New insights into the bactericidal activity of chitosan-Ag bionanocomposite: The role of the electrical conductivity

• We report the synthesis and characterization of films of chitosan (CS)/Ag nanoparticles with bactericidal activity.
• Bactericide effectiveness increases by increasing Ag nP concentrations up to 3 wt%, which is close to the electrical percolation threshold of ca. 3 wt%.
• XPS analysis shows the presence of ca. 15 vol.% of Ag ions that are a requisite for maximum bactericide activity.
• The elucidated correlation between electrical properties and antibacterial activity could be useful in the design of other nanocomposites.

The relationship between electrical conductivity, structure and antibacterial properties of chitosan-silver nanoparticles (CS/AgnP) biocomposites has been analyzed. To test the film's antimicrobial activity, Gram-positive and Gram-negative bacteria were studied. The interactions between silver nanoparticles with chitosan suggest the formation of silver ions which plays a major role in nanocomposite's bactericidal potency. In CS/AgnP biocomposites, the bactericide effectiveness increases by increasing AgnP concentrations up to 3 wt%, which is close to the electrical percolation threshold of ca. 3 wt%. As the AgnP concentration increases above this threshold, the bactericidal potency is greatly diminished. The elucidated correlation between electrical conductivity and antibacterial activity could be useful in the design of other nanocomposites that involve polymeric-based matrices.

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