Lateral Flow Immunochromatographic Assay for Sensitive Pesticide Detection by Using Fe3O4 Nanoparticle Aggregates as Color Reagents

Magnetic Fe3O4 particle aggregates were prepared by cross-linking Fe3O4 nanoparticles bearing surface carbonyl groups with poly-L-lysine. Upon further coupling with antiparaoxon methyl polyclonal antibody, the resultant particle aggregate-based probes were used in a lateral flow immunochromatographic assay (LFIA) of pesticide residue of paraoxon methyl. The results were compared with that achieved by using the mother Fe3O4 nanoparticles. More quantitative results on the signal amplification effect endowed by the controlled aggregation of Fe3O4 nanoparticles were extracted by relative optical density analysis. Under optimized conditions, a detection limit of 1.7 ng/mL for paraoxon methyl was achieved by using the particle aggregates, which is almost 40-fold lower than that based on the mother Fe3O4 nanoparticles.