Blood compatibility and interaction with endothelial cells of titanium modified by sequential immobilization of poly (ethylene glycol) and heparin

Abstract

In this study, poly(ethylene glycol) (PEG) and heparin were sequentially immobilized on a titanium surface by the carbodiimide covalent coupling method with the aim to improve the blood compatibility of titanium and enhance endothelial cell adhesion and proliferation. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed that PEG and heparin were successfully immobilized on the titanium surface. Compared to the pristine titanium, a highly hydrophilic layer was achieved after the immobilization, and the resulting heparin–PEG layer can significantly prevent human plasma fibrinogen adsorption. Analysis of platelet attachment to the modified surfaces, via scanning electron microscopy (SEM), showed strikingly fewer platelets attached to the PEG and heparin modified surfaces, compared to the control. The immobilized PEG and heparin effectively prolonged the activated partial thromboplastin time (APTT) and inhibit platelet activation significantly. Furthermore, the modified samples showed good cytocompatibility. Endothelial cells exhibited improved proliferative profiles in terms of a CCK-8 assay, as compared to those on the pristine titanium. The modified samples showed a better endothelial cell adhesion and spreading, than the pristine titanium. Therefore, the blood compatibility and cytocompatibility of the titanium surface can be enhanced by PEG immobilization and further, by subsequent heparin grafting. It could be concluded that the negatively charged heparin–PEG layer with excellent hydrophilicity could obviously improve the blood compatibility and enhance the endothelial cell adhesion and proliferation, and the approach of the present study is considered as an effective method to improve the hemocompatibility and cytocompatibility of biomaterials.