Surface modification of metallic materials designed for a new generation of artificial heart valves

Abstract

Purpose: The main goal of this work was to develop haemocompatibile thin film materials dedicated to novel flexible mechanical heart valves intended for pulsatile ventricle assist devices. Methods: The studies performed have led to the selection of a material for the surface modification of the metallic scaffold. Haemocompatible, biofunctional, ultra-elastic, thin carbon-based coatings were proposed. The surface was designed to eliminate thrombogenic and microbial construction by a reduction in turbulence and sufficient washing of the biofunctional-adapted surfaces, thus allowing for extended use for temporary heart support. The article presents the influence of the mechanical properties of coatings and their influence on the haemocompatibility. In this study, we investigated a simplified model of the whole blood shear stress based on a cone and plate rotational viscometer. Several indices of platelet activation were analysed, including platelet and granulocyte-platelet aggregates, platelet activation markers and platelet-derived microparticles. Results: The shear stress induced a platelet aggregate count in the range from 2% to 30% of the CD61 positive cells. For polyurethane (PU), the average value of platelet aggregates was on the level of 7%. The analyses have demonstrated that the cytometric methods of the direct determination of platelet-derived microparticles in plasma are reproducible and reliable. Considering the generation of microparticles on the tested coatings under hydrodynamic conditions, the best properties were observed for the coating a-C:H,N. Conclusion: The results indicate that a-C:H-based coatings with the thickness of 110 nm do not induce an immune response and do not influence the origin of platelet microparticle formation; thus, these type of coatings are the most promising for the parts which are planned to withstand blood contact under the high value of shear stress.