A Direct (Non-Competitive) Immunoassay for Gentamicin Residues with an Optical Biosensor

Using sensor chip immobilized anti-gentamicin monoclonal antibodies in an optical biosensor (BIACORE 3000) resulted in the first single antibody based and label free noncompetitive immunoassay for the direct detection of residues of a low molecular weight compound in a food product. Calibration curves for gentamicin (Mw 466 Da) in buffer and milk showed 50% binding at 20 and 35 ng ml^–1, respectively, which is well below the maximum residue limit of 100 ng ml^–1.