Ratiometric fluorescent probe with signals from two near-infrared channels for esterase activity and its application in biological imaging

Abstract

Esterase serves as a crucial biomarker for the diagnosis of tumors due to its overexpression in cancer cells. Ratiometric fluorescent probe has the advantage of having two distinct emission wavelengths, which allows for the elimination of the effects of light intensity and optical path length by using the fluorescence intensity ratio between the two emission wavelengths. In this work, a novel near-infrared (NIR) fluorescent probe P1 for ratiometric monitor esterase activity was developed. Compared with ordinary ratiometric probes, both emission wavelengths of this probe are in the NIR region, which can effectively eliminate various fluctuations and blurriness in image contrast and achieve precise quantitative analysis. P1 itself shows a fluorescence emission at 717 nm. After incubated with esterase, a new emission peak at 822 nm emerged due to esterase's catalysis, and the fluorescence intensity at 717 nm steadily decreased, which achieved the highly sensitive detection of esterase with a detection limit calculated as 0.25 mU/mL. What’s more, P1 showed high selectivity for esterase and was successfully applied for biological imaging in living cells and in vivo.