Microbiological investigations of oxygen plasma treated parylene C surfaces for metal implant coating.

Parylene C surface was modified by the use of oxygen plasma treatment and characterized by microscopic and surface-sensitive techniques (E-SEM, AFM, XPS, LDI-TOF-MS, contact angle). The influence of the treatment on surface properties was investigated by calculations of surface free energy (Owens-Wendt method). Moreover, early adhesion (Culture Plate Method, Optical Microscopy Test) and biofilm formation ability (Cristal Violet Assay) on the parylene C surface was investigated. The bacteria strains which are common causative agents of medical device-associated infections (Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa--reference strains and clinical isolates) were used. It was concluded that chemical (oxygen insertion) and physical (nanotopography generation) changes, have a significant impact on the biocompatibility in terms of increased hydrophilicity (θ w of unmodified sample = 88° ± 2°, θ w of 60 min modified sample = 17.6° ± 0.8°) and surface free energy (SFE of unmodified sample = 42.4 mJ/m(2), and for 60 min modified sample = 70.1 mJ/m(2)). At the same time, no statistical effect on biofilm production and bacteria attachment to the modified surface of any of the tested strains was observed.