Regeneration Approach to Enhance the Antimicrobial and Antioxidant Activities of Chitosan for Biomedical Applications.

Owing to its biodegradability, non-toxicity, and biocompatibility, chitosan (Cs) is a ubiquitous biopolymer. However, applications of Cs are limited owing to the existence of strong inter- and intra-molecular hydrogen bonds within its network. To address this issue, we regenerated medium-molecular-weight Cs to enhance the physico-chemical and functional properties using a cationic approach. Accordingly, alkaline modification was employed to introduce an additional positive charge to the amine functional groups of Cs and moderately disintegrate the inter- and intra-hydrogen bonds. The chemical structure of Cs and regenerated chitosan (RCs) was confirmed through Fourier transform infrared and ¹ H-NMR spectroscopy. RCs showed higher zeta potential value compared to Cs. Additionally, using X-ray diffraction, RCs exhibited low crystallinity, which can be attributed to the repulsive force caused by the positive surface charge and the destruction of hydrogen bonds. The RCs exhibited stronger antioxidant activity than Cs. Furthermore, the minimum inhibition concentrations (MICs) of RCs against Escherichia coli and Staphylococcus aureus were reduced by almost four times compared with those of Cs. The superior functional properties of RCs can be attributed to the formation of a polycationic structure after alkaline modification. Thus, RCs can be introduced as potent agents for various biomedical purposes.