Surface characterization of insulin-coated Ti6Al4V medical implants conditioned in cell culture medium: An XPS study

Highlights: • In the absence of FBS, chemically immobilized insulin layer remains intact; • The immobilized insulin expose hydrophobic domains outward the implant; • In the presence of FBS, a partial replacement of insulin occurs; • The immobilized insulin stabilizes the secondary structure of adsorbed proteins. - Abstract: Surface characterization of insulin-coated Ti6Al4V medical implants, after incubation in α-minimum essential medium (α-MEM), was done by X-ray photoelectron spectroscopy (XPS), in order to analyze the insulin behavior at the implant – α-MEM interface. In the absence of serum proteins in cell culture medium, the coated insulin layer remained intact, but experienced a time-dependent structural transformation exposing hydrophobic parts of the protein toward the solution. The presence of fetal bovine serum (FBS) in the medium resulted in partial substitution of insulin by serum proteins. In spite of some insulin release, the remaining coated layer demonstrated a direct surface effect by stabilizing the structure of protein competitors, and by supporting the accumulation of calcium and phosphate ions at the interface. A structurally stable protein layer with incorporated calcium and phosphate ions at the implant–tissue interface could be an important prerequisite for enhanced bone formation.