基于近红外光响应水凝胶的仿生ECM动态微环境的构建及其调控骨髓间充质干细胞骨向分化研究

Hydrogels are widely used biomaterials for bone tissue engineering and regenerative medicine because their similarity to the extracellular matrix (ECM). However, traditional hydrogels often are designed with static properties, and therefore fail to offer the dynamic environments that are important to direct cell behaviors. This proposed project intends to develop dynamic hydrogels that can be modulated by near-infrared light (NIR) to mimic the dynamic environment of natural tissue. In the hydrogel, hyaluronic acid (HA) and gelatin (Gel) are used as the primary structural units, because they are the natural components of the extracellular matrix to support cell growth. A sequential-crosslinking route was employed to in situ alter the mechanical properties of the hydrogel in the presence of cells under control of biocompatible near infrared light. For this purpose, acrylate-modified gelatin (Gel-MA), propiolic acid-modified gelatin (Gel-PA), acrylate-modified hyaluronic acid (HA-MA), and azido-modified hyaluronic acid (HA-AA) are obtained. Polydopamine-polyisopropylacrylamide (PNIPAM@PDA) core-shell nanoparticles are also incorporated into the hydrogel to serve as the growth factor carriers and NIR responsive agents...First, hydrogels with uniform mechanical properties are obtained via a free radical polymerization of Gel-MA and HA-MA. Second, the initial hydrogel is exposed under NIR irradiation. Thus, PNIPAM@PDA nanoparticles with the high photothermal efficiency will lead to the increase of temperature in the local hydrogel. The increased temperature will initiate the click reaction between Gel-PA and HA-AA, and then the hydrogel could be further crosslinked and stiffened. At the same time, the increased temperature leads to the shrink of PNIPAM layer to release growth factors. The crosslinking density and the release kinetics of growth factors can be controlled at a user-defined time of near-infrared light, resulting in dynamic physical and biochemical properties to the hydrogel...In summary, the hydrogel creates a dynamic microenvironment that can provide dynamic biochemical and biophysical signals to modulate cellular functions and induce osteogenic differentiation. Such a proposed strategy to prepare dynamic hydrogel are expected to be generalized to develop new biomaterials that recapitulate the unique dynamic features of native extracellular matrix (ECM) and direct multistep biological processes. The results of the project will reveal the mechanism of the cell-material interactions, and provide theoretical guidance for the development of biomaterials for tissue engineering and regenerative medicine.

水凝胶作为骨组织工程支架已成为再生医学研究的热点。然而传统的水凝胶，其物理、生化性能随时间保持相对静态，无法根据细胞生长需求发生相应的动态改变。本项目以双键化明胶、炔基化明胶、双键化透明质酸、叠氮化透明质酸为主体成分，复合具有近红外光响应的聚多巴胺-聚异丙基丙烯酰胺核壳纳米颗粒作为生长因子的载体，通过自由基聚合制备基于近红外光调控的动态水凝胶。该水凝胶能够在近红外光辐照下，发生时序交联改变机械性能，为细胞生长创造动态力学微环境；同时近红外光调控水凝胶中生长因子的程序式释放，实现细胞生长分化过程中生长因子在时空上的合理施用。项目的预期结果将阐明水凝胶机械性能变化传递的动态力学信号、时序释放的生长因子传递的生化信号、及近红外光产生的物理效应三者协同诱导细胞骨向分化的机制，为设计仿生细胞外基质时空复杂性的生物材料提供理论支持和科学依据，对于理解细胞-材料相互作用、推动骨修复材料发展具有重要意义。

水凝胶作为组织修复支架已成为再生医学研究的热点。然而传统的水凝胶，其物理、生 化性能随时间保持相对静态，无法根据细胞生长需求发生相应的动态改变。本项目以功能化天然高分子丝素和壳聚糖为水凝胶主体成分，在其中复合具有近红外光响应的聚多巴胺纳米颗粒，并在水凝胶中负载生长因子，制备具有近红外响应性的水凝胶。该水凝胶能够响应近红外光辐照，创造有利于组织再生仿生微环境；同时近红外光产生的物理刺激也能够促进组织再生。考察了在近红外光照下，水凝胶组分的比例与纳米颗粒的光热转换效率；考察了纳米颗粒包封对生长因子的固载效率，揭示了生长因子在水凝胶中的释放动力学与释放机理。研究了有近红外光辐照下，水凝胶对细胞粘附、增殖作用规律。阐明水凝胶支架构建的仿ECM微环境、生长因子释放引发的生物学化学变化、以及近红外光产生的物理效应三者的协同作用调控细胞行为的机制，进一步了解动态仿生微环境与细胞/组织的相互作用机理，从而为促进外场协同水凝胶支架促进组织再生提供了科学依据，对于理解细胞-材料相互作用、推动组织修复材料发展具有重要意义。