Food allergen analysis for processed food using a novel extraction method to eliminate harmful reagents for both ELISA and lateral-flow tests.

Enzyme-linked immunosorbent assay (ELISA) is commonly used to determine food allergens in food products. However, a significant number of ELISAs give an erroneous result, especially when applied to highly processed food. Accordingly, an improved ELISA, which utilizes an extraction solution comprising the surfactant sodium lauryl sulfate (SDS) and reductant 2-mercaptoethanol (2-ME), has been specially developed to analyze food allergens in highly processed food by enhancing analyte protein extraction. Recently, however, the use of 2-ME has become undesirable. In the present study, a new extraction solution containing a human- and eco-friendly reductant, which is convenient to use at the food manufacturing site, has been established. Among three chemicals with different reducing properties, sodium sulfite, tris(3-hydroxypropyl)phosphine, and mercaptoethylamine sodium sulfite was selected as a 2-ME substitute. The protein extraction ability of SDS/0.1 M sodium sulfite solution was comparable to that of SDS/2-ME solution. Next, the ELISA performance for egg, milk, wheat, peanut, and buckwheat was evaluated by using model-processed foods and commercially available food products. The data showed that the SDS/0.1 M sulfite ELISA significantly correlated with the SDS/2-ME ELISA for all food allergens examined (p < 0.01), thereby establishing the validity of the SDS/0.1 M sulfite ELISA performance. Furthermore, the new SDS/0.1 M sulfite solution was investigated for its applicability to the lateral-flow (LF) test. The result demonstrated the successful analysis of food allergens in processed food, showing consistency with the SDS/0.1 M sulfite ELISA results. Accordingly, a harmonized analysis system for processed food comprising a screening LF test and a quantitative ELISA with identical extraction solution has been established. The ELISA based on the SDS/0.1 M sulfite extraction solution has now been authorized as the revised official method for food allergen analysis in Japan.

A glass fiber sheet-based electroosmotic lateral flow immunoassay for point-of-care testing.

We have developed a quantitative immunoassay chip targeting point-of-care testing. To implement a lateral flow immunoassay, a glass fiber sheet was chosen as the material for the microfluidic channel in which the negative charge on the fiber surfaces efficiently generates the electroosmotic flow (EOF). The EOF, in turn, allows controllable bound/free separation of antigen/antibody interactions on the chip and enables precise determination of the antigen concentration. In addition, the defined size of the porous matrix was suitable for the filtration of undesired large particles. We confirmed the linear relationship between the concentration of analyte and the resulting fluorescence intensity from the immunoassay of two model analytes, C-reactive protein (CRP) and insulin, demonstrating that analyte concentration was quantitatively determined within the developed chip in 20 min. The limits of detection were 8.5 ng mL(-1) and 17 ng mL(-1) for CRP and insulin, respectively.