Structural and antimicrobial properties of irradiated chitosan and its complexes with zinc

• Gamma radiation is used to lower the molecular weight of chitosan.
• The effect of environment on radiation degradation of chitosan is studied.
• Its complexes with different amount of zinc are prepared and characterized.
• Radiation-degraded chitosan and complexes showed good antibacterial properties.

The aim of this research was to evaluate the structural and antimicrobial properties of irradiated chitosan and its complexes with zinc. Chitosan having a molecular weight (Mη) of 220 kDa was exposed to gamma rays in dry, wet and solution forms. The chitosan-zinc complexes were prepared by varying the Mη of chitosan and Zn content. Viscometeric analysis revealed a sharp decrease in the Mη of chitosan irradiated in solution form even at lower doses compared with the dry and wet forms. X-ray diffraction patterns demonstrated variation in the crystallinity of chitosan upon exposure to gamma rays. The antibacterial response of the irradiated chitosan and its complexes against gram-positive and gram-negative bacteria demonstrated wide spectrum of effective antimicrobial activities, which increased with the dose. Additionally, the complexes exhibited excellent antifungal activity with no growth of Aspergallious fumigatus and Fusarium solani even after two weeks. These results suggested that the irradiated chitosan and its complexes with Zn can be used as antimicrobial additives for various applications.