PT-1

Bisulfite (HSO₃^-) plays an important role in life activities. Abnormal content of HSO₃^- may cause cardiovascular, cancer and other diseases. Frequency upconverted luminescent (FUCL) probes are a class of anti-Stokes luminescent materials with long-wavelength excitation and short-wavelength emission properties, which offer advantages in a range of applications due to their higher sensitivity and photostability. In addition, FUCL imaging has the advantages of high tissue penetration depth and low photo-damage, thus, it is more suitable for fluorescence imaging. In this work, a FUCL probe based on an xanthene fluorophore was designed and synthesised to detect HSO₃^-. The Probe PT-1 could respond to HSO₃^- and had high selectivity and sensitivity. It also exhibited a quenched FUCL signal. The detection limit of FUCL concerning HSO₃^- was 43 nM (λ_ex = 730 nm), which is half the detection limit achieved under traditional excitation (93 nM, λ_ex = 643 nm). Cell fluorescence imaging showed that PT-1 could effectively target mitochondria and monitor endogenous/exogenous HSO₃^- in living cells. More importantly, PT-1 was successfully used to monitor the level of HSO₃^- in mice with drug-induced liver injury through FUCL imaging.