SummaryAntibody MC10E7 is one of a small number of monoclonal antibodies that bind specifically to [Arg4]‐microcystins, and it can be used to survey natural water sources and food samples for algal toxin contamination. However, the development of sensitive immunoassays in different test formats, particularly user‐friendly tests for on‐site analysis, requires a sensitive but also cost‐effective antibody. The original version of MC10E7 was derived from a murine hybridoma, but we determined the sequence of the variable regions using the peptide mass‐assisted cloning strategy and expressed a scFv (single‐chain variable fragment) format of this antibody in yeast and a chimeric full‐size version in leaves of Nicotiana tabacum and Nicotiana benthamiana to facilitate inexpensive and scalable production. The specific antigen‐binding activity of the purified antibody was verified by surface plasmon resonance spectroscopy and ELISA, confirming the same binding specificity as its hybridoma‐derived counterpart. The plant‐derived antibody was used to design a lateral flow immunoassay (dipstick) for the sensitive detection of [Arg4]‐microcystins at concentrations of 100–300 ng/L in freshwater samples collected at different sites. Plant‐based production will likely reduce the cost of the antibody, currently the most expensive component of the dipstick immunoassay, and will allow the development of further antibody‐based analytical devices and water purification adsorbents for the efficient removal of toxic contaminants.

Herein we describe the development of a homogeneous competitive colorimetric immunoassay using antigen-functionalized magnetic beads (MBs) and antibody-immobilized gold nanoparticles (AuNPs) combined with the established gold staining method for the determination of microcystin-leucine-arginine (MC-LR) in surface water.

Eutrophication of water bodies can promote cyanobacterial (blue-green algae) blooms, which has become a source of increasing concern for both recreational and drinking water use. Many bacterial species can produce toxins that pose threats to wildlife, domestic animals and humans. Microcystin-leucine-arginine (MC-LR) is the most frequent and most toxic microcystin congener. For the first time, lab-scale investigations were performed to test the application of a recombinant plant-derived anti-MC-LR antibody immobilized on an immunoaffinity support material to selectively extract the toxin from spiked freshwater samples. As a comparison, its hybridoma-derived counterpart (murine monoclonal antibody) was evaluated. The antibody-doped material was prepared via an optimized sol-gel process; its stability and binding efficiency of MC-LR in spiked freshwater samples were thoroughly tested using the ELISA and orthogonal LC-MS methods. For removal, two column-based procedures with sequential or continuous cyclic sample addition and a suspension mode (moving adsorbent) were tested. Noteworthy the results obtained with a crude antibody fraction were fully compatible with the highly purified preparation. This study paves the way for further investigation being focused on novel applications of plant-derived anti-MC-LR antibodies in bioremediation to selectively deplete the toxin from freshwater: a green and promising technology without secondary pollution.