Role of phosphate, calcium species and hydrogen peroxide on albumin protein adsorption on surface oxide of Ti6Al4V alloy

Protein adsorption and its conformational arrangements on the surface of metallic biomaterials directly influence the biocompatibility and the degradation process during the implant lifetime. However, the presence of various species such as phosphates, calcium and hydrogen peroxide (H₂O₂) in the human body not only control the electrochemical interactions on the biomaterial surface but could also modify the protein adsorption process and its impact on the metal degradation. To this aim bovine serum albumin (BSA) protein adsorption, morphology, surface potential and its impact on the corrosion resistance of a Ti6Al4V alloy was investigated in different solutions, including a sodium chloride (NaCl), a phosphate-buffered saline (PBS) and Hank's physiological solutions. The results indicated that the alloy in PBS solution was more resistant to corrosion than that in Hanks’ or NaCl solutions. Mott–Schottky analysis demonstrated that all solutions containing BSA and H₂O₂ had the highest donor charge carrier. Scanning electron microscopy (SEM) and surface potential images indicated that by changing the physiological solutions from NaCl to PBS and then to Hanks’, the morphology of adsorbed BSA protein changed from a globular or unfolded shape to a large micronetwork and then to a fine micro-nanonetwork, accompanied by a gradual increase in the surface potential. Moreover, it was figured out that the BSA protein/substrate interface and the top surface of the BSA protein were susceptible to corrosion initiation owing to the different surface potentials and thus are preferable sites for the adsorption of corrosive counterions, e.g., Cl⁻.