Table 1. General advantages and disadvantages of binders previously assessed for SPR analysis of PSP toxins. Binder Receptors Monoclonal antibodies Polyclonal antibodies Advantages Have a binding affinity that generally correlates with the biological response or toxicity of the toxins Can be isolated rapidly compared with antibody production Good sensitivity Constant renewable source of binder once pro- duced with minimal batch to batch variation During production less immunizing agent is required compared with polyclonal produc- tion and it is possible to select for specific epitope specificities and generate antibodies against a wider range of antigens React with a single epitope on an antigen with high specificity Binding affinity for the immunizing antigen is generally better than a receptor Less background signal than polyclonal antibodies For production relatively quick and inexpensive to produce compared with monoclonal anti- bodies Polyclonals will recognize multiple epitopes on any one antigen and are therefore more tolerant of minor changes in the antigen than monoclonal antibodies providing better cross- reactivity to structural antigens within a group The recognition of multiple epitopes generally provides more robust detection Binding affinity for the immunizing antigen is generally better than a monoclonal antibody or receptor Food Additives and Contaminants 717 Disadvantages Wider scope of binding to all compounds that act on the same receptor Have to be isolated form biological tissues and in some cases the species of origin is difficult to obtain May display poor stability May be temperature sensitive for analytical purposes For production, time, effort and commitment is high and use animals On average the binding affinity of a monoclonal antibody is lower than a polyclonal antibody As monoclonal antibodies are highly specific to a single epitope they may lose affinity to other antigens within a group with minor molecular modifications The binding affinity of an antibody does not correlate with biological response for a toxin group Antibodies sometimes display unexpected cross- reactivity with unrelated antigens in biological matrices Animals are required and are prone to batch to batch variability They produce large amounts of non-specific antibodies which can sometimes give background signal in some applications Multiple epitopes make it important to check for any cross-reactivity in biological matrixes The binding affinity of an antibody does not correlate with biological response for a toxin group toxins have been described since that time. These include radioimmunoassay (Carlson et al. 1984), immunoaffinity columns (Dietrich et al. 1996), lateral flow devices (Jellett et al. 1998; Laycock et al. 2010) and numerous competitive enzyme immunoassays (EIAs). Indirect EIAs have been developed for STX (Chu and Fan 1985; Cembella et al. 1990; Micheli et al. 2002), neosaxitoxin (NEO) (Chu et al. 1992; Bu¨ rk et al. 1995) and gonyautoxin (GTX) 2/3 (Kawatsu et al. 2002) and direct EIAs for STX and NEO (Usleber et al. 1991; Schneider et al. 1995; Chu et al. 1996; Huang et al. 1996; Dubois et al. 2010) and GTX 2/3 (Kawatsu et al. 2002). These assays all utilise antibodies produced using the previously mentioned protein conjugation chemistries with the primary modification being the PSP toxin to which the protein is conjugated. Although several EIAs and lateral flow test kits are commercially available (Laycock et al. 2010; http://www.abraxiskits.com; http:// www.biosense.com; http://www.r-biopharm.com), one shortcoming is that they are highly specific to certain toxins. This specificity, corresponding mainly to chemical structure but not proportionately to toxicity, limits an accurate measure of the total toxicity in a sample as required by regulatory authorities. For such diverse potency within this relatively large toxin group, whose small molecular weight structures are highly similar, it is extremely difficult to match the cross-reactivity profile of an antibody to the potency of each toxin for similar comparability as a receptor assay to the mouse bioassay. Usleber et al. (2001) state that from an immunological point of view the PSP toxin family must be subdivided into STX (non-hydroxy- lated) and NEO (hydroxylated) groups. Previous ELISA studies have demonstrated that when the antibodies are specific to either group they are less specific to the other. Therefore, to incorporate the full spectra of PSP toxins to an equivalent extent, antibodies produced to both the non-hydroxylated (STX) or hydroxylated toxins (NEO) will have to be utilised. Other drawbacks to these commercial kits are the high costs, primarily due to the availability and