Voltammetric detection of Domoic Acid at a multiwalled carbon-nanotube electrode

Domoic acid (DA) is a heterocyclic amino acid and a structural analogue of kainic acid and proline. In mammals, including humans, DA acts as a neurotoxin, causing loss of short-term memory, brain damage and, in severe cases, death. DA enters in the food chain via phytoplankton, which serves as food to marine organisms as crustaceans, anchovies and sardines. DA concentrations at the tissues of these marine species can reach high values as a result of bioaccumulation [1]. To protect consumers from amnesic shellfish poisoning (ASP), most countries have defined a regulatory limit for shellfish of 20 g/g (20 ppm) in accordance with the recommendations of Inverson and Farah [1]. The standard AOAC method, based on high performance liquid chromatography (HPLC), provides good reproducibility, high precision and the analysis of its isomers, although it is rather time-consuming [2, 3]. Thus, there is a need for a fast, selective and sensitive method suitable for a rapid screening of DA. The enzyme-linked immunosorbent assay (ELISA) is the only one that can be used for this aim [3]. Following an affinity recognition process, an electrochemical immunosensor has been developed based on screen-printed electrodes (SPEs). The detection is performed by means of the alkaline phosphatase activity in competitive assays [4, 5]. The use of this immunossensor did not become widespread, probably due to the intrinsic drawbacks that are typical of immunoassays, namely the long incubation times, high costs of the antibodies and the difficulties associated to their regeneration. The direct electrochemical detection of DA is not reported in literature, probably, because it is not electroactive on the most common electrode materials, such as carbon, gold or platinum. In this work we present the preliminary results of our work on the development of an electrochemical sensor based on the direct interaction between DA and a carbon SPE modified with graphitized carbon nanotubes. The voltammetric response of DA is controlled by its adsorption to the electrode surface. The concentrations range tested were in the range of ng/l. Acknowledgements: The authors thank to Ana Gago Team (UVigo) for their kind help and DA gift 1. Inverson, F., Truelove, J., Nat Toxins 1994, 2, 334–339. 2. Pineiro, N.; Vaquero, E.; Leao, J. M.; Gago-Martinez, A.; Vazquez, J. A. Rodriguez, Chromatographia 2001, 53, S231-S235. 3. Kawatsu, K., Hamano, Y., Noguchi, T.,Toxin 1999, 37, 1579–1589. 4. Micheli, L., Radoi, A., Guarrina, R., Massaud, R., Bala, C., Moscone, D., Palleschi, G., Biosens Bioelectron 2004, 20 (2), 190-196. 5. Kreuzer, M. P., Pravda, M., O'Sullivan, C. K., Guilbault, G. G., Toxicon 2002, 40 (9), 1267-1274