Sensitive immunochemical approaches for quantitative (FPIA) and qualitative (lateral flow tests) determination of gentamicin in milk

Three kinds of immunoassays for the determination of gentamicin in milk samples were developed and validated. First, a fast and easily-performed fluorescence polarization immunoassay was used for characterization of the employed polyclonal antibody. The calculated Kaff were (1.9±0.4)×109М−1 and (6.0±0.2)×106М−1 for the high- and low-affinity fractions respectively. The assay was characterized with a good sensitivity, the limit of detection being 5μgkg−1. Two different kinds of detection labels, i.e. colloidal gold (CG) and quantum dots (QDs), were evaluated for use in lateral-flow format with respect to rapid visual on-site testing. The cut-off levels for both qualitative formats were selected based on the maximum level for gentamicin in milk established by the European Commission, 100μgkg−1, resulting in a 10μgkg−1 cut-off considering sample dilution. The intra-laboratory validation was performed with sterilized milk samples artificially spiked with gentamicin at concentrations less than, equal to, and greater than the cut-off level. It was shown that milk products could be analyzed without any sample preparation, except for dilution with the buffer solution. The rates of false-positive and false-negative results were below 5% for both labels. The different developed immunoassays were tested towards gentamicin determination in artificially-spiked and naturally contaminated milk samples. [Display omitted] •A sensitive FPIA for the determination of gentamicin in milk was developed.•Colloidal gold-based lateral flow immunoassay for gentamicin detection was designed.•Quantum dots were used as label in lateral flow test against gentamicin.•The techniques were validated using naturally-contaminated and spiked milk samples.