Herbicide Detection with Nanoparticle-Amplified Immunoassays

Primary author: Eunice Kwon
Faculty sponsor: Bernard Van Wie

Primary college/unit: Voiland College of Engineering and Architecture
Campus: Pullman


New detection methods are being developed to monitor potentially harmful pesticides and herbicides, which are suspected of contributing to ailments ranging from diarrhea to death. In this study, we present the detection of the herbicide atrazine—approximately 65 million pounds of which are used in the United States per year—with two types of immunoassay while using a novel mesoporous palladium@platinum (Pd@Pt) core-shell nanoparticle (NP) detection label. Pd@Pt NPs have peroxidase-like catalytic activity, reducing hydrogen peroxide while oxidizing the substrate, resulting in higher pH- and thermo-stability than enzymes and greater catalytic activity than monometallic Pt black. We replaced the enzyme in the indirect ELISA method with Pd@Pt NPs, forming a nanoparticle-linked immunosorbent assay (NLISA) that eliminated a step in the detection process. We used this competitive NLISA on atrazine, yielding a limit of detection of 0.5 ppb (10% inhibition) with 0.1 – 500 ppb linear range, then on water samples spiked with atrazine at three concentrations, yielding 98 – 115 % recoveries. We then used LFIA with a Pd@Pt NP detection label on atrazine; in this case, test line intensity increased with decreasing atrazine concentration, because competitive immunoassays yield inverse results. Finally, we evaluated our methods by comparing our results with those obtained with the instrumental assay HPLC, which yielded an atrazine limit of detection of 10 ppb. We found that our novel Pd@Pt NP detection label has a higher sensitivity than HPLC and that NLISA saves time and reagents by eliminating the secondary antibody step.