A FRET ratiometric fluorescence biosensor for the selective determination of pyrophosphate ion and pyrophosphatase activity based on difunctional Cu-MOF nanozyme

Abstract

A ratiometric fluorescent method based on the difunctional copper (II)-based metal-organic framework (Cu-MOF) for label-free monitoring pyrophosphatase (PPase) activity and pyrophosphate ion (PPi) was developed. Difunctional Cu-MOF possessed peroxidase mimetic activity and fluorescent emission property. The catalytic activity of Cu-MOF would be inhibited by the coordination reaction between Cu2+ and PPi because of the good affinity between Cu2+ and PPi. However, the PPi can be hydrolyzed by PPase catalyzation to Pi which can hardly affect the Cu-MOF nanozyme activity. Once the PPase participated, the catalytic activity of Cu-MOF was recovered and catalyzed the decomposition of hydrogen peroxide to oxidize o-phenylenediamine (OPD) to form a 2,3-diaminophenazine (DAP) solution and turns on the Förster resonance energy transfer (FRET) from Cu-MOF as a donor to DAP as an acceptor. The LODs of the fluorescence sensing platform were 0.30 mU mL−1 for PPase and 0.53 μmol L−1 for PPi, respectively. This method will broaden the applications of nanozyme and shows a great potential application in the diagnosis of PPi or PPase-related diseases.