A bifunctional AIEgen fluorescent probe for detection viscosity and ONOO- in living cells

The peroxynitrite anion (ONOO - ) and viscosity play crucial roles in both physiological and pathological processes. In this study, we developed a bifunctional fluorescent probe MAR with an aggregation-induced emission (AIE) feature for detecting viscosity and ONOO - across different channels. MAR exhibited significant fluorescence enhancement to viscosity with a red emission at 600 nm and a good linear relationship in the range of 11.6 to 956 cP. Additionally, MAR could rapidly recognize and quantitatively respond to ONOO - with high selectivity, good sensitivity, a low detection limit (LOD = 6.97 nM), and a wide range of pH value (4.0 - 10.0), accompanied by visible blue fluorescence emission at 408 nm. The considerable wavelength separation (Δλ = 192 nm) between the maximum emission peaks of MAR for viscosity and ONOO - ensured minimal signal crosstalk in bioimaging. Cell imaging experiments indicated that MAR could target intracellular lipid droplets and respond to the changes of viscosity and ONOO - through independent red and blue channels. These results indicated that the AIEgen fluorescence sensor MAR was a promising candidate for detecting ONOO - levels and viscosity changes in live cells.