The effects of amorphous carbon films deposited on polyethylene terephthalate on bacterial adhesion

There is an increasing interest in developing new methods to reduce bacteria adhesion onto polymeric materials that are used in biomedical implants. The antibacterial behavior on polyethylene terephthalate (PET) treated by acetylene (C2H2) plasma immersion ion implantation-deposition (PIII-D) is investigated. The surface structure of the treated PET is determined by laser Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The results show that a thin amorphous polymer-like carbon (PLC) layer is formed on the PET surface. Atomic force micrographs (AFM) show that C2H2 PIII-D significantly changes the surface morphology of PET. The capacities of Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) to adhere onto PET are quantitatively determined by plate counting and Gamma-ray counting of 125I radio labeled bacteria in vitro. The results indicate that the adhesion of the two kinds of bacteria to PET is suppressed by PLC. The adhesion efficiency of SE on the coated surface is only about 14% of that of the untreated PET surface, and that of SA is about 35% of that of the virgin surface. The electrokinetic potentials of the bacterial cells and substrates are determined by zeta potential measurement. All the substrates as well as the bacterial strain have negative zeta potentials, and it means that bacterial adhesion is not mediated by electrostatic interactions. The surface energy components of the various substrates and bacteria are calculated based on measurements in water, formamide and diiodomethane. The surface free energies obtained are used to calculate the interfacial free energies of adhesion ( deltaFAdh ) of SA and SE onto various substrates, and it is found that bacterial adhesion is energetically unfavorable on the PLC deposited on PET by C2H2 PIII-D.