Preparation of peptides against immunocomplex of deltamethrin and application in noncompetitive lateral flow immunoassay

Lateral flow immunoassay (LFIA) has the advantages of simplicity and rapidness, and is widely used for the rapid detection of pesticides and other analytes. However, small molecule compounds such as pesticides are often analyzed using competitive LFIA (CLFIA), whose sensitivity often does not meet the actual needs. In this study, a noncompetitive LFIA (NLFIA) for deltamethrin (DM) with high sensitivity was developed by using anti-immunocomplex peptides (AIcPs). A total of 21 unique AIcPs were identified through the screening of phage-displayed cyclic peptide libraries. The AIcP containing the CYFDGAWYAC sequence in noncompetitive phage enzyme-linked immunosorbent assays (P-ELISA) exhibited a half signal saturation concentration (SC₅₀) of 1.49 ng/mL, achieving a remarkable 209-fold sensitivity enhancement compared to antigen-based competitive ELISA. The AIcP, in the form of CYFDGAWYACGGGSSK-biotin, was synthesized to prepare AIcP-conjugated gold nanoparticles (AuNPs) by reacting with streptavidin (SA)-labeled AuNPs and subsequently assembled into the NLFIA strip. After optimization, the NLFIA achieved a visual limit of detection (vLOD) of 6.25 ng/mL in Tris-HCl buffer and 0.5 mg/kg in wheat, Chinese cabbage, and celery within 8 min. Furthermore, NLFIA detection results for blind wheat samples matched those of a reference liquid chromatography method.