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 H 2 O 2 as well as H 2 O 2 -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 H 2 O 2 . The generated H 2 O 2 can transform Fe 2+ to Fe 3+ and free hydroxyl radical ( OH). The as-produced Fe 3+ and OH can simultaneously oxidize o -phenylenediamine (OPD) to 2,3-diaminophennazine (OPDox) and the Fe 3+ was reduced to Fe 2+ . The Fe 2+ produced from the redox processes between Fe 3+ 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 H 2 O 2 , 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.