Biocompatible hydrogels with defined mechanical properties are critical to tissue engineering and regenerative medicine. Thiol-acrylate photopolymerized hydrogels have attracted special interest for their degradability and cytocompatibility, and for their tunable mechanical properties through controlling factors that affect reaction kinetics (e.g., photopolymerization, stoichiometry, temperature, and solvent choice). In this study, we hypothesized that the mechanical property of these hydrogels can be tuned by photoinitiators via photobleaching and by thiol-Michael addition reactions. To test this hypothesis, a multiscale mathematical model incorporating both photobleaching and thiol-Michael addition reactions was developed and validated. After validating the model, the effects of thiol concentration, light intensity, and pH values on hydrogel mechanics were investigated. Results revealed that hydrogel stiffness (i) was maximized at a light intensity-specific optimal concentration of thiol groups; (ii) increased with decreasing pH when synthesis occurred at low light intensity; and (iii) increased with decreasing light intensity when synthesis occurred at fixed precursor composition. The multiscale model revealed that the latter was due to higher initiation efficiency at lower light intensity. More broadly, the model provides a framework for predicting mechanical properties of hydrogels based upon the controllable kinetics of thiol-acrylate photopolymerization.

具有明确机械性能的生物相容性水凝胶对于组织工程和再生医学至关重要。硫醇丙烯酸酯光聚合水凝胶因其可降解性和细胞相容性以及通过控制影响反应动力学的因素（例如光聚合、化学计量、温度和溶剂选择）而可调的机械性能而引起了人们的特别关注。在这项研究中，我们假设这些水凝胶的机械性能可以通过光引发剂通过光漂白和硫醇-迈克尔加成反应来调节。为了检验这一假设，开发并验证了结合光漂白和硫醇-迈克尔加成反应的多尺度数学模型。验证模型后，研究了硫醇浓度、光强度和 pH 值对水凝胶力学的影响。结果表明，水凝胶刚度 (i) 在特定于光强度的最佳硫醇基浓度下达到最大；(ii) 当合成发生在低光强度下时，随着 pH 值的降低而增加；(iii) 当合成以固定的前体组成进行时，随着光强度的降低而增加。多尺度模型表明，后者是由于较低光强度下较高的引发效率所致。更广泛地说，该模型提供了一个基于硫醇-丙烯酸酯光聚合的可控动力学预测水凝胶机械性能的框架。