Highly selective and sensitive FRET based ratiometric two-photon fluorescent probe for endogenous β-galactosidase detection in living cells and tissues

Abstract In vivo measurement of abnormal β-galactosidase (β-gal) in living cells and tissues is urgently required for early diagnosis and treatment of primary ovarian cancer. Herein, a FRET-based ratiometric two-photon fluorescent probe FTR-βgal with a large emission shift, rapid response and low cytotoxicity was developed for sensitively detecting β-gal activity in vivo. FTR-βgal was designed with a naphthalene derivative as the energy donor and a rhodol derivative as the energy acceptor, which provided an efficient FRET strategy. Remarkably, FTR-βgal was successfully applied in TP imaging of β-gal with the ratio signal rapidly transform from 0.15 to 5.9 (∼40-fold) between 540 nm and 450 nm. Furthermore, FTR-βgal was used to visualize β-gal levels in tumor upon tissue penetration of 30–150 μm achieved. Therefore, FTR-βgal was applicable for clinical detection in living cells and tissues as a promising strategy for diagnosis of various associated cancers.