兼具干细胞募集能力和成骨诱导功能的微纳结构活性材料的构建及快速成骨机制研究

In combination with bionic principles, development of bioactive scaffolds with bone-mimicking hierarchical structure may offer an effective approach to solving the serious problems faced by conventional bone implants (e.g., mechanical brittleness, low bioactivity and slow bone regeneration rate, and poor osseointegration quality). This project aims to develop robust scaffolds with hierarchichal architecture via infiltrating sponge with a viscous solution of “mesoporous bioactive glass (MBG) sol + MBG fiber + methyl cellulose microspheres”, followed by sinter treatment. The sintered sponge and cellulose microspheres can offer the macro/micro pores in the scaffolds, which together with MBG’s mesopores contribute to formation of their macro/micro/nano- hierarchical architecture. Incorporating MBG fiber in the scaffolds may favor their mechanical reinforcement. On the other hand, stromal-derived factor 1 (SDF-1) and bone morphogenetic protein 2 (BMP-2) will be separately loaded in gelatin-based nanogels which can be fabricated using an emulsion technique, followed by decoration of their surface with alendronate (AL, a specific inhibitor of osteoclast-mediated bone resorption). Then, triple-bioactive-factor scaffolds will be developed through encapsulating the SDF-1 or BMP-2-loaded nanogels into the scaffolds via complexation interactions between their surface calcium ions and the AL’s phosphate groups of the nanogels. The combinative delivery of the multiple bioactive factors can be achieved through structural adjustment of the scaffolds as well as the MMP-2-cleavability of the gelatin-based nanogels. As such, the scaffolds can deliver SDF-1 to acquire an endogenous stem cell recruitment ability to initiate “cell rapid responsiveness” in the early period of bone regeneration. The presence of BMP-2 will guide the osteogenesis of the recruited stem cells, accelerating the process of bone growth as well as blood vascularization. Simultaneously, alendronate delivered from the scaffolds will be useful for adjustment of osteoclast bioactivity and mediate dynamic osseointegration for improvement of regenerated bone quality. This study will not only enlighten a novel approach to exploring bioactive scaffolds with rapid bone regeneration ability, but also provide theoretic and experimental instruction for design and construction of other kinds of tissue engineering materials.

结合仿生原理发展多级微纳结构活性支架有望解决当前材料强度差、活性低、骨再生速度慢、骨整合质量差等突出问题。本项目拟通过将“生物活性玻璃(MBG)溶胶+MBG纤维棒+甲基纤维素微球”的粘性溶液对“海绵模板”均匀浸渍，结合“浸渍-烧结”技术，利用MBG的介孔结构和自增强功能、甲基纤维素微球和海绵的原位烧结成孔效应，构建高强度微纳结构多孔支架。为发展“多因子协同”的活性支架，我们首先采用乳液法制备分别装载趋化因子或骨转化因子、表面修饰阿仑膦酸盐的明胶纳米微球；利用微球表面磷酸根与支架表面钙离子间的络合作用将装载因子的纳米微球与支架复合。通过支架对多因子的时序管理，协同促进趋化因子的干细胞募集功能、骨转化因子的成骨诱导效应，同时利用骨吸收抑制因子阿仑膦酸盐动态调整骨吸收/增长/整合进程，促进快速成骨。本研究将为研制高活性骨修复材料提供新思路，并且为其它组织工程材料的设计和开发提供理论和实验指导。

针对目前临床用各种生物医用材料呈现强度差、活性低、骨再生速度慢等突出问题，本项目通过“原位掺杂MBG纤维棒（MSR）自增强技术”来实现支架的高强度，同时发展了多级微纳结构活性支架。制备的多级微纳结构支架可通过对多因子的时序管理，协同促进趋化因子的干细胞募集功能、骨转化因子的成骨诱导效应，该材料能动态调整骨吸收/增长/整合进程，促进快速成骨。本研究取得了以下创新研究结果：.1)成功合成了尺寸为100-150 nm的装载趋化因子或生长因子的微球或纳米棒，并具备对不同尺寸药物或蛋白具有可控的管理作用的能力。.2)制备了MBR杂化增强的MBG多孔支架，制备出了3-5种介孔为5-20 nm、微孔为10-20 μm和大孔为200-500 μm的多级孔支架材料。建立材料的化学组成和结构与材料力学/降解性之间的关系。.3)评价了支架材料对细胞行为和蛋白表达的协同作用规律和机制，多级微纳结构支架材料具有促进内源细胞募集、成骨诱导、骨整合、及快速成骨等能力。.基于以上成果，多级微纳结构活性支架可为开发出用于快速修复的骨组织修复材料提供新思路，更适于工程制备和实际应用，为我国现有骨组织修复材料的性能和竞争力提供技术支撑，具有良好的临床前景。