A fluorescent probe for detecting bisulfite/sulfite in lipid droplets and tracking the dynamics of lipid droplets

Intracellular lipid droplets (LDs) are important organelles regulating intracellular redox processes. Endogenous bisulfite/sulfite (HSO₃^-/SO₃^2-) is one of the metabolites of thiol metabolism. The variation in HSO₃^-/SO₃^2- content around LDs is closely related to cellular homeostasis. However, there is currently no effective method to visualize and quantify the dynamic changes in HSO₃^-/SO₃^2- content around LDs. In this work, a fluorescent probe MC-BEN utilizing a triphenylamine basic framework was developed to selectively recognize HSO₃^-/SO₃^2- via a nucleophilic addition reaction. The probe exhibits excellent anti-interference capability, short response time, outstanding photostability, and a low fluorescence detection limit (6.1 μM) for HSO₃^-/SO₃^2- recognition. More interesting, there is a trend of accelerated contact between LDs and lysosomes after MC-BEN targeting LDs and reacting with endogenous/exogenous HSO₃^-/SO₃^2-, which may provide new ideas for the study of intracellular lysosomal lipophagy.