Single biosensor immunoassay for the detection of five aminoglycosides in reconstituted skimmed milk

The application of an optical biosensor (Biacore 3000), with four flow channels (Fcs), in combination with a mixture of four specific antibodies resulted in a competitive inhibition biosensor immunoassay (BIA) for the simultaneous detection of the five relevant aminoglycosides in reconstituted skimmed milk. Four aminoglycosides (gentamicin, neomycine, kanamycin and a streptomycin derivative) were immobilised onto the sensor surface of a biosensor chip (CM5) in the four Fcs of the biosensor system by amine coupling. In the Biacore, milk (reconstituted from skimmed milk powder) was 10 times diluted with a mixture of the four specific antibodies and injected through the four serially connected Fcs (1 min at a flow rate of 20 μl min -1 ). The responses measured just prior to the injection (20 μl at a flow rate of 20 μl min -1 ) of the regeneration solution (0.2 M NaOH + 20% acetonitril) were indicative for the presence or absence of the aminoglycosides in reconstituted milk. The limits of detection were between 15 and 60 ng ml -1 , which was far below the maximum residue limits (MRLs) (varying from 100 to 500 ng ml -1 ) and the total run time between samples was 7 min.