Bifunctional fluorescent probe revealing viscosity and SO2 in cell, zebrafish and NASH model.

Clarifying the presence of viscosity and endogenous sulfur dioxide (SO2) in mitochondria is crucial for advancing the diagnosis and treatment of illnesses. Nevertheless, the advancement of fluorescent probes that concurrently satisfy the criteria of mitochondrial viscosity and endogenous recognition of SO2 remains significantly insufficient. In this work, we have engineered and synthesized two probes ID-OH and BID-OH, which exhibit a ratio-type response to SO2 and an off-on fluorescence response to viscosity. Due to the superior selectivity coupled with its outstanding wavelength and fluorescence quantum yield, BID-OH has been effectively utilized for the detection of exogenous SO2, endogenous SO2 and viscosity within living HepG2 cells. Additionally, BID-OH demonstrates the capability to offer comprehensive insights into the distribution of endogenous SO2 as it traverses through the transfer pathway in zebrafish. Notably, the remarkable capacity of BID-OH to differentiate between normal mice and nonalcoholic steatohepatitis (NASH) mice has been demonstrated, indicating its potential as an excellent diagnostic tool for detecting SO2 levels and viscosity under physiological conditions. It is anticipated that BID-OH will emerge as a valuable instrument for diagnosing mitochondrial irregularities, thereby contributing to the advancement of related medical research in this field.