The mechnical behaviors on nonthrombogenecity

Abstract

Synthetic polymers suitable for use in the cardiovascular system are needed as biomaterials for heart valve prostheses, artificial heart, veins, arteries and extracorporeal circulatory devices as heart-lung and kidney machines. Despite the wide variety of synthetic polymers that are available in the form of plastics or elastomers, none has proven eligible to clinical application for this purpose as a perfectly nonthrombogenic material. Currently, most investigations seem to be directed toward clarification of the blood biomaterial surface interaction, especially the mechanism whereby thrombi are formed in contact with such prosthetic. In many of these studies the surface properties of synthetic materials are being investigated from the angle where the foreign surface: blood interaction is taken as interface reaction, with the attention focused upon hydrophobicity, hydrophilicity and electronegativity of the materials. Findings obtained in our studies aimed at development of antithrombogenic materials have indicated importance of a definite distribution density of hydrophobicity and hydrophilicity for such polymers; namely, it appears unlikely that no surface factor is involved in the biomaterial: blood interface.Supposing, for example, that a synthetic venous prosthesis with a surface of about 15cm2 be introduced into the vascular system, this newly added surface of about 15cm2 undoubtedly would be so slight as to fall within the limits of errors as compared with the entire inner surface of the cardiovascular system and hence as viewed in terms of the concentration of heparin injected for inhibition of the clotting system. Thus it would be rational to introduce into the study the findings on the surface structure of cells exposed to the cardiovacular lumen. Our studies are based on this ground, pursued through physico-chemical analysis of the interface comprised of the prosthetic surface and the circulating plasma surface. By comparative evaluation of various synthetic polymer prostheses in terms of antithrombogencity, the interfacial condition of the vascular inner surface of the organism was determind to consist of γC(Zis.)=20 to 30erg/cm2, γC=68.5erg/cm2 and γSL(H2O)=0erg/cm2, or the surface endowed both with hydrophilicity and it was demonstrated that a synthetic polymer fulfilling the prerequisites of γC(Zis.)=29 to 30erg/cm2, γC=29 to 30erg/cm2 and γSL(H2O)=0erg/cm2 is remarkably antithrombogenic. The results, stress prime importance of the function of interface to protein at a synthetic polymer surface and indicate the presence of biomate rials with minimal bearing upon the clotting system of blood. Further studies aimed at clarification of the interaction with protein will be pursued, using such materials.