Coimmobilization of heparin/fibronectin mixture on titanium surfaces and their blood compatibility

Coimmobilization as a versatile biomodification technique has been widely used in the development of biomimetic materials with superior mechanical and biological properties. In this study, a mixture of heparin and fibronectin (Hep/Fn) was tested for its hemocompatibility after either physisorption or covalent coimmobilization to a titanium (Ti) substrate. The process of substrate activation and film deposition was associated with an increase of roughness; successful immobilization in both cases was demonstrated by FTIR. The immobilized heparin amount was probed by toluidine blue O binding, fibronectin by immunochemistry. Both molecules had slightly higher concentrations on the physisorbed film than after covalent coimmobilization. Plasmatic coagulation activation, tested as activated partial thromboplastin time APTT, and platelet adhesion were significantly improved on the covalently coimmobilized samples than on the physisorbed or blank ones. All these results suggest that the covalent coimmobilization of heparin with fibronectin improved the anticoagulant activity of heparin and caused a favorable blood compatibility. We envisage that this method will provide a potential and effective selection for biomaterials surface modification.