Label-free gold nanoclusters as quenchable fluorescent probes for sensing olaquindox assisted by glucose oxidase-triggered Fenton reaction

ABSTRACT

Glucose oxidase (GOx) catalyses oxidation of glucose accompanied with the generation of hydrogen peroxide. With the addition of Fe²⁺, hydroxyl radical produced by Fenton reaction between hydrogen peroxide and Fe²⁺ may quench the fluorescence of gold nanoclusters. In this work, a fluorescent enzyme-linked immunosorbent assay with gold nanoclusters was designed with a straightforward signal output, in which the fluorescence of gold nanoclusters was quenched by GOx-triggered Fenton reaction. Olaquindox was selected as a target analyte. Gold nanoclusters capped with bovine serum albumin and GOx-linked olaquindox conjugates were successfully prepared. Olaquindox in samples directly competed with the GOx-linked olaquindox conjugates for binding immobilized antibody. Consequently, the fluorescence signal increased with the amount of olaquindox. Under optimal conditions, the fluorescent enzyme-linked immunosorbent assay exhibited a favorable performance to detect olaquindox in swine feeds, demonstrating a good linear range from 1.0 µg kg⁻¹ to 150 µg kg⁻¹ with a reliable correlation coefficient (R² = 0.9918); the limit of detection was 0.68 µg kg⁻¹. Average recoveries in spiked samples were 85.3% to 113.5%. The proposed strategy is a promising approach for the detection of olaquindox and other harmful small molecules.

Graphical Abstract

KEYWORDS:

• Fluorescent enzyme-linked immunosorbent assay
• gold nanoclusters
• Fenton reaction
• glucose oxidase
• olaquindox

Acknowledgments

This study was supported by the National Natural Science Foundation (No. 31672600) and Sanming Project of Medicine in Shenzhen (SZSM201611068). And the authors appreciate the cooperation of other faculty members in the Department of Pharmacology and Toxicology of the College of Veterinary Medicine at China Agricultural University.

Compliance with ethical standards

This article does not contain any studies with human participants or animals performed by any of the authors.

Disclosure statement

All the authors declare no conflict of interest.

Informed Consent

Not applicable (it is not applicable to the study).

Supplementary material

Supplemental data for the article can be accessed on the publisher’s website.

Additional information

Funding

This work was supported by National Natural Science Foundation of China [31672600]; and the Sanming Project of Medicine in Shenzhen [SZSM201611068].