A deep-red hemicyanine fluorescent probe for imaging butyrylcholinesterase in living cells and in mice with APAP-induced liver injury.

As a serine hydrolase synthesized by the liver, butyrylcholinesterase (BChE) is an important biomarker in the clinical diagnosis of liver diseases. To track BChE activity in drug-induced liver injury, we designed a deep-red BChE-activatable fluorescent probe (CYL-BChE) with hemi-cyanine structure by using a cyclopropyl carbonyl group as a specific recognition moiety. Its near-infrared absorption wavelength (665 nm) and emission wavelength (762 nm) provide excellent tissue penetration capabilities, making it suitable for biological imaging. Additionally, CYL-BChE has a large Stokes shift (97 nm) and a low detection limit (0.96 U/L), effectively distinguishing BChE from the interfering substance acetylcholinesterase (AChE). Besides of detection of endogenous BChE in live cells, the resulting probe has been successfully used to detect BChE expression levels in an acetaminophen-induced (APAP-induced) drug liver injury mouse model. Therefore, this probe is expected to be a valuable biological tool in the detection of BChE activity.