In this study, a simple and amplified colorimetric assay is developed for the detection of the enzymatic activity of glucose oxidase (GOx) based on in situ formation of a photoswitchable oxidase mimetic of PO
43−-capped CdS quantum dots (QDs). GOx catalyzes
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In this study, a simple and amplified colorimetric assay is developed for the detection of the enzymatic activity of glucose oxidase (GOx) based on in situ formation of a photoswitchable oxidase mimetic of PO
43−-capped CdS quantum dots (QDs). GOx catalyzes the oxidation of 1-thio-β-
d-glucose to give 1-thio-β-
d-gluconic acid which spontaneously hydrolyzes to β-
d-gluconic acid and H
2S; the generated H
2S instantly reacts with Cd
2+ in the presence of Na
3PO
4 to give PO
43−-stabilized CdS QDs in situ. Under visible-light (λ ≥ 400 nm) stimulation, the PO
43−-capped CdS QDs are a new style of oxidase mimic derived by producing some active species, such as h
+,
•OH, O
2•− and a little H
2O
2, which can oxidize the typical substrate (3,3,5,5-tetramethylbenzydine (TMB)) with a color change. Based on the GOx-triggered growth of the oxidase mimetics of PO
43−-capped CdS QDs in situ, we developed a simple and amplified colorimetric assay to probe the enzymatic activity of GOx. The proposed method allowed the detection of the enzymatic activity of GOx over the range from 25 μg/L to 50 mg/L with a low detection limit of 6.6 μg/L. We believe the PO
43−-capped CdS QDs generated in situ with photo-stimulated enzyme-mimicking activity may find wide potential applications in biosensors.
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