A Membrane-Based ELISA Assay and Electrochemical Immunosensor for Microcystin-LR in Water Samples

We describe within this paper the development of an affinity sensor for the detection of the cyanobacterial toxin microcystin-LR The first stage of the work included acquiring and testing of the antibodies to this target. Following the investigation, a heterogeneous direct competitive enzyme-linked immunosorbent assay (ELISA) format for rnicrocystin-LR detection was developed, achieving a detection limit, LLD80 = 0.022 mu g L-1. The system was then transferred to an affinity membrane sorbent-based ELISA. This was an amenable format for immunoassay incorporation into a disposable amperometric immunosensor device. This membrane-based ELISA achieved a detection limit, LLD80 = 0.06 mu g L-1. A three-electrode immunosensor system was fabricated using thick-film screen-printing technology. Amperometric horseradish peroxidase transduction of hydrogen peroxide catalysis, at low reducing potentials, versus Ag/AgCl reference and carbon counter electrodes, was facilitated by hydroquinone-mediated electron transfer. A detection limit of 0.5 mu g L-1 for microcystin-LR was achieved. Similar levels of detection could be obtained using direct electrochemical sensing of the dye produced using the membrane-based ELISA. These techniques proved to be simple, cost-effective, and suitable for the detection of microcystin-LR in buffer and spiked tap and river water samples.