Oxidized dopamine as the interlayer between heparin/collagen polyelectrolyte multilayers and titanium substrate: An investigation of the coating's adhesion and hemocompatibility

To improve the adhesion and blood-compatibility of the titanium substrate coated with heparin/collagen multilayers, an oxidized dopamine was applied as the interlayer between the multilayers and the substrate. The oxidation condition of the dopamine interlayer was achieved by treating the dopamine solution under an atmospheric environment for 8 h. A dopamine interlayer built in a pure nitrogen environment was used as a benchmark. 4 and 9 multilayers were also built and studied for both samples. The film thickness was evaluated by the cross-sectional technique of focused ion beam microscopy. The hydrophilicity and surface topography of the films were investigated by water contact angle measurement and scanning electron microscopy. The adhesion of the multilayers was studied with scratch tests. The amount of heparin that attached to the samples was measured by toluidine blue O test. The hemocompatibility was verified by the platelet coverage area, activated partial thromboplastin time, and hemolysis ratio in vitro. The results indicated that the oxidized dopamine not only enhanced the uniformity and thickness of heparin/collagen multilayers on a titanium substrate but also promoted the sample's adhesion and hemocompatibility, especially that with a larger number of multilayers.