The development of a biotin-guided and mitochondria-targeting fluorescent probe for detecting SO precisely in cancer cells.

Mitochondrial sulfur dioxide (SO) is very closely associated with various activities of cancer cell. However, the specific physiological and pathological roles of mitochondrial SO in cancer cells are still not well defined. Lacking a powerful molecular tool for detecting mitochondrial SO in cancer cells precisely is an essential factor. So it is urgent to develop a specific method for monitoring mitochondrial SO in cancer cells. Herein, we described a distinct cancer cell-specific fluorescent probe NS for detecting mitochondrial SO accurately in cancer cells. Biotin, possessing of high affinity for cancer cells, was decorated into probe to provide its cancer cell-targeting property. Moreover, the positive charge hemicyanine group was used to anchor mitochondria selectively. A series of spectral results from concentration titration, dynamics and selectivity experiments showed that NS had high sensitivity, fast response and high selectivity to SO. These properties render NS ability for detecting SO in living cells. In biological imaging, the achievements in detecting exogenous and endogenous SO displayed the probe had favorable response to SO in living cells with well biocompatibility. Significantly, assisted by competitive experiments with excess biotin, NS demonstrated distinct cancer cell-targeting for detecting mitochondrial SO. Furthermore, NS could locate mitochondria specially and detect mitochondrial SO in cancer cells by co-localization. Moreover, NS can trace SO in zebrafish with long wavelength emission. Therefore, NS can achieve in tracing mitochondrial SO selectively in cancer cells. It would be a powerful tool for well defining the physiological and pathological roles of mitochondrial SO in cancer cells.