Dutta Ayan, Gramlich William M
Department of Chemistry, University of Maine, 5706 Aubert Hall, Room 154, Orono, Maine 04469-5706, United States.
Advanced Structures and Composites Center, University of Maine, Orono, Maine 04469, United States.
Biomacromolecules. 2025 Jul 14;26(7):4146-4157. doi: 10.1021/acs.biomac.5c00142. Epub 2025 Jun 6.
Typically, externally triggered initiators are required for norbornene-modified polysaccharides to undergo thiol-ene gelation into a hydrogel. However, anecdotal and reported evidence exists of these prehydrogel solutions undergoing spontaneous thiol-ene gelation without the trigger. Understanding the origin of this spontaneous process would improve the storage of prehydrogel solutions. We found that polysaccharides with carboxylic acids (e.g., carboxymethyl cellulose) can overcome the buffering capacity of phosphate-buffered saline (PBS), creating an acidic solution that is required for spontaneous gelation. Investigation using a small molecule model system revealed that acidic pH and trace metal ions increase the reaction rate and the conversion to the thiol-ene product. We concluded that the self-initiated thiol-ene reaction resulted from a Fenton-like reaction catalyzed by trace metal impurities, such as iron(II), that generate reactive oxygen species (ROS) that initiate the reaction. Using this knowledge, we developed strategies to inhibit spontaneous gelation and increase the working time of prehydrogel solutions.
通常情况下，降冰片烯改性多糖要通过硫醇-烯凝胶化形成水凝胶需要外部触发引发剂。然而，有轶事和报道证据表明，这些预水凝胶溶液在没有触发的情况下会自发进行硫醇-烯凝胶化。了解这种自发过程的起源将改善预水凝胶溶液的储存。我们发现含有羧酸的多糖（如羧甲基纤维素）可以克服磷酸盐缓冲盐水（PBS）的缓冲能力，形成自发凝胶化所需的酸性溶液。使用小分子模型系统进行的研究表明，酸性pH值和痕量金属离子会提高反应速率以及向硫醇-烯产物的转化率。我们得出结论，自引发的硫醇-烯反应是由痕量金属杂质（如亚铁离子）催化的类芬顿反应导致的，这些杂质会产生活性氧（ROS）引发反应。利用这一知识，我们开发了抑制自发凝胶化并延长预水凝胶溶液工作时间的策略。
