Redox reaction-modulated fluorescence biosensor for ascorbic acid oxidase assay by using MoS2 quantum dots as fluorescence probe

Herein, a sensitive fluorescence (FL) biosensor for the assay of ascorbic acid oxidase (AAO) was established based on the fluorescence resonance energy transfer (FRET) between MoS2 quantum dots (MQDs) and CoOOH nanoflakes. CoOOH nanoflakes as effective FL quencher could quench the FL signal of MQDs on the basis of FRET. When ascorbic acid (AA) was added to the MQDs/CoOOH nanoflakes system, the FL signal was restored due to the redox reaction between CoOOH nanoflakes and AA, in which CoOOH nanoflakes were reduced to Co2+ by AA. In the presence of AAO, the recovered FL signal of MQDs was quenched again because of the enzymatic catalytically reaction between AAO and AA, in which AA was oxidized to dehydroascorbic acid (DHA) and then prevented the decomposition of CoOOH nanoflakes. Under the optimal experimental conditions, this developed fluorescence method exhibited good linear ranges from 2 to 10 mU mL-1 and 10-40 mU mL-1 with a low detection of limit of 0.8 mU mL-1 for AAO detection. And the limit of quantification (LOQ) of 2.6 mU mL-1 was obtained. The proposed biosensor showed high sensitivity and selectivity, and was successfully applied for AAO determination in human serum samples.