Analysis of β-lactam antibiotics using a microbial receptor protein-based biosensor assay

Abstract

An optical biosensor assay for detection of β-lactam antibiotics in milk based on a microbial receptor protein was developed. The assay uses a general sensor surface previously described with a small organic molecule (HI) immobilized. A conjugate between a β-lactam (cephalosporin C) and a monoclonal HI antibody is injected across the sensor surface before injection of the sample mixed with receptor protein. Receptor inhibited by β-lactam residues in the milk sample will not bind to the sensor surface and the reduction in response is inversely related to the β-lactam concentration of the sample. The detection limit for a number of commonly used β-lactams was below or near the respective maximum residue limit and the relative standard deviation (CV) for penicillin G in milk was 6-12% in the interval 2.0-12.5 μg kg-1. For application in the field further optimization is needed to solve problems related to non-specific binding to the sensor surface.