A dual-salt fluorescent probe for specific recognition of mitochondrial NADH and potential cancer diagnosis

Reduced nicotinamide adenine dinucleotide (NADH) is a kind of coenzyme and widely works as a biomarker in cancer cells. It plays a crucial role in many cellular metabolic processes, especially NADH in mitochondria is indispensable for the mitochondrial respiration chain that produces ATP. Herein, we designed a fluorescent probe Mito-FCC based on an ethylene-bridging dual-salt structure, in which benzo[e]indolium fluorophore was used as the mitochondria-targeting group and 1-methylquinolinium moiety as the NADH recognition unit. Mito-FCC exhibited high sensitivity and selectivity for NADH with a rapid "turn-on" fluorescence signal. The dual-salt structure endowed the probe with a reliable mitochondria-targeted ability even after the recognition unit was reduced by NADH. With the help of the probe, the fluctuations of endogenous NADH induced by glucose or pyruvate were imaged. Besides, Mito-FCC had a capability to make a distinction between cancer cells and normal cells due that the content of NADH in cancer cells was distinctly higher than that in normal ones. Notably, the visualization of tumor in vivo through monitoring NADH using Mito-FCC was realized successfully. These experimental results showed that Mito-FCC hold a great perspective in study of mitochondrial function and potential diagnosis of cancer diseases.