A cyclic signal amplification strategy to fluorescence and colorimetric dual-readout assay for the detection of H2O2-related analytes and application to colorimetric logic gate

We report a novel facile upconversion fluorescent and colorimetric dual-readout assay for H2O2 as well as H2O2-related analytes via enzyme-controlled cyclic signal amplification strategy. As a proof of application demonstration, the highly sensitive detection of choline and acetylcholine chloride (ACh) was performed. This sensing strategy involves the reaction of ACh with acetylcholinesterase (AChE) to generate choline which is followed catalytically oxidized by choline oxidase (ChOx) to produce H2O2. The generated H2O2 can transform Fe2+ to Fe3+ and free hydroxyl radical (OH). The as-produced Fe3+ and OH can simultaneously oxidize o-phenylenediamine (OPD) to 2,3-diaminophennazine (OPDox) and the Fe3+ was reduced to Fe2+. The Fe2+ produced from the redox processes between Fe3+ and OPD could be cycle used to generate OPDox that can significantly quench upconversion nanoparticles (UCNPs) fluorescence based on inner filter effects (IFE) and cause a visible change from colorless to yellow color. The phenomenon is further designed as a colorimetric logic gate. Moreover, we also detected H2O2, glucose, lactate and uric acid (UA) with the higher sensitivity by utilizing the assay strategy, which revealed the extensive applications of the proposed sensing strategy in biomedical analysis.