Protein adsorption and platelet attachment and activation, on TiN, TiC, and DLC coatings on titanium for cardiovascular applications

The hemocompatibility of a TiN/TiC/diamond-like carbon (DLC) multilayer str ucture, deposited on titanium substrates for use as coatings for a heart va lve prosthesis, has been studied through the adsorption of blood proteins a nd the adhesion and attachment of blood platelets. All of the surfaces were characterized by stylus profilometry and water contact angles. The adsorpt ion of albumin and fibrinogen to the surfaces was assessed using the Amido Black assay, whereas platelet attachment was studied by scanning electron m icroscopy and quantified using stereological techniques. The degree of plat elet spreading on the surfaces was seen to correlate with differences in su rface energy, indicated from contact angle measurements. The greatest sprea ding was seen on the more hydrophilic surfaces. When studying protein adsor ption to the surfaces, no correlation could be determined between contact a ngle results and levels of adsorption, although the most hydrophilic surfac es did appear to promote greater amounts of fibrinogen adsorption. Thrombus formation was observed to some degree on all of the surfaces, with the exc eption of the DLC coating. This coating also promoted less spreading of pla telets than the other surfaces. The good hemocompatibility of the DLC coati ng is attributed to its hydrophobicity and smooth surface, resulting in a h igher ratio of albumin to fibrinogen than any of the other surfaces. (C) 20 00 John Wiley & Sons, Inc.