A fast responsive, highly selective and light-up fluorescent probe for the two-photon imaging of carboxylesterase in living cells.

A fast responsive and two photon fluorescent probe (HCyNAc) for carboxylesterase (CaE) has been designed based on the D-π-A structure of hemicyanine and naphthalene derivatives. After enzymatic reaction, HCyNAc enabled light-up fluorescence assay of CaE over other biologically-relevant species and enzymes, including ROS. Two-photon imaging of endogenous CaE was confirmed in HeLa cells using HCyNAc under 800 nm NIR excitation.