Immunochemical detection of penicillins by using biohybrid magnetic particles

An Enzyme Linked Immunosorbent Assay (ELISA) with the ability to detect some of the most widely used penicillins such as penicillin G, amoxicillin and ampicillin has been developed and validated in milk samples to ensure food safety. The assay can achieve limits of detection (0.1 μg L−1) much lower than the MRLs (Maximum Residue Levels) established by the EU (4 μg L−1). The procedure allows the analysis of the samples with a simple and fast treatment of the matrix with biohybrid magnetic particles to hydrolyze the β-lactam ring. A new immunizing hapten has been described and the polyclonal antibodies produced showed high specificity for open ring penicillins and no cross-reactivity with other antibiotic families. The assay has been designed to detect simultaneously both penicillin species in milk, the antibiotics and their hydrolyzed forms. Concerning the open-ringed forms their detection in food samples will be especially important in the next few years because of the illegal use of penicillinase enzymes by farmers to mask the real concentrations of β-lactams in milk.