Binding selectivity of N-alkylaminated modified chitosan nanoparticles produce a synergistic antibacterial effect against gram-negative strains

In recent years, nanoparticles have been gaining attention as a viable therapeutic option, and the synergistic combination of nanoparticles with antibiotics could constitute a promising alternative to combat antibiotic-resistant pathogens. In this study, the effect of a new biocompatible modified-chitosan polymer, N-alkylaminated chitosan (NAC), on enhancing the antibiotics efficiency has been evaluated. NAC showed significant antimicrobial activity against gram-negative bacterial strains (Escherichia coli and Salmonella typhimurium) with minimum inhibitory concentrations (MICs) of 0.0625 mg/mL, however, it appeared to be ineffectual in inhibiting gram-positive bacterial strains (Bacillus cereus and Staphylococcus aureus). Furthermore, NAC showed an excellent synergistic effect with various clinically relevant antibiotics by reducing the MICs of the antibiotics against E.coli and S. typhimurium to 2 μg/mL. Hence, this novel chitosan derivative, NAC, can be utilized as a cationic antimicrobial agent alone or in synergistic combination with various antibiotics to combat gram-negative infections.