A FRET-Based Ratiometric H_(2)S Sensor for Sensitive Optical Molecular Imaging in Second Near-Infrared Window

Second near-infrared(NIR-II)window optical molecular imaging kicks off a new revolution in high-quality imaging in vivo,but always suffers from the hurdles of inevitable tissue autofluorescence background and NIR-II probe development.Here,we prepare a Förster resonance energy transfer-based ratiometric NIR-II window hydrogen sulfide(H_(2)S)sensor through the combination of an H_(2)S-responsive NIR-II cyanine dye(acceptor,LET-1055)and an H_(2)S-inert rhodamine hybrid polymethine dye(donor,Rh930).This sensor not only exhibits high sensitivity and selectivity,but also shows rapid reaction kinetics(~20 min)and relatively low limit of detection(~96 nM)toward H_(2)S,allowing in vivo ratiometric NIR-II fluorescence imaging of orthotopic liver and colon tumors and visualization of the drug-induced hepatic H_(2)S fluctuations.Our findings provide the potential for advancing the feasibility of NIR-II activity-based sensing for in vivo clinical diagnosis.