A mitochondria-targeted colorimetric and two-photon fluorescent probe for biological SO2 derivatives in living cells

Abstract

Two colorimetric and two-photon fluorescent probes (PCB and MPCB) for SO2 derivatives were designed and synthesized with rapid response, high selectivity, low detection limits, and large Stokes shifts. The probes displayed “turn on” fluorescence response to SO2 derivatives probably due to the nucleophilic addition to the electron-poor CN bond, which was supported by the DFT/TDDFT calculations. Compared with PCB, MPCB was obtained by incorporating a methyl pyridinium group, which endowed MPCB with the red-shifted spectra properties, better water-solubility, larger two-photon excitation action cross-section (δ′) and the important ability of locating in mitochondria. Bio-imaging study established that MPCB can be used to detect SO2 derivatives in living cells under two-photon excitation with large δ′ value (1551 × 0.125 = 193.88 GM), little cytotoxicity and good biocompatibility. Meanwhile, standard co-staining experiments of MPCB and Mito Tracker Red FM (co-localization coefficient: 0.89) revealed that MPCB can be used for the real-time sensing and bioimaging of SO2 derivatives in mitochondria.