Food Additives and Contaminants Vol. 28, No. 6, June 2011, 711–725 Paralytic shellfish poisoning (PSP) toxin binders for optical biosensor technology: problems and possibilities for the future: a review K. Campbella*, D.F.K. Rawnb, B. Niedzwiadekb and C.T. Elliotta aInstitute of Agri-Food and Land Use, School of Biological Sciences, Queen’s University, David Keir Building, Stranmillis Road, Belfast BT9 5AG, UK; bFood Research Division, Bureau of Chemical Safety, Health Products and Food Branch, Health Canada, Sir Frederick Banting Research Centre, 251 Sir Frederick Banting Driveway, Address Locator: 2203C, Tunney’s Pasture, Ottawa, ON, Canada, K1A 0K9 (Received 3 June 2010; final version received 7 October 2010) This review examines the developments in optical biosensor technology, which uses the phenomenon of surface plasmon resonance, for the detection of paralytic shellfish poisoning (PSP) toxins. Optical biosensor technology measures the competitive biomolecular interaction of a specific biological recognition element or binder with a target toxin immobilised onto a sensor chip surface against toxin in a sample. Different binders such as receptors and antibodies previously employed in functional and immunological assays have been assessed. Highlighted are the difficulties in detecting this range of low molecular weight toxins, with analogues differing at four chemical substitution sites, using a single binder. The complications that arise with the toxicity factors of each toxin relative to the parent compound, saxitoxin, for the measurement of total toxicity relative to the mouse bioassay are also considered. For antibodies, the cross-reactivity profile does not always correlate to toxic potency, but rather to the toxin structure to which it was produced. Restrictions and availability of the toxins makes alternative chemical strategies for the synthesis of protein conjugate derivatives for antibody production a difficult task. However, when two antibodies with different cross-reactivity profiles are employed, with a toxin chip surface generic to both antibodies, it was demonstrated that the cross-reactivity profile of each could be combined into a single-assay format. Difficulties with receptors for optical biosensor analysis of low molecular weight compounds are discussed, as are the potential of alternative non-antibody-based binders for future assay development in this area. Keywords: screening – biosensor; screening – immunoassays; toxicology; phycotoxins – PSP; seafood Introduction Paralytic shellfish poisoning (PSP) toxins are naturally occurring potent neurotoxins synthesised by micro- scopic dinoflagellates from the genii Alexandrium, Gymnodinium and Pyrodinium in marine and freshwa- ter environments (Reis Costa et al. 2009). Increased temperatures, sunlight and nutrient-rich waters are considered to cause the rapid reproduction of dinofla- gellate species and thereby lead to potential ‘harmful algal blooms’. Climate change, increased ocean eutro- phication and commercial shipping are believed to contribute to the increasing frequency and occurrence of these blooms worldwide (Botana et al. 2009). Filter- feeding organisms, such as molluscan shellfish, con- suming dinoflagellates may thereby accumulate the PSP toxins and potentially transfer them through the trophic chain (Deeds et al. 2008). The toxins do not appear to harm shellfish directly, but are *Corresponding author. Email: katrina.campbell@qub.ac.uk ISSN 1944–0049 print/ISSN 1944–0057 online 2011 Her Majesty the Queen in right of Canada DOI: 10.1080/19440049.2010.531198 http://www.informaworld.com potentially lethal to humans or other consumers such as marine mammals and birds (Huang et al. 1996). No visible difference in appearance is observed between harmless and toxic shellfish. As the PSP toxins are heat stable they are not destroyed by cooking, but due to their solubility in water leaching into the cooking water occurs (Michalski 2007; Etheridge 2010), and canning procedures are reported to reduce toxin levels for this reason (Vieites et al. 1999). Following consumption the toxins bind with a high affinity to site 1 of the voltage-dependent sodium channel -subunit of muscle and nerve cells, blocking the influx of sodium and preventing the generation and propaga- tion of action potentials in these excitable cells (Cestele and Catterall 2000). Early symptoms follow- ing ingestion include tingling of the lips and tongue,