A green approach for depolymerization of chitosan: applications in hydrogels

Abstract

Chitooligosaccharides (COS) are depolymerized chains produced from the natural polymer chitosan and has been determined to exhibit improved biological activities, high solubility in neutral to slightly alkaline pH, because of the lower molecular weight (MW). This makes COS more attractive in biomedical applications. However, earlier studies focused on depolymerization techniques that were either cumbersome or expensive. Here, a convenient two-stage, green synthesis approach was developed and optimized, where gamma irradiation and oxidative degradation with H2O2 were used to depolymerize chitosan to produce COS for biomedical applications. The gamma radiation dose level, H2O2 degradation reaction’s temperature, time and H2O2 concentration were varied to obtain the mildest combination of reaction conditions. The most optimum set of conditions (15 kGy, 25oC, overnight reaction with 2% H2O2) yielded COS that was soluble in physiological pH range (7–8.5). The COS had a MW of 12.8 ± 1.6 kDa (which was a 95% reduction in MW), a 62.3% degree of deacetylation, and a crystallinity index of 33%. A photopolymerized hydrogel using this COS cross-linked with polyethylene glycol diacrylate (PEGDA) and carboxymethyl cellulose (CMC) was also developed. The hydrogel exhibited high swelling ratio (6.44–10.24), a porous morphology, a compression modulus of 4.5 ± 2.7 kPa (similar to soft tissues), and more than 95% biocompatibility with mammalian cells. This newly developed COS hydrogel involves a simple and green approach for the production of COS and shows promise as a scaffold for artificial soft tissue.

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“…The solubility of B44 and B46 chitooligosaccharides was investigated in various solvents, such as water, ethyl acetate, and glacial acetic acid, at room temperature. The solubility of chitooligosaccharide in water, ethanol, ethyl acetate, and glacial acetic acid except diethylether 44 , whereas in the present investigation, the chitooligosaccharide not dissolved in ethanol and diethylether Table 5. The chitooligosaccharides showed the highest zone of inhibition at 60μl for all pathogens in the study.…”