Antibody Functionalised Gold Nanoprobes Based Colorimetric Assay for the Direct Detection of Phenylurea Herbicide

One-step homogeneous colorimetric immunoassay format for direct detection of herbicide diuron is reported. Gold nanoparticles (30 nm) functionalised with specific anti-diuron antibody was used as bioprobes for the development of non-crosslinking hybridization method, where aggregation of the gold-nanoprobes is induced by an increasing salt concentration, and is prevented by the amount of antigen (diuron) present in sample solution. The aggregation profile of the antibody functionalised gold nanoparticles directed by the immunoreaction was investigated using transmission electron microscopy (TEM), dynamic light scattering (DLS) and was further confirmed colorimetrically by measuring the change in the absorption ratio (620/520 nm) with increasing amounts of diuron. The assay exhibited an excellent sensitivity and specificity based on absorbance profile showing the dynamic response range from 0.1-50 ng/mL for diuron with a detection limit of ~5 ng/mL. The new technique could be used for fast, high-throughput screening of pesticides in environmental diagnostics at a very low cost.