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ABSTRACT
The present study describes the synthesis of crosslinked chitosan (CS) hydrogel beads with chemical crosslinkers (glutaraldehyde and epichlorohydrin) and natural crosslinking reagent (genipin). Crosslinking was carried out for 24 h in case of glutaraldehyde and genipin and for 2 h in case of epichlorohydrin with constant stirring and heating at 30°C. Swelling study of crosslinked chitosan hydrogel beads was carried out in SIF (simulated intestinal fluid) and SGF (simulated gastric fluid) medium followed by diameter increase ratio (DIR). Increased swelling of hydrogels, under acidic conditions, was due to the protonation of primary amino groups on chitosan, as confirmed by FTIR analysis. Surface texture of hydrogel beads was analyzed by scanning electron microscopy (SEM), which revealed that crosslinked beads had smooth surface compared to non-crosslinked beads. Thermogravimetric analysis (TGA) suggested genipin crosslinked CS beads with highest thermal stability. The use of these hydrogels for drug release was studied using amoxicillin as the model drug. Release studies carried out in SGF showed the release mechanism to be anomalous in nature and suggested potential of these hydrogels in controlled drug delivery devices.
KEYWORDS: Chitosan, Crosslinking, Glutaraldehyde, Epichlorohydrin, Genipin, Swelling, Amoxicillin.
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INTRODUCTION
In recent years, a great attention has been paid to biopolymer hydrogels due to their potential applications in biomedical and pharmaceutical fields. Among the biopolymers, Chitosan (CS) has been the most widely studied polymers because of its intrinsic properties viz. hydrophilicity, mucoadhesivity, biocompatibility, nontoxicity and biodegradability that has rendered CS useful in many potential applications, for instance, in biomedical products, cosmetics, pharmaceutical processes, agriculture, food and chemical engineering [1-4]. It is one of the most abundantly available polymers in nature and is obtained by alkaline deacetylation of chitin which is the structural component in the outer skeletons of crustaceans, also found in other species of insects, molluscs and fungi [3]. CS is a cationic, linear polysaccharide consisting of b(1-4) 2- amino-2-deoxy-D-glucose (D-glucosamine) and 2-acetamido-2-deoxy-D-glucose (N-acetyl-D- glucosamine) units (Figure 1). Due to easy availability of free amino group in chitosan, it carries a positive charge and thus in turn reacts with many negatively charged surfaces/ polymers and also undergoes chelation with metal ion [5-8]. Chitosan is known to display unique chelating and film forming properties due to the presence of...