Biomaterials Center, Korea Institute of Science and Technology, P. O. Box 131, Cheongryang, Seoul, 130-650, Korea.
J Mater Sci Mater Med. 2011 Mar;22(3):507-14. doi: 10.1007/s10856-011-4235-5. Epub 2011 Jan 30.
Blood compatibility is the most important aspect for blood-contacting medical devices including cardiovascular stents. In this study, the surface of nickel-titanium (TiNi) stent was coated with diamond-like carbon (DLC) and then subsequently grafted by using zwitterion (N(+) and SO(3) (-))-linked poly(ethylene glycol) (PEG). We hypothesize that this coupling of zwitterion and PEG may significantly improve blood compatibility of DLC-coated TiNi stent. The surface modified TiNi stents, including PEG-grafted stent (DLC-PEG) and zwitterionic PEG-grafted one (DLC-PEG-N-S) were the main focus on the tests of surface characteristics and blood compatibility. The zwitterionic PEG derivatives were obtained from a series of chemical reactions at room temperature. The results exhibited that as compared to the DLC-PEG, the hydrophilicity was much better with DLC-PEG-N-S and significantly increased atomic percentage of oxygen and nitrogen proved the entity of zwitterions on the surface of DLC-PEG-N-S. Meanwhile, the adsorption of blood proteins such as, human serum albumin (HSA) and fibrinogen was found considerably down-regulated in DLC-PEG-N-S, due mainly to the protein-repellent effect of PEG and zwitterion. Microscopic observation also revealed that as compared with the other substrates without zwitterion, the degree of platelet adhesion was the lowest with DLC-PEG-N-S. In addition, DLC-PEG-N-S retained an extended blood coagulation time as measured by activated partial thromboplastin time (APTT). The present results suggested that surface grafting of zwitterionic PEG derivatives could substantially enhance the blood compatibility of TiNi-DLC stent. In conclusion, anti-fouling properties of PEG and zwitterions are expected to be very useful in advancing overall stent performance.
血液相容性是包括心血管支架在内的与血液接触的医疗器械最重要的方面。在这项研究中，镍钛（TiNi）支架的表面涂覆了类金刚石碳（DLC），然后通过使用两性离子（N(+) 和 SO(3) (-))-连接的聚乙二醇（PEG）接枝。我们假设这种两性离子和 PEG 的偶联可能会显著提高 DLC 涂层 TiNi 支架的血液相容性。表面改性的 TiNi 支架，包括接枝 PEG 的支架（DLC-PEG）和两性离子接枝的 PEG（DLC-PEG-N-S），是表面特性和血液相容性测试的主要关注点。两性离子 PEG 衍生物是在室温下通过一系列化学反应获得的。结果表明，与 DLC-PEG 相比，DLC-PEG-N-S 的亲水性更好，并且氧和氮的原子百分比显著增加，证明了两性离子在 DLC-PEG-N-S 表面的存在。同时，发现 DLC-PEG-N-S 对人血清白蛋白（HSA）和纤维蛋白原等血液蛋白的吸附明显下调，这主要归因于 PEG 和两性离子的蛋白质排斥作用。显微镜观察还表明，与没有两性离子的其他基底相比，血小板黏附程度在 DLC-PEG-N-S 中最低。此外，DLC-PEG-N-S 通过激活部分凝血活酶时间（APTT）测量保留了延长的凝血时间。目前的结果表明，表面接枝两性离子 PEG 衍生物可以显著提高 TiNi-DLC 支架的血液相容性。总之，PEG 和两性离子的抗污性能有望在提高整体支架性能方面非常有用。
