Department of Life Sciences , University of Trieste , Via Licio Giorgieri 5 , I-34127 Trieste , Italy.
Biomacromolecules. 2019 Aug 12;20(8):3070-3075. doi: 10.1021/acs.biomac.9b00636. Epub 2019 Jul 17.
We report on a controlled process allowing for the gelation of a diol-rich chitosan-derivative named CTL (lactose-modified chitosan) in the presence of boric acid as the cross-linker. A two-step approach is described, namely (i) the mixing of CTL and boric acid at pH = 5, a condition where the inorganic component is mildly reactive; (ii) the addition of sodium bicarbonate (NaHCO) as a trigger, allowing for the gradual and slow pH increase. The goal was to convert gradually the almost inert neutral boric acid into the much more reactive borate anion, the latter promoting the formation of borate esters with CTL diols. Gelling kinetics as well as mechanical behavior at small and large deformations was investigated by rheometry. CTL-boric acid gels behaved essentially as transient networks, hence continuously assembling and dissociating in a highly dynamic fashion. The present gelling mechanism preserves the strain-hardening behavior in the nonlinear region of stress-strain response, corroborating the already suggested potential applications of such gels as mimics of biological soft tissues.
我们报告了一个受控过程，该过程允许二醇丰富的壳聚糖衍生物 CTL（乳糖修饰的壳聚糖）在硼酸作为交联剂的存在下凝胶化。描述了一种两步法，即（i）CTL 和硼酸在 pH = 5 下混合，在该条件下无机成分反应性温和；（ii）添加碳酸氢钠（NaHCO）作为触发剂，允许 pH 逐渐缓慢增加。目标是逐渐将几乎惰性的中性硼酸转化为更具反应性的硼酸盐阴离子，后者促进与 CTL 二醇形成硼酸酯。流变仪研究了凝胶动力学和小变形及大变形下的力学行为。CTL-硼酸凝胶主要表现为瞬态网络，因此以高度动态的方式连续组装和解离。目前的凝胶化机制在应力-应变响应的非线性区域保留了应变硬化行为，这证实了这些凝胶作为生物软组织模拟物的潜在应用。
