Microcystin-(Leucine-Arginine) Immunosensor Based on Iron(II, III) Magnetic Nanoparticles

Abstract

An electrochemical immunosensor for microcystin-(leucine-arginine) based on magnetic bionanoparticles and iron(II, III) oxide was developed. The bionanoparticles were prepared by cross-linking antibodies of microcystin-(leucine-arginine) and amino-functionalized magnetic iron(II, III) oxide nanoparticles with glutaraldehyde, followed by immobilization on the surface of a magnetic electrode. The immunosensor was based on the model of direct competition, as microcystin-(leucine-arginine) and horseradish peroxidase-conjugated microcystin-(leucine-arginine) competitively combined with immobilizing antibodies. The peak current of differential pulse voltammetry (DPV) decreased with an increase of microcystin-(leucine-arginine) concentration after antigen-antibody reaction. When the background current was stabilized, the anodic peak current response and change in peak response were recorded. Under the optimized conditions, the change in response was proportional to the microcystin-(leucine-arginine) concentration between 0.010 and 100 µg/L with a limit of detection equal to 0.009 µg/L. Amperometry was adopted to determine microcystin-(leucine-arginine); the linear dynamic range was 0.10 to 100 µg/L with a detection limit of 0.08 µg/L. The method was successfully applied in the determination of microcystin-(leucine-arginine) in river water and the recoveries were between 90.2% and 110.5%.