Chemical modification of metallic implant surfaces with biofunctional proteins (Part 2). Corrosion resistance of a chemically modified NiTi alloy.

The corrosion resistance of a NiTi alloy, chemically modified with a human plasma fibronectin (pFN) using an aminosilane and a glutaraldehyde, was examined by electrochemical techniques in a 0.9% NaCl solution and a cell culture medium containing serum. The role of serum proteins in influencing the passive behavior of the alloy was extensively studied by anodic polarization and X-ray photoelectron spectroscopy (XPS). The passive current density increased in the presence of serum proteins. The enhanced dissolution of the passive film appears to be a consequence of quick adsorption of the serum proteins and the subsequent formation of metal ion-protein complexes on the film surface. With the chemical modification, the corrosion rate was reduced by approximately 50% in both solutions due to a highly cross-linked siloxane network formed on the alloy surface. This network layer limited the diffusion of dissolved oxygen, metal ions, and biological molecules involved in the corrosion reactions.