An impedimetric immunosensor for determination of porcine epidemic diarrhea virus based on the nanocomposite consisting of molybdenum disulfide/reduced graphene oxide decorated with gold nanoparticles

Sensitive Competitive Electrochemical Immunosensor for Hg (II) Based on Molybdenum Disulfide/Reduced Graphene Oxide/Gold Nanocomposites

A sensitive and specific competitive electrochemical immunosensor for the detection of Hg (II) using a modified electrode based on molybdenum disulfide/reduced graphene oxide/gold (MoS2/rGO/Au) nanocomposites was developed in this study. The nanocomposites were characterized and assembled with an antibody against Hg (II) for the immunosensor, demonstrating good electrical activity, high affinity and high specificity. Free Hg (II) in a solution can be measured by the competitive reaction of the Hg element in the sample and the antigen with the antibody fixed on the electrode. A differential pulse voltammetry (DPV) method was used, and the competitive current changed in accordance with the concentration of Hg (II). Under optimal conditions, the sensor showed a linear relationship from 0.1 to 600 ng/mL, and the limit of detection (LOD) was 63 pg/mL. The proposed immunosensor showed an acceptable recovery from 98.4% to 100.3% in spiked samples. Satisfactory stability and reproducibility were obtained. Competitive species, including Zn (II), Mg (II), Al (III), Cu (II), Pb (II), Ba (II), Cd (II), Ag (I), MNA, CH3Hg (I) and CH3Hg-MNA, were selected and applied according to the procedure of the assay, and their significantly different response compared to Hg (II) indicated that the assay displayed not only high sensitivity but also high selectivity. This immunosensor offers a useful model for the detection of Hg (II).

Recent development of gold nanochips in biosensing and biodiagnosis sensibilization strategies in vitro based on SPR, SERS and FRET optical properties

Gold nanomaterials have become attractive nanomaterials for biomedical research due to their unique physical and chemical properties, and nanochips are designed to manufacture high-quality substrates for loading gold nanoparticles (GNPs) to achieve specific and selective detection. By utilizing multiple optical properties of different gold nanostructures, the sensitivity, specificity, speed, contrast, resolution, and other performance of biosensing and biological diagnosis can be significantly improved. This paper summarized the sensitivity enhancement strategies of optical biosensing techniques based on the three main optical properties of gold nanomaterials: surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS) and fluorescence resonance energy transfer (FRET). The aim is to comprehensively review the development direction of in vitro diagnostics (IVDs) from two aspects: detection strategies and modification of gold nanomaterials. In addition, some opportunities and challenges that gold-based IVDs may encounter at present or in the future are also mentioned in this paper. In summary, this paper can enlighten readers with feasible strategies for manufacturing potential gold-based nanobiosensors.

An innovative label-free electrochemical aptamer sensor: utilizing Ti3C2Tx/MoS2/Au NPs for accurate interleukin-6 detection

In the medical field, changes in interleukin-6 (IL-6) concentration serve as essential biomarkers for monitoring and diagnosing various conditions, including acute inflammatory responses such as those seen in trauma and burns, and chronic illnesses like cancer. This paper detailed a label-free electrochemical aptamer sensor designed for IL-6 quantification. A composite material consisting of Ti3C2Tx and MoS2 was successfully synthesized to fabricate this sensor. The synergistic effect of MoS2's catalytic action on hydrogen peroxide (H2O2), used as a signalling marker, when combined with the exceptional conductivity and large specific surface area of Ti3C2Tx, not only enables an increased loading of MoS2 but also significantly boosts the electrochemical response. The in situ-reduced Au NPs provided stable immobilization sites for DNA aptamers (DNAapt) and facilitated electron transfer, ensuring accurate IL-6 recognition. Under optimal conditions, the aptamer sensor exhibited a wide linear range (5 pg/mL to 100 ng/mL) and a low limit of detection (LOD) of 2.9 pg/mL. Its sensing performance in human serum samples highlights its potential as a promising clinical analysis tool.

A portable transistor immunosensor for fast identification of porcine epidemic diarrhea virus

Widespread distribution of porcine epidemic diarrhea virus (PEDV) has led to catastrophic losses to the global pig farming industry. As a result, there is an urgent need for rapid, sensitive and accurate tests for PEDV to enable timely and effective interventions. In the present study, we develop and validate a floating gate carbon nanotubes field-effect transistor (FG CNT-FET)-based portable immunosensor for rapid identification of PEDV in a sensitive and accurate manner. To improve the affinity, a unique PEDV spike protein-specific monoclonal antibody is prepared by purification, and subsequently modified on FG CNT-FET sensor to recognize PEDV. The developed FET biosensor enables highly sensitive detection (LoD: 8.1 fg/mL and 100.14 TCID50/mL for recombinant spike proteins and PEDV, respectively), as well as satisfactory specificity. Notably, an integrated portable platform consisting of a pluggable FG CNT-FET chip and a portable device can discriminate PEDV positive from negative samples and even identify PEDV and porcine deltacoronavirus within 1 min with 100% accuracy. The portable sensing platform offers the capability to quickly, sensitively and accurately identify PEDV, which further points to a possibility of point of care (POC) applications of large-scale surveillance in pig breeding facilities.

An ultrasensitive electrochemical sensor for detecting porcine epidemic diarrhea virus based on a Prussian blue-reduced graphene oxide modified glassy carbon electrode

This study developed a novel, ultrasensitive sandwich-type electrochemical immunosensor for detecting the porcine epidemic diarrhea virus (PEDV). By electrochemical co-deposition of graphene and Prussian blue, a Prussian blue-reduced graphene oxide-modified glassy carbon electrode was made, further modified with PEDV-monoclonal antibodies (mAbs) to create a new PEDV immunosensor using the double antibody sandwich technique. The electrochemical characteristics of several modified electrodes were investigated using cyclic voltammetry (CV). We optimized the pH levels and scan rate. Additionally, we examined specificity, reproducibility, repeatability, accuracy, and stability. The study indicates that the immunosensor has good performance in the concentration range of 1 × 10^1.88 to 1 × 10^5.38 TCID₅₀/mL of PEDV, with a detection limit of 1 × 10^1.93 TCID₅₀/mL at a signal-to-noise ratio of 3σ. The composite membranes produced via co-deposition of graphene and Prussian blue effectively increased electron transport to the glassy carbon electrode, boosted response signals, and increased the sensitivity, specificity, and stability of the immunosensor. The immunosensor could accurately detect PEDV, with results comparable to real-time quantitative PCR. This technique was applied to PEDV detection and served as a model for developing additional immunosensors for detecting hazardous chemicals and pathogenic microbes.

A novel electrochemical immunosensor based on PdAgPt/MoS2 for the ultrasensitive detection of CA 242

Dynamic monitoring of tumor markers is an important way to the diagnosis of malignant tumor, evaluate the therapeutic effect of tumor and analyze the prognosis of cancer patients. As a tumor marker of digestive tract, CA242 is often used to Assess the therapeutic effect of colorectal cancer and pancreatic cancer. In this study, immunosensor technology was used to detect CA242. PdAgPt nanocomposites, which have great advantages in biocompatibility, electrical conductivity and catalytic properties, were prepared by hydrothermal synthesis method. The prepared PdAgPt nanocomposites were loaded onto the surface of molybdenum disulfide (MoS₂) with large surface area, and the new nanocomposites were synthesized. Using PdAgPt/MoS₂ as signal amplification platform, the label-free CA242 electrochemical immunosensor has a wide detection range that extends from 1*10⁻⁴ U/ml to 1*10² U/ml and a low detection limit (LOD, 3.43*10⁻⁵ U/ml) after optimization of experimental conditions. In addition, the CA242 immunosensor designed in this study also performed well in the evaluation of repeatability, selectivity and stability, and was successfully used for the detection of CA242 in human serum sample. Therefore, the label-free electrochemical immunosensor constructed in this study has a broad application prospect in the detection of clinical biomarkers.

Two-dimensional material-based virus detection

Cost-effective, rapid, and accurate virus detection technologies play key roles in reducing viral transmission. Prompt and accurate virus detection enables timely treatment and effective quarantine of virus carrier, and therefore effectively reduces the possibility of large-scale spread. However, conventional virus detection techniques often suffer from slow response, high cost or sophisticated procedures. Recently, two-dimensional (2D) materials have been used as promising sensing platforms for the high-performance detection of a variety of chemical and biological substances. The unique properties of 2D materials, such as large specific area, active surface interaction with biomolecules and facile surface functionalization, provide advantages in developing novel virus detection technologies with fast response and high sensitivity. Furthermore, 2D materials possess versatile and tunable electronic, electrochemical and optical properties, making them ideal platforms to demonstrate conceptual sensing techniques and explore complex sensing mechanisms in next-generation biosensors. In this review, we first briefly summarize the virus detection techniques with an emphasis on the current efforts in fighting again COVID-19. Then, we introduce the preparation methods and properties of 2D materials utilized in biosensors, including graphene, transition metal dichalcogenides (TMDs) and other 2D materials. Furthermore, we discuss the working principles of various virus detection technologies based on emerging 2D materials, such as field-effect transistor-based virus detection, electrochemical virus detection, optical virus detection and other virus detection techniques. Then, we elaborate on the essential works in 2D material-based high-performance virus detection. Finally, our perspective on the challenges and future research direction in this field is discussed.

A minireview on nanoparticle-based sensors for the detection of coronaviruses

Coronaviruses (CoVs) are a class of viruses that cause respiratory tract infections in birds and mammals. Severe acute respiratory syndrome and Middle East respiratory syndrome are pathogenic human viruses. The ongoing coronavirus causing a pandemic of COVID-19 is a recently identified virus from this group. The first step in the control of spreading the disease is to detect and quarantine infected subjects. Consequently, the introduction of rapid and reliable detection methods for CoVs is crucial. To date, several methods were reported for the detection of coronaviruses. Nanoparticles play an important role in detection tools, thanks to their high surface-to-volume ratio and exclusive optical property enables the development of susceptible analytical nanoparticle-based sensors. The studies performed on using nanoparticles-based (mainly gold) sensors to detect CoVs in two categories of optical and electrochemical were reviewed here. Details of each reported sensor and its relevant analytical parameters are carefully provided and explained.

Electrochemical detection of matrix metalloproteinase-7 using an immunoassay on a methylene blue/2D MoS2/graphene oxide electrode

Methylene blue (MB) adsorption onto a two-dimensional molybdenum disulfide (2D MoS₂)/graphene oxide (GO) nanocomposite sitting on a screen-printed carbon electrode (SPCE) is used to develop a new sensitive label-free electrochemical immunosensor for the detection of matrix metalloproteinase-7 (MMP-7) cancer biomarkers. The 2D MoS₂/GO nanocomposite deposited onto an SPCE provides a large specific surface area, fast electron transfer, and exceptional electrical conductivity. Furthermore, MB adsorbed onto the 2D MoS₂/GO nanocomposite architecture can be used for signal amplification in electrochemical immunosensors. Moreover, an immunosensor platform was fabricated by the adsorption of anti-MMP-7 capture antibodies onto the MB/2D MoS₂/GO nanocomposite surface via electrostatic interactions for the detection of the MMP-7 immunocomplex. Under optimum conditions, the label-free immunosensor exhibits a decrease in the current response for MB corresponding to the MMP-7 concentration. The sensor affords a linear logarithmic range of 0.010-75 ng mL^-1 with a limit of detection (LOD) of 0.007 ng mL^-1. The developed electrochemical immunosensor provides high selectivity, good reproducibility, and excellent stability. Furthermore, the proposed immunosensor can be applied for the detection of MMP-7 in human serum samples with good recovery. Thus, this device can be applied for the early clinical diagnosis of pancreatic and colorectal cancers.

Two-Dimensional Nanostructures for Electrochemical Biosensor

Current advancements in the development of functional nanomaterials and precisely designed nanostructures have created new opportunities for the fabrication of practical biosensors for field analysis. Two-dimensional (2D) and three-dimensional (3D) nanomaterials provide unique hierarchical structures, high surface area, and layered configurations with multiple length scales and porosity, and the possibility to create functionalities for targeted recognition at their surface. Such hierarchical structures offer prospects to tune the characteristics of materials-e.g., the electronic properties, performance, and mechanical flexibility-and they provide additional functions such as structural color, organized morphological features, and the ability to recognize and respond to external stimuli. Combining these unique features of the different types of nanostructures and using them as support for bimolecular assemblies can provide biosensing platforms with targeted recognition and transduction properties, and increased robustness, sensitivity, and selectivity for detection of a variety of analytes that can positively impact many fields. Herein, we first provide an overview of the recently developed 2D nanostructures focusing on the characteristics that are most relevant for the design of practical biosensors. Then, we discuss the integration of these materials with bio-elements such as bacteriophages, antibodies, nucleic acids, enzymes, and proteins, and we provide examples of applications in the environmental, food, and clinical fields. We conclude with a discussion of the manufacturing challenges of these devices and opportunities for the future development and exploration of these nanomaterials to design field-deployable biosensors.

Biosensing strategies for the electrochemical detection of viruses and viral diseases - A review

Viruses are the causing agents for many relevant diseases, including influenza, Ebola, HIV/AIDS, and COVID-19. Its rapid replication and high transmissibility can lead to serious consequences not only to the individual but also to collective health, causing deep economic impacts. In this scenario, diagnosis tools are of significant importance, allowing the rapid, precise, and low-cost testing of a substantial number of individuals. Currently, PCR-based techniques are the gold standard for the diagnosis of viral diseases. Although these allow the diagnosis of different illnesses with high precision, they still present significant drawbacks. Their main disadvantages include long periods for obtaining results and the need for specialized professionals and equipment, requiring the tests to be performed in research centers. In this scenario, biosensors have been presented as promising alternatives for the rapid, precise, low-cost, and on-site diagnosis of viral diseases. This critical review article describes the advancements achieved in the last five years regarding electrochemical biosensors for the diagnosis of viral infections. First, genosensors and aptasensors for the detection of virus and the diagnosis of viral diseases are presented in detail regarding probe immobilization approaches, detection methods (label-free and sandwich), and amplification strategies. Following, immunosensors are highlighted, including many different construction strategies such as label-free, sandwich, competitive, and lateral-flow assays. Then, biosensors for the detection of viral-diseases-related biomarkers are presented and discussed, as well as point of care systems and their advantages when compared to traditional techniques. Last, the difficulties of commercializing electrochemical devices are critically discussed in conjunction with future trends such as lab-on-a-chip and flexible sensors.

Graphene-based field-effect transistor biosensors for the rapid detection and analysis of viruses: A perspective in view of COVID-19

Current situation of COVID-19 demands a rapid, reliable, cost-effective, facile detection strategy to break the transmission chain and biosensor has emerged as a feasible solution for this purpose. Introduction of nanomaterials has undoubtedly improved the performance of biosensor and the addition of graphene enhanced the sensing ability to a peerless level. Amongst different graphene-based biosensing schemes, graphene field-effect transistor marked its unique presence owing to its ability of ultrasensitive and low-noise detection thereby facilitating instantaneous measurements even in the presence of small amounts of analytes. Recently, graphene field-effect transistor type biosensor is even successfully employed in rapid detection of SARS-CoV-2 and this triggers the interest of the scientific community in reviewing the current developments in graphene field-effect transistor. Subsequently, in this article, the recent progress in graphene field-effect transistor type biosensors for the detection of the virus is reviewed and challenges along with their strengths are discussed.