A Space‐Dependent ‘Enzyme‐Substrate’ Type Probe based on ‘Carboxylesterase‐Amide Group’ for Ultrafast Fluorescent Imaging Orthotopic Hepatocellular Carcinoma

Abstract Fast and selective fluorescence imaging for a biomarker to related‐disease diagnosis remains a significant challenge due to complex physical environment. Human carboxylesterase (CE) is expected to be a potential biomarker of hepatocellular carcinoma (HCC) to improve the accuracy of diagnosis. However, existing probes for CE has slow response rate and low selectivity. Herein, the amide group is selected as CE‐responsive sites based on the “substrate‐hydrolysis enzymatic reaction” approach. From a series of off–on probes with leave groups in the amide unit, probe JFast is screened with the optimal combination of rapid response rate and high selectivity toward CE. JFast requires only 150 s to reach the maximum fluorescence at 676 nm in the presence of CE and free from the interference of other esterase. Computational docking simulations indicate the shortest distance between the CE and active site of JFast. Cell and in vivo imaging present that the probe can turn on the liver cancer cells and tumor region precisely. Importantly, JFast is allowed to specifically image orthotopic liver tumor rather than metastatic tumor and distinguish human primary liver cancer tissue from adjacent ones. This study provides a new tool for CE detection and promotes advancements in accurate HCC diagnosis.