面向具有原位成骨活性植入材料制备的表面引发蛋白印迹聚合研究

Currently, implantation of orthopedic prostheses such as artificial joints and interbody cages may be associated with many complications including loosening and dislocation, which eventually lead to failure of prostheses. Therefore, the next generation of orthopaedic implants should possess excellent osteogenic activity in order to enhance the integration of implant and host bone tissue. Immobilizing the bone morphogenetic protein 2 (BMP-2) at the surface of implants appears to be an effective approach toward this goal. However, its application is largely limited as a result of the rapid activity loss and complications of recombinant BMP-2. Recently, we and other groups have found that endogenous BMP-2 can be immobilized at the bone defect area by BMP-2 antibody to promote bone repair. Our previous studies have also shown that protein imprinted polymers possess excellent affinity and specific recognition ability toward template protein molecules, and can therefore be used for identifying and capturing that protein. Therefore, the proposed study aims to improve the osteogenic activity of orthopedic implants through the combined use of surface-initiated living polymerization and molecular imprinting technologies. A layer of imprinted polymers containing specific recongnition sites toward BMP-2 will be immobilized on the surface of titanium alloy in a controllable fashion. Then the imprinted titanium will be tested both in vitro and in vivo to evaluate its efficacy of capturing BMP-2. Ultimately, a novel type of orthopaedic implants is expected to be developed, which will be capable of capturing and enriching highly effective endogenous BMP-2 in-situ, thereby promoting new bone formation consistently. Upon successful completion, this study will bring in an innovative approach toward bioactive surface functionalization of materials. It will also provide a solid foundation for further development of smart implants with stable and continuous biological functionalities.

鉴于目前骨科植入物如人工关节、椎间融合器可能因固定松动导致假体失效，新一代植入材料需表面能诱导成骨，以增强骨组织与假体界面骨性结合。在材料表面固定骨形态发生蛋白-2（BMP-2）是可行方案，但受限于外源性BMP-2易失活和副作用多。近期发现，高效的内源性BMP-2可在骨缺损部位被相应抗体识别并富集，促进骨修复。同时，我们已证实分子印迹聚合物对模板蛋白分子具有特异性识别能力，能可逆捕获与释放该蛋白。据此，本项目以提高材料成骨活性为目标，通过结合表面引发的活性聚合与分子印迹技术，在钛合金表面可控固定含BMP-2识别位点的印迹聚合物薄层，通过体内外试验考察其捕获BMP-2的效率。最终可望发展一类可在体内"原位"选择性富集内源性BMP-2、从而获得稳定成骨活性的新型骨科植入材料。这一基于分子印迹技术的材料表面功能化新理念的成功实施，将为开发具有持续生物活性的植入材料提供理论基础和实践依据。

项目背景：骨科植入物因固定松动可导致假体失效， 因此要求植入材料表面能诱导成骨，以增强界面骨性结合。本项目致力于在钛表面制备骨形态发生蛋白（BMP-2）分子印迹层，通过原位富集内源性生长因子促进植入物表面骨再生，增强其与骨组织之间的整合。同时，基于通过材料表面功能化手段促进骨整合和在体募集干细胞/生物因子以促进骨再生这一思路，我们还开发了多种方法和材料，有效促进骨整合与骨缺损修复。.主要研究内容与重要结果：我们探索了不同方法在二氧化钛表面形成分子印迹层，得到具有较高吸附量和选择性的分子印迹材料，对复杂蛋白混合物中的目标蛋白具有特异性识别效果。以壳聚糖微球作为载体，在表面制备BMP-2印迹层，以探讨其体内富集生长因子和促骨再生能力。利用聚多巴胺涂层在壳聚糖微球表面装载CD271抗体，在体外成功实现对骨髓间充质干细胞（BMSC）捕获和筛选，以及在体内原位募集BMSC，促进骨缺损修复。还发现药物分子Kartogenin募集BMSC效果明显，同时可诱导BMSC发生成骨分化。通过聚多巴胺辅助沉积法得到了表面含银和铜涂层的骨植入材料，具有良好抗菌性能，且能在感染环境下促进假体周围骨形成。此外，通过在复合支架中负载二甲基草酰甘氨酸，有效促进血管生成，提高新骨形成效率。 .关键数据及其科学意义：本项目开发了多种表面功能化技术，获得能在体内募集干细胞或生物因子、具有成骨活性的新型骨科植入材料，为开发具有持续生物活性的功能生物材料提供理论基础和实践依据。 .项目执行期间发表论文16篇（其中SCI论文15篇），参编专著3部，获授权发明专利2项，申请1项。项目团队在国内外学术会议上做特邀报告10 次(Keynote 报告4次)、口头报告4次，获研究生奖励4次。