Receptor binding protein amperometric affinity sensor for rapid β-lactam quantification in milk Original Research Article

Screen-printed devices, incorporating working electrode immobilised β-lactam specific receptor binding protein, were employed to measure penicillin G levels in milk. Quantification was achieved through ELISA-based affinity-assay format coupled to amperometric determination of bound enzyme label activity. Assay inhibition increased from zero, in the absence of penicillin G in milk, to 33.5 and 77.1% reduction in signal response in the presence of 5 μg kg−1 and 10 μg kg−1 penicillin G, respectively. The maximum residue limit of penicillin G in milk for consumption is 5 μg kg−1, as defined by the FDA. Coefficient of variation values varied from 4.2–26.4%. The assay incorporates a 2–4 min incubation step, a rapid washing step and 1–2 min measurement step. The receptor binding protein is specific for the major β-lactam antibiotic types. The assay is simple to perform and requires minimum reagent usage, making it ideal as a field-based screening tool for β-lactam quantification in milk.