Journal
ANALYTICAL CHEMISTRY
Volume 88, Issue 22, Pages 10816-10820Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.analchem.6b03448
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Funding
- East China University of Science and Technology
- Fundamental Research Funds for the Central Universities [WY1213013]
- Pujiang Talent Project [14PJ1402200]
- National Science Foundation of China [21577037]
- China 111 Project [B07023]
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gamma-Glutamyltranspetidase (GGT) is a cell-membrane-bound enzyme which selectively catalyzes cleavage of the gamma-glutamyl bond of glutathione (GSH). It has been identified to be overexpressed in a number of malignant tumor cells. Therefore, fluorescent probes for fast and selective detection of GGT activities are greatly needed. However, the majority of currently available GGT fluorescent probes based on direct conjugation of a gamma-glutamyl group to a specific fluorophore generally has slow enzymatic kinetics due to bulky fluorophore too close to the enzyme's active site. Moreover, the uncaged fluorophore with a free amine group might undergo oxidation or other enzymatic transformation and resulted in a complicated time dependent fluorescence response. Herein, we reported design of a novel fluorescent GGT probe NM-GSH (2), which incorporated a fast intramolecular transcyclization cascade for rapid detection of GGT activities after enzymatic cleavage of the gamma-glutamyl group. This design strategy allows introduction of bulky 1,8-naphthalimide fluorophore with improved enzymatic kinetics and lowered detection limit. The transcyclized product 4 gives more than 200-fold fluorescence increment. The probe NM-GSH showed both good selectivity and fast detection of GGT activities with the detection limit as low as 0.21 mU/mL. In addition, the fluorescent product 4 contains no free amine group and is more stable for detection. Most importantly, cell imaging studies showed that the transcyclized product 4 was enriched in lysosomes for selectively lighting up GGT-overexpressed ovarian cancer cells (OVCARS) but not normal cells (HUVEC), indicating NM-GSH's potentials as an imaging agent in cancer diagnosis and treatment.
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