Abstract: Objective: A suspension array assay was established for the detection of gentamicin residues and compared with regular enzyme-linked immunosorbent assay (ELISA). Methods: Monoclonal antibody against gentamicin was covalently coupled with polystyrene microspheres with carboxyl groups on their surface by amido bonds to form detection probes. The phycoerythrin (PE)-labeled gentamicin obtained by carbodiimide (EDC) method was allowed to couple with anti-gentamicin monoclonal antibody in an aqueous phase by direct competition method. Then based on the fluorescence signal of the resulting products, a competitive curve for gentamicin was obtained. Meanwhile, a direct ELISA curve for gentamicin was established. Both assays were compared with each other to find variations in detection limit, linear range and spike recovery rate. Results: The IC10 and IC50 of suspension array assay were 0.1 ng/m and 2.8 ng/mL, respectively, and its linear range was 0.1–100 ng/mL; in contrast, the IC10 and IC50 of ELISA assay were 0.27 ng/mL and 1.95 ng/mL, respectively, and its linear range. Each of the assays showed a spike recovery rate varying from 80% to 120% for gentamicin in milk, chicken meat, chicken liver, pork and porcine liver. In addition, suspension array assay had no cross-reactivity with other aminoglycosides, showing a good specificity. Conclusions: Suspension array assay is simple, sensitive and specific and superior to the conventional ELISA assay. As a result, suspension array assay can provide a new technique for the detection of pesticides and veterinary residues.

Key words: gentamicin, veterinary residue, suspension array, enzyme-linked immunosorbent assay (ELISA)