Dual signal-enhanced immunochromatographic test strip based on Au@PtNPs: From sensitive detection of thiamethoxam to multiplex pesticide screening in vegetables

Au@PtNPs displayed superiority in antibody binding efficiency and signal intensity. • Multifunctional Au@PtNPs were employed to construct dual-signal ICTS. • Au@PtNPs-ICTS demonstrated excellent performance in thiamethoxam detection. • Au@PtNPs-ICTS could change identification components to detect different targets. Immunochromatographic test strip (ICTS) is a rapid analytical technique widely used in environmental and food detection owing to its merits of simple operation and short analysis time. Herein, three-dimensional nanoflower-structured gold‑platinum nanoparticles (Au@PtNPs) were synthesized via a seed-growth method. Compared with conventional gold nanoparticles (AuNPs), Au@PtNPs exhibited stronger signal intensity, excellent catalytic performance, and efficient antibody binding efficiency. Colorimetric Au@PtNPs-ICTS and catalytic colorimetric Au@PtNPs-ICTS were developed for the sensitive detection of thiamethoxam (THI) in vegetables. The limits of detection (LODs) for colorimetric Au@PtNPs-ICTS and catalytic colorimetric Au@PtNPs-ICTS quantitative analysis were 0.18 ng/mL and 0.093 ng/mL, respectively, representing approximately 3-fold and 6-fold improvement compared to AuNPs-ICTS (0.56 ng/mL). Furthermore, highly sensitive detection of multiple pesticide residues (chlorpyrifos, acetamiprid, and imidacloprid) was achieved by replacing the corresponding target antigens and antibodies, which further verified the universality of this immunochromatographic strategy. Fig. 1. (A) Schematic of the preparation process of AuNPs and Au@PtNPs; (B) Schematic of the preparation process of Au@PtNPs-mAb and AuNPs-mAb probes; (C) Schematic diagram of ICTS structure; (D) Schematic diagram of the detection process of Au@PtNPs-ICTS. Download: Download high-res image (151KB) Download: Download full-size image