Integration of antibody-antigen and receptor-ligand reactions to establish a gold strip biosensor for detection of 33 β-lactam antibiotics

A novel lateral flow immunoassay biosensor, combining the receptor-ligand reaction and antigen-antibody reaction was developed for the detection of β-lactam antibiotics in milk. The receptor protein, the carboxy-terminal domain of β-lactam sensor-transducer mutant from Bacillus. licheniformis , served as the recognition element. Colloidal gold (CG)-labelled receptor antibody-receptor ternary complex was applied as a signal transducer probe. The presence of β-lactams was identified through a color change in the test zone, where the reaction between the complex of CG/anti-receptor antibody/receptor and β-lactam antigen on the test line could be inhibited by β-lactam residues in the sample, thus leading to a reduction in color signal. Based on the indirect labeling of the receptor with an antibody as a linker, the ability to detect 33 β-lactams was below or near the corresponding maximum residue limit. The proposed lateral flow immunoassay biosensor appears to be an excellent field-based screening tool for the qualitative screening of β-lactams in milk.