Colorimetric engineered immunoprobe for the detection and quantification of microcystins

Microcystins (MCs) are heptapeptide toxins produced by cyanobacteria. Their global occurrence in aquatic ecosystems has prompted the development of several detection methods, including antibody-based methods. Here, we propose to apply recombinant antibody technologies to the production of a bivalent colorimetric immunoprobe (scFv-AP) made of the so-called scFv fused to the alkaline phosphatase (AP) of Escherichia coli. Recombinant antibody technologies allow the development of specific probes with improved properties and suitable for the detection of MCs. The fusion protein was produced in the periplasm of recombinant bacteria and was used to develop a direct competitive enzyme immunoassay for specific detection of MCs without requiring further purification. The epitope recognized by the recombinant molecule was circumscribed to a motif common to all MCs. Such a genetic approach offers many advantages over chemical cross-linking of antibodies to colorimetric enzymes and may be adaptable to the analysis of water samples and in situ detection.