Creation of High Performance Biocompatible Surface by Surface modification agent which Constructs High Density Tethered Chains

我们合成了几种类型的亲水-疏水嵌段共聚物，由于嵌段共聚物的自组装，它们在水介质中形成了超分子纳米结构。例如，聚乙二醇/聚丙交酯嵌段共聚物在水介质中形成球形的核壳型聚合物胶束，其尺寸为20-40 nm。胶束的壳层是由链状聚乙二醇链构成的，由于热力学平衡，聚乙二醇链的密度原则上很高，我们研究的目的是构建聚合物胶束覆盖表面。如果表面被致密的球形聚合物胶束覆盖，系链链的密度应该比传统的刷链表面高得多。其中之一是聚(甲基丙烯酸2-羟乙酯)-b-聚烷基硅基苯乙烯(HA)嵌段共聚胶束。通过将这种聚合物胶束浇注在衬底表面，胶束密集地吸附在表面上。对改性后的表面进行了血小板粘附性研究。羟基磷灰石胶束修饰表面的粘附性比天然基质和聚(HEMA)表面的粘附性都受到明显的抑制。另外，合成了聚乙二醇链末端含醛基团、聚乳酸链端含甲基丙烯酰基的聚乙二醇/聚乳酸嵌段共聚物。所述嵌段共聚物在水介质中形成表面带有醛基团的核壳型聚合物胶束。核中的甲基丙烯酰基可以自由基聚合形成不解离的胶束。在含有伯氨基的底物表面，通过还原胺化反应对醛-胶束进行共价修饰。所得表面具有极高的聚合物胶束密度和极高的无污垢特性，这些类型的高度系链表面有望成为新型生物相容性表面改性剂。

We have synthesized seceral types of hydrophilic-hydrophobia block copolymers which forms supramolecular nanostructure in aqueous media due to the self-assembly of the block copolymers. For example, poly(ethylene glycol)/poly(lactide) block copolymer forms spherical core-shell type polymeric micelle in aqueous media, the size of which was 20-40 nm. The shell of the micelle was constructed by tethered PEG chains, whose density was very high in principle because of the thermodynamic balance.The objective of our study was to construct polymer micelle covered surface. If the surface was covered by spherical polymer micelles densely, the density of tethered chains should be much higher that conventional brushed chain surface.We prepared two types of polymer micelle. One of them is poly(2-hydroxyethyl methacrylate)-b-poly(alkylsilylstyrene) (HA) block copolymer micelle. By casting this polymer micelle on the substrate surface, the micelle adsorbed on the surface densely. Platelet adhesion to the modified surface was investigated. The adhesion on the HA-micelle modified surface was mush suppressed than that of not only native substrate but also poly(HEMA) surface. Entropy elastic effect of dense tethered chain may be the reason for this phenomena.Alternately, PEG/PLA block copolymers possessing aldehyde group at PEG chain end and methacryloyl group at PLA chain end was prepared. The block copolymer in aqueous media forms core shell type polymer micelle possessing aldehyde groups on the surface. The methacryloyl group in the core could be polymerized radically to form non dissociative micelle. To a primary-amino containing substrate surface, the aldehyde-micelle was modified covalently via reductive amination reaction. The obtained surface was very dence in polymer micelle and extremely high non-fouling character.These types of highly tethered chain surface was anticipating as new biocompatible surface modification agents.