A combined "AIE + ESIPT" fluorescent probe for detection of lipase activity

Lipases are acyl hydrolases that play a key role in fat digestion and monitoring of acute pancreatitis by cleaving long-chain triglycerides into polar lipids. Due to an opposite polarity between the hydrophilic enzyme and their lipophilic substrates, lipase reaction occurs at the interface between the aqueous and the oil phases. It is quite challenging to develop a specific probe to detect lipase activity, especially in homogeneous systems. Herein we designed a blue fluorescent probe HBT-LDC for specific detection of lipase activity based on both aggregation induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) effect. The probe shows significant advantages, such as high selectivity and excellent sensitivity, no self-quenching at high concentration, large Stokes shift, low cytotoxicity, and good biocompatibility. The linear range for in vitro quantification of lipase is 0.2-1.3 mg/mL with a detection limit of 0.01 mg/mL. The probe has been successfully applied to the evaluation of commercial lipase and the in vivo bioimaging sensing exogenous lipase activity in HeLa cells. The results revealed that the probe could serve as a potential tool in lipase related drug discovery and disease diagnostics.