PROTEIN ADSORPTION ON LOW-TEMPERATURE ISOTROPIC CARBON .5. HOW IS IT RELATED TO ITS BLOOD COMPATIBILITY

Based on our research on blood protein interactions with low temperature isotropic carbon (LTIC) and data from the literature, we propose that the carbon surface has strong interactions with adsorbed proteins. In this paper we focus on how a relatively blood-compatible material interacts with plasma proteins. We present our results on the structure and properties of the LTIC surface utilizing SEM, STM, XPS, and contact angle measurements. We briefly review protein adsorption on LTIC using DSC, impedance, radioisotopes, and two-dimensional gel electrophoresis. LTIC is characterized by a microporous, oxidized, hydrophobic, and domain mosaic structure. Surface polishing smoothens the roughness and removes the porosity, while largely destroying the ordered atomic texture, making the surface more random and more amorphous. The LTIC surface denatures all adsorbed proteins studied. The rate of protein adsorption is high and the surface concentration is large. The LTIC surface adsorbs all proteins without preference. The surface also tenaciously retains proteins such that they cannot be displaced by buffer or exchanged by proteins in solution. We conclude that LTIC accomplishes its blood compatibility through a passivating film of strongly adsorbed bland proteins, which do not interact with platelets nor participate in blood coagulation. We also suggest mechanisms for the production of such a film by the LTIC surface.