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Preparation and characterization of microporousbionanocomposites for biomedical applications 25
SANTOSH KUMAR1*,MRIDULA KUMARI2,M. A. MALLICK2, B.S. SWAIN3,A. J. F. N. SOBRAL1and P. K. DUTTA4
1Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, Coimbra, 3004-535, Portugal
2University Department of Biotechnology, VinobhaBhave University,St. Columba’s College Campus, Hazaribagh, India
3Department of Advanced Materials Engineering, Kookmin University, Seoul, South Korea
4Department of Chemistry, MN National Institute of Technology, Allahabad-211004, India
ABSTRACT
This article describes the preparation and characterisation of micro porous chitosan-silicon dioxidebionanocomposite via the incorporation of nano silicon dioxide nanoparticles into chitosan hydrogel. To explore the properties of prepared bionanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-visible spectroscopy and high resolution transmission electron microscopy (HR-TEM). TEM observation revealed that the silica was dispersed in the chitosan matrix. The bionanocomposites showed enhanced porous properties. All these results suggested that the prepared bionanocomposite could be used for various biotechnological and environmental applications.
KeyWords: chitosan biopolymer, nano silica dioxide,microporousbionanocomposites
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INTRODUCTION
The utilization of low cost and environmentally friendly natural products is also a challenging task for cleaner production. The interface of biological systems with silicon dioxide is of great interest as it plays a crucial role in the development of microarrays, catalysis, imaging agents, adsorptive materials, drug delivery and environmental engineering applications1-3. Silica nanostructures allow one to encapsulate biomolecules, produce sensing and imaging nanoparticles for biotechnology and deliver multiple clinical functions. The most important properties of these materials are their high surface area and pore structure, tunable and uniform pore size, and the convenience with which chemical modifications can be carried out due to the presence of surfacesilanol groups4.Biopolymer chitosan are suitable candidates for the organic counterpart in inorganic-organic hybrid materials because of their low cost, non-toxicity, biocompatibility, biodegradabilityand multifunctional properties5-7. Chitosan are most important derivative of chitin and second most scarce biopolymer after cellulose. There hybrid materials are biocompatible and have been used as bone substituents, cements for bone repair and reconstruction, and also for immobilization of cells and enzymes7.Lee et al. have reported membrane of hybrid chitosan-silica xerogel for guided bone regeneration and investigated in terms of their in vitro cellular activity and in vivo bone regeneration ability8. Witoon et al. reported the effect of acidity on the formation of silica-chitosan hybrid materials and thermal conductive property9.In this article, we have discussed the preparation, physiochemical and interaction properties of microporouschitosan-SiO2 bionanocompositefor various biotechnological applications.
EXPERIMENTAL
Materials and methods
Chitosan with 79% degree of deacetylation (DD), silicon dioxide and glacial acetic acid were purchased from Sigma-Aldrich. The vibrational monogram of chitosan-silicon dioxide bionanocomposites were analyzed by Fourier transform infrared (FT-IR) spectra using FTIR spectrometer (FTIR 300E (Tokyo, Japan) with an attenuated total reflectance (ATR) mode. The Raman spectra were obtained by a Raman spectroscopy (Horiba JobinYvon/LabRamAramis) using laser 514 nm (Ar-ion laser) with power on the samples ~ 0.5mW. The surface morphology was analyzed by high resolution transmission electron microscope (HR-TEM, JEM 3010, JEOL Ltd., Japan). UV-visible absorption spectra were measured by an UV-Visible spectrometer (Agilent 8453 spectrophotometer, USA).
Preparation of chitosan-silicon dioxide bionanocomposites
1 g of chitosan was dissolved into 50 mL of 1% aqueous acetic acid to prepare chitosan solution. The mixture was stirred continuously at room temperature for 12 h. The silicon dioxide nano powder (40 mg) was taken into 3 mL of distilled water and was treated by mild ultrasound for 30 min to forms a colloidal solution. The silicon dioxide was added in chitosan solution under stirring at 30oC for 4 h followed by sonication for 2 h to ensure a homogeneous dispersion of chitosan/silicon dioxide in solution. The mixed solution was cast on glass plate to a desired thickness and dried under vaccum pressure at 40oC for 24 h. Different ratio of SiO2 in chitosan-silicon dioxide bionanocomposites(CS+SiO2-80 and CS+SiO2-140) was also prepared by above procedure to study the effect of SiO2 in bionanocomposites.
RESULTS AND DISCUSSION
The sol-gel method has been successfully used for the synthesis of homogenous composites containing chitosan and silicon dioxide. Chitosan was hybridized with a SiO2 to form a chitosan-SiO2bionanocomposite, which is intended to combine the effects of the constituent components. Fig. 1 shows the schematic of chitosan-SiO2bionanocomposites prepared by mixing, solution casting and solvent evaporation method.
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Fig.1.Figure illustrating the schematic representation of chitosan-SiO2bionanocomposite
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FT-Infrared spectra
FT-IR spectroscopy was used to examine the interaction between the chitosan and silicon dioxide nanoparticle, as shown in Fig. 2. The main characteristic bands observed for pure chitosan film (Fig. 2) is assigned to the stretching of intra and intermolecular O-H vibrations at 3411-3248 cm-1 overlapped with N-H stretching mode. The signature at ~2950-2865 cm-1 corresponds to symmetric and asymmetric C-H vibrations. The amide I vibration band at 1640 cm-1is due to C-O stretch of acetyl group and the amide II band at 1552 cm-1is due to N-H stretching mode.. The absorption peak at 1062 cm-1is assigned to skeletal vibration of the bridge C-O stretch of glucosamine residue6. The silica showed (not in figure) IR bands in the following regions: 1250-1000, 960-900 and 500-450 cm-1, which were assigned to Si-O-Si (stretching mode), Si-OH and Si-O-Si, respectively9. Residual silanol (Si-OH) groups, reflecting the presence of a polycondensation is often incomplete, and is celebrated in many sol-gel derived materials. The absorption bands were observed, actually due to the integrated components of chitosan and the silica nanoparticles. There were no new peaks observed in the spectra of the chitosan-SiO2bionanocomposites.
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Fig.2. FT-IR spectra of and chitosan-SiO2bionanocomposites [pure CS (a), CS + 40 mg SiO2 (b), CS + 80 mg SiO2 (c) and CS + 140 mg SiO2 (d)]
Raman spectra
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The Raman spectra of the pure chitosan and chitosan-SiO2bionanocomposite are shown in Fig 3. Chitosan-SiO2bionanocomposite (Fig. 3) shows a band at 1591 cm-1 is attributed to deformation mode of amino group10. The Raman bands at 1462 and 1369 cm-1 is apportionedto various deformation vibrations of polysaccharides backbones. The band at 1109 cm-1 was attributed to the symmetric stretching vibration of glycosidic C-O-C groups.
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Fig.3. Raman spectra of pure chitosan composite (a) and bionanocomposites (b)
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Morphology study
The TEM images Fig.4 A and B reveal that the morphology of bionanocompositeis porous. The structures consist of densely packed and loosely packed aggregates of nano silica particles. Small amounts of inter-particle voids (circle) caused by the aggregation of the larger silica clusters. The sponge-like structure with the enhanced porosity with smaller cluster silica size was observed. This result revealed that the silica was successfully attached in the chitosan matrix to form a nanocomposite through a mixingprocess.High specific surface areas and well-ordered pore structures make the hierarchically structured SiO2 based chitosan bionanocomposite a promising for environmental applications.
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Fig.4. High resolution transmission electron microscopy of chitosan-SiO2bionanocomposite
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UV-visible spectra
Fig.5 shows the UV- visible spectra of pure chitosan and chitosan-SiO2 bionanocomposites. By increasing the nano-SiO2 content in the chitosan, the intensity of absorption peak is increasing. The absorption spectra recorded for nanocompositesshows two broad absorption bands centered at 245 and 287 nm. The absorption band centered at 245 nm originates from the silica nanoparticles, which also agrees with the spectra of previous observations11. The UV-Visible spectra in Fig. 5apparently reveal that the effect of shell thickness on the optical absorption spectra of chitosan-SiO2bionanocomposites as compared with the pure chitosan. The peak at~233 nm, which shifts to a longer wavelength (245 nm) due to the changes in the dielectric constant of the surroundings near the SiO2 surface. The shift exhibited by the absorption band could be correlated to a change in coordination geometry and symmetry of the material. This reflects that the Si-OH donor group interacts with the amino group of chitosan.
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Fig.5. UV-visible absorption spectra of and chitosan-SiO2bionanocomposites [Pure CS (a), CS + 40 mg SiO2 (b), CS + 80 mg SiO2 (c) and CS + 140 mg SiO2 (d)]
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CONCLUSIONS
In conclusion, chitosan-SiO2bionanocompositewas prepared by simple solution casting method. The ratio of chitosan to SiO2 leads tosignificant changes in the UV-visible properties of these bionanocomposites. These bionanocopmpositesmaterials may finduses in diverse applications such asbiotechnology and biomedical applications.Further work on the applications and extension of the bionanocomposite is currently underway in our laboratory.
Acknowledgements:The authors thank the FCT, Portugal for providing postdoc fellowship to SK.
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Received: 14 April 2015
Accepted: 27 May 2015
Asian Chitin Journal June 2015