely applied in biomedical fields, such as molecular imaging, drug/gene delivery and molecular detection.7–9 MNPs can be also used as removal adsorbents since they are easily separated by an external magnetic field. Surface functionalized magnetic adsorbents were reported for elimination of microcystins,6 heavy metal ions,10 and dyes;11 however, few studies documented drug removal.12 Herein, we report an approach to fabricate b-cyclodextrin (b-CD) conjugated magnetic nanoparticles that shows great potential for diazepam removal from blood plasma. b-Cyclodextrin was employed in this study since it is widely used as a drug carrier with good biocompatibility.13 The b-CD has a truncated
Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing, P. R. China. E-mail:
[email protected]; Fax: (+)86-23-65112619; Tel: (+)86-23-65112877 w Electronic supplementary information (ESI) available. See DOI: 10.1039/c1cc11855b
This journal is
c
The Royal Society of Chemistry 2011
cone-like three-dimensional structure with a hydrophilic exterior and a hydrophobic cavity.14,15 Hydrophobic drugs were easily adsorbed by b-CD through a mechanism of inclusion and hydrophobic interactions.16 Recently, b-CD was used for the synthesis of hollow magnetic graphitic carbon microspheres.17 Thus, we hypothesized that b-CD conjugated magnetic nanoparticles could be employed as an efficient absorbent for removal of hydrophobic diazepam from solution and blood plasma. The design of b-CD conjugated magnetic nanoparticles adsorbent for diazepam removal has advantages as follows: first, it is easily separated by an external magnetic field since it has a magnetic core; second, it is biocompatible for blood contacting application with b-CD conjugation. To conjugate b-CD with magnetic nanoparticles (MNPs), we first synthesized MNPs via a solvent thermal reaction.18 The obtained MNPs powder was then conjugated with 3-aminopropyltriethoxysilane (APTES) to afford reactive amino groups, denoted as MNPs@APTES. Subsequently, 1,1-carbonyldiimidazole-b-cyclodextrin (CD-CDI) was synthesized according to a previous report.19 Finally, the prepared MNPs@APTES were conjugated to synthesized CD-CDI, leading to b-CD conjugated MNPs, denoted as MNPs@APTES@b-CD. When MNPs@APTES@b-CD were added into diazepam containing solution or plasma, conjugated b-CD adsorbed the diazepam through inclusion and hydrophobic interaction. The diazepam adsorbed particles were then separated from solution by applying an external magnetic field (Scheme 1). To construct the complex particles for diazepam removal, magnetic Fe3O4 particles were employed as cores. Previously, magnetic Fe3O4 particles were used for various biological applications, such as drug delivery,7 bioseparation,20 hyperthermia therapy,21 molecular imaging etc.22 However, to the best of our knowledge, this is the first study to conjugate magnetic Fe3O4 particles with b-CD for diazepam removal from blood plasma. SEM and TEM images demonstrated that the synthesized magnetic particles had well dispersed morphology with round features. The average diameter of the particles was around 196.1 19.8 nm (Fig. 1a and b, Mean SD, n = 400). More detailed information can be found elsewhere.17 No detectable layer of b-CD was observed for MNPs@APTES@b-CD since the b-CD layer was too thin. The prepared Fe3O4 particles displayed a magnetization value of 76.4 emu g1 (Fig. 1c), which was consistent with that of a previous study.6 However, the magnetization value of MNPs@APTES@b-CD decreased to Chem. Commun., 2011, 47, 7719–7721
7719
Published on 07 June 2011. Downloaded by Imperial College London Library on 27/02/2015 19:04:57.
View Article Online
Scheme 1 Schematic illustration of the fabrication of b-cyclodextrin modified magnetic adsorbent and mechanism for drug removal (delineated by ChemDraw).
in one minute. The result suggests that b-CD was successfully conjugated to magnetic Fe3O4 particles. Moreover, thermal gravitational analysis, TGA, was employed to quantitatively characterize the conjugation of b-CD. Around 1.2% weight loss was observed between 200 1C and 450 1C when comparing samples of MNPs@APTES and MNPs@APTES@b-CD (Fig. 1d). The result again confirmed the successful conjugation of b-CD. To further confirm that b-CD was conjugated to magnetic nanoparticles, Fourier transform infrared (FTIR) spectroscopy, elemental analysis, fluorescamine detection and X-ray diffraction (XRD) were employed for characterization, respectively. FTIR spectra demonstrated that the b-CD conjugation to MNPs occurred (Supplementary Information, Fig. S1). Elemental analysis reflected the successful conjugation of b-CD (Table S1) while fluorescamine detection revealed that around 68% of functional groups of NH2 were involved in the conjugation (Table S2). XRD results indicated that conjugations with APTES or b-CD did not lead to the phase change of magnetic Fe3O4 particles (Fig. S2). To confirm our hyphothesis that b-CD conjugated magnetic nanoparticles could efficiently remove diazepam, we performed the experiments of diazepam removal either from solution or plasma. Typically, 100 mg of MNPs@APTES@b-CD was added into 10 mL of solution containing diazepam. We systematically investigated the effects of pH, time and initial concentration on the removal efficiency (Fig. 2). The amount of diazepam adsorbed was calculated from the following equation: Qt ¼
Fig. 1 Characterization of MNPs and MNPs@APTES@b-CD: (a) SEM image of MNPs (scale bar: 2 mm); (b) TEM image of MNPs (scale bar: 100 nm); (c) magnetic hysteresis loops of MNPs and MNPs@APTES@b-CD; and (d) TGA curves of MNPs@APTES and MNPs@APTES@b-CD.
62.9 emu g1 after conjugation of b-CD (Fig. 1c). However, the MNPs@APTES@b-CD still displayed strong magnetic response to an applied magnetic field, and could be absolutely separated 7720
Chem. Commun., 2011, 47, 7719–7721
C0 Ct V m
ð1Þ
where Qt (in mg g1) is the amount of diazepam adsorbed per gram of adsorbent; C0 (in mg L1) is the initial concentration of diazepam and Ct (in mg L1) is the concentration of diazepam after adsorption; V (in L) represents the volume of the solution and m (in g) means the mass of the adsorbent used. Thus, the Ct/C0 indicates residuary percentage of diazepam and (C0 Ct)/C0 means the removal rate of diazepam. Around 74% of diazepam in solution was removed by MNPs@APTES@b-CD at the initial 1.5 h, in comparison with that of only 7% removal by naked MNPs and around 20% removal by MNPs@APTES (Fig. 2a). The removal efficiency of MNPs@APTES@b-CD demonstrated a pH dependence. Around 80% of diazepam was removed after 3 h adsorption when the pH value of the solution was located in the range of 7 to 8 (Fig. 2b). This phenomenon was related to the fact that the environmental pH value interfered with the electrostatic interactions between diazepam and conjugated b-CD.14 The initial concentration of diazepam highly affected the removal efficiency. Around 76% of diazepam was removed by MNPs@APTES@b-CD at low concentrations of 10 mg L1 and 20 mg L1, in comparison with that of around 45% removal efficiency for a high concentration of 40 mg L1 (Fig. 2c). This result could be interpreted as follows: the absorption capacity of conjugated b-CD against diazepam might be saturated at such conditions with a high concentration of diazepam. To preliminarily investigate the feasibility for diazepam removal from plasma by using MNPs@APTES@b-CD, This journal is
c
The Royal Society of Chemistry 2011
Published on 07 June 2011. Downloaded by Imperial College London Library on 27/02/2015 19:04:57.
View Article Online
Fig. 2 Diazepam removal characterization: (a) effect of time on removal efficiency; (b) effect of pH on removal efficiency; (c) effect of concentration on removal efficiency, pH 7.4, time 3 h, temperature 37 1C; and (d) static removal of diazepam from plasma. Except for (c), the initial diazepam concentration: 20 mg L1; pH 7.4, temperature: 37 1C (n = 6).
we first characterized the blood compatibility of the samples. The data of hemolysis ratio (HR), coagulation time and platelet adhesion suggest that MNPs@APTES@b-CD were blood compatible (Table S3 and Fig. S3). Next, we performed a static adsorption experiment. Rabbits were orally injected to generate diazepam containing plasma, which was adjusted to 20 mg L1 in each case. Meanwhile, activated carbon (YTS 100) was employed as traditional hemoadsorbent in this study to compare the removal efficiency of our prepared absorbent of MNPs@APTES@b-CD. No difference of removal efficiency (around 50%) was observed at the intial 1.5 h between activated carbon and MNPs@APTES@b-CD. For a 3 h period of absorption, around 50.6% diazepam was eliminated by magnetic adsorbent; around 54.9% diazepam was removed by activated carbon; whereas there was only around 10% removal of diazepam by MNPs@APTES (Fig. 2d). The result suggested that MNPs@APTES@b-CD was feasible to be a hemoadsorbent. The mechanism was that diazepam was arrested by the cavity of conjugated b-CD due to inclusion and hydrophobic interactions, then adsorbed diazepam was removed by an external magnetic field along with magnetic particles. However, the drawback of this system is that it has no selection so far. Taken together, we confirmed our hypothesis that b-CD conjugated magnetic nanoparticles could be employed for removal of diazepam from solution and blood plasma. When diazepam is taken orally, peak plasma levels occur between 30 min and 90 min after oral administration. Around 96% to 99% of the digested drug is bound to plasma proteins.1 Hemoperfusion is necessary to be performed to reduce the level of toxin. The presented MNPs@APTES@b-CD demonstrated the feasibility to be a potential novel hemoadsorbent for fast diazepam removal. However, further investigations
This journal is
c
The Royal Society of Chemistry 2011
should be performed to verify its feasibility in vivo. On the one hand, one needs to design the system with specific selectivity for reducing the risk of removing undesired proteins; on the other hand, to establish an appropriate device for hosting the magnetic particles in practical application. In summary, we fabricated and characterized b-CD conjugated magnetic particles with high magnetization. They demonstrated great potential to be a novel hemoadsorbent for efficient removal of diazepam both from solution and plasma. The b-CD conjugated magnetic nanoparticles reported here have potential application in hemoperfusion or separation of other toxins and hydrophobic drugs. This work was funded by China Ministry of Science and Technology (973 Project No. 2009CB930000), Natural Science Foundation of China (11032012), Fok Ying Tung Education Foundation (121035), Natural Science Foundation of Chongqing Municipal Government (CSTC, 2010AB5116) and ‘‘111 project’’ (B06023).
Notes and references 1 J. Riss, J. Cloyd, J. Gates and S. Collins, Acta Neurol. Scand., 2008, 118, 69. 2 W. A. Watson, T. L. Litovitz, W. Klein-Schwartz, G. C. Rodgers, J. Youniss, N. Reid, W. G. Rouse, R. S. Rembert and D. Borys, Am. J. Emerg. Med., 2004, 22, 335. 3 S. Rosin´ski, D. Lewin´ska and W. Pia˛ztkiewicz, Carbon, 2004, 42, 2139. 4 S. Yachamaneni, G. Yushin, S. Yeon, Y. Gogotsi, C. Howell, S. Sandeman, G. Phillips and S. Mikhalovsky, Biomaterials, 2010, 31, 4789. 5 S. Xia, N. Hodge, M. Laski and T. F. Wiesner, Ind. Eng. Chem. Res., 2010, 49, 1359. 6 Y. Deng, D. Qi, C. Deng, X. Zhang and D. Zhao, J. Am. Chem. Soc., 2008, 130, 28. 7 R. Hao, R. Xing, Z. Xu, Y. Hou, S. Gao and S. Sun, Adv. Mater., 2010, 22, 2729. 8 C. Yang, J. Wu and Y. Hou, Chem. Commun., 2011, 47, 5130. 9 L. Zhang, F. Zhang, W. F. Dong, J. F. Song, Q. S. Huo and H. B. Sun, Chem. Commun., 2011, 47, 1225. 10 H. Y. Lee, D. R. Bae, J. C. Park, H. Song, W. S. Han and J. H. Jung, Angew. Chem., Int. Ed., 2009, 48, 1239. 11 L. Zhou, C. Gao and W. Xu, ACS Appl. Mater. Interfaces, 2010, 2(5), 1483. 12 C. H. Yu, A. Al-Saadi, S. Shih, L. Qiu, K. Y. Tam and S. C. Tsang, J. Phys. Chem. C, 2009, 113, 537. 13 R. C. Smith, R. Mariawy, A. Leung and P. T. Hammond, Angew. Chem., Int. Ed., 2009, 48, 8974. 14 F. Manakker, T. Vermonden, C. F. Nostrum and W. E. Hennink, Biomacromolecules, 2009, 10(12), 3157. 15 A. Douhal, Chem. Rev., 2004, 104, 1955. 16 S. Murai, S. Imajo, Y. Takasu, K. Takahashi and K. Hattori, Environ. Sci. Technol., 1998, 32, 782. 17 K. Cai, Z. Luo, Y. Hu, X. Chen, Y. Liao, L. Yang and L. Deng, Adv. Mater., 2009, 21, 4045. 18 S. Feng, Z. Ren, Y. Wei, B. Jiang, Y. Liu, L. Zhang, W. Zhang and H. Fu, Chem. Commun., 2010, 46, 6276. 19 H. Yao, S. S. Ng, W. O. Tucker, Y. Tsang, K. Man, X. Wang, B. K. C. Chow, H. Kung, G. Tang and M. C. Lin, Biomaterials, 2009, 30, 5793. 20 H. M. Chen, C. H. Deng and X. M. Zhang, Angew. Chem., Int. Ed., 2010, 49, 607. 21 S. Laurent, D. Forge, M. Port, A. Roch, C. Robic, L. V. Elst and R. N. Muller, Chem. Rev., 2008, 108, 2064. 22 N. A. Frey, S. Peng, K. Cheng and S. Sun, Chem. Soc. Rev., 2009, 38, 2532.
Chem. Commun., 2011, 47, 7719–7721
7721
