Amphiphilic Azulene-Based Fluorescent Probe for Simultaneous Monitoring of Fluctuations in Carboxylesterase Activity in Diverse Biological Samples from a Single Organism

Carboxylesterase (CEs), as a key enzyme in ester metabolism, is simultaneously found with varying expression levels in diverse biological samples from a single organism, such as tissues, cells, bacteria and blood. However, the lack of integrated universal tools for the comprehensive detection of CEs'activity fluctuations in diverse biological samples from a single organism severely hinders the diagnosis and treatment of related diseases. Herein, we have developed an amphiphilic fluorescent probe (AZU-β) targeted toward CEs using an azulene derivative (AZU-OH) as a fluorophore. Using a "hydroxyl protection-deprotection" strategy, AZU-β incorporates a specific recognition group (acetyl ester) that activates the intramolecular charge transfer process to regulate the recognition signal toward CEs. AZU-β exhibits selectivity and highly sensitivity (the minimum detection limit is 1.8 × 10