Detection of streptomycin residues in whole milk using an optical immunobiosensor

The development of an assay for the detection of streptomycin residues in p asteurized whole milk using an optical biosensor (Biacore) is reported. Str eptomycin-adipic hydrazide coupled to bovine thyroglobulin was used to prod uce a sheep polyclonal antibody. The antibody displayed excellent cross-rea ctivity with dihydrostreptomycin (106%). There was no significant cross-rea ction with other aminoglycosides or common antibiotics. Streptomycin was al so immobilized onto a CM5 sensor chip to provide a stable, reusable surface . The developed assay permitted the direct analysis of whole milk samples ( similar to3.5% fat) without prior centrifugation and defatting. Results wer e available in 5 min. The limit of detection of the assay was determined as 4.1 ng/mL, well below the European maximum residue limit (MRL) of 200 ng/m L. Repeatability (or coefficient of variation) between runs was determined as 3.5% (100 ng/mL; 0.5 x MRL), 5.7% (200 ng/mL; MRL), and 7.6% (400 ng/mL; 2 x MRL).