Departamento de Engenharia Química e Biológica, Instituto Superior de Engenharia de Coimbra, R. Pedro Nunes, 3030-199 Coimbra, Portugal.
Biomacromolecules. 2011 Sep 12;12(9):3275-84. doi: 10.1021/bm200731x. Epub 2011 Jul 28.
In situ forming chitosan hydrogels have been prepared via coupled ionic and covalent cross-linking. Thus, different amounts of genipin (0.05, 0.10, 0.15, and 0.20% (w/w)), used as a chemical cross-linker, were added to a solution of chitosan that was previously neutralized with a glycerol-phosphate complex (ionic cross-linker). In this way, it was possible to overcome the pH barrier of the chitosan solution, to preserve its thermosensitive character, and to enhance the extent of cross-linking in the matrix simultaneously. To investigate the contributions of the ionic cross-linking and the chemical cross-linking, separately, we prepared the hydrogels without the addition of either genipin or the glycerol-phosphate complex. The addition of genipin to the neutralized solution disturbs the ionic cross-linking process and the chemical cross-linking becomes the dominant process. Moreover, the genipin concentration was used to modulate the network structure and performance. The more promising formulations were fully characterized, in a hydrated state, with respect to any equilibrium swelling, the development of internal structure, the occurrence of in vitro degradability and cytotoxicity, and the creation of in vivo injectability. Each of the hydrogel systems exhibited a notably high equilibrium water content, arising from the fact that their internal structure (examined by conventional SEM, and environmental SEM) was highly porous with interconnecting pores. The porosity and the pore size distribution were quantified by mercury intrusion porosimetry. Although all gels became degraded in the presence of lysozyme, their degradation rate greatly depended on the genipin load. Through in vitro viability tests, the hydrogel-based formulations were shown to be nontoxic. The in vivo injection of a co-cross-linking formulation revealed that the gel was rapidly formed and localized at the injection site, remaining in position for at least 1 week.
通过离子和共价交联的偶联，制备了原位形成的壳聚糖水凝胶。因此，加入不同量的京尼平（0.05、0.10、0.15 和 0.20%（w/w）），作为化学交联剂，加入到壳聚糖溶液中，该溶液先前已用甘油-磷酸盐复合物（离子交联剂）中和。通过这种方式，有可能克服壳聚糖溶液的 pH 障碍，保持其热敏特性，并同时增强基质中的交联程度。为了分别研究离子交联和化学交联的贡献，我们制备了没有加入京尼平或甘油-磷酸盐复合物的水凝胶。京尼平加入到中性溶液中会干扰离子交联过程，而化学交联成为主导过程。此外，京尼平的浓度用于调节网络结构和性能。有前途的配方在水合状态下进行了充分的表征，包括任何平衡溶胀、内部结构的发展、体外降解和细胞毒性的发生以及体内可注射性的产生。每个水凝胶系统都表现出非常高的平衡含水量，这是由于其内部结构（通过常规 SEM 和环境 SEM 检查）具有高度多孔性和相互连接的孔。通过压汞法对孔隙率和孔径分布进行了量化。尽管所有凝胶在溶菌酶存在下都会降解，但它们的降解速率很大程度上取决于京尼平的负载。通过体外活力测试，表明水凝胶配方无毒。共交联配方的体内注射表明，凝胶迅速形成并定位在注射部位，至少保持 1 周的位置。
