Development of a barcode-style lateral flow immunoassay for the rapid semi-quantification of gliadin in foods.

In this work, a barcode-style lateral flow immunoassay is developed using two cut-off values (10 and 50 mg kg(-1) gliadin) to provide a semi-quantification for identifying "gluten-free" and "very low gluten" foods, based on the international Codex Alimentarius Standard. This developed assay exhibits favorable specificity in differentiating wheat from seven commonly used grains, with only a slight cross-reaction with barely. The intra-assay and inter-assay CV values of this assay were 1.5-1.7% and 2.5-4.5%, respectively, revealing high reproducibility. In the analysis of 48 food samples, the results of this assay closely agreed with those obtained using AOAC-approved ELISA or strip kits, as the Cohen's kappa coefficients for both comparisons exceeded 0.8. Thus, this developed assay can be used to quickly estimate the gliadin content in foods in order to protect people with wheat allergy or celiac disease from the accidental ingestion of gliadin.

Sensitive detection and quantification of gliadin contamination in gluten-free food with immunomagnetic beads based liposomal fluorescence immunoassay.

Gliadin from wheat is a common food allergen that can induce baker's asthma, wheat-dependent exercise-induced anaphylaxis, atopic dermatitis, and celiac disease. This gliadin assay focuses on rapidly screen and check for gluten contamination in raw materials and in the gluten-free food production process, not only for wheat-sensitive patients but also for the industries producing gluten-free foodstuffs. The developed assay incorporates the use of anti-gliadin antibody-conjugated immunomagnetic beads (IMBs) to capture the gliadin in samples and fluorescent dyes-loaded immunoliposomal nanovesicles (IMLNs) to produce and enhance the detection signal. Hence, a sandwich complex is formed as "IMBs-gliadin-IMLNs". Experimental results indicate that this detection platform exhibits good sensitivity for gliadin with a detection limit as low as 0.6 µg mL(-1) of gliadin; as the polyclonal antibody showed slight cross-reactions with barley and rye. Excellent recovery rates were found ranging from 83.5 to 102.6% as testing the spiked samples. Moreover, the CV (%) of intra- and inter-assay of this developed assay are 4.8-10.6% and 3.5-9.9%, respectively. Based on a parallel analysis of twenty food samples, the results of this developed assay provide a good consistency with those of an AOAC-approved ELISA kit without any false-negative results. The proposed assay method is thus a highly promising alternative method for detecting the contamination of gliadin in the food industry.

Detection of gliadin in foods using a quartz crystal microbalance biosensor that incorporates gold nanoparticles.

This work develops a label-free gliadin immunosensor that is based on changes in the frequency of a quartz crystal microbalance (QCM) chip. A higher sensitivity was obtained by applying 25 nm gold nanoparticles (AuNPs) to the surface of a bare QCM electrode. Subsequently, chicken anti-gliadin antibodies (IgY) were immobilized directly on the AuNP-modified surface by cross-linking amine groups in IgY with glutaraldehyde. Experimental results revealed that the change in frequency exhibited when 2 ppm gliadin was bound to the AuNP-modified electrode was 35 Hz (48%) greater than that of the bare gold electrode. The linear dynamic range in 60% ethanol was from 1 × 10(1) to 2 × 10(5) ppb gliadin, and the calculated limit of detection (LOD) was 8 ppb. The entire detection process was completed in 40 min and was highly repeatable. Additionally, the AuNP-modified QCM system generated results in the detection of gliadin in 10 commercial food products that were consistent with those obtained using an AOAC-approved gliadin kit. In conclusion, the QCM platform provides a potential alternative means of ensuring that people with wheat allergies and celiac patients have access to gliadin-free food.