Influence of O2 and CO2 plasma treatment on the deposition of chitosan onto polyethylene terephthalate (PET) surfaces

Oxygen and carbon dioxide plasma treatments were applied in order to study their influences on chitosan adhesion onto PET foils. Modification of the surface and the adsorption of chitosan were monitored by the determination of XPS spectra, titrations, zeta potential, contact angles, and AFM. asma treatment resulted in hydrophilization of the surface through the introduction of new polar oxygen-containing groups. The treatment also yielded binding-sites for amino groups of chitosan. This led to a decrease in accessible protonated amino groups after chitosan binding onto plasma-activated foils in comparison with the plasma-non-activated ones. Consequently, the layer of chitosan adsorbed after plasma treatment was less antimicrobially active in the case of O2-treated foils. Surprisingly, the layer of chitosan adsorbed after CO2 plasma treatments were, in general, more active as antimicrobial agents than those of the non-plasma treated PET surfaces.