A MnO2 nanosheets–o-phenylenediamine oxidative system for the sensitive fluorescence determination of alkaline phosphatase activity

Abstract

Alkaline phosphatase (ALP) plays a crucial role in the regulation of intracellular processes and acts as an important biomarker for diagnosis of diverse diseases. Herein, we report a selective, sensitive and convenient sensing assay for detecting ALP based on a MnO₂ nanosheets–o-phenylenediamine (OPDA) oxidative system. In this system, the MnO₂ nanosheets could effectively oxidize OPDA to produce fluorescent OPDAox for fluorescence detection, while the incubation of MnO₂ nanosheets with ascorbic acid (AA) would first lead to the reduction of the MnO₂ nanosheets and then inhibit the formation of fluorescent OPDAox. Based on this principle, a sensitive and rapid method for fluorescence sensing of AA with a good linear relationship from 0.1 to 50 μM (R² = 0.9962) was achieved. ALP can enzymatically hydrolyze 2-phospho-L-ascorbic acid (AAP) to produce AA, which could reduce the MnO₂ nanosheets and inhibit the oxidation of OPDA to fluorescent OPDAox. Then, the MnO₂ nanosheets–OPDA sensing system was applied to detect ALP. This fluorescence sensing system could detect ALP activity selectively, sensitively and conveniently with a good linear relationship from 0.1 to 200 U L⁻¹ (R² = 0.9946); meanwhile, this system was also applied to detect ALP in human serum samples. Taken together, the proposed MnO₂–OPDA oxidative system shows promising potential in biomedical applications.