Semi-automated membrane based chemiluminescent immunosensor for flow injection analysis of okadaic acid in mussels

A chemiluminescent immunosensor integrated in a flow injection analysis system was developed for the detection of the 'diarrheic shellfish poisoning' (DSP) toxin okadaic acid (OA). Anti-GA monoclonal antibodies were labelled with horseradish peroxidase for their use in a competitive assay,in which the free antigen of the sample competes with immobilised OA. Based on commercially available polyethersulfone membranes, this bioanalytical system exhibits low non-specific binding of antibodies in the presence of mussel homogenate. The immunosensor was used in a semi-automated analysis procedure in which the free OA containing sample was injected in the flow system concomitantly with the labelled antibodies. With an overall measurement time of 20 min, the immunosensor has a detection limit of 0.2 mu g OA/100g mussel homogenate (0.1 mu g OA/L in the assay solution), and measurements could be performed over three decades, from 0.2 to 200 mu g OA/100 g of mussel homogenate. The operational stability of the sensor for the detection of critically contaminated mussels (40 mu g/100 g of mussel homogenate) has been investigated over 38 OA determination cycles. A stable response was obtained under the 34 first measurements with a CV of 11.7%. Moreover, no significant change in the immunosensor performances was observed during shea and long term storage periods of the membranes (1 month). The performances of five immunosensors (five different membranes) showed a good repeatability with a variation of the negative control and the critically contaminated signal equal to 7% and 12.6%, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.