Grafting and Characterization of Zwitter Ionic Poly(ethylene glycol) on Gold-Coated Nitinol Surface Chemisorbed with L-Cysteine

Abstract

Nitinol alloy (TiNi) has been widely used in vascular stents. To improve the blood compatibility of Nitinol alloy, its surface was chemically modified in this study. Nitinol was first coated with gold. then chemisorbed with L-cysteine (C/N), and followed by grafting of zwitter ionic poly(ethylene glycol) (PEG) (PEG-N+-SO3-) to produce TiNi-C/N-PEG-N-S. The zwitter ionic PEG grafted on the Nitinol surface was identified by ATR-FTIR, ESCA and SEM. The hydrophilized surface was proven by the decrease of water contact angle. In addition, from the blood compatibility tests such as protein adsorption, platelet adhesion, and blood coagulation time, the surface-modified TiNi alloy exhibited a better blood compatibility as compared to the untreated Nitinol control. These results indicated a feasibility of synergistic effect of hydrophilic PEG and antithrombotic zwitter ion.