A small-molecule probe for ratiometric photoacoustic imaging of hydrogen sulfide in living mice.

A small-molecule photoacoustic probe based on cyanine dyes was developed by taking advantage of the nucleophilic substitution reaction of H2S with chlorine. The probe demonstrated specific response to H2S with ratiometric photoacoustic signals in the NIR region, which enabled real-time, accurate, high-resolution imaging of endogenous H2S in vivo.