Effect of oleoyl-chitosan nanoparticles as a novel antibacterial dispersion system on viability, membrane permeability and cell morphology of Escherichia coli and Staphylococcus aureus

A novel chitosan antibacterial dispersion system was prepared by oleoyl-chitosan (O-chitosan) nanoparticles (OCNP) and the bactericidal activity against Escherichia coli and Staphylococcus aureus was evaluated by the enumeration of viable organisms at different incubation times. We further investigated the antimicrobial mode of OCNP using a combination of approaches, including cell integrity measurements, outer membrane (OM) and inner membrane (IM) permeabilization assays, SDS–PAGE and transmission electron microscopy (TEM). Results showed that when treated with OCNP, release of intracellular components quickly increased for both E. coli and S. aureus. OCNP also rapidly increased the 1-N-phenylnaphthylamine (NPN) uptake and the release of cytoplasmic β-galactosidase via increasing the permeability of OM and IM. Besides, SDS–PAGE indicated the content of cellular soluble proteins decreased significantly in OCNP-treated bacteria. TEM observations demonstrated adsorption behaviors of OCNP on bacteria and extensive cell surface alterations of OCNP-treated bacteria. OCNP has potential value in the determination of antibacterial mechanism of chitosan.