Heparin Contained Multilayer Composite Coatings on NiTi Alloy for Cardiovascular Stents

• Main Authors: Po-Yin Cheng, 鄭博尹
• Other Authors: Shiow-Kang Yen
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/01856005936605595944

碩士 === 國立中興大學 === 材料科學與工程學系所 === 100 === Although the initial success of bare metal stents (BMS) has significantly reduced the restenosis rate from 35% for Percutaneous transluminal coronary angioplasty (PTCA) to 25%, the biological mechanism such as smooth muscle cell proliferation and neointimal hyperplasia may still induce in-stent restenosis (ISR). Therefore, some drug eluting stents have been introduced to reduce ISR. In this study, heparin (Hep) combined with calcium phosphate (CaP) and gelatin (Gel) is co-deposited on NiTi alloy in order to promote the hemocompatibility of NiTi substrate and fabricate the sustained heparin releasing system. Polarization tests are carried out in several solutions to investigate deposition mechanisms. Heparin contained composite coatings are characterized by X-ray diffractometry (XRD), Field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), toluidine blue colorimetric assay, UV-visible spectrometer and kinetic clotting tests. The consequences indicate that heparin accompanied with CaP, and Gel through ionic bonds can be loaded on the NiTi alloy, respectively. The porous post HA coating can enhance drug content from 147.06±68.66 μg/cm2 of single layer coating (CaP-Hep) to 191.58±11.87 μg/cm2 of bilayer coating (HA/CaP-Hep) and further to 324.87±4.94 μg/cm2 of trilayer coating (HA/CaP-Hep/Gel-Hep) by adding the third layer which also results in the in vitro heparin release prolonging from 1 day burst to more than 35 days sustaining. As the result of clotting tests, drug loaded composite coatings reveal good anticoagulant property which is proportional to the cumulative content of drug release in an hour, indicating no denaturalization of heparin found during the electrochemical process.