Albumin adsorption onto pyrolytic carbon: A molecular mechanics approach

A number of implants of cardiac valve prosthesis, vascular prosthesis, and coronary stents present a pyrolytic carbon interface to blood. Plasma prote in adsorption is essential for the hemocompatibility of the implanted devic es. This work quantitatively evaluates the molecular interaction force betw een a biomaterial surface (pyrolytic carbon) and plasma protein (albumin) b inding sites through a simplified molecular model of the interface consisti ng of (i) multioriented graphite micro crystallites; (ii) selected fragment s of albumin; and (iii) a water environment. A number of simplifying assump tions were made in the calculation: the albumin molecule was divided into h ydrophobic and hydrophilic subunits (helices); an idealized clean, nonoxidi zed polycrystalline graphite surface was assumed to approximate the surface of pyrolytic carbon. The interaction forces between albumin helices and py rolytic carbon surfaces are evaluated from potential energy data. These for ces are decomposed into a normal and a tangential component. The first one is calculated using a docking procedure (F-perpendicular to tot MAX = 4.16 x 10(-20) N). The second one (F-parallel to), calculated by mean of geometr ic models estimating the energy variation associated with the protein slidi ng on the material surface, varies within the range +/-9.62 x 10(-21) N. Th e molecular simulations were performed using the commercial soft-ware packa ge Hyperchem 5.0 (Hyperchem, Hypercube, Canada). (C) 2001 John Wiley & Sons , Inc.