A ratiometric two-photon fluorescent probe for detecting carboxylesterase in living cells

Abstract

Abnormal regulation or deficiency of carboxylesterase (CaE) is directly linked to human diseases such as hepatic steatosis, hyperlipidemia, and cancer. To understand the physiological and pharmacological roles of CaE, it is crucial to develop a simple and rapid method for CaE detection in biological samples. In this work, we report a red-light two-photon fluorescent probe for highly selective and ratiometric detection of CaE based on intramolecular charge transfer. CaE-mediated hydrolysis can produce the deacetylated derivative of the probe, and the fluorescence spectra of the sensing system were significantly changed due to enzymatic reaction, thus realizing the ratiometric detection of CaE. This ratiometric probe system showed several advantages including better selectivity, lower detection limit and a wide pH range. Moreover, intracellular two-photon fluorescence imaging experiments demonstrated that the probe DCM-CE was able to facilitate visualization of endogenous CaE in living cells.