Antithrombogenic surfaces

Biomaterials with Low Thrombogenicity. Poly(ethylene oxide) exhibits extraordinary inertness toward most proteins and biological macromolecules. The polymer is therefore used in bulk and surface modification of biomaterials to develop antithrombogenic surfaces for blood contacting materials. Such modified surfaces result in reduced concentrations of ceU adhesion and protein adsorption when compared to the nonmodifted surfaces. 

Antithrombogenic Surface Coatings on Implantable Artificial Organs... 

This article describes polymer surfaces the blood compatibility of which is achieved neither by the use of heparin nor by the formation of neointima, but by the antithrombogenic surface by itself. Thus, a blood-compatible polymer here means an mti-thrombogenic biomaterial and not a water-soluble polymer which is completely soluble in blood and works as plasma expander or anticoagulant. 

In this article it is shown that a completely antithrombogenic surface can be obtained from synthetic polymers without any help of bioactive polymers as heparin and urokinase. Such a surface has a diffuse structure, which essentially differs from that of so-called hydrogels which have a relatively low water content. There is no reason to suspect that the interaction of the polymer surface with plasma proteins initiates a series of complex biochemical events leading to thrombus formation. Rec i% it has been reported that even if proteins deposit on a material to a multilayer, the proteins at the outermost layer of multi-layered protein deposit might remain intact, which would eventually prevent platelet adhesion... 

Finally, it should be stressed that an antithrombogenic surface is merely one condition of the blood compatibility of biomaterials which can be used in medicine. If the biomaterial is implanted as blood pumps of artificial heart and vascular grafts, we should also take into consideration other important properties such as mechanical durability, calcification, bonding strength with respect to host tissue, etc. Studies on blood-compatible polymers have been started only since recently. 

Matsumoto, H., Kimura, T., Fuse, K., Yamamoto, M., Saigusa, M., Takamatsu, T., and Fiokada, E. Studies on expanded polytetrafluoroethylene as the vascular prosthesis ( the third report) its antithrombogenicity, surface properties and porosity. Artificial Organs. 3 3379197. ... 

Small-diameter vascular prostheses with incorporated matrices can be absorbed into a growing anastomotic neointima. It was pointed out that a gelatin-heparin complex when adequately cross-linked, could simultaneously function as a temporary antithrombogenic surface and as an exceptional substructure for an anastomotic... 

There are two main approaches to design biocompatible surfaces. The first approach is to create a non-interacting surface where undesirable biointeractions are reduced. Low fouling coatings resistant to protein adsorption and cell adhesion and antithrombogenic surfaces have been studied. The second approach is to design a bioactive surface, which enhances desirable bio-interaction by immobilization of biomolecules with desirable interactions (bio-recognitions). 

Also several serinprotease inhibitors will be adsorbed to surfaces. They may inactivate activated serinproteases via complex formation resulting in antithrombogenic surfaces. These reactions may be catalytically modulated by surface bound polysaccharides such as heparan sulphate, heparin, dermatan sulphate and covalently bound chondroitin sulphate in thrombomoduline . Most of the heparan sulphates on the luminal surface of blood vessels, in the glycocalix, have been reported to be AT III inactive. The endothelial cell surface heparan sulphate (ESHS) isolated by us is AT... 

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