Li Meng, He Maoting, An Peng
School of Chemical Science and Technology Yunnan University Kunming 650091 P. R. China
Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, Yunnan University Kunming 650091 P. R. China.
Chem Sci. 2025 Jun 24. doi: 10.1039/d5sc03279b.
Photoactivatable fluorophores enable selective fluorescence activation within a defined region of interest at a precisely controlled time point. This high degree of spatiotemporal control over fluorescence emission facilitates advanced imaging modalities and super-resolution microscopy techniques, allowing real-time monitoring of dynamic processes and nanoscale visualization of structural features. The development of photocage groups is the general and most popular strategy for designing photoactivatable fluorophores. Herein, we present hydroxy-pendant phenyl tetrazole as a novel photocage for push-pull photoactivatable fluorophores. Upon photolysis, this tetrazole-based photocage undergoes rapid cleavage with nitrogen extrusion, followed by nitrile imine-mediated nucleophilic addition and subsequent proton transfer to afford the corresponding hydrazone photoproduct. This tetrazole to hydrazone photoconversion leads to an electronic inversion from electron-withdrawing to electron-rich character, thereby triggering fluorescence turn-on charge recombination. This phenyl tetrazole photocage was applicable in coumarin (Cou), nitrobenzoxadiazole (NBD), and naphthalimide (NP) fluorophores. The NP-based photoactivatable fluorophores enabled spatiotemporally resolved, targeted live-cell fluorescence imaging in both confocal and stimulated emission depletion (STED) microscopy, exhibiting rapid photoresponse, non-toxic byproduct release, bright fluorescence emission, and a high signal-to-background ratio.
光可激活荧光团能够在精确控制的时间点，在定义的感兴趣区域内实现选择性荧光激活。这种对荧光发射的高度时空控制促进了先进的成像模式和超分辨率显微镜技术的发展，能够实时监测动态过程并对结构特征进行纳米级可视化。光笼基团的开发是设计光可激活荧光团的通用且最流行的策略。在此，我们提出羟基取代的苯基四唑作为一种用于推拉式光可激活荧光团的新型光笼。光解后，这种基于四唑的光笼会通过氮的挤出进行快速裂解，随后通过腈亚胺介导的亲核加成以及随后的质子转移，得到相应的腙光产物。这种从四唑到腙的光转换导致电子从吸电子特性转变为富电子特性，从而触发荧光开启和电荷复合。这种苯基四唑光笼适用于香豆素（Cou）、硝基苯并恶二唑（NBD）和萘二甲酰亚胺（NP）荧光团。基于NP的光可激活荧光团能够在共聚焦显微镜和受激发射损耗（STED）显微镜中实现时空分辨的靶向活细胞荧光成像，表现出快速的光响应、无毒副产物释放、明亮的荧光发射以及高信噪比。
