title: Enzymatic recycling-based amperometric immunosensor for the ultrasensitive detection of okadaic acid in shellfish.
abstract: Electrochemical immunosensors based on a competitive indirect enzyme-linked immunosorbent assay (ciELISA) and an enzymatic recycling system were developed for the detection of okadaic acid (OA). OA-ovalbumin (OA-OVA) conjugate was immobilised on screen-printed electrodes (SPEs) and competition of a newly generated monoclonal antibody (MAb) for free and immobilised OA was subsequently performed. Secondary antibodies labelled with alkaline phosphatase (ALP) or horseradish peroxidase (HRP) were used for signal generation. Experimental parameters were firstly optimised by colorimetric ELISA on microtiter wells and on SPEs. The ELISA system was then tested by amperometry at +300 mV vs. Ag/AgCl (detection of p-aminophenol produced by the reaction of p-aminophenyl phosphate with ALP) or -200 mV vs. Ag/AgCl (detection of 5-methyl-phenazinium methyl sulfate, redox mediator in the HRP bioelectrocatalysis). The limits of detection (LODs) with standard solutions were 1.07 and 1.98 microgL(-1) when using ALP and HRP labels, respectively. An electrochemical signal amplification system based on diaphorase (DI) recycling was integrated into the ALP-based immunosensor, decreasing the LOD to 0.03 microgL(-1) and enlarging the working range by two orders of magnitude. Preliminary results with mussel and oyster extracts were obtained and compared with the colorimetric immunoassay, the colorimetric protein phosphatase inhibition assay (PPIA) and LC-MS/MS.
authors.affiliation: IMAGES EA 4218, Université de Perpignan, 52 Avenue Paul Alduy, 66860 Perpignan Cedex, France.
authors.forename: Mònica
authors.initials: M
authors.lastname: Campàs
authors.forename: Pablo
authors.initials: P
authors.lastname: de la Iglesia
authors.forename: Marie
authors.initials: M
authors.lastname: Le Berre
authors.forename: Marian
authors.initials: M
authors.lastname: Kane
authors.forename: Jorge
authors.initials: J
authors.lastname: Diogène
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Marty
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D004563:Electrochemistry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005504:Food Analysis / Q000295:instrumentation*; D005506:Food Contamination / Q000032:analysis*; D007118:Immunoassay / Q000295:instrumentation*; D008974:Mollusca / Q000737:chemistry*; D019319:Okadaic Acid / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012758:Shellfish / Q000032:analysis*
chemical_list: D019319:Okadaic Acid