Determination of microcystin-LR in surface water by a magnetic bead-based colorimetric immunoassay using antibody-conjugated gold nanoparticles

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. Solid phase extraction proved to be the most beneficial sample preparation method in order to reduce matrix effects which might lead to agglomeration of the AuNPs and failing of the assay. The developed method could detect MC-LR in a linear range from 0.51-11.68 mu g L super(-1) with a limit of detection (LOD) of 0.38 mu g L super(-1). The recovery rates of the toxin in spiked water samples were in the range from 88.8% to 117.5%. This proposed immunoassay constitutes a simple and cost-effective method for the detection of sanitary relevant concentrations around 1 mu g L super(-1) of MC-LR in fresh waters without any expensive or challenging equipment.