Thiol–ene radical coupling is increasingly used for the biofunctionalization of biomaterials and the formation of 3D hydrogels enabling cell encapsulation. Indeed, thiol–ene chemistry presents interesting features that are particularly attractive for platforms requiring specific reactions of peptides or proteins, in particular in situ, during cell culture or encapsulation: thiol–ene coupling occurs specifically between a thiol and a nonactivated alkene (unlike Michael addition); it is relatively tolerant to the presence of oxygen; and it can be triggered by light. Despite such interest, little is known about the factors impacting polymer thiol–ene chemistry in situ. Here, we explore some of the molecular parameters controlling photoinitiated thiol–ene coupling (with UV and visible-light irradiation), with a series of alkene-functionalized polymer backbones. ¹H NMR spectroscopy is used to quantify the efficiency of couplings, whereas photorheology allows correlation to gelation and mechanical properties of the resulting materials. We identify the impact of weak electrolytes in regulating coupling efficiency, presumably via thiol deprotonation and regulation of local diffusion. The conformation of associated polymer chains, regulated by the pH, is also proposed to play an important role in the modulation of both thiol–ene coupling and cross-linking efficiencies. Ultimately, suitable conditions for cell encapsulations are identified for a range of polymer backbones and their impact on cytocompatibility is investigated for cell encapsulation and tissue engineering applications. Overall, our work demonstrates the importance of polymer backbone design to regulate thiol–ene coupling and in situ hydrogel formation.

中文翻译：

---

通过聚合物主链的分子环境调节硫醇-烯偶联以形成水凝胶和细胞封装

硫醇-烯自由基偶联越来越多地用于生物材料的生物功能化和形成能够包裹细胞的 3D 水凝胶。事实上，硫醇-烯化学呈现出有趣的特征，这些特征对于需要肽或蛋白质的特定反应的平台特别有吸引力，特别是在细胞培养或封装期间的原位反应：硫醇-烯偶联特别发生在硫醇和未活化的烯烃之间（不像迈克尔添加）; 它对氧气的存在相对耐受；它可以由光触发。尽管有这种兴趣，但对影响聚合物硫醇-烯原位化学的因素知之甚少。在这里，我们探索了一些控制光引发硫醇-烯偶联的分子参数（使用紫外线和可见光照射），¹H NMR光谱用于量化耦合的效率，而光流变学允许与所得材料的凝胶化和机械性能相关。我们确定了弱电解质对调节耦合效率的影响，可能是通过硫醇去质子化和局部扩散的调节。由pH调节的相关聚合物链的构象也被认为在硫醇-烯偶联和交联效率的调节中起重要作用。最终，为一系列聚合物骨架确定了适合细胞封装的条件，并研究了它们对细胞相容性的影响，以用于细胞封装和组织工程应用。全面的，