Surface biofunctionalization by covalent co-immobilization of oligopeptides.

Functionalization of implants with multiple bioactivities is desired to obtain surfaces with improved biological and clinical performance. Our objective was developing a simple and reliable method to obtain stable multifunctional coatings incorporating different oligopeptides. We co-immobilized on titanium surface oligopeptides of known cooperative bioactivities with a simple and reliable method. Appropriately designed oligopeptides containing either RGD or PHSRN bioactive sequences were mixed and covalently bonded on CPTES-silanized surfaces. Coatings made of only one of the two investigated peptides and coatings with physisorbed oligopeptides were produced and tested as control groups. We performed thorough characterization of the obtained surfaces after each step of the coating preparation and after mechanically challenging the obtained coatings. Fluorescence labeling of RGD and PHSRN peptides with fluorescence probes of different colors enabled the direct visualization of the co-immobilization of the oligopeptides. We proved that the coatings were mechanically stable. The surfaces with co-immobilized RGD and PHSRN peptides significantly improved osteoblasts response in comparison with control surfaces, which assessed the effectiveness of our coating method to bio-activate the implant surfaces. This same simple method can be used to obtain other multi-functional surfaces by co-immobilizing oligopeptides with different targeted bioactivities--cell recruitment and differentiation, biomineral nucleation, antimicrobial activity--and thus, further improving the clinical performance of titanium implants.