A robust and sensitive enhanced immunochromatographic assay based on UiO-66-NH2 @Au for simultaneous detection of carbofuran and 3-hydrox- y-carbofuran in fruits and vegetables

Robustness is essential to improve the analytical performance of immunochromatography. The traditional immunochromatographic assay (ICA) based on colloidal gold (AuNPs) has defects of low sensitivity and insufficient robustness. Herein, a novel composite nanocarrier of zirconium-based metal-organic frameworks@gold (UiO-66-NH2 @Au) was composed. The carrier has the same optical properties of AuNPs, and the metal-organic framework substrate can protect the antibody from extreme environments. The detection limit of the ICA based on UiO-66-NH2 @Au was about 0.1 mu g/kg for carbofuran (CBF) and 3-hydroxy-carbofuran (3-OH-CBF) in pear, bean, cucumber, and cabbage. In comparison with the ICA based on AuNPs, the sensitivity has increased by 2-10 fold. In complex environments, UiO-66-NH2 @Au significantly enhances the robustness of ICA. The pH tolerance range increased from pH 6-8 to pH 4-10, and the organic solvent tolerance increased from 20% to 40%. The recovery rates (88.6-115.4%) and coefficient of variation (2.5-14.9%) all meet the requirements of residue detection. The novel composite nano-carrier provides a new idea for establishing immunoassay methods with enhanced sensitivity and robustness.