Fluorescent Determination of Esterase in Living Cells by A Low-Dosage, Ultra-Sensitive Probe Based on Aggregation Induced Emission (AIE)

Esterase is an essential hydrolase in organisms. Many severe diseases are caused by its abnormal expression. Sensitive probes for the esterase activity need to be developed. However, the currently reported fluorescence probes for esterase have drawbacks, such as long response times, low sensitivity, and high dosages. In this work, three fluorophores with the cyano group were designed and synthesized. The optical properties of these fluorophores were measured. A turn-on fluorescence detector for the determination of esterase with a fast response speed and high sensitivity at low doses was developed that was based upon aggregation-induced emission (AIE). The mechanism was studied by high-resolution mass spectrometry (HRMS), dynamic light scattering (DLS), and high-performance liquid chromatography (HPLC). In addition, the probe had excellent stability and biocompatibility and specifically recognized esterase with a short response time (less than 5 min) and ultra-high sensitivity. The detection limit was 1.03 × 10−4 U/mL, with a linear range from 1.03 × 10−4 to 0.05 U/mL. Furthermore, the probe had low cytotoxicity, and cellular imaging of exogenous esterase was achieved. This probe is anticipated to offer many applications in biomedical science.