Abstract
Development of simple, convenient, and sensitive assay methods for pyrophosphatase (PPase) activity is of importance, for disease diagnosis and drug discovery. Herein, a simple, rapid, label-free, and sensitive fluorescence sensor for PPase activity assay is developed, using Cu2+ doping-induced quantum dot (QD) photoluminescence as a signal reporter. The Cu2+ doping of ZnSe QD can induce a dopant-dependent emission response, which will be inhibited after the premixing of Cu2+ with pyrophosphate (PPi), to form a Cu2+-PPi complex. Then, the hydrolysis of PPi into phosphate (Pi), specifically catalyzed by PPase, liberates the free Cu2+ to regain the QD doping for the fluorescence response, which is highly dependent on the PPase activity. The PPase can be sensitively and selectively assayed, with a detection limit of 0.1 mU/mL. The developed sensing strategy can be also employed for the PPase inhibitor screening. Thus, the current QD doping-based sensing strategy offers an efficient and promising avenue for Cu2+, PPi, or PPase-related target analysis, and might hold great potential for the further applications in the clinical disease diagnosis.
Highlights
Inorganic pyrophosphatase (PPase), as a ubiquitous hydrolytic enzyme in biological systems, can catalyze the hydrolysis of pyrophosphate (PPi) into orthophosphate (Pi)
The abnormal level of PPase has been directly connected with several clinical diseases, including hyperthyroidism, colorectal cancer, and lung adenocarcinomas [7,8,9]
ZnSe quantum dot (QD) was obtained with the use of Zn(OAc)2 and NaHSe as precursors and glutathione, as ligand
Summary
Inorganic pyrophosphatase (PPase), as a ubiquitous hydrolytic enzyme in biological systems, can catalyze the hydrolysis of pyrophosphate (PPi) into orthophosphate (Pi). The abnormal level of PPase has been directly connected with several clinical diseases, including hyperthyroidism, colorectal cancer, and lung adenocarcinomas [7,8,9] It has served as an important therapeutic target for drug development. The organic dye-based PPase activity assays were reported, based on click chemistry [16], Cu2+-regulated o-phenylenediamine oxidation [17], or the synthesized organic probes for the direct discrimination between phosphate and pyrophosphate [18] These optical strategies have achieved the effective detection of PPase, the synthesis, modification, and even purification operation of organic probes or nanoprobes involved in most of these methods increases the assay complexity, restricting their wide applications to some extent. The developed system could be applied for PPase inhibitor screening
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