Mitochondrial-targeted near-infrared fluorescence probe for selective detection of fluoride ions in living cells.

Fluoride ions (F-), as a strongest electron withdrawing anion of the smallest size, have played an indispensable role in biological systems. Here a mitochondria-targeted near-infrared (NIR) fluorescent probe (Mito-FP) is developed for selective detection of F- in living cells. Mito-FP is designed using a NIR hemicyanine as a fluorophore and tert-butyldimethylsilyl (TBDMS) as a recognition site which is linked to the fluorophore via a 4-hydroxylbenzyl alcohol self-immolative linker. Mito-FP is essentially nonfluorescent. F- can specifically cleave the Si-O bond which triggers the elimination of the quinone methide intermediate and generates the initial NIR hemicyanine fluorophore with distinct intramolecular charge transfer and activated fluorescence signal. The Mito-FP probe is responsive to the concentrations of F- in the range of 10-120 μM with an estimated limit of detection of 3.2 μM. Mito-FP also exhibits high selectivity toward F- with good stability in the physiological pH conditions. Mito-FP is successfully introduced to detect and image F- in HeLa cells. Moreover, Mito-FP is also demonstrated to exhibit excellent mitochondrial-targeting ability. This NIR fluorescence probe could provide a useful tool for studying F- in mitochondria.