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.