Two new colorimetric and ratiometric fluorescent probes based on diketopyrrolopyrrole (DPP) for detecting and imaging of mitochondrial SO 2 derivatives in cancer cells

Two new fluorescent probes (DPP-FI/DPP-BI) based on diketopyrrolopyrrole (DPP) were designed and synthesized for colorimetric and ratiometric detection of SO2 derivatives. Both of them displayed obvious ratiometric changes with about 21 folds of fluorescent ratio transformation from red to yellow upon treating with bisulfite to interrupt the π-conjugation of probes. In addition, the calculated detection limit of DPP-FI and DPP-BI was down to 2.34 × 10−6 M and 1.73 × 10−6 M towards HSO3−, respectively. Besides, DPP-FI/DPP-BI showed outstanding selectivity toward HSO3−/SO32− over other nucleophilic anions. More importantly, these two probes could successfully detect mitochondrial HSO3− in HepG2 cells, which is to our knowledge the first example using DPP as colorimetric and ratiometric fluorescent probes to detect small molecules in organelles.