基于胶原自组装性能与氧化CMC/纳米ZnO的调控作用协同构建高强度水凝胶及其构效关系研究

Collagen hydrogel is widely used in tissue engineering due to its excellent biological properties and swollen three-dimensional network structure. In general, chemical cross-linking is adopted to improve the mechanical strength, thermal stability and anti-enzymolysis of collagen hydrogel. However, the mechanical strength of the collagen hydrogel only depending on cross-linking has so far not been adequate for the application in scaffold materials. Aiming at this problem, the cross-linking bonds and nano zinc oxide (ZnO) were introduced into collagen system to obtain hydrogels with high mechanical strength. In this project, a series of oxidized carboxymethyl cellulose (OCMC) with different oxidization degrees are prepared as cross-linking agent for collagen and dispersant for ZnO. The effect of oxidation degrees and amounts of OCMC on the structure and properties of collagens and the dispersion of ZnO are investigated. Then the homogeneous ternary compound systems (COL/OCMC/ZnO) are prepared via adding OCMC/ZnO into collagen solutions, and the interactions among collagen, OCMC and ZnO are discussed. Furthermore, it is expected that the collagen hydrogels with high mechanical strength can be constructed by the synergism of collagen self-assembly and OCMC/ZnO regulation. Moreover, the structure-activity relationships between the microstructures and macro-properties of COL/OCMC/ZnO hydrogels could be obtained via studying the effect of the amounts and addition sequences of OCMC/ZnO on the aggregation structure and properties of collagen hydrogels, which are useful for the controllable preparation of collagen hydrogels with high mechanical strength.

胶原（COL）水凝胶具有良好生物学性能且具有可高度膨胀的立体网状结构，广泛应用于组织工程。纯胶原水凝胶的力学性能和热稳定性差、降解速率快，常引入交联键弥补这些缺陷。然而，仅依靠交联制得水凝胶的力学性能仍不满足支架材料的要求。针对此问题，本项目拟将交联键和纳米ZnO同时引入胶原体系，达到协同增强增韧效果，以期获得高强度水凝胶。首先制备不同氧化度的氧化羧甲基纤维素（OCMC）作为胶原交联剂与ZnO分散剂，并考察OCMC氧化度、用量对胶原结构、性能及ZnO分散性的影响。在此基础上，将OCMC、ZnO同时引入胶原溶液制备均一的COL/OCMC/ZnO体系并探究三者之间的相互作用，进而借助胶原自组装性能与OCMC/ZnO调控作用协同构建高强度水凝胶；重点考察OCMC/ZnO用量、加入顺序对水凝胶聚集态结构、力学强度等性能的影响规律，建立水凝胶微观结构与宏观性能的构效关系，实现高强度水凝胶的可控制备。

胶原是动物体内含量最为丰富的一种蛋白质，具有低抗原性、良好生物相容性、凝血作用、促进细胞增殖生长等优异的生物学性能，因此广泛应用于组织工程。然而，迄今为止仅仅依靠胶原自组装性能与常规化学交联作用所形成的水凝胶的力学性能远远达不到生物支架材料领域的要求，特别是在临床矫形、心血管外科和神经外科方面，因此研究高强度的胶原水凝胶是必要的。本项目以浸酸牛皮为原料快速提取未变性胶原并制备了天然高分子交联剂——氧化羧甲基纤维素钠（OCMC），研究了不同用量OCMC对胶原结构与性能，尤其是流变学性能与自组装性能的影响。结果表明OCMC与胶原之间主要发生静电作用及希夫碱共价交联作用并以后者为主，可有效提高胶原的热稳定性和力学性能，并对胶原的自组装性能具有先促进后抑制的作用；在OCMC/胶原达到0.3:1时，胶原的自组装性能最佳。进一步通过调节OCMC的用量或加入顺序制备了多种性能的胶原水凝胶，有效调控了水凝胶的力学性能、热稳定性等。将羧甲基纤维素钠（CMC）加入氧化锌制备液中原位生成了具有良好分散性的不同粒径球状纳米氧化锌（ZnO），结果表明CMC用量越多，所得到的ZnO粒径越小，且所制得ZnO具有完整的晶体结构与较高的分散稳定性。基于此，将不同粒径ZnO引入胶原水凝胶，制备了胶原/ZnO复合水凝胶，有效提高了水凝胶的力学性能，模量约达2000 Pa，说明引入ZnO是提高水凝胶强度的途径之一，并以此为依据对ZnO的粒径进行了筛选。此外，除引入纳米粒子外，本项目还研究了脱水对胶原水凝胶力学性能的影响。以戊二醛为交联剂对ZnO自组装所得到的胶原水凝胶进行处理后，借助加热和乙醇两种方式进行脱水以降低水凝胶中的水含量，制备了具有高强度的胶原水凝胶，模量高达28000 Pa以上。研究结果对胶原基生物材料尤其是水凝胶的制备具有较好的理论指导意义，并在后续工作中将功能型高性能胶原水凝胶材料推向医学高值转化应用。