Ratiometric detection and bioimaging of endogenous alkaline phosphatase by a NIR fluorescence probe

A novel near-infrared (NIR) fluorescent probe (SWJT-3) was designed based on phosphate protection of the electron donating group of the hemicyanine for the ratiometric determination of ALP at 590 and 670 nm. Notably, SWJT-3 could be used in the endogenous detection of ALP in vitro and vivo. Moreover, it was the first NIR and ratiometric fluorescent probe for the imaging of ALP in mice. It has large Stokes shift (185 nm), and also showed high selectivity, low detection limit (0.87 U/L). Meanwhile, SWJT-3 exhibited obvious color change in aqueous solution which could be observed by naked-eyes. In addition, the probe displayed low lifetime (0.74 ns), high substrate affinity (Km = 8.89 µM) and excellent fluorescence characterization under various polarity and viscosity conditions.