Magnetic beads-based electrochemical immunosensor for monitoring allergenic food proteins

Electrochemical flow-through biosensors based on microfiber enzymatic filter discs placed at printed electrodes

A new type of electrochemical biosensors in a flow injection system with printed electrodes were developed and tested. A filter disc (7 mm diameter) with immobilized enzyme was placed at the printed electrode. This conception combines the advantages of biosensors with a bioreceptor at the electrode surface and systems with spatially separated enzymatic and detection parts. Filters of different composition (glass, quartz, and cellulose), thickness, porosity, and ways of binding enzyme to their surface were tested. Only covalent bonds throughout a filter-aminosilane-glutaraldehyde-enzyme chain ensured a long-time and reproducible biosensor response. The developed method of biosensor preparation has been successfully applied to enzymes glucose oxidase, laccase and choline oxidase. The dependences of peak current on detection potential, flow rate, injection volume, analyte concentration as well as biosensor lifetime and reproducibility were investigated for glucose oxidase biosensor. The sensitivity of measurements was two or more times higher than that of biosensor with a mini-reactor filled by powder with immobilized enzyme. The developed biosensor with laccase was tested by determining dopamine in the pharmaceutical infusion product Tensamin®. Results of the analysis (40.0 ± 0.7 mg mL-1, SD = 0.8 mg mL-1, RSD = 1.85 %, N = 11) show a good agreement with the manufacturer's declared value.

An Impedance-Based Immunosensor for the Detection of Ovalbumin in White Wine

Food allergies are an exceptional response of the immune system caused by the ingestion of specific foods. The main foods responsible for allergic reactions are milk, eggs, seafood, soy, peanuts, tree nuts, wheat, and their derived products. Chicken egg ovalbumin (OVA), a common allergen molecule, is often used for the clarification process of wine. Traces of OVA remain in the wine during the fining process, and they can cause significant allergic reactions in sensitive consumers. Consequently, the European Food Safety Authority (EFSA) and the American Food and Drug Administration (FDA) have shown the risks for allergic people to assume allergenic foods and food ingredients, including eggs. Commonly, OVA detection requires sophisticated and time-consuming analytical techniques. Intending to develop a faster assay, we designed a proof-of-concept non-Faradaic impedimetric immunosensor for monitoring the presence of OVA in wine. Polyclonal antibodies anti-OVA were covalently immobilised onto an 11-mercaptoundecanoic-acid (11-MUA)-modified gold surface. The developed immunosensor was able to detect OVA in diluted white wine without the need for an external probe or any pre-treatment step with a sensitivity of 0.20 µg/mL, complying with the limit established by the resolution OIV/COMEX 502-2012 for the quantification of allergens in wine.

Iron/iron oxide-based magneto-electrochemical sensors/biosensors for ensuring food safety: recent progress and challenges in environmental protection

Foodborne diseases have arisen due to the globalization of industry and the increase in urban population, which has led to increased demand for food and has ultimately endangered the quality of food. Foodborne diseases have caused some of the most common public health problems and led to significant social and economic issues worldwide. Food quality and safety are affected by microbial contaminants, growth-promoting feed additives (β-agonists and antibiotics), food allergens, and toxins in different stages from harvesting to storage and marketing of products. Electrochemical biosensors, due to their reduced size and portability, low cost, and low consumption of reagents and samples, can quickly provide valuable quantitative and qualitative information about food contamination. In this regard, using nanomaterials can increase the sensitivity of the assessment. Magnetic nanoparticle (MNP)-based biosensors, especially, are receiving significant attention due to their low-cost production, physicochemical stability, biocompatibility, and eco-friendly catalytic characteristics, along with magnetic, biological, chemical and electronic sensing features. Here, we provide a review on the application of iron-based magnetic nanoparticles in the electrochemical sensing of food contamination. The types of nanomaterials used in order to improve the methods and increase the sensitivity of the methods have been discussed. Then, we stated the advantages and limitations of each method and tried to state the research gaps for each platform/method. Finally, the role of microfluidic and smartphone-based methods in the rapid detection of food contamination is stated. Then, various techniques like label-free and labelled regimes for the sensitive monitoring of food contamination were surveyed. Next, the critical role of antibody, aptamer, peptide, enzyme, DNA, cells and so on for the construction of specific bioreceptors for individual and simultaneous recognition by electrochemical methods for food contamination were discussed. Finally, integration of novel technologies such as microfluidic and smartphones for the identification of food contaminations were investigated. It is important to point out that, in the last part of each sub-section, attained results of different reports for each strategy were compared and advantages/limitations were mentioned.

Tracking a Major Egg Allergen to Assess Commercial Food Label Compliance: Towards a Simple and Fast Immunosensing Device

An amperometric immunosensor was developed for the analysis of the major egg-white allergen ovotransferrin (Gal d 3) in commercial food products because the (accidental) intake, skin contact with, and/or inhalation of eggs can lead to severe disorders in allergic individuals. Employing a sandwich-type immunosensing strategy, screen-printed carbon electrodes (SPCE) were biomodified with anti-Gal d 3 (capture) antibodies, and the allergen’s detection was achieved with anti-Gal d 3 antibodies labelled with horseradish peroxidase (HRP). The 3,3′,5,5′-tetramethylbenzidine (TMB)/H2O2 reaction with HRP was used to obtain the electrochemical (amperometric) signal. An attractive assay time of 30 min and a remarkable analytical performance was achieved. The quantification range was established between 55 and 1000 ng·mL−1, with a limit of detection of 16 ng·mL−1. The developed method demonstrated good precision (Vx0 = 5.5%) and provided precise results (CV < 6%). The sensor also detected extremely low amounts (down to 0.010%) of egg. The analysis of seven raw and/or cooked egg and egg-white samples indicated that food processing influences the amount of allergen. Furthermore, to assure the compliance of product labelling with EU legislation, 25 commercial food ingredients/products were analysed. The accuracy of the results was confirmed through an ELISA assay. The stability of the ready-to-use sensing surface for 20 days allows a reduction of the reagents’ volumes and cost.

Amperometric immunosensor developed for sensitive detection of SARS-CoV-2 spike S1 protein in combined with portable device

In this present study, an amperometric immunosensor was developed based on disposable screen-printed carbon electrode (SPCE) for specific and sensitive detection of SARS-CoV-2 S1 protein. Anti-SARS-CoV-2 S1 monoclonal antibody was firstly immobilized onto the electrode surface. Then, the sandwich complex was formed by addition of S1 protein, secondary antibody and HRP-IgG, respectively. Chronoamperometry measurements were done in the presence of TMB mediator and the detection of SARS-CoV-2 S1 protein was performed by using 10 μL sample. The limit of detection (LOD) was found to be 0.19 ng/mL (equals to 24.7 amol in 10 μL sample) in the linear range of 0.5–10 ng/mL obtained in buffer medium. The applicability of this assay was investigated in the linear range of 0.5–3 ng/mL S1 protein in artificial saliva medium with the LOD as 0.13 ng/mL (equals to 16.9 amol in 10 μL sample). The selectivity study was examined in the presence of Hemagglutinin antigen (HA) in both mediums; buffer and artificial saliva while resulting with the successful discrimination between S1 protein and HA. The one of ultimate goals of our study is to present the possible implementation of this assay to point of care (POC) analysis. Under this aim, this assay was performed in combination with a portable device that is the commercial electrochemical analyzer. Amperometric detection of S1 protein in the range of 0.5–5 ng/mL was also successfully performed in artificial saliva medium with a resulting LOD as 0.15 ng/mL (equals to 19.5 amol in 10 μL sample). In addition, a selectivity study was similarly carried out by portable device.

Disposable electrochemical microfluidic device for ultrasensitive detection of egg allergen in wine samples

Food allergies have been increasing all over the world. Egg is an important component in the food industries and the second most common cause of food allergy, shortly after milk. In the wine industry, egg white is applied as a fining agent for tannin removal. In this study, a sandwich-based immunoassay for ultrasensitive detection of ovalbumin (OVA) in wine samples was developed. The assay involves the use of magnetic beads (MBs) decorated with a polyclonal anti-OVA antibody (Ab₂) and horseradish peroxidase (HRP), used as label for the quantification in a disposable electrochemical microfluidic device (DEμD) here developed. The Ab₂-MB-HRP prepared was applied to capture, separate, and pre-concentrate OVA from wine samples. In the DEμD, OVA was immune-magnetically captured (OVA-Ab₂-MB-HRP), producing a sandwich structure (GO-Ab₁-OVA-Ab₂-MB-HRP) on the electrode's surface. This arrangement results in an ultrasensitive device, achieving the ultralow limit of detection of 0.2 fg mL^-1 OVA. Five samples of wines were analyzed by using the immuno-magneto-assay which presents excellent accuracy compared with enzyme-linked immunosorbent assay (ELISA).

A biomimetic "intestinal microvillus" cell sensor based on 3D bioprinting for the detection of wheat allergen gliadin

A biomimetic "intestinal microvillus" electrochemical cell sensor based on three-dimensional (3D) bioprinting was developed, which can specifically and accurately detect wheat gliadin. Self-assembled flower-like copper oxide nanoparticles (FCONp) and hydrazide-functionalized multiwalled carbon nanotubes (MWCNT-CDH) were innovatively synthesized to improve the sensor performance. A conductive biocomposite hydrogel (bioink) was prepared by mixing FCONp and MWCNT-CDH based on GelMA gel. The cluster-shaped microvillus structure of small intestine was accurately printed on the screen printing electrode with the prepared bioink using stereolithography 3D-bioprinting technology, and then the Rat Basophilic Leukemia cells were immobilized on the gel skeleton. Next, the developed cell sensor was used to effectively detect wheat allergen gliadin. The experimental results show that the bioprinted cell sensor sensitively detects wheat gliadin when the optimized cell numbers and immobilized time are 1 × 10⁶ cells/mL and 10 min, respectively. The linear detection range is 0.1-0.8 ng/mL, and the detection limit is 0.036 ng/mL. The electrochemical cell sensor based on 3D printing technology has excellent stability and reproducibility. Thus, a simple and novel electrochemical detection approach for food allergens was established in this study with potential application in food safety detection and evaluation.

Whey allergens: Influence of nonthermal processing treatments and their detection methods

Whey and its components are recognized as value-added ingredients in infant formulas, beverages, sports nutritious foods, and other food products. Whey offers opportunities for the food industrial sector to develop functional foods with potential health benefits due to its unique physiological and functional attributes. Despite all the above importance, the consumption of whey protein (WP) can trigger hypersensitive reactions and is a constant threat for sensitive individuals. Although avoiding such food products is the most successful approach, there is still a chance of incorrect labeling and cross-contamination during food processing. As whey allergens in food products are cross-reactive, the phenomenon of homologous milk proteins of various species may escalate to a more serious problem. In this review, nonthermal processing technologies used to prevent and eliminate WP allergies are presented and discussed in detail. These processing technologies can either enhance or mitigate the impact of potential allergenicity. Therefore, the development of highly precise analytical technologies to detect and quantify the existence of whey allergens is of considerable importance. The present review is an attempt to cover all the updated approaches used for the detection of whey allergens in processed food products. Immunological and DNA-based assays are generally used for detecting allergenic proteins in processed food products. In addition, mass spectrometry is also employed as a preliminary technique for detection. We also highlighted the latest improvements in allergen detection toward biosensing strategies particularly immunosensors and aptasensors.

New applications of advanced instrumental techniques for the characterization of food allergenic proteins

Current approaches based on electrophoretic, chromatographic or immunochemical principles have allowed characterizing multiple allergens, mapping their epitopes, studying their mechanisms of action, developing detection and diagnostic methods and therapeutic strategies for the food and pharmaceutical industry. However, some of the common structural features related to the allergenic potential of food proteins remain unknown, or the pathological mechanism of food allergy is not yet fully understood. In addition, it is also necessary to evaluate new allergens from novel protein sources that may pose a new risk for consumers. Technological development has allowed the expansion of advanced technologies for which their whole potential has not been entirely exploited and could provide novel contributions to still unexplored molecular traits underlying both the structure of food allergens and the mechanisms through which they sensitize or elicit adverse responses in human subjects, as well as improving analytical techniques for their detection. This review presents cutting-edge instrumental techniques recently applied when studying structural and functional aspects of proteins, mechanism of action and interaction between biomolecules. We also exemplify their role in the food allergy research and discuss their new possible applications in several areas of the food allergy field.

A simple method to construct a low-cost immunosensor based on a dithiol-functionalized polydopamine platform

A simple and low-cost electrochemical CEA immunosensor was investigated via the self-polymerization of dopamine and a dithiol compound spacer for the covalent immobilization of antibodies. The designed CEA immunosensor exhibited a linear response and a low detection limit.

Nanostructure-based Sensitive Electrochemical Immunosensors

It is well-known that electrochemical immunosensors have many advantages, including but not limited to high sensitivity, simplicity in application, low-cost production, automated control and potential miniaturization. Due to specific antigen–antibody recognition, electrochemical immunosensors also have provided exceptional possibilities for real-time trace detection of analytical biotargets, which consists of small molecules (such as natural toxins and haptens), macromolecules, cells, bacteria, pathogens or viruses. Recently, the advances in the development of electrochemical immunosensors can be classified into the following directions: the first is using electrochemical detection techniques (voltammetric, amperometric, impedance spectroscopic, potentiometric, piezoelectric, conductometric and alternating current voltammetric) to achieve high sensitivity regarding the electrochemical change of electrochemical signal transduction; the second direction is developing sensor configurations (microfluidic and paper-based platforms, microelectrodes and electrode arrays) for simultaneous multiplex high-throughput analyses; and the last is designing nanostructured materials serving as sensing interfaces to improve sensor sensitivity and selectivity. This chapter introduces the working principle and summarizes the state-of-the-art of electrochemical immunosensors during the past few years with practically relevant details for: (a) metal nanoparticle- and quantum dot-labeled immunosensors; (b) enzyme-labeled immunosensors; and (c) magnetoimmunosensors. The importance of various types of nanomaterials is also thoroughly reviewed to obtain an insight into understanding the theoretical basis and practical orientation for the next generation of diagnostic devices.

Surface plasmon resonance (SPR) biosensors for food allergen detection in food matrices

Food allergies are recognized as a growing public health concern, with an estimated 3% of adults and 6-8% of children affected by food allergy disorders. Hence, food allergen detection, labeling, and management have become significant priorities within the food industry, and there is an urgent requirement for reliable, sensitive, and user-friendly technologies to trace food allergens in food products. In this critical review, we provide a comprehensive overview of the principles and applications of surface plasmon resonance (SPR) biosensors in the identification and quantification of food allergens (milk, egg, peanut, and seafood), including fiber-optic surface plasmon resonance (FOSPR), surface plasmon resonance imaging (SPRI), localized surface plasmon resonance (LSPR), and transmission surface plasmon resonance (TSPR). Moreover, the characteristics and fitness-for-purpose of each reviewed SPR biosensor is discussed, and the potential of newly developed SPR biosensors for multi-allergen real-time detection in a complex food system is highlighted. Such SPR biosensors are also required to facilitate the reliable, high-throughput, and real-time detection of food allergens by the food control industry and food safety control officials to easily monitor cross-contamination during food processing.

Advances in electrochemical immunosensors

Immunosensors are compact tools on which antibody and antigen interactions are formed. The specific interaction between antibody and antigen is detected by using a transducer and an electrical signal is measured. This specific interaction between these molecules makes immunosensor very attractive for several applications in different fields. Electrochemical immunosensors are successful devices in selective and sensitive detection of several analytes. Electrochemical transducing methods such as voltammetric, potentiometric, conductometric or impedimetric have been utilized in different applications due to their excellent properties such as being low-cost, sensitivity and simplicity. In this chapter, the fundamentals of electrochemical immunosensors are summarized and different applications in food, environmental and clinical analyses are investigated and discussed.

Electrochemical immunosensors - A powerful tool for analytical applications

Immunosensors are biosensors based on interactions between an antibody and antigen on a transducer surface. Either antibody or antigen can be the species immobilized on the transducer to detect antigen or antibody, respectively. Because of the strong binding forces between these biomolecules, immunosensors present high selectivity and very high sensitivity, making them very attractive for many applications in different science fields. Electrochemical immunosensors explore measurements of an electrical signal produced on an electrochemical transductor. This signal can be voltammetric, potentiometric, conductometric or impedimetric. Immunosensors utilizing electrochemical detection have been explored in several analyses since they are specific, simple, portable, and generally disposable and can carry out in situ or automated detection. This review addresses the potential of immunosensors destined for application in food and environmental analysis, and cancer biomarker diagnosis. Emphasis is given to the approaches that have been used for construction of electrochemical immunosensors. Additionally, the fundamentals of immunosensors, technology of transducers and nanomaterials and a general overview of the possible applications of electrochemical immunosensors to the food, environmental and diseases analysis fields are described.

Electrochemical Affinity Biosensors Based on Disposable Screen-Printed Electrodes for Detection of Food Allergens

Food allergens are proteins from nuts and tree nuts, fish, shellfish, wheat, soy, eggs or milk which trigger severe adverse reactions in the human body, involving IgE-type antibodies. Sensitive detection of allergens in a large variety of food matrices has become increasingly important considering the emergence of functional foods and new food manufacturing technologies. For example, proteins such as casein from milk or lysozyme and ovalbumin from eggs are sometimes used as fining agents in the wine industry. Nonetheless, allergen detection in processed foods is a challenging endeavor, as allergen proteins are degraded during food processing steps involving heating or fermentation. Detection of food allergens was primarily achieved via Enzyme-Linked Immuno Assay (ELISA) or by chromatographic methods. With the advent of biosensors, electrochemical affinity-based biosensors such as those incorporating antibodies and aptamers as biorecognition elements were also reported in the literature. In this review paper, we highlight the success achieved in the design of electrochemical affinity biosensors based on disposable screen-printed electrodes towards detection of protein allergens. We will discuss the analytical figures of merit for various disposable screen-printed affinity sensors in relation to methodologies employed for immobilization of bioreceptors on transducer surface.

Magnetic Particles Coupled to Disposable Screen Printed Transducers for Electrochemical Biosensing

Ultrasensitive biosensing is currently a growing demand that has led to the development of numerous strategies for signal amplification. In this context, the unique properties of magnetic particles; both of nano- and micro-size dimensions; have proved to be promising materials to be coupled with disposable electrodes for the design of cost-effective electrochemical affinity biosensing platforms. This review addresses, through discussion of selected examples, the way that nano- and micro-magnetic particles (MNPs and MMPs; respectively) have contributed significantly to the development of electrochemical affinity biosensors, including immuno-, DNA, aptamer and other affinity modes. Different aspects such as type of magnetic particles, assay formats, detection techniques, sensitivity, applicability and other relevant characteristics are discussed. Research opportunities and future development trends in this field are also considered.

An electrochemical immunosensor for efficient detection of uropathogenic E. coli based on thionine dye immobilized chitosan/functionalized-MWCNT modified electrode

Uropathogenic Escherichia coli (UPEC) is the major cause of 150 million Urinary Tract Infections (UTI) reported annually world-wide. High prevalence of multi-drug-resistance makes it dangerous and difficult to cure. Therefore simple, quick and early diagnostic tools are essential for effective treatment and control. We report an electrochemical immunosensor based on thionine dye (Th) immobilized on functionalized-multiwalled carbon nanotube+chitosan composite coated on glassy carbon electrode (GCE/f-MWCNT-Chit@Th) for quick and sensitive detection of UPEC in aqueous solution. This immunosensor was constructed by sequential immobilization of UPEC, bovine serum albumin, primary antibody and Horse Radish Peroxidase (HRP) tagged secondary antibody on the surface of GCE/f-MWCNT-Chit@Th. When analyzed using 2.5mM of hydrogen peroxide reduction reaction using cyclic voltammetry in phosphate buffer, pH 7.0, the immunosensor showed excellent linearity in a range of 10(2)-10(9)cfu of UPEC mL(-1) with a current sensitivity of 7.162μA {log(cfumL(-1))}(-1). The specificity of this immunosensor was tested using other UTI and non-UTI bacteria, Staphylococcus, Klebsiella, Proteus and Shigella. The clinical applicability of the immunosensor was also successfully tested directly in UPEC spiked urine samples (simulated sample).

Thionine-Modified Poly(glycidyl methacrylate) Nanospheres as Labels of Antibodies for Biosensing Applications

Monodisperse poly(glycidyl methacrylate) (PGMA) nanospheres were obtained by emulsifier-free emulsion polymerization and characterized by physicochemical methods. The effects of various reaction parameters on the particle properties were investigated. The particle size was controlled in the range of 350-420 nm. To introduce carboxyl groups, the PGMA nanospheres were hydrolyzed and oxidized with KMnO4. Subsequently, the enzyme horseradish peroxidase (HRP) and the electron mediator thionine were covalently attached to the PGMA nanospheres to obtain an antibody indicator suitable for enzyme-based electrochemical immunosensors. Combined HRP and thionine binding to the nanospheres had beneficial effects for the labeling efficiency and at the same time prevented the formation of soluble electron mediators.