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

Screen-printed devices, incorporating working electrode immobilised beta-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 mu g kg(-1) and 10 mu g kg(-1) Penicillin G, respectively. The maximum residue limit of penicillin G in milk for consumption is 5 mu g kg-l, 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 beta-lactam antibiotic types. The assay is simple to perform and requires minimum reagent usage, making it ideal as a field-based screening tool for beta-lactam quantification in milk. (C) 1999 Elsevier Science B.V. All rights reserved.