Studies on the visual screening method for fluoroquinolones based on the chain reaction of gold nanoparticles and its application in milk samples

Abstract

Antibiotic residues are of concern for public health and food safety. Selectivity on a single compound is of current interest; however, screening methods are the first step in the control of antibiotic residues in food of animal origin with the simultaneous detection of an analyte or a family of antibiotics. In this article, a visual, simple and rapid system based on the chain recognition of gold nanoparticles (AuNPs) is presented for the screening detection of fluoroquinolone residues. The results of the Zeta potential analysis show that the addition of bicarbonate takes the place of citrate, which weakens the repulsion between AuNPs. Furthermore, in the presence of positively charged fluoroquinolones (FQs) under acidic conditions, bicarbonate, as a sensitive response promoter, could more easily induce the color of AuNPs shifting from wine red to blue by electrostatic adsorption. Furthermore, the results of the transmission electronic microscopy indicate that the positively charged FQs allow AuNPs to connect as a nanochain through the hydrophobic-hydrophobic interaction of a quinolone ring and/or the hydrogen bond of the carboxyl group between the molecules of FQs. Under optimal conditions, a good linear range of 0.2–10 μM was obtained for eight FQs with a limit of detection as low as 78 nM (3σ). The recognition interaction in situ by the naked eye or UV–Visible spectroscopy successfully monitored for the simultaneous determination of FQs in milk. This screening method is time saving and cost effective to control FQs residues before confirmatory methods.