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ABSTRACT
Prior studies have shown that fluorescent molecular probes based on cyclopropyl esters are good substrates for butyrylcholine esterase (BChE), which is a biomarker of several human diseases. We tested two fluorescent cyclopropyl ester derivatives as BChE-activated fluorogenic probes. One was a known fluorescein probe, and the other was a newly designed near-infrared probe based on a heptamethine cyanine dye. As expected, both probes were good substrates for BChE, but they were also good substrates for carboxylesterase (CE). The probes were efficiently cleaved in mouse blood and serum which contains high levels of CE, but they were not cleaved in human serum which contains negligible CE. There are two major implications of these results. One is a cautionary note that esterase levels in different organisms can vary substantially. Researchers developing fluorescent cyclopropyl ester probes for BChE imaging should anticipate high levels of background signal in preclinical mouse models due to ester cleavage by the abundant CE in mouse blood. However, there is very little cleavage of fluorescent cyclopropyl ester probes in human blood, which contains low levels of CE. Therefore, fluorescent cyclopropyl ester probes should be viable in humans as imaging agents that identify disease sites with overexpressed levels of CE or BChE.
GRAPHICAL ABSTRACT
Acknowledgments
This work was supported by the NIH under grant number R35GM136212. We thank Janeala J. Morsby for conducting early experiments and Alejandro Lopez Ramirez for expert technical assistance with biosample preparation.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Supplementary material
Supplemental data for this article can be accessed online at https://doi.org/10.1080/10610278.2024.2388731.