Experimental Modeling of Interaction between the Carbon Pyroceram Heart Valve with the Human Blood Plasma and Formation of a Protective Nanosized Coating

Abstract

The nanocrystalline material of an artificial heart valve obtained by sintering of 15 wt.% B₄C with crystals <10 nm in size, uniformly distributed in 85 wt.% carbon with particles about 10 nm in size, has exceptionally high chemical stability in the human blood plasma. The electrochemical interaction resulting from contact with a potential microadditive, for example iron, on the valve surface is experimentally modeled by polarization from an external current source to simulate an extreme corrosion event. The interaction kinetics is studied at 37 °C using the method of anodic polarization curves. The elemental composition of interaction products with blood plasma is ana-lyzed by emission spectroscopy using a DFS-13 device; the composition and thickness of the film layers formed on the valve surface during electrolysis are determined with quantitative Auger-electron spectroscopy using a LAS-2000 Riber device. It is established that a nanocrystalline film 350 nm thick forms after 3 h electrolysis on the ceramic surface of the heart valve. The film contains to 94.0 at.% C and to 6.0 at.% N ( including to 89.5 at.% C as nanocrystalline graphite and to 4.5 at.% C as nano-crystalline C₃N₄, as well as to 6.0 at.% N in C₃N₄) and an insignificant amount of sulfur and inclusions of boron and oxygen atoms. It is shown that this film results from the discharge of anions of corresponding α-amino blood acids (amino acid remains of complicated chains of blood proteins) containing heterocycle rings on the valve surface.