pH值对动态Thia-Michael加成键交联水凝胶性能的影响《ACS Polymers Au》

pH值对动态Thia-Michael加成键交联水凝胶性能的影响

摘要

与动态共价键交联的水凝胶具有时间依赖性，使其成为从生物材料到自愈网络等各种应用的有利平台。然而，这些平台的交联交换动力学、材料性质和稳定性之间的关系尚未完全了解，尤其是在添加外部刺激后。在这项工作中，pH被用作操纵交联交换动力学的手柄，并在生理相关窗口中控制由此产生的水凝胶力学和稳定性。在pH3和pH7之间的水缓冲液中，聚乙二醇基水凝胶通过可逆的Thia-Michael加成反应交联。测定了每个pH值的键交换速率常数和平衡常数，并将这些数据与所得到的大块水凝胶的力学特性进行了关联。随着pH值的增加，正、反向速率常数均增大，而平衡常数减小。这些变化导致在更碱性的pH值下，应力松弛更快，水凝胶硬度更低。pH值升高还导致质量损失增加，封装模型牛血清白蛋白荧光蛋白的释放速率加快。动力学、力学和分子释放曲线之间的联系为动态共价水凝胶的结构-性能关系提供了重要的见解，该系统为生理相关pH值条件下的控制释放提供了一个很有前景的平台。

关键词：水凝胶，粘弹性，自愈，生物材料，释放，动态共价，Thia-Michael

Figure 1. (A) Chemical structures for the two macromers used in this study. The conjugate acceptor is a four-arm benzylcyanoacetamide-functionalized poly(ethylene glycol) (PEG-BCA). The nucleophile is a four-arm PEG-thiol. (B) Schematic of the effect pH plays on the reaction. With increasing pH, both the forward and reverse rate constants increase, while the equilibrium constant decreases.

Effect of pH on the Properties of Hydrogels Cross-Linked via Dynamic Thia-Michael Addition Bonds

Thomas M. FitzSimons, Eric V. Anslyn, and Adrianne M. Rosales*

McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States

ACS Polym. Au 2022, 2, 2, 129–136

Publication Date: December 28, 2021

https://doi.org/10.1021/acspolymersau.1c00049

Abstract

Hydrogels cross-linked with dynamic covalent bonds exhibit time-dependent properties, making them an advantageous platform for applications ranging from biomaterials to self-healing networks. However, the relationship between the cross-link exchange kinetics, material properties, and stability of these platforms is not fully understood, especially upon addition of external stimuli. In this work, pH was used as a handle to manipulate cross-link exchange kinetics and control the resulting hydrogel mechanics and stability in a physiologically relevant window. Poly(ethylene glycol)-based hydrogels were cross-linked with a reversible thia-Michael addition reaction in aqueous buffer between pH 3 and pH 7. The rate constants of bond exchange and equilibrium constants were determined for each pH value, and these data were correlated with the resulting mechanical profiles of the bulk hydrogels. With increasing pH, both the forward and the reverse rate constants increased, while the equilibrium constant decreased. These changes led to faster stress relaxation and less stiff hydrogels at more basic pH values. The elevated pH values also led to an increased mass loss and a faster rate of release of an encapsulated model bovine serum albumin fluorescent protein. The connection between the kinetics, mechanics, and molecular release profiles provides important insight into the structure–property relationships of dynamic covalent hydrogels, and this system offers a promising platform for controlled release between physiologically relevant pH values.

KEYWORDS: hydrogel, viscoelastic, self-healing, biomaterial, release, dynamic covalent, thia-Michael

SUBJECTS: Equilibrium constant, Hydrogels, Kinetic parameters, Kinetics, Nucleic acid structure

来源：《ACS Polymers Au》

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