Facile Surface Modification of Nitinol with Dopamine-Conjugated Hyaluronic Acid for Improving Blood Compatibility

Abstract

Nitinol (NiTi) has been used in a wide range of medical applications, specifically endovascular devices such as catheters, stents, and superelastic needles due to their unique mechanical properties and shape memory behavior. However, there have been still limitations because of the poor blood compatibility of NiTi which causes thrombogenicity and platelet activation and aggregation. In this study, the surface of NiTi substrates was modified by grafting dopamine-conjugated hyaluronic acid (HADA) to improve blood compatibility of NiTi. HADA conjugates were synthesized by carbodiimide coupling reaction and characterized using H-1-NMR, ATR-FTIR, and UV spectrometers. HADA conjugates with different concentrations (1, 4, and 8 mg/mL) were immobilized on NiTi surfaces at pH 8.5, indicating an oxidation of dopamine. The physico-mechanical properties of hyaluronic acid immobilized NiTi (NiTi/HADA) substrates were analyzed with FE-SEM, water contact angle, XPS, AFM, and micro BCA assay. The blood compatibility results showed that not only protein adsorption but also platelet adhesion on NiTi/HADA substrates were reduced, compared with bare NiTi control. Also, their proper cytocompatibility was confirmed using Live/Dead assay with human umbilical vein endothelial cells. The obtained results demonstrate that NiTi/HADA substrates would be promising for blood-contacting medical applications including stents, vena cava filters, and atrial septal defect closure devices.