The role of oxygen and nitrogen plasma treatments in improving bioactivity and long-term stability of PEO-modified titanium

Electrochemical processes on titanium and its alloys play a crucial role in the biomaterials industry. Such methods, as a plasma electrolytic oxidation (PEO) are commonly used in the process of producing a porous surface, which provides a better interaction at the bone-implant interface. Nevertheless, PEO surfaces tend to lose their hydrophilicity and bioactivity after certain amount of time. It is a phenomenon called surface ageing. By using surface-activating processes like plasma treatment, it is possible to prevent it and increase the association between the endoskeleton and implant. The main objective of that study is to quantitatively evaluate how O₂ and N₂ plasma treatments influence surface ageing, wettability, morphology, and composition of PEO-coated titanium over 14 days. The O₂/N₂ plasma cleaning seem to detach carbon contaminants, which made the surfaces extra hydrophilic. That modification of the coatings also made the surfaces more bioactive by enhancing the cell adhesion and proliferation. Wettability has slightly diminished with time. Nonetheless, the process of ageing has decelerated. Obtained results suggest that plasma cleaning affects positively on the surface properties, what makes the treatment worthy of further investigations. That study is one of a few, which examine the time-dependent degradation of PEO coatings after plasma treatment, providing an overview of their long-term performance.