Microfluidic origami nano-aptasensor for peanut allergen Ara h1 detection

Direct Evolution of Matrix-Resistant Circular Bivalent DNA Aptamers for Ara h1

Peanut allergenic protein Ara h1 is a serious food allergen due to its potentially life-threatening effects, and its accurate detection holds significant importance. While several selections were previously reported to isolate DNA aptamers for Ara h1, little success was achieved for binding in a complex food matrix. In this work, circular bivalent aptamers for Ara h1 were obtained by employing a dumbell-shaped DNA library with dual random domains for selection. The highest affinity aptamer, named as CB-APT1, exhibited a dissociation constant (Kd) of 36.3 nM, as determined by microscale thermophoresis. Notably, a similar binding affinity was observed even in a complex matrix that contained 80% w/w total peanut proteins. Further analysis indicates that each random domain acts as a unique binding moiety, working together to enhance the overall affinity. Subsequently, a label-free fluorescent aptasensor was developed for Ara h1, which demonstrated a low detection limit of 1.3 nM and performed well, even in food samples. Our evolution-based approach for developing circular bivalent DNA aptamers does not rely on structural information on the target protein, making it applicable to a wide range of protein targets. We believe this strategy can be leveraged to generate a diverse set of high-quality circular bivalent DNA aptamers that are both stable and functional in real biological samples, thus enhancing the practical applications of DNA aptamers in real-world applications.

Update on hazelnut allergy: Allergen characterization, epidemiology, food processing technique and detecting strategy

Hazelnuts are popular among people due to their dense nutrient component. However, eating them may be quite dangerous for those who are allergic. To improve food safety, this research examines current developments in the characterization, processing, and detection of hazelnut allergens. The identification and molecular knowledge of certain proteins that cause allergic responses are necessary for the characterization of hazelnut allergens. Proteomics and genomics are two techniques that have helped to advance our knowledge of hazelnut allergens and facilitate the creation of more precise diagnostic instruments. One important factor to reduce but not to eliminate the exposure to hazelnut allergens is food processing. The extractability of hazelnut proteins with regard to food processing plays a crucial role in determining allergenicity. Innovative technologies have been created to lessen allergenicity in foods containing hazelnuts while preserving their flavor and quality. These technologies include thermal and nonthermal processing techniques. To further safeguard consumers with hazelnut allergies, innovations in ingredient labeling and cross-contamination avoidance techniques have been put into place. For the purpose of management, if foods contain hazelnut, they must label it. Technological developments in analytical methods, including mass spectrometry, polymerase chain reaction, and enzyme-linked immunosorbent assays, have made it possible to identify hazelnut allergens with high specificity and sensitivity in a range of dietary matrices. Moreover, the advancement of point-of-care testing instruments presents the possibility of prompt on site identification, hence enhancing food safety for people with hazelnut allergies. The multidisciplinary efforts of researchers, food technologists, and allergists to enhance the safety of products containing hazelnuts are highlighted in this study.

Aptamer selection via versatile microfluidic platforms and their diverse applications

Aptamers are synthetic oligonucleotides that bind with high affinity and specificity to various targets, making them invaluable for diagnostics, therapeutics, and biosensing. Microfluidic platforms can improve the efficiency and scalability of aptamer selection, especially through advancements in systematic evolution of ligands by exponential enrichment (SELEX) methods. Microfluidic SELEX methods are less time-consuming and labor-intensive and include critical steps like library preparation, binding, partitioning, and amplification. This review examines the contributions of microfluidic technology to SELEX-based aptamer identification, with alternative methods like conditional SELEX, in vivo-like SELEX and Non-SELEX for selecting aptamers and also discusses critical SELEX steps over the past decade. This work also examined the integrated microfluidic systems for SELEX, highlighting innovations such as conditional SELEX and in vivo-like SELEX. These advancements provide potential solutions to existing challenges in aptamer selection using conventional SELEX, especially concerning biological samples. A trend toward non-SELEX methods was also reviewed and discussed, wherein nucleic acid amplification was eliminated to improve aptamer selection. Microfluidic platforms have demonstrated versatility not only in aptamer selection but also in various detection applications; they allow for precise control of liquid flow and have been essential in the advancement of therapeutic aptamers, facilitating accurate screening, enhancing drug delivery systems, and enabling targeted therapeutic interventions. Although advances in microfluidic technology are expected to enhance aptamer-based diagnostics, therapeutics, and biosensing, challenges still persist, especially in up-scaling microfluidic systems for various clinical applications. The advantages and limitations of integrating microfluidic platforms with aptamer development are further addressed, emphasizing areas for future research. We also present a perspective on the future of microfluidic systems and aptamer technologies, highlighting their increasing significance in healthcare and diagnostics.

An integrated microfluidic platform for on-site qPCR analysis: food allergen detection from sample to result

Improving food safety is crucial in the context of a "One Health" approach. To guarantee product quality and safety, the food industry, which has a very high turnover rate, needs short time-to-result analyses. Therefore, user-friendly systems at the point-of-need are necessary, presenting relevant analytical information and fulfilling the current regulations. To answer these challenges, a microfluidic platform integrating sample preparation and subsequent multiplex qPCR detection has been developed for on-site testing. The system consists of a fully automated instrument driving a microfluidic cartridge dedicated to the detection of multiple allergens in complex food matrices. The first part of the microfluidic cartridge contains pumps, reservoirs, valves and a filter to achieve DNA extraction, concentration and purification. Multiplex qPCR detection is carried out in the second part of the cartridge including a negative control chamber and five chambers for target analyte detection. The in-house developed instrument contains all functions to autonomously drive the microfluidic cartridge: pneumatic control for fluid actuation, thermal control for qPCR amplification and an optical system using three fluorescent wavelengths for multiplex detection of the target analytes and controls. We demonstrate the simultaneous detection of four different allergens - gluten, sesame, soy and hazelnut - from various complex food matrices. The turn-around-time from sample to result is close to two hours and controls in place validate the obtained results. For gluten, a direct comparison with ELISA shows that the regulatory threshold of 20 ppm is comfortably fulfilled. Moreover, all results are in agreement with external laboratory analyses performed in parallel on the same samples. Our findings confirm that the system can be used safely on-site without the risk of cross contamination between the various samples being analysed. In conclusion, our microfluidic platform offers a robust method for on-site allergen management.

Screening, identification, and application of aptamers against allergens in food matrices

Food allergies have become one of the most pressing issues in food safety and public health globally along with their incidence increasing in recent years. The reliable recognition of allergens from different sources, especially food-hidden allergens, is essential for preventing and controlling food allergies. Recently, aptamers, as emerging recognition elements, have gained considerable attention in food allergy, especially in the detection of food allergens. This review systematically summarizes the latest progress in screening, identification, and application of aptamers against food allergens over the past five years. We first introduce a brief overview of food allergy and aptamers, followed by a detailed focus on the aptamers' research against different food allergens broadly based on the major categories of the Big-8 allergens: highlighting the newly screened aptamers and their applied systematic evolution of ligands by exponential enrichment (SELEX) strategies, and emphasizing their practical applications including aptasensors, allergy inhibitors, or affinity adsorptions. Finally, the remaining challenges and future exploitations faced by aptamers in food allergens are comprehensively discussed and depicted. This review holds the promise of inspiring a broader range of researchers to gain an in-depth understanding of food allergy assisted by aptamer recognition and to facilitate improved biochemical analyses and successful application.

Design and application of microfluidics in aptamer SELEX and Aptasensors

Aptamers are excellent recognition molecules obtained from systematic evolution of ligands by exponential enrichment (SELEX) that have been extensively researched for constructing aptasensors. However, in the process from SELEX to the construction of aptasensors, there are many disadvantages, such as tedious and repetitive operations, interference from external factors, and low efficiency, which seriously limits their application scope and development. Introducing the microfluidic technology can realize the integration and intelligence of SELEX and aptasensing, improve the efficiency of SELEX, and enhance the detection performance and convenience of aptasensing. Hence, in this review, the characteristics of various chips based on different driving forces are described firstly. And then summarizing the design of microfluidic devices based on different SELEX methods and showing the strategies of microfluidic aptasensors based on different detection modes. Finally, discussing the difficulties and challenges encountered when microfluidic is integrated with the SELEX and the aptasensors.

Biosensor in smart food traceability system for food safety and security

The burden of food contamination and food wastage has significantly contributed to the increased prevalence of foodborne disease and food insecurity all over the world. Due to this, there is an urgent need to develop a smarter food traceability system. Recent advancements in biosensors that are easy-to-use, rapid yet selective, sensitive, and cost-effective have shown great promise to meet the critical demand for onsite and immediate diagnosis and treatment of food safety and quality control (i.e. point-of-care technology). This review article focuses on the recent development of different biosensors for food safety and quality monitoring. In general, the application of biosensors in agriculture (i.e. pre-harvest stage) for early detection and routine control of plant infections or stress is discussed. Afterward, a more detailed advancement of biosensors in the past five years within the food supply chain (i.e. post-harvest stage) to detect different types of food contaminants and smart food packaging is highlighted. A section that discusses perspectives for the development of biosensors in the future is also mentioned.

Quantifying allergenic proteins using antibody-based methods or liquid chromatography-mass spectrometry/mass spectrometry: A review about the influence of food matrix, extraction, and sample preparation

Accurate quantification of allergens in food is crucial for ensuring consumer safety. Pretreatment steps directly affect accuracy and efficiency of allergen quantification. We systematically reviewed the latest advances in pretreatment steps for antibody-based methods and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) protein quantification methods in food. For antibody-based methods, the effects induced by food matrix like decreased allergen solubility, epitope masking, and nonspecific binding are of the upmost importance. To mitigate interference from the matrix, effective and proper extraction can be used to obtain the target allergens with a high protein concentration and necessary epitope exposure. Removal of interfering substances, extraction systems (buffers and additives), assistive technologies, and commercial kits were discussed. About LC-MS/MS quantification, the preparation of the target peptides is the crucial step that significantly affects the efficiency and results obtained from the MS detector. The advantages and limitations of each method for pre-purification, enzymatic digestion, and peptide desalting were compared. Additionally, the application characteristics of microfluidic-based pretreatment devices were illustrated to improve the convenience and efficiency of quantification. A promising research direction is the targeted development of pretreatment methods for complex food matrices, such as lipid-based and carbohydrate-based matrices.

Microfluidic programmable strategies for channels and flow

This review summarizes programmable microfluidics, an advanced method for precise fluid control in microfluidic technology through microchannel design or liquid properties, referring to microvalves, micropumps, digital microfluidics, multiplexers, micromixers, slip-, and block-based configurations. Different microvalve types, including electrokinetic, hydraulic/pneumatic, pinch, phase-change and check valves, cater to diverse experimental needs. Programmable micropumps, such as passive and active micropumps, play a crucial role in achieving precise fluid control and automation. Due to their small size and high integration, microvalves and micropumps are widely used in medical devices and biological analysis. In addition, this review provides an in-depth exploration of the applications of digital microfluidics, multiplexed microfluidics, and mixer-based microfluidics in the manipulation of liquid movement, mixing, and splitting. These methodologies leverage the physical properties of liquids, such as capillary forces and dielectric forces, to achieve precise control over fluid dynamics. SlipChip technology, which branches into rotational SlipChip and translational SlipChip, controls fluid through sliding motion of the microchannel. On the other hand, innovative designs in microfluidic systems pursue better modularity, reconfigurability and ease of assembly. Different assembly strategies, from one-dimensional assembly blocks and two-dimensional Lego®-style blocks to three-dimensional reconfigurable modules, aim to enhance flexibility and accessibility. These technologies enhance user-friendliness and accessibility by offering integrated control systems, making them potentially usable outside of specialized technical labs. Microfluidic programmable strategies for channels and flow hold promising applications in biomedical research, chemical analysis and drug screening, providing theoretical and practical guidance for broader utilization in scientific research and practical applications.

DNA Meets Protein─Development, Characterization, and Application of Aptamers against Peanut Allergen

Allergen detection methods support food labeling and quality assessment at the allergen component level of allergen preparations used for allergy diagnosis and immunotherapy (AIT). Commonly applied enzyme-linked immunosorbent assay (ELISA) requires animal antibodies but potentially shows batch variations. We developed synthetic aptamers as alternative binders in allergen detection to meet the replacement, reduction, and refinement (3R) principle on animal protection in science. ssDNA aptamers were specifically selected against the major peanut allergen Ara h 1 and identified by next-generation sequencing. Application in various detection systems (ELISA-like assays, western blot, and surface plasmon resonance) was demonstrated. The ELISA-like assay comprised a sensitivity of 10 ng/mL Ara h 1, comparable to published antibody-based ELISA, and allowed Ara h 1 detection in various peanut flours, similar to those used in peanut AIT as well as in processed food. This ELISA-like aptamer-based assay proofs antibody-free allergen detection for food labeling or quality assessment of diagnostic and therapeutic allergen products.

Microfluidic paper-based analysis device applying black phosphorus nanosheets@MWCNTs-COOH: A portable and efficient strategy for detection of β-Lactoglobulin in dairy products

This study prepared a novel, portable and cost-effective microfluidic paper-based electrochemical analysis device (μ-PAD) using black phosphorus nanosheets@carboxylated multi-walled carbon nanotubes (BPNSs@MWCNTs-COOH) nanocomposites for β-lactoglobulin (β-LG) detection. At the appreciate ratio, the synthesized BPNSs@MWCNTs-COOH was demonstrated to not only serve as a high-quality substrate for the specific aptamer immobilization, but also improve the electron transfer capability of the sensing interface. The μ-PADs, utilizing BPNSs@MWCNTs-COOH and aptamer recognition, exhibited a wider detection range (10-1000 ng mL-1) and lower detection limit (LOD: 0.12 ng mL-1) for β-LG, and demonstrated enhanced specificity, satisfactory anti-interference ability and stability. When applied to the β-LG determination in dairy samples, the μ-PAD yielded β-LG concentrations highly correlated with those obtained using the HPLC method (R2: 0.9982). These results emphasized the reliable performance of the developed μ-PADs in β-LG allergen quantification, highlighting their potential as an efficient platform for the rapid screening of β-LG allergens.

Paper-Based Electrochemical (Bio)Sensors for the Detection of Target Analytes in Liquid, Aerosol, and Solid Samples

The last decade has been incredibly fruitful in proving the multifunctionality of paper for delivering innovative electrochemical (bio)sensors. The paper material exhibits unprecedented versatility to deal with complex liquid matrices and facilitate analytical detection in aerosol and solid phases. Such remarkable capabilities are feasible by exploiting the intrinsic features of paper, including porosity, capillary forces, and its easy modification, which allow for the fine designing of a paper device. In this review, we shed light on the most relevant paper-based electrochemical (bio)sensors published in the literature so far to identify the smart functional roles that paper can play to bridge the gap between academic research and real-world applications in the biomedical, environmental, agrifood, and security fields. Our analysis aims to highlight how paper's multifarious properties can be artfully harnessed for breaking the boundaries of the most classical applications of electrochemical (bio)sensors.

Research progress of microfluidics-based food safety detection

High demands for food safety detection and analysis have been advocated with people's increasing living standards. Even though numerous analytical testing techniques have been proposed, their widespread adoption is still constrained by the high limit of detection, narrow detection ranges, and high implementation costs. Due to their advantages, such as reduced sample and reagent consumption, high sensitivity, automation, low cost, and portability, using microfluidic devices for food safety monitoring has generated significant interest. This review provides a comprehensive overview of the latest microfluidic detection platforms (published in recent 4 years) and their applications in food safety, aiming to provide references for developing efficient research strategies for food contaminant detection and facilitating the transition of these platforms from laboratory research to practical field use.

Electrochemically assisted DNA and thioaromatic assembly as sensing and antifouling interface for food allergens

Food allergies have become a global issue and are estimated to affect approximately 220 million people worldwide. Allergy to peanuts can easily become life-threatening and induce anaphylactic reactions. Mislabeling and cross-contamination during food processing can occur in the frame of world population growth and pose a serious health issue. As the mandatory allergen list is not uniform worldwide, the development of routine analytical strategies with high specificity and sensitivity is a demanding task to aid in the rapid identification of allergenic foods. In this work, an electrochemical aptasensor for Ara h1 peanut allergen was developed by immobilizing the specific aptamer by the inserting method. First, a layer of p-aminothiophenol (p-ATP) was immobilized on the gold surface of screen-printed electrodes (GSPE) to improve the aptamer insertion and reduce the fouling effects at the electrode surface. The grafting of the p-ATP and Ara h1 aptamer on the GSPE surface was monitored by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The resulting disposable aptasensor allowed for indirect electrochemical detection of Ara h1 protein in the presence of 5 mM ferro/ferricyanide as a redox probe. The electrochemical response upon aptamer-target interaction was monitored in the concentration range 1-250 nM, and two limits of detection in the nanomolar range were estimated based on DPV (2.78 nM Ara h1) and EIS (0.82 nM Ara h1) measurements. The aptasensor was successfully applied to real sample analysis.

Paper-based microfluidic device for selective detection of peanut allergen Ara h1 applying black phosphorus-Au nanocomposites for signal amplification

This paper developed a portable microfluidic paper-based analysis device (μ-PAD) combined with the electrochemical technique for efficient and sensitive detection of peanut allergen Ara h1. The proposed μ-PAD works based on the variation of differential pulse voltammetry (DPV) response current induced by peanut allergen Ara h1. Black phosphorus (BP)-Au nanocomposites were introduced both to improve the electron transfer rate at the electrode interface for signal amplification, and to immobilize the specific Ara h1 aptamers through Au-S bonding to recognize the target in food matrices. This μ-PAD had good specificity and detection stability for Ara h1 allergen and could complete the entire analysis process within 20 min, achieving a wide linear response range (25-800 ng mL-1) and a low detection limit (LOD, 11.8 ng mL-1). In the Ara h1 allergen detection applied to real peanut products (cookies, milk, and bread), the constructed μ-PAD obtained acceptable recoveries (93.50%-101.86%) with relative standard deviations (RSDs) of 0.36-2.97% (n = 3), with a good correlation with the ELISA results (R2 = 0.9956). Therefore, the portable μ-PAD based on BP-Au nanocomposites was demonstrated to provide an effective strategy for rapid analysis and screening of Ara h1 allergen in food, which has broad application prospects.

Paper as smart support for bioreceptor immobilization in electrochemical paper-based devices

The use of paper as a smart support in the field of electrochemical sensors has been largely improved over the last 15 years, driven by its outstanding features such as foldability and porosity, which enable the design of reagent and equipment-free multi-analysis devices. Furthermore, the easy surface engineering of paper has been used to immobilize different bioreceptors, through physical adsorption, covalent bonding, and electrochemical polymerization, boosting the fine customization of the analytical performances of paper-based biosensors. In this review, we focused on the strategies to engineer the surface of the paper for the immobilization of (bio)recognition elements (eg., enzymes, antibodies, DNA, molecularly imprinted polymers) with the overriding goal to develop accurate and reliable paper-based electrochemical biosensors. Furthermore, we highlighted how to take advantage of paper for designing smart configurations by integrating different analytical processes in an eco-designed analytical tool, starting from the immobilization of the (bio)receptor and the reagents, through a designed sample flow along the device, until the analyte detection.

Advances in paper-based electrochemical immunosensors: review of fabrication strategies and biomedical applications

Cellulose paper-based sensing devices have shown promise in addressing the accuracy, sensitivity, selectivity, analysis time and cost of current disease diagnostic tools owing to their excellent physical and physiochemical properties, high surface-area-to-volume ratio, strong adsorption capabilities, ease of chemical functionalization for immobilization, biodegradability, biocompatibility and liquid transport by simple capillary action. This review provides a comprehensive overview of recent advancements in the field of electrochemical immunosensing for various diseases, particularly in underdeveloped regions and globally. It highlights the significant progress in fabrication techniques, fluid control, signal transduction and paper substrates, shedding light on their respective advantages and disadvantages. The primary objective of this review article is to compile recent advances in the field of electrochemical immunosensing for the early detection of diseases prevalent in underdeveloped regions and globally, including cancer biomarkers, bacteria, proteins and viruses. Herein, the critical need for new, simplistic early detection strategies to combat future disease outbreaks and prevent global pandemics is addressed. Moreover, recent advancements in fabrication techniques, including lithography, printing and electrodeposition as well as device orientation, substrate type and electrode modification, have highlighted their potential for enhancing sensitivity and accuracy.

Recent Advances in Electrochemical Biosensors for Food Control

The rapid and sensitive detection of food contaminants is becoming increasingly important for timely prevention and treatment of foodborne disease. In this review, we discuss recent developments of electrochemical biosensors as facile, rapid, sensitive, and user-friendly analytical devices and their applications in food safety analysis, owing to the analytical characteristics of electrochemical detection and to advances in the design and production of bioreceptors (antibodies, DNA, aptamers, peptides, molecular imprinted polymers, enzymes, bacteriophages, etc.). They can offer a low limit of detection required for food contaminants such as allergens, pesticides, antibiotic traces, toxins, bacteria, etc. We provide an overview of a broad range of electrochemical biosensing designs and consider future opportunities for this technology in food control.

Robust tag-free aptasensor for monitoring of tobramycin: Architecting of rolling circle amplification and fluorescence synergism

With the unpredictable risks on human health and ecological safety, tobramycin (TOB) as an extensively applied antibiotic has embraced global concern. Herein, a label-free fluorescent aptasensor was developed that opened up an innovative sensing strategy for monitoring trace TOB levels. Based on the rolling circle amplification (RCA) process, a giant DNA building was established by the catalytic action of T4 DNA ligase and Phi 29 DNA polymerase with the cooperation of the specific aptamer as a primer skeleton. By having the role of signal amplifier template, the RCA product with the G-quadruplex sequence duplications was decorated by a high number of the thioflavin T (ThT) fluorescent dyes. The aptasensor with good selectivity toward TOB achieved a detection limit as low as 150 pM. Thanks to its accurate target quantification, ease of operation, economic manufacture, as well as high potency for real-time and point-of-care testing, the represented aptasensor is superb for clinical application and food safety control.

Microfluidic platforms integrated with nano-sensors for point-of-care bioanalysis

Microfluidic technology provides a portable, cost-effective, and versatile tool for point-of-care (POC) bioanalysis because of its associated advantages such as fast analysis, low volumes of reagent consumption, and high portability. Along with microfluidics, the application of nanomaterials in biosensing has attracted lots of attention due to their unique physical and chemical properties for enhanced signal modulation such as signal amplification and signal transduction for POC bioanalysis. Hence, an enormous number of microfluidic devices integrated with nano-sensors have been developed for POC bioanalysis targeting low-resource settings. Herein, we review recent advances in POC bioanalysis on nano-sensor-based microfluidic platforms. We first briefly summarized the different types of cost-effective microfluidic platforms, followed by a concise introduction to nanomaterial-based biosensors. Then, we highlighted the application of microfluidic platforms integrated with nano-sensors for POC bioanalysis. Finally, we discussed the current limitations and perspective trends of the nano-sensor-based microfluidic platforms for POC bioanalysis.

Paper-Based Electrochemical Biosensors for Food Safety Analysis

Nowadays, foodborne pathogens and other food contaminants are among the major contributors to human illnesses and even deaths worldwide. There is a growing need for improvements in food safety globally. However, it is a challenge to detect and identify these harmful analytes in a rapid, sensitive, portable, and user-friendly manner. Recently, researchers have paid attention to the development of paper-based electrochemical biosensors due to their features and promising potential for food safety analysis. The use of paper in electrochemical biosensors offers several advantages such as device miniaturization, low sample consumption, inexpensive mass production, capillary force-driven fluid flow, and capability to store reagents within the pores of the paper substrate. Various paper-based electrochemical biosensors have been developed to enable the detection of foodborne pathogens and other contaminants that pose health hazards to humans. In this review, we discussed several aspects of the biosensors including different device designs (e.g., 2D and 3D devices), fabrication techniques, and electrode modification approaches that are often optimized to generate measurable signals for sensitive detection of analytes. The utilization of different nanomaterials for the modification of electrode surface to improve the detection of analytes via enzyme-, antigen/antibody-, DNA-, aptamer-, and cell-based bioassays is also described. Next, we discussed the current applications of the sensors to detect food contaminants such as foodborne pathogens, pesticides, veterinary drug residues, allergens, and heavy metals. Most of the electrochemical paper analytical devices (e-PADs) reviewed are small and portable, and therefore are suitable for field applications. Lastly, e-PADs are an excellent platform for food safety analysis owing to their user-friendliness, low cost, sensitivity, and a high potential for customization to meet certain analytical needs.

A portable electrochemiluminescence aptasensor for β-lactoglobulin detection

Cow’s milk allergy is one of the most common food allergies in children with a prevalence of around 2.5%. Milk contains several allergens; the main ones are caseins and β-lactoglobulin (β-LG). At regulatory level, β-LG is not explicitly named, but milk is included in the list of substances or products causing allergies or intolerances. Hence, the presence of β-LG can be a useful marker for determining the presence of milk in food. In this work, we present an aptasensor based on electrochemiluminescence (ECL) for the quantification of β-LG in real food matrices displaying integrated advantages consisting of high specificity, good sensitivity, portability, and cost effectiveness. The performance and applicability of this sensor were tested by analyzing a sample of skimmed milk and an oat-based drink proposed as a vegetable substitute for milk of animal origin. We obtained a linear correlation between the intensity of the signal and the concentration of β-LG standard solutions (y = x * 0.00653 + 1.038, R² = 0.99). The limit of detection (LOD) and the limit of quantification (LOQ) were found to be 1.36 and 4.55 μg L⁻¹, respectively.

A Label-Free Fluorescence Aptasensor Based on G-Quadruplex/Thioflavin T Complex for the Detection of Trypsin

A novel, label-free fluorescent assay has been developed for the detection of trypsin by using thioflavin T as a fluorescent probe. A specific DNA aptamer can be combined by adding cytochrome c. Trypsin hydrolyzes the cytochrome c into small peptide fragments, exposing the G-quadruplex part of DNA aptamer, which has a high affinity for thioflavin T, which then enhances the fluorescence intensity. In the absence of trypsin, the fluorescence intensity was inhibited as the combination of cytochrome c and the DNA aptamer impeded thioflavin T’s binding. Thus, the fluorescent biosensor showed a linear relationship from 0.2 to 60 μg/mL with a detection limit of 0.2 μg/mL. Furthermore, the proposed method was also successfully employed for determining trypsin in biological samples. This method is simple, rapid, cheap, and selective and possesses great potential for the detection of trypsin in bioanalytical and biological samples and medical diagnoses.

Recent Advances in Electrochemical Sensing Strategies for Food Allergen Detection

Food allergy has been indicated as the most frequent adverse reaction to food ingredients over the past few years. Since the only way to avoid the occurrence of allergic phenomena is to eliminate allergenic foods, it is essential to have complete and accurate information on the components of foodstuff. In this framework, it is mandatory and crucial to provide fast, cost-effective, affordable, and reliable analysis methods for the screening of specific allergen content in food products. This review reports the research advancements concerning food allergen detection, involving electrochemical biosensors. It focuses on the sensing strategies evidencing different types of recognition elements such as antibodies, nucleic acids, and cells, among others, the nanomaterial role, the several electrochemical techniques involved and last, but not least, the ad hoc electrodic surface modification approaches. Moreover, a selection of the most recent electrochemical sensors for allergen detection are reported and critically analyzed in terms of the sensors’ analytical performances. Finally, advantages, limitations, and potentialities for practical applications of electrochemical biosensors for allergens are discussed.

Transducer Technologies for Biosensors and Their Wearable Applications

The development of new biosensor technologies and their active use as wearable devices have offered mobility and flexibility to conventional western medicine and personal fitness tracking. In the development of biosensors, transducers stand out as the main elements converting the signals sourced from a biological event into a detectable output. Combined with the suitable bio-receptors and the miniaturization of readout electronics, the functionality and design of the transducers play a key role in the construction of wearable devices for personal health control. Ever-growing research and industrial interest in new transducer technologies for point-of-care (POC) and wearable bio-detection have gained tremendous acceleration by the pandemic-induced digital health transformation. In this article, we provide a comprehensive review of transducers for biosensors and their wearable applications that empower users for the active tracking of biomarkers and personal health parameters.

Detection of Allergenic Proteins in Foodstuffs: Advantages of the Innovative Multiplex Allergen Microarray-Based Immunoassay Compared to Conventional Methods

Several factors can affect the allergen content and profile of a specific food, including processing procedures often leading to a decrease in allergenicity, although no change, or even an increase, have also been reported. Evaluation of the effectiveness of a processing procedure requires the availability of reliable methodologies to assess the variation in molecules able to induce allergic reactions in the analyzed food. Conventional and innovative strategies and methodologies can be exploited to identify allergenic proteins in foodstuffs. However, depending on the specific purposes, different methods can be used. In this review, we have critically reviewed the advantages of an innovative method, the multiplex allergen microarray-based immunoassay, in the detection of allergens in foodstuffs. In particular, we have analyzed some studies reporting the exploitation of an IgE-binding inhibition assay on multiplex allergen biochips, which has not yet been reviewed in the available literature. Unlike the others, this methodology enables the identification of many allergenic proteins, some of which are still unknown, which are recognized by IgE from allergic patients, with a single test. The examined literature suggests that the inhibition test associated with the multiplex allergen immunoassay is a promising methodology exploitable for the detection of IgE-binding proteins in food samples.

Aptamer based point of care diagnostic for the detection of food allergens

Aptamers, due to their small size, strong target affinity, and ease of chemical modification, are ideally suited for molecular detection technologies. Here, we describe successful use of aptamer technology in a consumer device for the detection of peanut antigen in food. The novel aptamer-based protein detection method is robust across a wide variety of food matrices and sensitive to peanut protein at concentrations as low as 12.5 ppm (37.5 µg peanut protein in the sample). Integration of the assay into a sensitive, stable, and consumer friendly portable device will empower users to easily and quickly assess the presence of peanut allergens in foods before eating. With many food reactions occurring outside the home, the type of technology described here has significant potential to improve lives for children and families.

An immunochromatographic assay utilizing magnetic nanoparticles to detect major peanut allergen Ara h 1 in processed foods

This study describes an immunomagnetic nanoparticle (IMNP)-based lateral flow assay (LFA) for detecting the major peanut allergen Ara h 1. We developed a clearly specific method in identifying peanut from ten other seeds and nuts, and a good visual limit of detection (vLOD) of 0.01 μg/mL Ara h 1 in PBS. PBS that contains 1 M NaCl and 2% Tween 20 was determined to be the optimal extraction buffer for isolating Ara h 1 from cookie, milk and chocolate with vLOD values of 0.5 μg/g, 0.5 μg/mL, and 1 μg/g, respectively. Forty two processed foods were simultaneously analyzed using this method and an AOAC-approved ELISA kit. The specificity and sensitivity of this assay were thus determined to be 100 and 95%, respectively. This new IMNP-based LFA has potential as a rapid tool for screening processed foods for Ara h 1 residues.

Origami Paper-Based Electrochemical (Bio)Sensors: State of the Art and Perspective

In the last 10 years, paper-based electrochemical biosensors have gathered attention from the scientific community for their unique advantages and sustainability vision. The use of papers in the design the electrochemical biosensors confers to these analytical tools several interesting features such as the management of the solution flow without external equipment, the fabrication of reagent-free devices exploiting the porosity of the paper to store the reagents, and the unprecedented capability to detect the target analyte in gas phase without any sampling system. Furthermore, cost-effective fabrication using printing technologies, including wax and screen-printing, combined with the use of this eco-friendly substrate and the possibility of reducing waste management after measuring by the incineration of the sensor, designate these type of sensors as eco-designed analytical tools. Additionally, the foldability feature of the paper has been recently exploited to design and fabricate 3D multifarious biosensors, which are able to detect different target analytes by using enzymes, antibodies, DNA, molecularly imprinted polymers, and cells as biocomponents. Interestingly, the 3D structure has recently boosted the self-powered paper-based biosensors, opening new frontiers in origami devices. This review aims to give an overview of the current state origami paper-based biosensors, pointing out how the foldability of the paper allows for the development of sensitive, selective, and easy-to-use smart and sustainable analytical devices.