A highly sensitive and selective enzyme activated fluorescent probe for in vivo profiling of carboxylesterase 2.

Carboxylesterase 2 (CES2) is a serine-type hydrolase that plays important roles in xenobiotic detoxification and lipid metabolism. Its abnormal expression is highly associated with diseases such as diabetes and carcinoma. To date, intense attention has been attracted to CES2 targeted drug discovery and disease diagnosis. Thus, to further explore the physiological function of CES2 is of great importance. However, until now, most medical research on CES2 function and activity assays is still dependent on conventional methods, which could hardly specify CES2 activity. Therefore, there is an urgent need to develop efficient tools for selective measurement and sensing of endogenous CES2 in complicated biological system. In this study, we report the design and construction of an enzyme-activated fluorescent probe for CES2 activity sensing. The acquired probe DXMB was characterized as a highly specific and sensitive fluorescent probe for CES2 and possessed superior binding affinity, overall catalytic efficiency, and reaction velocity when compared with the reported CES2 probes. By application of DXMB into living system, it was capable of sensing endogenous CES2 in living cells, dynamic monitoring CES2 in zebrafish development, and visualizing tissue distribution of CES2 in nude mice. Most importantly, abnormally elevated CES2 activity in the intestine of diabetic model mice was first revealed, while significantly decreased CES2 activity in the liver was validated by DXMB. These results indicated that DXMB could serve as a vital tool for further CES2-related biological and medical research.