Improvement of antibacterial activity of Ag-poly(vinyl-alcohol)/chitosan hydrogel by optimizing the procedure of radiolytic synthesis

Abstract

Hydrogels consisting of radiation-degraded chitosan, poly(vinyl alcohol), and Ag nano-filler, were prepared by γ-irradiation in two-stage and single-stage procedures to examine the role of the synthesis procedure in improving the antibacterial activity. The light scattering method showed that radiation-degradation of chitosan occurred both by breaking the glucoside bonds and by Maillard's reaction. Elemental analysis indicated a reduction in the degree of deacetylation after degradation. The product of Amadori rearrangement and pigmented product melanoidins were determined by 1H NMR, FTIR, UV–Vis, and fluorescence spectroscopy. Enhancement of in vitro antibacterial activity of nanocomposites against Staphylococcus aureus and Escherichia coli was achieved by a single-stage procedure which results in greater mobility of radiation-modified chitosan in the network. This allows the exploitation of its potential, which is reflected in the possibility of the complexing of ultrasmall molecular Ag clusters. These complexes have a considerably stronger antibacterial effect. Ag in molecular form was confirmed by XPS analysis.