Stainless steel is really interesting in biomedical applications. In contact with biological environment, proteins adsorb on the stainless steel surfaces. The control of the biocompatibility requires knowledge at the molecular level of the biomolecule-surface interaction. We developed a "bottom up" approach of this interaction following three lines of inquiry: Surface complexity: The passive film formed on the stainless steel surfaces is made of chromium and iron oxides and the (0001)-Cr2O3 surface is a good model for the passive film. First, we studied the adsorption of amino acids (AA) on anhydrous Cr2O3 surface. The acidic and basic amino acids interact more strongly with Cr2O3. We highlighted a difference of reactivity between Cr2O3, Fe2O3 and iron enriched Cr2O3 films, incoming from the electronic structure of Cr3+ and Fe3+. Water activity: Hydroxylated surfaces and solid-liquid interface were used. The study of the adsorption of AA on hydroxylated surfaces (outer sphere) and the substitution of -OH groups on these surfaces showed that only amino acids (Glu, Asp) can be adsorbed in inner sphere. The formation of self-assembled layers (outer sphere) is favoured for the hydrophobic amino acids. Size of the biomolecule: In this part, we developed a new methodology to study the adsorption of peptides on well-defined surfaces. This methodology has been applied to the adsorption of the glutamic acid dipeptide Glu2 on Cr2O3. An adsorption by multi-anchoring points (inner sphere) was calculated.
