Detection of Allergenic Lysozyme during Winemaking with an Electrochemical Aptasensor

Aggregation of gold nanoclusters in amyloid fibers: a luminescence assay for amyloid fibrillation detection and inhibitor screening

Amyloid fibrillation is associated with a great variety of human diseases, such as Alzheimer's and Huntington's diseases. A fluorescence assay for amyloid fibrillation detection and inhibitor screening was developed based on the fact that the fluorescence emission of gold nanoclusters (Au NCs) is largely enhanced upon adding amyloids, such as lysozyme amyloid fibers. A good linear relationship exists between the enhanced fluorescence intensity of Au NCs and lysozyme fiber within the concentration range of 0-0.05 mg mL-1. This ultra-sensitive method can detect the protein fiber earlier than thioflavin T (THT), allowing more time for disease treatment. Furthermore, Au NCs have many advantages over the classical probe (i.e., THT), such as large Stokes shifts and low toxicity. We selected ascorbic acid as a representative inhibitor and used this method to screen inhibitors. If inhibitors are added when incubating lysozyme, the lysozyme fibrosis process will be crimped, decreasing the amount of lysozyme fibers.

Electrostatic-Mediated Binding of DNA to Lysozymes: Evaluation of Aptamer-Based Assays for Highly Positively Charged Targets

Lysozymes are a highly popular protein target for the development of aptamer-based biosensors. Because a lysozyme is a polycation and DNA is a polyanion, it is essential to separate the contribution of nonspecific electrostatic interactions from specific aptamer binding. In this study, various factors affecting the binding of DNA and lysozymes, including the DNA sequence, DNA length, pH, and salt concentration, were explored using fluorescence polarization. We concluded that direct fluorescence polarization and fluorescence intensity changes are unlikely to be directly applicable for aptamer-based biosensors to detect lysozymes because all of the tested DNA sequences showed binding. These fundamental studies confirm the dominant role of electrostatic binding. We further evaluated three other methods, including label-free fluorescent detection using a DNA staining dye, label-free colorimetric detection using gold nanoparticles, and a fluorescent sensor based on the strand displacement reaction. In each case, we focused on a random DNA sequence that is not expected to bind to the lysozyme as an aptamer. Of all the methods, only the strand displacement strategy can be potentially used to evaluate aptamer binding, as the other methods all responded to nonaptamer sequences. This study provides valuable insights for assaying aptamer binding to cationic proteins that can exhibit a nonspecific attraction to DNA.

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.

Preparation and Self-Assembly of pH-Responsive Hyperbranched Polymer Peptide Hybrid Materials

In recent years, the coupling of structurally and functionally controllable polymers with biologically active peptide materials to obtain polymer-peptide hybrids with excellent properties and biocompatibility has led to important research progress in the field of polymers. In this study, a pH-responsive hyperbranched polymer hPDPA was prepared by combining atom transfer radical polymerization (ATRP) with self-condensation vinyl polymerization (SCVP) using a three-component reaction of Passerini to obtain a monomeric initiator ABMA containing functional groups. The pH-responsive polymer peptide hybrids hPDPA/PArg/HA were obtained by using the molecular recognition of polyarginine (β-CD-PArg) peptide modified with β-cyclodextrin (β-CD) on the hyperbranched polymer, followed by the electrostatic adsorption of hyaluronic acid (HA). The two hybrid materials, h₁PDPA/PArg₁₂/HA and h₂PDPA/PArg₈/HA could self-assemble to form vesicles with narrow dispersion and nanoscale dimensions in phosphate-buffered (PB) at pH = 7.4. The assemblies exhibited low toxicity as drug carriers of β-lapachone (β-lapa), and the synergistic therapy based on ROS and NO generated by β-lapa had significant inhibitory effects on cancer cells.

Synthesis and Self-Assembly of Hyperbranched Multiarm Copolymer Lysozyme Conjugates Based on Light-Induced Metal-Free Atrp

In recent years, the coupling of structurally and functionally controllable polymers with biologically active protein materials to obtain polymer-protein conjugates with excellent overall properties and good biocompatibility has been important research in the field of polymers. In this study, the hyperbranched polymer hP(DEGMA-co-OEGMA) was first prepared by combining self-condensation vinyl polymerization (SCVP) with photo-induced metal-free atom transfer radical polymerization (ATRP), with 2-(2-bromo-2-methylpropanoyloxy) ethyl methacrylate (BMA) as inimer, and Di (ethylene glycol) methyl ether methacrylate (DEGMA) and (oligoethylene glycol) methacrylate (OEGMA, M_n = 300) as the copolymer monomer. Then, hP(DEGMA-co-OEGMA) was used as a macroinitiator to continue the polymerization of a segment of pyridyl disulfide ethyl methacrylate (DSMA) monomer to obtain the hyperbranched multiarm copolymers hP(DEGMA-co-OEGMA)-star-PDSMA. Finally, the lysozyme with sulfhydryl groups was affixed to the hyperbranched multiarm copolymers by the exchange reaction between sulfhydryl groups and disulfide bonds to obtain the copolymer protein conjugates hP(DEGMA-co-OEGMA)-star-PLZ. Three hyperbranched multiarm copolymers with relatively close molecular weights but different degrees of branching were prepared, and all three conjugates could self-assemble to form nanoscale vesicle assemblies with narrow dispersion. The biological activity and secondary structure of lysozyme on the assemblies remained essentially unchanged.

Determination of trace levels of organic fining agents in wines: Latest and relevant findings

The production of red wine plays a key role in the local and international economies of several nations. During the winemaking process, to clarify the final product, before bottling, and to remove undesired substances (proteins, phenols, and tannins), fining agents are commonly added to wines. These substances have different origins (animal and vegetable proteins or mineral compounds), and they show a potential risk for the health of allergic subjects. For these reasons, the residues of fining agents, constituted by exogenous proteins based on gluten, egg, and milk proteins, should not be present in the final product and their trace residues should be quantified with accuracy. In the last decade, several analytical approaches have been developed for their quantitative determination using different sample treatment protocols and analytical techniques. These methods are based on liquid chromatography coupled with mass spectrometry or enzyme-linked immunosorbent assays (ELISAs). Recently, biosensors have been proposed as a potential alternative to immunoassay approaches, allowing rapid, cheap, and simple multi-residue detection. This short review aimed to report the most recent and relevant findings in the field.

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.

An electrochemical sensor for high sensitive determination of lysozyme based on the aptamer competition approach

Protein is a kind of basic substance that constitutes a life body. The determination of protein is very important for the research of biology, medicine, and other fields. Lysozyme is relatively small and simple in structure among all kinds of proteins, so it is often used as a standard target detector in the study of aptamer sensor for protein detection. In this paper, a lysozyme electrochemical sensor based on aptamer competition mechanism is proposed. We have successfully prepared a signal weakening electrochemical sensor based on the lysozyme aptamer competition mechanism. The carboxylated multi-walled carbon nanotubes (MWCNTs) were modified on the glassy carbon electrode, and the complementary aptamer DNA with amino group was connected to MWCNTs. Because of the complementary DNA of daunomycin into the electrode, the electrochemical signal is generated. When there is a target, the aptamer binds to lysozyme with higher binding power, and the original complementary chain breaks down, resulting in the loss of daunomycin inserted into the double chain and the weakening of electrochemical signal. Differential pulse voltammetry was used to determine lysozyme, the response range was 1–500 nM, the correlation coefficient was 0.9995, and the detection limit was 0.5 nM. In addition, the proposed sensor has good selectivity and anti-interference.

Aptasensors for lysozyme detection: Recent advances

Lysozyme is an enzyme existing in multiple organisms where it plays various vital roles. The most important role is its antibacterial activity in the human body; in fact, it is also called "the body's own antibiotic". Despite its proven utility, lysozyme can potentially trigger allergic reactions in sensitive individuals, even in trace amounts. Therefore, lysozyme determination in foods is becoming of paramount importance. Traditional detection methods are expensive, time-consuming and they cannot be applied for fast in-situ quantification. Electrochemical and optical sensors have attracted an increasing attention due to their versatility and ability to reduce the disadvantages of traditional methods. Using an aptamer as the bioreceptor, the sensor selectivity is amplified due to the specific recognition of the analyte. This review is presenting the progresses made in lysozyme determination by means of electrochemical and optical aptasensors in the last five years. A critical overview on the methodologies employed for aptamer immobilization and on the strategies for signal amplification of the assays will be described. Different optical and electrochemical aptasensors will be discussed and compared in terms of analytical performances, versatility and real samples applications.

Electrochemical Affinity Biosensors Based on Selected Nanostructures for Food and Environmental Monitoring

The excellent capabilities demonstrated over the last few years by electrochemical affinity biosensors should be largely attributed to their coupling with particular nanostructures including dendrimers, DNA-based nanoskeletons, molecular imprinted polymers, metal-organic frameworks, nanozymes and magnetic and mesoporous silica nanoparticles. This review article aims to give, by highlighting representative methods reported in the last 5 years, an updated and general overview of the main improvements that the use of such well-ordered nanomaterials as electrode modifiers or advanced labels confer to electrochemical affinity biosensors in terms of sensitivity, selectivity, stability, conductivity and biocompatibility focused on food and environmental applications, less covered in the literature than clinics. A wide variety of bioreceptors (antibodies, DNAs, aptamers, lectins, mast cells, DNAzymes), affinity reactions (single, sandwich, competitive and displacement) and detection strategies (label-free or label-based using mainly natural but also artificial enzymes), whose performance is substantially improved when used in conjunction with nanostructured systems, are critically discussed together with the great diversity of molecular targets that nanostructured affinity biosensors are able to quantify using quite simple protocols in a wide variety of matrices and with the sensitivity required by legislation. The large number of possibilities and the versatility of these approaches, the main challenges to face in order to achieve other pursued capabilities (development of antifouling, continuous operation, wash-, calibration- and reagents-free devices, regulatory or Association of Official Analytical Chemists, AOAC, approval) and decisive future actions to achieve the commercialization and acceptance of these devices in our daily routine are also noted at the end.

Graphene oxide as a cartridge enable on-line assembly of photosensitizer for 1O2-based electrochemical aptasensing

An ultrasensitive ¹O₂-based electrochemical aptasensor by on-line assembly of photosensitizers using graphene oxide (GO) as a cartridge is reported. In the presence of target protein lysozyme, the interaction of lysozyme with aptamer led to the dissociation of dsDNA and release of the aptamer-lysozyme complex to solution, with DNA-c retaining on the electrode; then, the photosensitizer phloxine B (PB) was assembled on the electrode since GO can simultaneously adsorb DNA-c and PB molecules. Upon irradiation by a green LED, ¹O₂ was generated by photocatalysis of PB molecules and then cleaved the DNA-c, leading to remarkably decreased impedance signals that linearly respond with the logarithm of lysozyme concentration. Benefitting from the efficient photosensitization ability of PB and the high PB-loading capacity of GO, the developed sensor allowed determination of 0.001 to 100 nM lysozyme with a limit of detection of about 0.14 pM. The relative standard deviation (RSD) for five independent electrodes with 1 nM lysozyme was 3.1%, indicating satisfactory reproducibility. The sensor also showed excellent selectivity toward lysozyme in the presence of interfering substances and was applied to the determination of lysozyme in urine samples with recoveries ranging from 91 to 101%. The on-line assembly of photosensitizer technique opens a new way for amplified electrosensing of biomolecules. Graphical abstract An on-line assembly of photosensitizers and DNA on electrode was developed using graphene oxide a cartridge and the photocatalytic electrosensor can be used for label-free detection of lysozyme as low as 1 pM.

Immobilization Techniques for Aptamers on Gold Electrodes for the Electrochemical Detection of Proteins: A Review

The development of reliable biosensing platforms plays a key role in the detection of proteins in clinically and environmentally derived samples for diagnostics, as well as for process monitoring in biotechnological productions. For this purpose, the biosensor has to be stable and reproducible, and highly sensitive to detect potentially extremely low concentrations and prevent the nonspecific binding of interfering compounds. In this review, we present an overview of recently published (2017–2019) immobilization techniques for aptamers on gold electrodes for the electrochemical detection of proteins. These include the direct immobilization of thiolated aptamers and the utilization of short linkers, streptavidin/biotin interaction, as well as DNA nanostructures and reduced graphene oxide as immobilization platforms. Applied strategies for signal amplification and the prevention of biofouling are additionally discussed, as they play a crucial role in the design of biosensors. While a wide variety of amplification strategies are already available, future investigations should aim to establish suitable antifouling strategies that are compatible with electrochemical measurements. The focus of our review lies on the detailed discussion of the underlying principles and the presentation of utilized chemical protocols in order to provide the reader with promising ideas and profound knowledge of the subject, as well as an update on recent discoveries and achievements.

Cutting-Edge Advances in Electrochemical Affinity Biosensing at Different Molecular Level of Emerging Food Allergens and Adulterants

The presence of allergens and adulterants in food, which represents a real threat to sensitized people and a loss of consumer confidence, is one of the main current problems facing society. The detection of allergens and adulterants in food, mainly at the genetic level (characteristic fragments of genes that encode their expression) or at functional level (protein biomarkers) is a complex task due to the natural interference of the matrix and the low concentration at which they are present. Methods for the analysis of allergens are mainly divided into immunological and deoxyribonucleic acid (DNA)-based assays. In recent years, electrochemical affinity biosensors, including immunosensors and biosensors based on synthetic sequences of DNA or ribonucleic acid (RNA), linear, aptameric, peptide or switch-based probes, are gaining special importance in this field because they have proved to be competitive with the methods commonly used in terms of simplicity, test time and applicability in different environments. These unique features make them highly promising analytical tools for routine determination of allergens and food adulterations at the point of care. This review article discusses the most significant trends and developments in electrochemical affinity biosensing in this field over the past two years as well as the challenges and future prospects for this technology.

Progress in Electrochemical (Bio)Sensors for Monitoring Wine Production

Electrochemical sensors and biosensors have been proposed as fast and cost effective analytical tools, meeting the robustness and performance requirements for industrial process monitoring. In wine production, electrochemical biosensors have proven useful for monitoring critical parameters related to alcoholic fermentation (AF), malolactic fermentation (MLF), determining the impact of the various technological steps and treatments on wine quality, or assessing the differences due to wine age, grape variety, vineyard or geographical region. This review summarizes the current information on the voltamperometric biosensors developed for monitoring wine production with a focus on sensing concepts tested in industry-like settings and on the main quality parameters such as glucose, alcohol, malic and lactic acids, phenolic compounds and allergens. Recent progress featuring nanomaterial-enabled enhancement of sensor performance and applications based on screen-printed electrodes is emphasized. A case study presents the monitoring of alcoholic fermentation based on commercial biosensors adapted with minimal method development for the detection of glucose and phenolic compounds in wine and included in an automated monitoring system. The current challenges and perspectives for the wider application of electrochemical sensors in monitoring industrial processes such as wine production are discussed.