Aldenhoff Y B, Koole L H
Biomaterials and Polymer Research Institute Maastricht-Eindhoven (Bioprime), University of Limburg, The Netherlands.
J Biomed Mater Res. 1995 Aug;29(8):917-28. doi: 10.1002/jbm.820290803.
A new methodology to improve the hemocompatibility of polyurethane (medical grade Pellethane D-55) surfaces is reported. The approach is essentially based on a photochemical immobilization reaction. Two new conjugate molecules, compounds 2 and 3, were prepared. They consist of (i) dipyridamole, a well-known inhibitor of platelet activation, and a vasodilating drug with clinical application, for instance before and during pecutaneous transluminar coronary angioplasty (Dottering); and (ii) an aryl azide, a moiety that exhibits marked photoreactivity. In 2, the dipyridamole unit is directly linked to the aryl azide (via an ester bond), while a short spacer chain separates both units in 3. Upon irradiation of 2 or 3, adsorbed onto the polyurethane foil, the aryl azide is converted into a highly reactive species which reacts with a nucleophilic group on the polymer surface. In this way, the dipyridamole is covalently linked to the polymer. The underlying principle is also used in photoaffinity labeling, a well-known technique in biochemical studies on enzyme structure and function. From UV extinction experiments it could be deduced that the surface-density of immobilized 2 is 4.9 nmol/cm2. The surface density for 3 was 14.6 nmol/cm2. The surfaces were subjected to an in vitro thrombin generation assay. This assay gives a valuable impression about the hemocompatibility of artificial surfaces. These experiments revealed that the clotting times were substantially prolonged as a result of the photoimmobilization of dipyridamole. This was especially the case for immobilized 3. This effect cannot be readily explained. Possibly, the enhanced activity of immobilized 3 is due to the spacer chain. An alternative explanation is that the surface density is larger for 3 than for 2. In addition, the photomodified surfaces were incubated with platelet-rich blood plasma (37 degrees C, 30 min) and subsequently examined by scanning electron microscopy. The morphology of the blood platelets adhered to the surface also showed that hemocompatibility increased in the order untreated polyurethane < polyurethane with immobilized 2 < polyurethane with immobilized 3. Future work will concentrate on evaluation of the role of the spacer (length, hydrophilicity, etc.), as well as on the possible use of this approach with respect to the construction of biomaterials with improved in vivo biocompatibility, in particular hemocompatibility.
报道了一种改善聚氨酯（医用级聚醚氨酯D - 55）表面血液相容性的新方法。该方法主要基于光化学固定反应。制备了两种新的共轭分子，即化合物2和化合物3。它们由（i）双嘧达莫组成，双嘧达莫是一种著名的血小板活化抑制剂，也是一种具有临床应用价值的血管舒张药物，例如在经皮腔内冠状动脉成形术（Dottering）之前和期间使用；以及（ii）芳基叠氮化物，该部分具有显著的光反应活性。在化合物2中，双嘧达莫单元通过酯键直接与芳基叠氮化物相连，而在化合物3中，两个单元由一个短的间隔链隔开。当吸附在聚氨酯箔上的化合物2或化合物3受到光照时，芳基叠氮化物会转化为一种高活性物种，该物种会与聚合物表面的亲核基团发生反应。通过这种方式，双嘧达莫与聚合物共价连接。该基本原理也用于光亲和标记，这是生物化学研究中关于酶结构和功能的一种著名技术。从紫外消光实验可以推断，固定化的化合物2的表面密度为4.9 nmol/cm²。化合物3的表面密度为14.6 nmol/cm²。对这些表面进行了体外凝血酶生成测定。该测定能让人对人工表面的血液相容性有一个有价值的认识。这些实验表明，由于双嘧达莫的光固定作用，凝血时间显著延长。对于固定化的化合物3来说尤其如此。这种效应难以轻易解释。可能是固定化的化合物3活性增强是由于间隔链的作用。另一种解释是化合物3的表面密度比化合物2大。此外，将光改性表面与富含血小板的血浆在37℃下孵育30分钟，随后通过扫描电子显微镜进行检查。附着在表面的血小板形态也表明，血液相容性按未处理的聚氨酯＜固定化化合物2的聚氨酯＜固定化化合物3的聚氨酯的顺序增加。未来的工作将集中于评估间隔链（长度、亲水性等）的作用，以及这种方法在构建具有改善的体内生物相容性，特别是血液相容性的生物材料方面的可能应用。
