多元骨生长因子程序控释系统的构建及其促成骨作用研究

In bone tissue engineering, growth factors (GFs) played an important role in cell proliferation, differentiation and bone formation. However, the application of bone growth factor was highly limited by the high cost, short biological half-lives, and easily to be deactivated. GFs that are provided exogenously in solution are generally not effective because GFs tend to diffuse away from wound locations and are enzymatically digested or deactivated, and the excess concentration of GFs will cause toxicity and carcinogenesis. To spatiotemporally control the dose, sequence and profile of release of GFs so as to regulate cellular fates during tissue regeneration, we aimed to design a gelatin@Hydroxyapatite@gelatin (Gel@HA@Gel) system which shows sequential release of multiple GFs with independently tunable kinetics, to mimic the natural microenvironments of bone tissue formation and improve the success of bone tissue regeneration at different stages. Core-shell structured composite Gel@HA@Gel will be fabricated through a sol-gel method, for the delivery of three GFs at an optimised ratio, each at a physiological dose, in a specific spatiotempral pattern. The release profile of a GF can be altered by manipulating the cross-linking degree of gelatin, the thickness and porosity of HA shell, and the immobilization methods of GFs. The delivery system will be further employed for promoting the cell-mediated mineralization and in vivo bone formation. Research on this concept will begin to harness advances in the development of sophisticated GFs delivery platforms and could improve the widely applications of bio-inspired smart materials in bone tissue engineering.

在骨组织工程中，生长因子在细胞的诱导分化以及骨生成过程中起着关键的作用。然而，骨生长因子代价昂贵、半衰期短、容易变性，局部给药后容易扩散，会因为酶的作用失活，而过量使用则具有潜在的毒性和致癌作用。为了有效发挥骨生长因子的适时、适量效用，本项目拟构建基于明胶@羟基磷灰石@明胶(Gel@HA@Gel)纳米复合材料的仿生化多元骨生长因子控释体系，从而模拟自然成骨过程中的微环境变化，使各种骨生长因子在不同环节上参与不同时期骨生长代谢的调节。首先利用溶胶-凝胶法合成“核壳”结构的Gel@HA@Gel作为生长因子的载体。其次，通过调节Gel的交联度、HA层的厚度和孔隙度、生长因子负载方式实现对于三种生长因子的独立可控性释放。最后通过细胞和动物试验考察程序控释系统的促成骨作用。本研究将为复杂的多元程序释放系统的设计提供新的材料和相关理论基础，有望推动智能化仿生支架材料在骨组织工程中的广泛应用。

生长因子在细胞的诱导分化以及骨生成过程中起着关键的作用，而过量的生长因子则具有潜在的毒性和致癌作用。本项目主要设计合成纳米材料作为生长因子的载体,通过控制纳米材料的结构实现多个生长因子的控制释放。在研究生长因子的释放动力学过程中，我们发现对于生长因子的定量检测存在较大误差，所以对于生长因子的准确定量检测是本项目首先需要解决的关键技术。因此, 我们构建了一系列基于纳米材料的光电传感器，通过核酸适配体与生长因子的识别作用引起光电流信号的变化，从而实现了生长因子的高灵敏定量检测，检测限达到3 fM，为生长因子控释体系中释放动力学的进一步研究奠定了良好的基础。同时，传感器亦可用于生长因子过量表达引起的相关癌症的检测。本项目提出的传感器构建策略对于其他目标物的光电传感器的设计也具有重要的指导意义，有望在分析检测、疾病诊断等领域得到实际应用。