Inhibitory activity of biofunctionalized silver-capped N-methylated water-soluble chitosan thiomer for microbial and biofilm infections.

One of the most important self-defense strategies employed by bacteria to resist the action of antibiotics is a biofilm formation upon the infected surface. Thus, there is an urgent need to explore novel candidates that have potent antibacterial and anti-biofilm effects to tackle this challenge. In this endeavor, we have transformed shrimp shell wastes to N-methylated water-soluble chitosan thiomer (MWSCT) which was used as either a chelating agent or bio-reductant and capping agent for Ag(I) ions in the preparation of a Ag(I)MWSCT complex or silver nanocomposite (Ag(0)MWSCT), for targeting antibacterial and anti-biofilm applications. The antibacterial and anti-biofilm performance of the new methylated chitosan thiomer (MWSCT) and its silver architectures (Ag(I)MWSCT, Ag(0)MWSCT) were assessed in vitro against E. coli and S. aureus. These new materials have significant capacities to synergistically inhibit the proliferation of the targeted bacterial cells and biofilm formation, in a structure- and species-dependent manner. Ag(0)MWSCT emerged as the most potent compound in inhibiting the growth of bacterial strains (MIC _{E. coli} / MIC _{S. aureus}  = 0.05/ 0.34 μg/mL, 1.6-/ 2.5-times lower than that recorded for the clinical drug (ciprofloxacin, Cipro). Also, this nanocomposite showed the highest anti-biofilm effects (only 1.7% E. coli biofilm growth; 11.8% staphylococcal biofilm growth).
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