Frank Saskia, Wegner Seraphine V
Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Waldeyerstraße 15, 48149, Münster, Germany.
Chemistry. 2025 Mar 17;31(16):e202404360. doi: 10.1002/chem.202404360. Epub 2025 Jan 22.
Light-responsive hydrogels are highly valued for their dynamic mechanical properties and biocompatibility. In this study, we present a hydrogel system that can either soften or strengthen on green light exposure, or remain unresponsive to light, depending on the addition of adenosyl cobalamin (AdoCbl) and Co. These protein-based hydrogels were formed using genetically encoded SpyTag-SpyCatcher chemistry and included green light-sensitive CarH protein domains. As previously reported, these hydrogels formed in the dark with the addition of AdoCbl, due to the tetramerization of the CarH domains. Upon green light exposure, the CarH tetramers disassembled, leading to a rapid transition from gel to sol. Interestingly, we discovered that an excess of AdoCbl leads to photo-strengthening rather than photo-weakening. This occurred because light exposure induces interchain crosslinks between AdoCbl and poly-histidine tags (His-tags) of the proteins. Furthermore, incorporating Co ions enhanced hydrogel stiffness by coordinating to His-tags. This not only suppressed photo-weakening but also promoted photo-strengthening behaviour. These findings highlight the role of His-tags in photochemical crosslinking with excess AdoCbl and in coordination to Co ions, providing a novel strategy for designing tuneable, light responsiveness in materials.
光响应水凝胶因其动态力学性能和生物相容性而备受重视。在本研究中，我们展示了一种水凝胶系统，根据腺苷钴胺素（AdoCbl）和钴的添加情况，该系统在绿光照射下可以软化或强化，或者对光无响应。这些基于蛋白质的水凝胶是使用基因编码的SpyTag-SpyCatcher化学方法形成的，并且包含对绿光敏感的CarH蛋白结构域。如先前报道的那样，由于CarH结构域的四聚化，这些水凝胶在添加AdoCbl的情况下于黑暗中形成。在绿光照射下，CarH四聚体分解，导致从凝胶迅速转变为溶胶。有趣的是，我们发现过量的AdoCbl会导致光强化而非光弱化。这是因为光照会诱导AdoCbl与蛋白质的多组氨酸标签（His-tag）之间形成链间交联。此外，引入钴离子通过与His-tag配位增强了水凝胶的硬度。这不仅抑制了光弱化，还促进了光强化行为。这些发现突出了His-tag在与过量AdoCbl进行光化学交联以及与钴离子配位中的作用，为设计材料中可调谐的光响应性提供了一种新策略。
