Indirect enzyme-linked immunosorbent assay for saxitoxin in shellfish

An indirect enzyme-linked immunosorbent assay (ELISA) was developed for the detection of saxitoxin (STX). Antibodies against STX were demonstrated in rabbits 5 weeks after immunizing with STX-bovine serum albumin (STX-HCHO-BSA). In the ELISA, STX-HCHO-BSA or polylysine-STX was coated onto the microtiter plate, followed by incubation with standard toxin and anti-STX antibody. The amount of antibody bound to the solid phase was determined by incubation with goat anti-rabbit IgG peroxidase conjugate and a reaction with chromogenic substrate. Competitive indirect ELISA revealed that the anti-serum did not cross-react with either carbamoyl-neo-STX-sulfate or tetrodotoxin. The antibodies for STX cross-reacted with decarbamoyl-STX and neo-STX about 56% and 16% as much as they did with STX, respectively. The lower detection limits for STX, decarbamoyl-STX, and neo-STX in this system were about 25, 45, and 156 pg per assay, respectively. When STX added to clams or mussels was assayed, the detection limit for STX was about 50-100 ppb, and recoveries were in the range of 86.8-107%.