Production of a Recombinant Single-Domain Antibody for Gluten Detection in Foods Using the Pichia pastoris Expression System

Electrochemical tracking of gluten in marketed foods by using a recombinant antibody fragment based-platform

The only treatment to effectively manage celiac disease is the avoidance of gluten containing foods. Therefore, and given its high prevalence, it is of utmost importance to have reliable and efficient methods for the detection of gluten to ensure the well-being and quality of life of celiacs. This work presents the development of an electrochemical immunoplatform exhibiting many practical advantages including simplicity, reduced cost and high sensitivity for the screening of gluten-containing products. The methodology exploited the unique features offered by a recombinant antibody fragment with high affinity towards gliadin together with the use of magnetic microcarriers (MμCs) as scaffolds for the implementation of an indirect competitive immunoassay. Using amperometric transduction on disposable electrodes and the horseradish peroxidase/hydrogen peroxide/hydroquinone system, a dynamic range between 7.3 and 1982 ng mL-1 was obtained for gliadin standards, with a limit of detection of 1.4 ng mL-1. The developed immunoplatform was successfully employed for the analysis of a variety of processed foodstuffs, demonstrating the ability to discriminate between gluten-free and gluten-containing foods according to the legislated threshold (20 mg kg-1 of gluten). The agreement with the results provided by the R5-based ELISA and qPCR methods confirmed the suitability of the bioplatform as a competitive tool in terms of assay time (results in just 60 min after gliadin extraction) sensitivity and applicability, even at the point of need.

Simple dual-readout immunosensor based on phosphate-triggered and potassium permanganate for visual detection of fenitrothion

Multicolor-based visual immunosensor is a promising tool for rapid analysis without the use of bulky instruments. Herein, an anti-fenitrothion nanobody-alkaline phosphatase fusion protein (VHHjd8-ALP) was employed to develop a multicolor visual immunosensor (MVIS) and a ratiometric fluorescence MVIS (RFMVIS, respectively). After one-step competitive immunoassay, the VHHjd8-ALP bound to microplate catalyzed phenyl phosphate disodium salt (ArP) into phenol. Under high alkaline condition (pH 12), the phenol reduced KMnO4 to intermediate (K2MnO4) and further to MnO2 in alkaline condition (pH 12), accompanied by a visible color transition of purple-green-yellow, which can be used for semiquantitative visual analysis or qualitative detection by measuring RGB value. RFMVIS was proposed on the basis of MVIS to further improve sensitivity. The CdTe quantum dot and fluorescein were used as signal probes to develop the fluorescent immunosensor. The CdTe dots with red emission (644 nm) was quenched by oxidation of KMnO4, whereas the fluorescein with green emission (520 nm) remained constant, accompanied by a fluorescent color transition of green-yellow-red. By measuring the ratio of the fluorescence intensity (I644/I520), the ratiometric fluorescence immunosensor was developed for qualitative analysis. The two visual immunosensors were sensitive and simple, and they showed good accuracy and practicability in the recovery test, thus are ideal tools for rapid screening.

Production and Characterization of Novel Fabs Generated from Different Phage Display Libraries as Probes for Immunoassays for Gluten Detection in Food

Gluten is the main fraction of wheat proteins. It is widely used in the food industry because of the properties that are generated in the dough, but it is also able to trigger diseases like allergies, autoimmunity processes (such as celiac disease), and intolerances in sensitized persons. The most effective therapy for these diseases is the total avoidance of gluten in the diet because it not only prevents damage but also enhances tissue healing. To ensure the absence of gluten in food products labeled as gluten-free, accurate detection systems, like immunoassays, are required. In this work, four recombinant Fab antibody fragments, selected by phage display technology, were produced and tested for specificity and accuracy against gluten in experimental flour mixtures and commercial food products. A high-affinity probe (Fab-C) was identified and characterized. An indirect ELISA test was developed based on Fab-C that complied with the legal detection limits and could be applied in the assessment of gluten-free diets.

A highly sensitive fluorescence immunochromatography strip for thiacloprid in fruits and vegetables using recombinant antibodies

Thiacloprid (TCL) is a neonicotinoid insecticide. Its widespread use has led to high levels of residue in fruits and vegetables. Hence, it is important to detect TCL rapidly, accurately, and sensitively in fruits and vegetables. Recombinant antibodies (rAbs) can be synthesized rapidly with little batch-to-batch variation. In this study, recombinant single-chain variable fragment (scFv) antibody and full-length recombinant antibody against TCL were produced using three different expression systems (E. coli, yeast, and mammalian cell). The results of SDS-PAGE and non - competitive enzyme-linked immunosorbent assay (ELISA) indicated that the full-length rAb exhibited promising characteristics, and the IC₅₀ value of indirect competitive ELISA (ic-ELISA) was 2.63 μg L^-1. However, recombinant scFv antibody had little affinity for the antigen. To understand antibody recognition, the three-dimensional (3D) model of the variable fragment (Fv) was built via homologous modeling. The interaction between Fv and TCL was analyzed via molecular docking and the results of molecular docking showed that VAL-158, ALA-211, PHE-220, TRP-218, TRP-49, and ILE-100 were mainly responsible for antibody recognition. In addition, a time-resolved fluorescent microsphere-immunochromatographic test strip (TRFM-ICTS) was developed with a linear range and limit of detection of 0.01-10 ng mL^-1 and 0.003 ng mL^-1 within 15 min under optimal conditions. The IC₅₀ value was 4.268 ng mL^-1, and the recovery ranged between 79.4% and 118.6%, which was consistent with HPLC-MS. The TRFM-ICTS has great advantages in sensitivity and applicability.

Analytical Methods for Allergen Control in Food Processing

Food allergy and food-related anaphylaxis have become a growing public health and food safety issue worldwide [...]

Nanobody and Nanozyme-Enabled Immunoassays with Enhanced Specificity and Sensitivity

Immunoassay as a rapid and convenient method for detecting a variety of targets has attracted tremendous interest with its high specificity and sensitivity. Among the commonly used immunoassays, enzyme-linked immunosorbent assay has been widely used as a gold standard method in various fields that consists of two main components including a recognition element and an enzyme label. With the rapid advances in nanotechnology, nanobodies and nanozymes enable immunoassays with enhanced specificity and sensitivity compared with conventional antibodies and natural enzymes. This review is focused on the applications of nanobodies and nanozymes in immunoassays. Nanobodies advantage lies in their small size, high specificity, mass expression, and high stability. Nanozymes with peroxidase, phosphatase, and oxidase activities and their applications in immunoassays are highlighted and discussed in detail. In addition, the challenges and outlooks in terms of the use of nanobodies and the development of novel nanozymes in practical applications are discussed.