Biological Responses and Hemocompatibility of Diamond-Like Carbon Thin Films on Different PEO Interlayers for Potential Cardiovascular Stent Applications

Plasma electrolytic oxidation (PEO) considerably affects controlling the degradation rate of magnesium-based implants to approach the healing period. However, the biological properties still require further improvement, particularly for blood-contact applications, such as cardiovascular stents. This research aims to study in vitro biological properties of the duplex diamond-like carbon (DLC)/plasma electrolytic oxidation (PEO) coatings as a function of various PEO middle layers for potential cardiovascular stent applications. To this aim, two different PEO coatings including silicate and phosphate compounds were applied on AZ31 substrate as middle-layers, and a top DLC layer with 1 mu m thickness was successfully synthesized on them. Moreover, the role of different PEO interlayers on the degradation behavior, biocompatibility, hemocompatibility, and its mechanism are studied. Results showed a considerable decrease in degradation rate after applying the PEO process and the PEO-Ph revealed the optimized degradation performance in just PEO-coated samples. On the other side, the best degradation performance between duplex-coated samples was obtained for DLC/PEO-Si according to its higher diamond-like structure. Moreover, the viability of human umbilical vein endothelial cells on DLC/PEO-Ph was higher than that of the DLC/PEO-Si, which might be attributed to higher protein adsorption on its surface. In the case of hemocompatibility, a considerable decrease in hemolysis ratio along with remarkable improvement in clotting behavior was observed by applying the PEO process. However, the hemolysis ratio was reduced as being safe for blood-contact applications just for duplex-coated samples. In conclusion, a promising coating for blood-contact applications based on DLC/PEO in particular in the case of DLC/PEO-Si has been provided in this study.