A water-soluble lysosome-targetable fluorescent probe for carboxylesterase detection and its application in biological imaging

Carboxylesterases (CEs) are involved in biotransformation of numerous drugs, environmental toxicants, and carcinogens containing ester groups. Abnormal CEs levels are associated with various diseases. Herein, we developed a novel water-soluble merocyanine-based probe 1 to detect CEs activity using acetate ester as a recognition site. The notable emission at 510 nm of the probe in neat aqueous solution was partially quenched and red-shifted to 580 nm after adding CEs. The fluorescent ratiometric response of 1 toward CEs activity is sensitive (with the detection limit of 0.98 × 10 −6 U/ml), rapid (within 10 min), and effective in a wide pH range (4.0–10.0). Due to the existence of morpholine as a lysosome-targeting group, the probe was successfully utilized to monitor lysosomal CEs activity. More importantly, the probe was successfully applied to detect and image carboxylesterase activity in zebrafish. • A water-soluble lysosome-targetable fluorescent probe has been developed. • The probe could monitor carboxylesterases activity with the detection limit (0.98 × 10 −6 U/mL) in neat aqueous solution. • The probe works within a wide pH rang of 4.0–10.0 along with a rapid hydrolytic process within 10 min. • The probe has been successfully sensing carboxylesterases activity in lysosomes of living cells and zebrafish.