Improving blood-compatibility of titanium by coating collagen–heparin multilayers

This work deals with improving the blood-compatibility of titanium by coating it with heparin (Hep) and collagen (Col) using a layer-by-layer (LBL) self-assembly technique. In the work described here, LBL-produced Hep–Col film growth is initialized by deposition of a layer of positively charged polyl-Lysine (PLL) on a titanium surface, which is negatively charged after treatment with NaOH, followed by formation of a multilayer thin film formed by alternating deposition of negatively charged heparin and positively charged collagen utilizing electrostatic interaction. The chemical composition, wettability, surface topography, mass and thickness of the film were investigated by Fourier transform infrared spectroscopy, water contact angle measurement, scanning electron microscopy, atomic force microscopy, electronic analytical semi-microbalances, and XP stylus profilometry. The in vitro platelet adhesion and activation were investigated by a static platelet adhesion test probing the lactate dehydrogenase (LDH) release of adherent platelets after lysis and by a P-selectin assay. The clotting time was examined by activated partial thromboplastin time (APTT) and prothrombin time (PT) assays. All obtained data showed that the LBL film can significantly decrease platelet adhesion and activation, and prolong clotting time of APTT and PT compared to untreated titanium. LBL-produced Hep–Col films on titanium display more excellent anticoagulation performance than on the surface of titanium.