Experimental modeling of interaction between the carbon pyroceram heart valve and human blood plasma and formation of a protective nanosized coating

Abstract

The nanocrystalline material of an artificial heart valve sintered from 15 wt.% B 4 C 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 human blood plasma. The electrochemical interaction resulting from contact of the valve surface with a potential trace impurity (for example, iron) 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 is analyzed by emission spectroscopy using a DFS-13 spectrograph; the composition and thickness of the film layers formed on the valve surface during electrolysis are determined with quantitative Auger electron spectroscopy using a Riber LAS-2000 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 nanocrystalline C 3 N 4 , as well as to 6.0 at.% N in C 3 N 4 ) and an insignificant amount of sulfur and inclusions of boron and oxygen atoms. It is shown that the film results from the discharge of anions of corresponding α-amino acids (amino acid remains of complex blood protein chains) containing heterocycle rings.

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“…Heterocycles may be part of the emerging protective nanoscale coating that appears on the surface during experimental modeling of the interaction of a heart valve made of carbon pyroceramics with human blood plasma [ 19 ]. The film is formed as a result of the release of anions of the corresponding α-amino acids (amino acid residues of complex chains of blood proteins) containing heterocyclic rings.…”