Highly Sensitive Detection of Bovine β-Lactoglobulin with Wide Linear Dynamic Range Based on Platinum Nanoparticles Probe

Designing tannic acid-polyethyleneimine-modified electrode and novel affinity peptide for β-lactoglobulin detection in milk

Harmful substances that cause food allergies can pose a significant threat to consumers along with food safety. According to the World Health Organization (WHO), approximately 10 % of the global population is currently affected by food allergies. Therefore, there is an urgent need for the development of more accurate and precise biosensors capable of detecting these hazardous substances including beta-lactoglobulin. Although numerous detection and analysis methods have been developed, they still suffer from various limitations. In this study, a tannic acid-polyethyleneimine (TA-PEI) network modified screen-printed electrodes (SPE) are newly developed and the binding sequence of peptide against β-LG was successfully screened using random peptide library. A novel affinity peptide with the desired sequence of S-L-S-P-S-L-W-Q-V-S-M-L-G-G-G-G-E-P-L-Q-L-K-M against β-lactoglobulin (β-LG) is designed and synthesized. The synthesized affinity peptide was immobilized on TA-PEI modified SPE to develop peptide-based sensor against β-LG for the first time. Under successful optimization, the developed sensor exhibited a linear relationship between 50 and 750 ng, with a Kd of 213.9 ng. In addition, the sensor was able to detect β-LG in cow and goat milk, with average recoveries of 88.5 % and 92.2 %, respectively.

"Fluorescence-wavelength" label-free POCT tandem with "fluorescence-photothermal" nanobody-immunosensor for detecting BSA and β-lactoglobulin

Two carbon dots (CDs) (λEm = 525 nm, G-CDs and λEm = 640 nm, R-CDs) were synthesized from citric acid and urea. The bovine serum albumin (BSA) responsiveness of the R-CDs was used to develop a "fluorescence-wavelength" label-free point of care testing (POCT) for the detection of the milk quality marker BSA with the detection limit (LOD) of 4.89 μg/mL for fluorescence mode and 3.38 μg/mL for wavelength mode. In addition, R-CDs were found to have hydroxyl radical (·OH)-dependent fluorescence quenching properties, and a "fluorescence-photothermal" immunosensor based on nanobodies was constructed by introducing the fluorescence signal of R-CDs@BSA and the photothermal signal of oxTMB for the detection of β-lactoglobulin (β-LG) with the LOD of 0.034 ng/mL for fluorescence mode and 0.075 ng/mL for photothermal mode. The tandem detection of POCT and immunosensor enables the simultaneous and highly sensitive detection of BSA and β-LG after only simple dilution of less than 5 µL of sample.

One-Step Purification of IgE Epitope-Specific Antibody Using Immunomagnetic Beads and Highly Sensitive Detection of Bovine β-Lactoglobulin for the Prediction of Milk Allergenicity in Foods

Bovine β-lactoglobulin (BLG) is a common allergen found in milk, and the immunoglobulin E (IgE) epitope plays a crucial role in cow milk allergy. Therefore, targeting the IgE epitope could be useful in accurately detecting BLG and assessing its allergenicity. However, producing an IgE epitope-specific antibody (IgE-EsAb) through traditional methods requires complex and time-consuming procedures. Here, IgE-EsAb was purified from rabbit anti-BLG sera by immunomagnetic beads in one step. Then, a sandwich ELISA (sELISA) based on the IgE-EsAb was developed to detect BLG and predict the potential milk allergenicity in foods. The obtained IgE-EsAb could specifically recognize the target IgE epitope of BLG and exhibited high affinity and specificity. The developed IgE-EsAb-based sELISA demonstrated an ultra-wide linear range of 3.9-1.28 × 105 ng/mL, with a limit of detection of 0.49 ng/mL for BLG. Additionally, the proposed immunoassay showed high specificity and recoveries (91.24-109.61%). The ability of the IgE-EsAb-based sELISA to evaluate the potential milk allergenicity in foods was validated using sera from cow milk allergy patients. These results suggest that immunomagnetic beads are an effective tool for rapidly obtaining the IgE-EsAb, and our proposed sELISA could be a reliable and user-friendly method for monitoring trace amounts of BLG and predicting the potential milk allergenicity of food samples.

Nanotechnology in Food and Plant Science: Challenges and Future Prospects

Globally, food safety and security are receiving a lot of attention to ensure a steady supply of nutrient-rich and safe food. Nanotechnology is used in a wide range of technical processes, including the development of new materials and the enhancement of food safety and security. Nanomaterials are used to improve the protective effects of food and help detect microbial contamination, hazardous chemicals, and pesticides. Nanosensors are used to detect pathogens and allergens in food. Food processing is enhanced further by nanocapsulation, which allows for the delivery of bioactive compounds, increases food bioavailability, and extends food shelf life. Various forms of nanomaterials have been developed to improve food safety and enhance agricultural productivity, including nanometals, nanorods, nanofilms, nanotubes, nanofibers, nanolayers, and nanosheets. Such materials are used for developing nanofertilizers, nanopesticides, and nanomaterials to induce plant growth, genome modification, and transgene expression in plants. Nanomaterials have antimicrobial properties, promote plants' innate immunity, and act as delivery agents for active ingredients. Nanocomposites offer good acid-resistance capabilities, effective recyclability, significant thermostability, and enhanced storage stability. Nanomaterials have been extensively used for the targeted delivery and release of genes and proteins into plant cells. In this review article, we discuss the role of nanotechnology in food safety and security. Furthermore, we include a partial literature survey on the use of nanotechnology in food packaging, food safety, food preservation using smart nanocarriers, the detection of food-borne pathogens and allergens using nanosensors, and crop growth and yield improvement; however, extensive research on nanotechnology is warranted.

Detection of β-lactoglobulin under different thermal-processing conditions by immunoassay based on nanobody and monoclonal antibody

The problems of inaccurate detection values of thermal-processed β-lactoglobulin (β-LG) content seriously affect the screening of allergens. A monoclonal antibody (mAb) against β-LG was successfully prepared and a highly sensitive sandwich ELISA (sELISA) was constructed with specific nanobody (Nb) as the capture antibody with detection limit of 0.24 ng/mL. Based on this sELISA, the ability of Nb and mAb to recognize β-LG and β-LG interacting with milk components was explored. Combined with protein structure analysis to elaborate the mechanism of shielding β-LG antigen epitopes during thermal-processing, thus enabling the differentiation between pasteurized and ultra-high temperature sterilized milk, the detection of milk content in milk-containing beverages, and the highly sensitive detection and analysis of β-LG allergens in dairy-free products. The method provides methodological support for identifying the quality of dairy products and reducing the risk of β-LG contamination in dairy-free products.

Allergenicity reduction of cow milk treated by alkaline protease combined with Lactobacillus Plantarum and Lactobacillus helveticus based on epitopes

This paper has investigated the residual allergenicity of cow's milk treated by enzymatic hydrolysis combined with Lactobacillus fermentation (Lb. Plantarum and Lb. helveticus). The treated products were comprehensively evaluated by SDS-PAGE, RP-HPLC, ELISA, and Caco-2 models. And the allergenic changes of residual allergenic peptides were explored by DC-T co-culture. The results showed that alkaline protease was the most suitable protease that targeted to destroy epitopes of milk major allergen than trypsin, pepsin, and papain by prediction. And the residual epitopes were reduced to four which was treated by alkaline protease combined with Lb. helveticus. The transport absorption capacity of treated products was almost twice than milk. Meanwhile, the seven residual allergenic peptides were obtained from treated products. Among them, αs₁-casein (AA84-90) can be used as an immune tolerance peptide for further study. Lb. helveticus combined with alkaline protease treatment may be considered promising strategy of protect from cow's milk allergy.

Accurate determination of the milk protein allergen β-lactoglobulin by on-line aptamer affinity solid-phase extraction capillary electrophoresis-mass spectrometry

An on-line aptamer affinity solid-phase extraction capillary electrophoresis-mass spectrometry (AA-SPE-CE-MS) method was developed to purify, preconcentrate, separate, and characterize the milk allergenic protein β-lactoglobulin (β-LG) in food samples. The sorbent to pack into the SPE microcartidges was prepared by immobilizing an aptamer against β-LG onto magnetic bead particles. After optimizing the SPE-CE-MS method, the sample (ca. 75 μL) was loaded in separation background electrolyte (BGE, 2 M acetic acid pH 2.2), while a solution of 100 mM NH₄OH (pH 11.2) (ca. 100 nL) was used for the protein elution. The linearity of the method ranged between 0.1 and 20 μg mL^-1 and the limit of detection (LOD) was 0.05 μg mL^-1, which was 200 times lower than by CE-MS. The method was repeatable in terms of relative standard deviation (RSD) for migration times and peak areas (<0.5% and 2.4%, respectively) and microcartridge lifetime was more than 25 analyses. The applicability of the method for the determination of low levels of β-LG was shown by analyzing milk-free foods (i.e. a 100% cocoa dark chocolate, a hypoallergenic formula for infants, and a dairy-free white bread) and milk-containing white breads. Results were satisfactory in all cases, thus demonstrating the great potential of the developed method for accurate food safety and quality control.

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.

A solid-state electrochemiluminescence aptasensor for β-lactoglobulin using Ru-AuNP/GNP/Naf nanocomposite-modified printed sensor

An electrochemiluminescence (ECL) aptasensor for the detection of the milk protein allergen β-lactoglobulin (β-LG) using nanocomposite as luminophore was fabricated. The Ru-AuNPs/GNP/Naf complex was formed by combining the Rubpy₃²⁺-AuNPs complex (Ru-AuNPs), prepared by modifying the negatively charged surface of gold nanoparticles (AuNPs) with positively charged Rubpy₃²⁺ through electrostatic interactions and the graphene nanoplatelets-Nafion (GNP/Naf) at a ratio of 2:1. The nanocomposite was coated on the surface of the screen-printed electrode (SPCE) through the film-forming properties of Nafion. A layer of chitosan (CS) was coated onto this modified electrode, and later amine-terminated β-LG aptamers were covalently attached to the CS/Ru-AuNP/GNP/Naf via glutaraldehyde (GLUT) cross-linking. When β-LG was incubated with the aptasensor, a subsequent decrease in ECL intensity was recorded. Under the optimal conditions, the ECL intensity of the aptasensor changed linearly with the logarithmic concentration of β-LG, in the range 0.1 to 1000 pg/ml, and the detection limit was 0.02 pg/mL (3σ/m). The constructed aptasensor displayed simple and fast determination of β-LG with excellent reproducibility, stability, and high specificity. Additionally, the proposed ECL aptasensor displayed high recoveries (92.5-112%) and low coefficients of variation (1.6-7.8%), when β-LG fortified samples were analyzed. Integrating Ru-AuNPs/GNP/Naf nanocomposite in the ECL aptasensor paves the way towards a cost-effective and sensitive detection of the milk allergen β-LG.

Dual signal light detection of beta-lactoglobulin based on a porous silicon bragg mirror

In this work, a new dual signal light detection method based on porous silicon Bragg mirror (PSBM) and biological labelling with quantum dots (QDs) is proposed for the detection of beta-lactoglobulin (β-lg). The first signal light is a probe light emitted by a laser with wavelength of 633 nm, which enters the PSBM and is reflected from the surface. The wavelength of the probe light is located at the edge of the PSBM band gap, where it has the lowest reflectivity. β-lg antibodies is labelled with CdSe/ZnS QDs and reacts with β-lg molecules have been fixed to the inner wall of the porous silicon pores. Due to the specific binding of biomolecules in PSBM, the refractive index of the device increases, resulting in the enhancement of detection reflected light. The QDs play the role of refractive index amplification. The second signal light is the fluorescence of QDs in immune reactants. QDs produce fluorescence at 630 nm when excited by a short-wavelength laser. The fluorescence signal is further enhanced by PSBM. The superimposed images of two kinds of light on the surface of PSBM are obtained by digital microscope at the same time. By calculating the average grey value change of the image before and after biological reaction, β-lg can be detected with high sensitivity. The detection limit of β-lg was 0.12 ng/mL. The experimental results showed that the PSBM-based dual signal light method could be used to detect the content of cow milk adulterated in β-lg free camel milk.

An electrochemical aptasensor for the milk allergen β-lactoglobulin detection based on a target-induced nicking site reconstruction strategy

Food allergy is an immune system reaction to a particular food, milk being the most common one. β-Lactoglobulin (β-Lg) is the main ingredient of milk protein and the main cause of infant milk allergy. On such an occasion, the determination of β-Lg is very important and the electrochemical sensors are a good alternative for this purpose since they are sensitive, selective and inexpensive. In this work, an electrochemical aptasensor was fabricated for the quantitative detection of β-Lg in hypoallergenic formula (HF) milk. A tri-functional hairpin (HP) was designed, which was composed of an aptamer sequence, a nicking site and a DNA sequence (T1). In the absence of β-Lg, the aptamer part hybridized with T1 to form a stable stem-loop structure. However, in the presence of β-Lg, the capture of the aptamer sequence towards β-Lg caused the reconstruction of HP and thus the nicking sites were exposed. Then, the nicking enzyme was activated and T1 could be released, which bound with the end of the hairpin 1-methylene blue (HP1-MB)/HP2-MB conjugation on the Au nanoparticle (AuNP) modified electrode surface. Thus, the insulating property of the electrode was enhanced and the current response of MB decreased, which built the quantitative basis for β-Lg detection. In this way, the proposed aptasensor exhibited a wide linear range of 0.01-100 ng mL^-1 and a low detection limit of 5.7 pg mL^-1. This aptasensor also displayed high selectivity, reproducibility and stability, and became a promising platform for β-Lg detection in real food samples.

A label-free photoelectrochemical immunosensor for detection of the milk allergen β-lactoglobulin based on Ag2S -sensitized spindle-shaped BiVO4/BiOBr heterojunction by an in situ growth method

Food allergies have become a nonnegligible food safety issue, and milk allergies are one of the most common food allergies, that has attracted large consumer attention. In this work, a novel label-free photoelectrochemical (PEC) immunosensor for the detection of the allergen β-lactoglobulin (β-LG) in dairy products was designed that used the specific recognition of allergen β-LG and antibodies in dairy products in combination with biosensing technology. Here, Ag₂S-sensitized spindle-shaped BiVO₄/BiOBr heterojunction was fixed on the surface of the ITO electrode as an excellent photoactive substrate and effectively improved the photocurrent responses and sensitivity. Thioglycolic acid (TGA) was used as a linker to immobilize the β-LG antibody on the surface of the electrode. The photocurrent was detected at different antigen concentrations, which realized the quantitative testing of β-LG. Under the optimal experimental conditions, the PEC immunosensor proved an ideal linear relationship ranging from 10 pg/mL to 100 ng/mL, with a low detection limit of 3.7 pg/mL. The designed immunosensor showed good stability, a wide linear range, high sensitivity and good reproducibility and could be used for the detection of actual samples. The PEC immunosensor had a strong ability to specifically recognize β-LG, which was not affected by other proteins in the milk without pretreatment. Meanwhile, the developed immunosensor provided a promising PEC detection platform and reference idea for the detection of other proteins in milk.

Electrochemical detection of β-lactoglobulin based on a highly selective DNA aptamer and flower-like Au@BiVO4 microspheres

Beta-lactoglobulin is a natural milk protein and the main cause of infant milk allergy. In this work, a sensitive, selective and inexpensive electrochemical biosensor for the detection of β-lactoglobulin was developed. In this sensor, a DNA aptamer was used instead of an expensive antibody as the recognition group highly selective for β-lactoglobulin. The flower-like BiVO₄ microspheres were firstly found to have peroxidase mimic catalytic activity and used to amplify the electrochemical signal. The aptamer can bind β-lactoglobulin and fall off from the working electrode, after which the DNA2/Au/BiVO₄ probe can be fixed to the DNA1/AuNPs/ITO working electrode by the hybridization of DNA2 with DNA1. Therefore, a higher concentration of β-lactoglobulin leads to increased fabrication of the DNA2/Au/BiVO₄ probe on the surface of the working electrode, and thereby increases the electrochemical signal. This electrochemical biosensor exhibited a wide detection range from 0.01 to 1000 ng mL^-1, with a limit of detection (LOD) of 0.007 ng mL^-1, which indicates a good potential application in the field of food analysis.

Folding-Based Electrochemical Aptasensor for the Determination of β-Lactoglobulin on Poly-L-Lysine Modified Graphite Electrodes

Nowadays, food allergy is a very important health issue, causing adverse reactions of the immune system when exposed to different allergens present in food. Because of this, the development of point-of-use devices using miniaturized, user-friendly, and low-cost instrumentation has become of outstanding importance. According to this, electrochemical aptasensors have been demonstrated as useful tools to quantify a broad variety of targets. In this work, we develop a simple methodology for the determination of β-lactoglobulin (β-LG) in food samples using a folding-based electrochemical aptasensor built on poly-L-lysine modified graphite screen-printed electrodes (GSPEs) and an anti-β-lactoglobulin aptamer tagged with methylene blue (MB). This aptamer changes its conformation when the sample contains β-LG, and due to this, the spacing between MB and the electrode surface (and therefore the electron transfer efficiency) also changes. The response of this biosensor was linear for concentrations of β-LG within the range 0.1-10 ng·mL-1, with a limit of detection of 0.09 ng·mL-1. The biosensor was satisfactorily employed for the determination of spiked β-LG in real food samples.

Development of Nanozymes for Food Quality and Safety Detection: Principles and Recent Applications

The public concerns about agrifood safety call for innovative and reformative analytical techniques to meet the inspection requirements of high sensitivity, specificity, and reproducibility. Enzyme-mimetic nanomaterials or nanozymes, which combine enzyme-like properties with nanoscale features, emerge as an excellent tool for quality and safety detection in the agrifood sector, due to not only their robust capacity in detection but also their attraction in future-oriented exploitations. However, in-depth understanding about the fundamental principles of nanozymes for food quality and safety detection remains limited, which makes their applications largely empirical. This review provides a comprehensive overview of the principles, designs, and applications of nanozyme-based detection technique in the agrifood industry. The discussion mainly involves three mimicking types, that is, peroxidase, oxidase, and catalase-like nanozymes, capable of detecting major agrifood analytes. The current principles and strategies are classified and then discussed in details through discriminating the roles of nanozymes in diverse detection platforms. Thereafter, recent applications of nanozymes in detecting various endogenous ingredients and exogenous contaminants in foods are reviewed, and the outlook of profound developments are explained. Evidenced by the increasing publications, nanozyme-based detection techniques are narrowing the gap to practical-oriented food analytical methods, while some challenges in optimization of nanozymes, diversification of recognition-to-signal manners, and sustainability of methodology need to conquer in the future.

Thionin functionalized signal amplification label derived dual-mode electrochemical immunoassay for sensitive detection of cardiac troponin I

A sensitive sandwich-type electrochemical immunosensor was established by employing Au@Pt core-shell multi-branched nanoparticles, and thionin functionalized nitrogen/sulfur co-doped graphene oxide (N/S-cGO/L-lys/Au@Pt MBs/Thi) as a double signal label to detect cardiac troponin I (cTnI). In this work, Au nanorods functionalized polydopamine (Au NR@PDA) with high adsorption capacity and superior electroconductivity can provide an efficient substrate for immobilizing primary antibodies (Ab₁). In the proposed N/S-cGO/L-lys/Au@Pt MBs/Thi, an electrochemically active molecule, Thi was covalently bonded in the N/S-cGO/L-lys/Au@Pt MBs. It presented a strong differential pulse voltammetry (DPV) current signal without electron transfer mediators, and showed a high electrocatalytic activity toward H₂O₂ reduction by using amperometric i-t (i-t). Impressively, with the synergistic effect of N/S-cGO/L-lys/Au@Pt MBs/Thi and Au NR@PDA, the developed dual-mode electrochemical immunosensor for cTnI detection showed a wide linear concentration range (50 fg/mL to 250 ng/mL, 750 fg/mL to 100 ng/mL) and a low detection limit (16.7 fg/mL, 250 fg/mL) via i-t and DPV, respectively. Furthermore, this immunosensor exhibited acceptable reproducibility, high sensitivity and good stability under optimal conditions. More importantly, the satisfactory results were obtained in detection of cTnI-spiked human serum samples, and the presented method may be a promising application in clinical bioanalysis.