Biocompatible PEG Grafting on DLC-coated Nitinol Alloy for Vascular Stents

Hong-Sub Shin, Kwideok Park, Ji Heung Kim, Jae-Jin Kim, and Dong Keun Han, Myoung-Woon Moon, Kwang-Ryeol Lee, Ji Hoon Shin
 

The surface of Nitinol (TiNi), a popular metal alloy for arterial stents, was thin-coated with diamond-like carbon (DLC) and then grafted with the hydrophilic poly(ethylene glycol) (PEG) to increase its biocompatibility. The reactive isocyanated PEG was synthesized through a two-step processing using hydrophilic PEG. Along with TiNi control and DLC-coated TiNi (TiNi-DLC), the PEG-grafted TiNi-DLC (TiNi-DLC-PEG) was subjected to the evaluation of surface characteristics and biocompatibility. The hydrophilicity of the TiNi-DLC-PEG significantly increased and the atomic percents of both oxygen and nitrogen on the TiNi-DLC-PEG also increased as compared to those of TiNi control and TiNi-DLC by means of the grafted PEG. Tested with human blood components, the ratio between albumin and fibrinogen was higher in the PEG-grafted surface than the other samples, and platelet adhesion was found decreased the most on the surface of TiNi-DLC-PEG, as an indicative of improved blood compatibility. For in vivo test, the implanted samples for 6 weeks formed fibrous tissues around them but the thickness was much thinner for the PEG-grafted sample than other ones. The present results suggest that PEG-grafted TiNi-DLC surface may be effective in enhancing biocompatibility of bloodcontacting biomaterials including vascular stents.