Synergistic antibacterial activity of chitosan–silver nanocomposites on Staphylococcusaureus

Abstract

The approach of combining different mechanisms of antibacterial action by designinghybrid nanomaterials provides a new paradigm in the fight against resistant bacteria. Here,we present a new method for the synthesis of silver nanoparticles enveloped in thebiopolymer chitosan. The method aims at the production of bionanocomposites withenhanced antibacterial properties. We find that chitosan and silver nanoparticlesact synergistically against two strains of Gram-positive Staphylococcus aureus(S. aureus). As a result the bionanocomposites exhibit higher antibacterial activitythan any component acting alone. The minimum inhibitory (MIC) and minimumbactericidal (MBC) concentrations of the chitosan–silver nanoparticles synthesized at0 °C were found to be lower than those reported for other types of silver nanoparticles. Atomicforce microscopy (AFM) revealed dramatic changes in morphology of S. aureus cells due todisruption of bacterial cell wall integrity after incubation with chitosan–silvernanoparticles. Finally, we demonstrate that silver nanoparticles can be used not only asantibacterial agents but also as excellent plasmonic substrates to identify bacteria andmonitor the induced biochemical changes in the bacterial cell wall via surface enhancedRaman scattering (SERS) spectroscopy.