Development of a dual-mode lateral flow assay based on structure-guided aptamers for the detection of capsaicin in gutter oils

The construction of structure-guided aptamers and the ultra-sensitive aptamer-based lateral flow assays (Apt-LFA) integrated detection method hold significant potential for food analysis. Using an engineered modified sequence strategy, we successfully developed the aptamer Cap-1-2M4, significantly enhancing its affinity for capsaicin (CAP) to 0.6197 ± 0.0689 nM. We developed a highly sensitive method for CAP detection based on Vap@AuNFs, leveraging their superior colorimetric and photothermal signals and high aptamer coupling performance. The Vap@AuNFs-based Apt-LFA (Vap@AuNFs-Apt-LFA) achieve signal amplification through catalytic hairpin assembly (CHA) and exonuclease III (Exo III). Additionally, dual-mode (colorimetric and photothermal) quantitative detection via lateral flow test strips was achieved by capturing the nucleic acid effect of Vap@AuNFs. The limit of detection (LOD) of Vap@AuNFs-Apt-LFA by colorimetric/photothermal method was 0.043 ng mL^-1 and 0.011 ng mL^-1, with linear ranges of 0.1-500 ng mL^-1 and 0.05-500 ng mL^-1, respectively. This aptamer engineering strategy and the developed Vap@AuNFs-Apt-LFA offer new directions for food safety and provide a reference for feasible portable detection methods.