Development and Application of Two Modes of Immunochromatographic Assay Strips for Vanillin Rapid Detection in Food Products

Improper use of vanillin as a food flavor additive presents a potential threat, and its effective supervision is therefore essential. Rapid biosensing is a beneficial supplementary or alternative strategy for current detection methods. Two modes of immunochromatographic assay (ICA) strips, based on gold nanoparticles (GNP) and fluorescent microparticles (FMP) labeled with a monoclonal antibody against vanillin, were separately assembled to obtain a GICA strip and an FICA strip for the detection of vanillin. The colorimetric/fluorescence signals of the strips were directly judged for semi-quantification by the naked eye and then digitally quantified by strip readers. The GICA demonstrated a linear range of 15.6–500 ng/mL, having a limit of detection (LOD) of 10.3 ng/mL. For the FICA strip, the enhanced sensitivity achieved an LOD value as low as 2.04 ng/mL and showed a linear range between 3.12 ng/mL and 200 ng/mL, representing a 5-fold improvement over the GICA strip. The two modes of ICA strips all had high specificity, stability, accuracy and precision for on-site vanillin detection within 10 min. For vanillin levels in authentic food product samples, the results were well correlated with the measurements obtained via the referenced ELISA and HPLC methods. The results indicated that two modes of ICA strips were capable of rapid, sensitive, on-site, semi-quantitative and quantitative detection of vanillin in food products, ultimately guaranteeing food safety and consumer health.