A sensitive ratiometric fluorescent probe for quantitive detection and imaging of alkaline phosphatase in living cells

Abstract

We report a sensitive fluorescence probe Ratio-ALP for in vivo ratiometric imaging of alkaline phosphatase (ALP). The probe was designed by conjugating a naphthalimide with a phosphate group as the responsive moiety for enzymatic reactions. The fluorescence intensity ratio displayed a linear relationship against the concentration of ALP in the concentration range from 0 to 200 U/L, its LOD is as low as 0.25 U/L. Ratio-ALP has good selectivity and sensitivity, high cell permeability, and low cytotoxicity. Furthermore, probe Ratio-ALP was also successfully applied to image endogenous ALP activity in living cells.