High-strength ceramics as innovative candidates for cardiovascular implants.

Cytocompatibility and hemocompatibility are essential features for tissue- and blood-contacting implants such as artificial heart valves, vascular grafts and stents. Platelet activation as the main trigger of thrombosis results in implant failures. The purpose of this study results from the demands on anti-coagulant and non-corrosive innovative biomaterials for cardiovascular implants. Therefore, hemocompatibility and cytocompatibility of various high-strength ceramics, such as alumina, zirconia, silicon nitride and silicon carbide, were examined to identify the most appropriate ceramic for cardiovascular implants. In addition to the material species, different crystallographic structures (single- and poly-crystalline) and surface terminations (Si and C faces) of silicon carbide were used in order to reveal the interactions between blood and material surface. Three cell types, i.e. human umbilical vein endothelial cells, mesenchymal stem cells and blood cells, were cultured on the substrates and their interactions with material surfaces were analyzed. Cytotoxicity of the materials was tested by live/dead staining. Hemocompatibility in terms of platelet and white blood cell activation was examined via scanning electron microscopy and indirect ELISA. To mimic physiological conditions in vitro, the hemocompatibility of the materials was additionally analyzed in a bioreactor under dynamic flow conditions in comparison to static incubation. All ceramics were found to be cytocompatible for mesenchymal stem cells, human umbilical vein endothelial cells and blood cells. The highest number of resting, non-activated platelets was observed on the monocrystalline silicon carbide demonstrating that this material triggers the platelet activation less compared to the other materials. It is found to be the most appropriate ceramic for blood-contacting implants in terms of cell adhesion, cell viability, and hemocompatibility. [ABSTRACT FROM AUTHOR]