Improved blood compatibility and cyto-compatibility of Zn-1Mg via plasma electrolytic oxidation

Abstract

Compared to magnesium (Mg) or iron (Fe) based biodegradable alloys, Zinc (Zn) alloys exhibit moderate degradation rates, thus regarded as promising implant materials for orthopedic and cardiovascular applications. However, Zn2+ released from degradation process may result certain degrees of cytotoxicity. Thus it is necessary to modify the surface of biodegradable Zn alloys for better biocompatibility. In this paper, a porous ceramic coating was successfully prepared on a Zn-1Mg alloy using plasma electrolytic oxidation (PEO). The effect of the PEO coating on the corrosion resistance and in vitro cyto-compatibility of the Zn-1Mg alloy were evaluated. It was noted that the thickness of the PEO coatings could be adjusted from 6.7 ± 0.5 µm to 28.6 ± 2 µm by increasing the oxidation time from 30 s to 120 s. Longer oxidation time led to a more rough and hydrophobic surface, which was consisted of ZnO and Zn2SiO4. The stable and protective oxide layer enhanced the corrosion resistance of the Zn-1Mg alloy. The PEO coated Zn-1Mg exhibited better blood compatibility and cyto-compatibility. Decreased hemolytic ratio and lower platelet adhesion was observed on the PEO coated Zn-1Mg sample. The enhanced cyto-biocompatibility is mainly attributed to small amount of Si2+ and Mg2+ released during the early degradation of the PEO coating.