Fenton-like reaction triggered chemical redox-cycling signal amplification for ultrasensitive fluorometric detection of H2O2 and glucose

An ultrasensitive fluorescent biosensor is reported for glucose detection based on a Fenton-like reaction triggered chemical redox-cycling signal amplification strategy. In this amplified strategy, Cu²⁺ oxidizes chemically o-phenylenediamine (OPD) to generate photosensitive 2,3-diaminophenazine (DAP) and Cu⁺/Cu⁰. On the one hand, the generated Cu⁰ catalyzes the oxidation of OPD. On the other hand, H₂O₂ reacts with Cu⁺ to produce hydroxyl radicals (˙OH) and Cu²⁺ through a Cu⁺-mediated Fenton-like reaction. The generated ˙OH and recycled Cu²⁺ ions take turns oxidizing OPD to produce more photoactive DAP, triggering a self-sustaining chemical redox-cycling reaction and a remarkable fluorescent enhancement. It is worth mentioning that the cascade reaction did not stop until OPD molecules were completely consumed. Benefiting from H₂O₂-triggered chemical redox-cycling signal amplification, the strategy was exploited for the development of an ultrasensitive fluorescent biosensor for glucose determination. Glucose content monitoring was realized with a linear range from 1 nM to 1 μM and a limit of detection of 0.3 nM. This study validates the practicability of the chemical redox-cycling signal amplification on the fluorescent bioanalysis of glucose in human serum samples. It is expected that the method offers new opportunities to develop ultrasensitive fluorescent analysis strategy.