Engineering an ESIPT-based fluorescent probe for dual-channel (Vis/NIR) ratiometric monitoring of intracellular sulfur dioxide by single wavelength excitation

ESIPT-based probes have large stokes shift and dual emission, and can quantify the analytes through dual channel LSCM imaging under one excitation wavelength without of the need of two lasers or corresponding parameter corrections. To exploit these advantages of ESIPT mechanism and achieve a big breakthrough in their excitation-emission wavelength and solubility which of the old probes dissatisfied the requirements of biology experiments, we challenged to develop a favorable and practical SO2 probe. In this work, the benzopyrylium moiety which had both a built-in SO2 site and good water solubility, was conjugated with 10-hydroxybenzo[h] quinoline to construct ESIPT-based probe NIR-PT with dual emission (enol form:544 nm; keto form: 733 nm). NIR-PT could ratiometricly visualize SO2 levels in aqueous solution with 460 nm as a excitation. Moreover, we have successfully applied NIR-PT to visualize SO2 levels in cells and mice under oxidative stress.