Biotechnological Manipulations of Chitosan Polymer for Biomedical Applications

Abstract

Chitosan is a deacetylated derivative of chitin found in a wide range of natural sources. Chitosan as a natural polymer has been modified into a number of formulations based on its important characteristics such as biodegradability, biocompatibility, antibiotic activity and antitumor activity etc. Naturally available chitosan of high molecular weight has limited the efficiency of these polymers for antimicrobial activities. One of the techniques for improving chitosan antimicrobial efficiency is reducing its molecular weight. In this regard, irradiation is a widely used method for achieving reduction in molecular weight of polymers, which may improve some of its characteristics. In this study, chitosan was extracted from crab shells and irradiated by gamma radiations at different doses. Effect of radiation dose on chitosan structure was analyzed by Fourier Transform Infrared (FTIR) spectroscopy. Furthermore, un-irradiated and irradiated chitosans were blended with poly(vinyl alcohol) and crosslinked with tetraethylorthosilicate to form membranes. The membranes were found to be transparent and crosslinked macroporous in structure, exhibiting high tensile strength (TS: 27- 47MPa) and elongation at break (EB: 292.6-407.3%). The response of membranes towards water absorption capacities at different temperatures, pHs and salt solutions were studied. Chitosan membranes were found to be temperature and pH responsive. So, chitosan membrane was used for controlled release of insulin as a model drug at intestine’s pH value (6.8). Un-irradiated and irradiated chitosan and their membranes were studied for their antibacterial properties against bacterial pathogens i.e., Pseudomonas aeruginosa (SS29), Escherichia coli (SS1, SS2, and SS9), Proteus mirabilis (SS77), Staphylococcus aureus (LM15) and Bacillus subtilis. Irradiated low molecular weight chitosan and its membranes showed higher antibacterial activities. Analysis of bacterial metabolites by Liquid Chromatography Mass Spectrometry (LCMS) exhibited the suppression of virulence factors by chitosan in Pseudomonas aeruginosa. The production of aflatoxins B1, B2, G1 and G2 by Aspergillus flavus was considerably reduced by irradiated chitosan (CHI50) as validated by LC-MS analysis. It was found that low molecular weight chitosan inhibited the production of aflatoxin and Aspergillus flavus which increased with increasing concentrations of chitosan.