Two new fluorescent probes based on a coumarin core have been developed for the detection of nitramines (RDX and HMX) via responding to their photo-degradated nitrogen dioxide (NO 2 ). Although both probes contain the same fluorophore and recognition site, they display different fluorescent responses to NO 2 and nitramines. 8- O xime-7-dimethylamino-coumarin (8-ODC) emits traditional turn-on fluorescence toward NO 2 , which is based on the C N isomerization. In contrast, 3- O xime-7-dimethylamino-coumarin (3-ODC) exhibits a unique turn-off response with strong fluorescence quenching (about 98%) as a result of a twisted intramolecular charge transfer mechanism (TICT). In addition, 3-ODC offers a highly selective and sensitive determination of nitramines via detecting NO 2 in solution. The limit of detection of 3-ODC for NO 2 , HMX and RDX was 90 ppb, 60 nM and 90 nM, respectively. Notably, main interferents such as TNT, PETN, NO, NO 2 + and H 2 O 2 showed no obvious interference to the detection of NO 2 and nitramines. Therefore, a novel fluorescent probe (3-ODC) based on the TICT mechanism was firstly developed to detect NO 2 and nitramines by fluorescence quenching with high selectivity and sensitivity.
Lingchen Wang,Wenqiang Song,Fengxia Li,Shaomin Shuang,Shengmei Song,Yunfeng Yang,Yue Huang,Kun Wang
A mitochondria-immobilized fluorescent probe Mito-CDM was designed and synthesized for viscosity sensing via the twisted intramolecular charge transfer (TICT) mechanism. The N , N -diethylaminophenyl group is the viscosity-sensitive unit in the prepared Mito-CDM molecular structure, while the pyridinium cation is the mitochondria-targeting group that is responsible for monitoring mitochondrial viscosity. As the viscosity increased from 0.55 cp (0% glycerol) to 950 cp (100% glycerol), the fluorescence intensity of Mito-CDM at 586 nm enhanced gradually and there is a good linear relationship between fluorescence intensity and viscosity ( n = 11, R 2 = 0.9957). In high-viscosity media, Mito-CDM exhibits a 166-fold fluorescence enhancement at 586 nm. It is crucial to note that the benzyl chloride group has the ability to react with highly reactive thiols on mitochondrial proteins, which enables Mito-CDM to be immobilized on mitochondria for extended periods. Additionally, Mito-CDM was successfully used to monitor mitochondrial viscosity changes during nystatin and lipopolysaccharide-induced inflammation in HeLa cells.
Mitochondrial structural remodeling under oxidative stress is central to the pathogenesis of skin photoaging. Here, we report Mito-Py, a robust mitochondria-targeted probe with a special functional donor-π-acceptor (D-π-A) configuration. Featuring a large Stokes shift (∼130 nm) for minimal self-absorption and viscosity-sensitive emission via a twisted intramolecular charge transfer (TICT) mechanism, Mito-Py enables real-time mapping of mitochondrial viscosity fluctuations during UV-induced oxidative stress in HaCaT keratinocytes. Unlike membrane-potential-dependent dyes, Mito-Py achieves membrane-potential-independent mitochondrial retention, ensuring stable suborganellar localization even during depolarization events. Its exceptional resistance to photobleaching permits super-resolution structured illumination microscopy (SIM) to resolve UV-induced cristae fragmentation with ultrahigh spatial precision (sub-100 nm). Beyond cellular models, Mito-Py was applied to paraffin-embedded skin sections from a UV-induced murine photoaging model, where staining revealed markedly stronger fluorescence in photoaged skin compared to normal skin. These results underscore Mito-Py’s capability to detect mitochondrial alterations in complex tissue environments, providing a powerful, photostable tool for dissecting mitochondrial stress responses and exploring organelle crosstalk in photoaging and related dermatological disorders.
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