Detection of influenza virus: traditional approaches and development of biosensors

Highly reproducible electrochemical biosensor for Influenza A virus towards low-resource settings

A highly reproducible electrochemical biosensor, employing a five-stranded four-way junction (5S-4WJ) system through square wave voltammetry, has been successfully validated for the detection of Influenza A virus (InfA). A comprehensive assessment of its linearity, precision, accuracy, and robustness has demonstrated its compliance with FDA standards. Integration with Nucleic Acid-Based Amplification (NASBA) has showcased its selectivity for InfA, enabling the detection of InfA RNA with a standard heater set at 41 °C. This platform offers a straightforward setup well-suited for use at low-resource facilities.

Nanodot zirconium trisulfide modified conducting thread: A smart substrate for fabrication of next generation biosensor

In present work, we report an eco-friendly, flexible and highly conducting cotton thread (CT) as a smart substrate for the development of biosensing platform towards ultrasensitive detection of swine flu serum amyloid A (SAA) biomarker. The biosensor was fabricated by optimized coating of CT with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) conductive ink followed by incorporation of nanodot zirconium trisulfide (nZrS3) which helped in enhancing the electrochemical properties and improving stability of PEDOT:PSS polymeric film. The fabricated nZrS3/PEDOT:PSS/CT electrode was then used for sequential immobilization of monoclonal antibodies of SAA (anti-SAA) and bovine serum albumin (BSA). The synthesized nanomaterials and fabricated electrodes were characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and contact angle analyser techniques. The electrochemical response of the fabricated smart thread based biosensor (BSA/anti-SAA/ZrS3/PEDOT:PSS/CT) was recorded against SAA using chronoamperometry technique which revealed superior sensitivity {30.2 μA [log (μg mL-1)]-1 cm-2}, excellent lower detection limit (0.72 ng mL-1) and prolonged shelf life up to 48 days. The response of the biosensor was also validated by analysing the electrochemical response of SAA spiked serum samples and the obtained results showed good correlation with that of standard samples.

Capacitance Contribution of NIH/3T3 Cells Existing on and between Electrodes of an Impedance Biosensor

In this study, an impedance biosensor capable of real-time monitoring of the growth and drug reactions using NIH/3T3 cells was fabricated through a semiconductor process. With the fabricated impedance biosensor, the cell growth and drug reaction states are monitored in real-time, showing the validness of the developed biosensor. By using the developed impedance biosensor, we have investigated the capacitance contribution of NIH/3T3 cells existing on electrodes and between electrodes. To compare the capacitance value contributions of the cells on and between electrodes, wide- and narrow-gap electrode patterns are manufactured with 3.7 and 0.3 mm electrode gap spacings, respectively. From the detailed analysis, the capacitance contributions of NIH/3T3 cells existing on electrodes are estimated around less than 20 percent compared to the cells existing between electrodes. In other words, a minimized electrode area with maximized electrode spacing is the promising impedance biosensor design guide for accurate cell capacitance measurements.

Nanoengineered phosphorus doped graphitic carbon nitride based ultrasensitive biosensing platform for Swine flu detection

In the present study, we developed an amino-polyindole modified phosphorus doped graphitic carbon nitride nanomaterial (APIN/P-g-C3N4) based immunosensing biochip for Serum amyloid A (SAA) biomarker towards early diagnosis of Swine flu. The P-g-C3N4 was synthesis via polycondensation and functionalized with APIN. Further, the biochip was fabricated by modifying the working area of SPE with APIN/P-g-C3N4 using drop cast method, APIN introduced the larger loading of -NH2 group moieties onto P-g-C3N4 matrix and benefitted to reinforced the biomolecules via covalent linkages. The monoclonal anti-SAA was conjugated onto APIN/P-g-C3N4/SPE using EDC-NHS chemistry and BSA was added for non-specific site blocking. The structural, chemical, composition and morphological characteristics of the synthesized, functionalized nanomaterial and fabricated biochips were investigated by XRD, XPS, FT-IR spectroscopy, SEM, FE-SEM and TEM techniques. Further, the electrochemical characterization and response studies of fabricated biochip were analyzed using the CV and DPV techniques. Based on the analytical performance of the proposed immunosensing biochip i.e. BSA/anti-SAA/APIN/P-g-C3N4/SPE, it is capable to detect SAA protein with ultra sensitivity of 79.5 μA log (mL ng-1) cm-2, ultralow limit of detection of 5 ng mL-1 and wider linear detection range of 5 ng mL-1-500 μg mL-1 with quick response time of 10 min. Moreover, the fabricated immunosensing biochips was used to analyse SAA protein in spiked serum samples and the achieved results demonstrated the good agreement with the electrochemical response observed in standard SAA protein samples in analytical solution. The proposed biochip can provide insights for developing a wide range of clinical screening tools for detecting various contagious diseases.

Recent Advances in Plasma-Engineered Polymers for Biomarker-Based Viral Detection and Highly Multiplexed Analysis

Infectious diseases remain a pervasive threat to global and public health, especially in many countries and rural urban areas. The main causes of such severe diseases are the lack of appropriate analytical methods and subsequent treatment strategies due to limited access to centralized and equipped medical centers for detection. Rapid and accurate diagnosis in biomedicine and healthcare is essential for the effective treatment of pathogenic viruses as well as early detection. Plasma-engineered polymers are used worldwide for viral infections in conjunction with molecular detection of biomarkers. Plasma-engineered polymers for biomarker-based viral detection are generally inexpensive and offer great potential. For biomarker-based virus detection, plasma-based polymers appear to be potential biological probes and have been used directly with physiological components to perform highly multiplexed analyses simultaneously. The simultaneous measurement of multiple clinical parameters from the same sample volume is possible using highly multiplexed analysis to detect human viral infections, thereby reducing the time and cost required to collect each data point. This article reviews recent studies on the efficacy of plasma-engineered polymers as a detection method against human pandemic viruses. In this review study, we examine polymer biomarkers, plasma-engineered polymers, highly multiplexed analyses for viral infections, and recent applications of polymer-based biomarkers for virus detection. Finally, we provide an outlook on recent advances in the field of plasma-engineered polymers for biomarker-based virus detection and highly multiplexed analysis.

Advanced Point-of-Care Testing Technologies for Human Acute Respiratory Virus Detection

The ever-growing global threats to human life caused by the human acute respiratory virus (RV) infections have cost billions of lives, created a significant economic burden, and shaped society for centuries. The timely response to emerging RVs could save human lives and reduce the medical care burden. The development of RV detection technologies is essential for potentially preventing RV pandemic and epidemics. However, commonly used detection technologies lack sensitivity, specificity, and speed, thus often failing to provide the rapid turnaround times. To address this problem, new technologies are devised to address the performance inadequacies of the traditional methods. These emerging technologies offer improvements in convenience, speed, flexibility, and portability of point-of-care test (POCT). Herein, recent developments in POCT are comprehensively reviewed for eight typical acute respiratory viruses. This review discusses the challenges and opportunities of various recognition and detection strategies and discusses these according to their detection principles, including nucleic acid amplification, optical POCT, electrochemistry, lateral flow assays, microfluidics, enzyme-linked immunosorbent assays, and microarrays. The importance of limits of detection, throughput, portability, and specificity when testing clinical samples in resource-limited settings is emphasized. Finally, the evaluation of commercial POCT kits for both essential RV diagnosis and clinical-oriented practices is included.

Broad-Spectrum Antiviral Peptides and Polymers

As the human cost of the pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still being witnessed worldwide, the development of broad-spectrum antiviral agents against emerging and re-emerging viruses is seen as a necessity to hamper the spread of infections. Various targets during the viral life-cycle can be considered to inhibit viral infection, from viral attachment to viral fusion or replication. Macromolecules represent a particularly attractive class of therapeutics due to their multivalency and versatility. Although several antiviral macromolecules hold great promise in clinical applications, the emergence of resistance after prolonged exposure urges the need for improved solutions. In the present article, the recent advancement in the discovery of antiviral peptides and polymers with diverse structural features and antiviral mechanisms is reviewed. Future perspectives, such as, the development of virucidal peptides/polymers and their coatings against SARS-CoV-2 infection, standardization of antiviral testing protocols, and use of artificial intelligence or machine learning as a tool to accelerate the discovery of antiviral macromolecules, are discussed.

Advances and insights in the diagnosis of viral infections

Viral infections are the most common among diseases that globally require around 60 percent of medical care. However, in the heat of the pandemic, there was a lack of medical equipment and inpatient facilities to provide all patients with viral infections. The detection of viral infections is possible in three general ways such as (i) direct virus detection, which is performed immediately 1-3 days after the infection, (ii) determination of antibodies against some virus proteins mainly observed during/after virus incubation period, (iii) detection of virus-induced disease when specific tissue changes in the organism. This review surveys some global pandemics from 1889 to 2020, virus types, which induced these pandemics, and symptoms of some viral diseases. Non-analytical methods such as radiology and microscopy also are overviewed. This review overlooks molecular analysis methods such as nucleic acid amplification, antibody-antigen complex determination, CRISPR-Cas system-based viral genome determination methods. Methods widely used in the certificated diagnostic laboratory for SARS-CoV-2, Influenza A, B, C, HIV, and other viruses during a viral pandemic are outlined. A comprehensive overview of molecular analytical methods has shown that the assay's sensitivity, accuracy, and suitability for virus detection depends on the choice of the number of regions in the viral open reading frame (ORF) genome sequence and the validity of the selected analytical method.

A competitive-type electrochemical immunosensor based on Ce-MOF@Au and MB-Au@Pt core-shell for nitrofuran metabolites residues detection

A novel competitive-type electrochemical immunosensor based on square wave voltammetry (SWV) response was developed for the quantitative detection of 1-Aminohydantoin (AHD). To improve the conductivity of this immunosensor nanocomposites with good electrical conductivity were prepared as a signal amplification platform for the immunosensor by growing Au nanoparticles on the surface of Ce-based metal-organic framework (Ce-MOF). In addition, methylene blue (MB)-loaded Au@Pt and coating antigen (OVA-AHD) connected as a signal label. When the target was introduced, it competed with the coating antigen for the Ab, which led to a reduction in the number of signal probes bound to the Ab. The concentration of AHD can be determined by SWV detection of the MB signal loaded on the signal labels. Under optimal conditions, the wide linear range of 0.001-1000 μg /L and a low detection limit of 1.35 × 10^-7 μg/L were achieved. Ultimately, the developed method displayed excellent specificity in practical applications, providing a promising probability to detect nitrofuran metabolites residues to guarantee food safety.

Upconversion Fluorescence Resonance Energy Transfer Aptasensors for H5N1 Influenza Virus Detection

Influenza A virus (IAV) poses a significant threat to human health, which calls for the development of efficient detection methods. The present study constructed a fluorescence resonance energy transfer (FRET) system based on novel fluorescent probes and graphene oxide (GO) for detecting H5N1 IAV hemagglutinin (HA). Here, we synthesized small (sub-20 nm) sandwich-structured upconversion nanoparticles (UCNPs) (SWUCNPs for short) with a high energy transfer efficiency, which allows for controlling the emitter in a thin shell. The π-π stacking interaction between the aptamer and GO shortens the distance between the fluorescent probe and the receptor, thereby realizing fluorescence resonance energy transfer (FRET). When HA is present, the aptamer enables changes in their conformations and move away from GO surface. Fluorescence signals display a linear relationship between HA quantitation in the range of 0.1-15 ng mL^-1 and a limit of detection (LOD) of 60.9 pg mL^-1. The aptasensor was also applicable in human serum samples with a linear range from 0.2 to 12 ng mL^-1 and a limit of detection of 114.7 pg mL^-1. This strategy suggested the promising prospect of the aptasensor in clinical applications because of the excellent sensing performance and sensitivity. This strategy may be promising for vitro diagnostics and provides new insights into the functioning of the SWUCNPs system.

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.

Dual-mode detection of avian influenza virions (H9N2) by ICP-MS and fluorescence after quantum dot labeling with immuno-rolling circle amplification

Avian influenza virus (AIVs), hosted in poultry, are the pathogens of many poultry diseases and human infections, which bring huge losses to the poultry breeding industry and huge panic to society. Therefore, it is of great significance to establish accurate and sensitive detection methods for AIVs. In this work, a dual-mode detection method based on immuno-rolling circle amplification (immuno-RCA) and quantum dots (QDs) labeling for inductively coupled plasma mass spectrometry (ICP-MS) and fluorescence detection of H9N2 AIV was developed. The dual-mode detection of the QDs by ICP-MS and fluorescence is used to achieve mutual verification within the analysis results, thus improving the accuracy of the method. With the immuno-RCA, the sensitivity of the method was increased by two orders of magnitude. The limit of detection of the proposed method is 17 ng L^-1 and 61 ng L^-1, and the linear range of the proposed method is 0.05-5 ng mL^-1 and 0.1-5 ng mL^-1 with ICP-MS and fluorescence detection, respectively. The relative standard deviation (n = 7) is 4.9% with ICP-MS detection and 3.1% with fluorescence detection. Furthermore, the proposed method was applied to the analysis of chicken serum samples, no significant different was found for two modes detection and the recoveries of the spiking experiments are acceptable, indicating that the method has good practical potential for real sample analysis.

A Novel Diagnostic System for Infectious Diseases Using Solid-State Nanopore Devices

Nanopore-based diagnostic systems are a promising tool for counting viruses in a specimen one by one. However, despite intensive R&D efforts, it remains difficult to recognize virus subtypes by nanopore devices. We thus propose a novel diagnostic system that combines a specialized virus recognition procedure with a nanopore detection procedure. This recognition procedure consists of three steps: 1) capture target viruses using specific probes for recognition; 2) release captured targets; and 3) detect released targets by nanopore. Proof-of-concept tests are conducted using avidin-modified fluorescent particles (as a model for viruses) and biotin-modified alkane thiol (as a model for probes). The avidin-modified particles are confirmed to be captured on electrode by biotin-modified probes and then, the particles are electrochemically released from the electrode. Consequently, the released particles are successfully detected by nanopore devices. Furthermore, the concept is also proved by using human influenza viruses (H1N1, A/PR/8/34) and sugar chain (6'-sialyllactose)-modified probes. This suggests that our concept is applicable to various infectious diseases by changing probes (ligands).

Rapid, Sensitive, and Selective Detection of H5 Hemagglutinin from Avian Influenza Virus Using an Immunowall Device

Avian influenza virus (AIV) infection, caused by influenza virus type A, is an infectious, acute respiratory disease of birds related to influenza outbreaks worldwide. The highly pathogenic AIV subtype H5N1 has crossed species barriers to infect mammals, including humans, with fatal outcomes and has received attention as a potential pandemic threat. A rapid and timely detection in poultry is vitally important to prevent the virus spread. Despite their great sensitivity, conventional detection methods such as real-time reverse transcription-polymerase chain reaction and the agar gel precipitation test are time-consuming and labor-intensive and require special training. In this work, an immunowall device was evaluated as an easier and faster way for detecting AIV H5-hemagglutinin (AIV H5-HA). For detection, fluorescence-labeled or enzyme-labeled antibody was employed as a labeling antibody in a sandwich immunoassay. Both were shown in this paper to be easier and faster assays for detection compared with the conventional enzyme-linked immunosorbent assay (ELISA) kit. In addition, high selectivity was achieved for AIV H5-HA detection after the evaluation of other different HA virus subtypes. The limit of detection was 0.23 ng/mL for the enzyme-labeled antibody. This value was equivalent to that of the conventional ELISA kit but 8 times faster (31 min compared to 260 min). The detection range was 0.23-100 ng/mL. The immunowall device with the enzyme-labeled antibody offers a rapid, sensitive, selective, and simple immunoassay system for future H5 AIV real sample detection.

Application of an immunoglobulin Y-alkaline phosphatase bioconjugate as a diagnostic tool for influenza A virus

The diagnosis of influenza A virus is essential since it can be confused with influenza A like illness and lead to inaccurate drug prescription. In this study, the M2e peptide, a strategic antigen that is conserved in all virus subtypes, was used as a diagnostic marker of influenza A. For the first time, M2e-specific IgY antibody was covalently conjugated to alkaline phosphatase (ALP) enzyme in the presence of glutaraldehyde. The antibody-enzyme bioconjugate was characterized by fluorescence and Fourier-transform infrared spectroscopy. Subsequently, the diagnostic value of this bioconjugate was evaluated by direct sandwich ELISA using nasopharyngeal swab samples positive/negative for H1N1 and H3N2, which were previously analyzed by rRT-PCR for influenza. In conclusion, the M2e-specific IgY-ALP bioconjugate demonstrated positive results for Influenza A in samples that were diagnosed as Influenza A via the RT-PCR method.

Detection of Influenza a Virus in Swine Nasal Swab Samples With a Wash-Free Magnetic Bioassay and a Handheld Giant Magnetoresistance Sensing System

The dissemination of Influenza A virus (IAV) throughout the world has become one of the main concerns for the health of both animals and human beings. An efficient and sensitive diagnostic tool is thus needed for the early detection of IAV. Here, we developed a wash-free magnetic bioassay and further integrated it with a handheld platform based on giant-magnetoresistance (GMR) sensors. The wash-free magnetic bioassay significantly accelerates and simplifies the detection process. This brand-new system was successful in detecting both IAV nucleoprotein and IAV-contained nasal swab samples from pigs on the farm. The limit of detection (LOD) is 0.3 nM for IAV nucleoprotein and 250 TCID₅₀/mL for IAV-spiked nasal swab samples. The detection of nasal swab samples containing unpurified IAV was also performed, demonstrating the capability of the magnetic wash-free assay in the detection of biomarkers in complex sample matrix.

Progress in the Development of Intrinsically Conducting Polymer Composites as Biosensors

Biosensors are analytical devices which find extensive applications in fields such as the food industry, defense sector, environmental monitoring, and in clinical diagnosis. Similarly, intrinsically conducting polymers (ICPs) and their composites have lured immense interest in bio-sensing due to their various attributes like compatibility with biological molecules, efficient electron transfer upon biochemical reactions, loading of bio-reagent, and immobilization of biomolecules. Further, they are proficient in sensing diverse biological species and compounds like glucose (detection limit ≈0.18 nm), DNA (≈10 pm), cholesterol (≈1 µm), aptamer (≈0.8 pm), and also cancer cells (≈5 pm mL-1) making them a potential candidate for biological sensing functions. ICPs and their composites have been extensively exploited by researchers in the field of biosensors owing to these peculiarities; however, no consolidated literature on the usage of conducting polymer composites for biosensing functions is available. This review extensively elucidates on ICP composites and doped conjugated polymers for biosensing functions of copious biological species. In addition, a brief overview is provided on various forms of biosensors, their sensing mechanisms, and various methods of immobilizing biological species along with the life cycle assessment of biosensors for various biosensing applications, and their cost analysis.

Specific detection of avian influenza H5N2 whole virus particles on lateral flow strips using a pair of sandwich-type aptamers

We report a selection of a cognate pair of aptamers for whole avian influenza virus particles of H5N2 by using graphene-oxide based systemic evolution of ligands by exponential enrichment (GO-SELEX), and the application of a pair of sandwich-type binding aptamers on the lateral flow strips. The aptamers were characterized by GO-FRET assay, and Kd values of the selected aptamers were estimated to be from 6.913 × 10⁵ to 1.27 × 10⁶ EID₅₀/ml (EID₅₀/ml: 50% egg infective dose). Based on the evidence from confocal laser scanning microscope (CLSM), surface plasmon resonance (SPR), and circular dichroism (CD) spectrum analysis, the aptamers, J₃APT and JH₄APT, were found to be working as a cognate pair that binds to the target virus at the different sites simultaneously. This cognate pair of aptamers then was successfully applied on the lateral flow strips, clearly showing sandwich-type binding images with the presence of the certain numbers of H5N2 virus particles. On the newly developed lateral flow strips, the target virus was detectable down to 6 × 10⁵ EID₅₀/ml in the buffer and 1.2 × 10⁶ EID₅₀/ml in the duck's feces, respectively, by the naked eye. By using the ImageJ software, the LOD was found to be 1.27 × 10⁵ EID₅₀/ml in the buffer and 2.09 × 10⁵ EID₅₀/ml in the duck's feces, respectively. Interestingly, on the lateral flow strips, enhanced specificity towards the target virus (H5N2) appeared over other subtypes of H5Nx. To the best of our knowledge, this is the first report about the application of the cognate pair of aptamers for the detection of influenza virus on the lateral flow strips. This study shows the promising perspective of a cognate pair of aptamers for the on-site detection system which could be useful for rapid detection of avian influenza viruses for preventing the pandemic influenza viruses from spreading.

Establishment of sandwich ELISA for detecting the H7 subtype influenza A virus

Avian H7N9 subtype influenza virus infects human with high case-fatality rate since it emerged in 2013. Although the vaccination has been rapidly used in poultry due to the emergence of highly pathogenic strain, this virus remains prevalent in this region. Thus, rapid diagnosis both in poultry and human clinic is critically important for the control and prevention of H7N9 infection. In this study, a batch of H7 subtype-specific monoclonal antibodies (mAbs) were developed and a pair of mAb, 2B6, and 5E9 were used to establish a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) to quantify H7 protein and detect influenza A virus baring H7 subtype HA. The lowest detection limit for the recombinant H7 protein was 10 ng/mL and 0.5 HAU/50 μL of A/Guangdong/17SF003/2016(H7N9), 2 HAU/50 μL of A/Netherlands/219/2003(H7N7) and A/Anhui/1/2013(H7N9) for live virus, respectively. The ELISA could not only detect the prevailing H7N9 virus, but also antigenic drift H7 subtype viruses, showing excellent sensitivity and high specificity. Hence, it could serve as a valuable approach to diagnose H7 subtype virus which showed great potential to cause pandemic, as well as antigen quantification.

A Rapid On-Site Assay for the Detection of Influenza A by Capillary Convective PCR

BACKGROUND

Morbidity and mortality from influenza A (Flu A) have increased in recent years. Timely diagnosis and management are critical for disease control. Therefore, the development of a rapid, accurate, and portable analytical method for on-site analysis is imperative.

OBJECTIVES

The aim of this work was to develop a rapid, on-site, automated assay for the detection of Flu A and to evaluate the assay.

METHODS

A handheld instrument (TD-01) based on capillary convective polymerase chain reaction (PCR) was developed for rapid on-site detection of Flu A. Since a previous version of the instrument, an automated motion mechanism has been introduced to TD-01 to achieve RNA automated testing. The primers and probe used for Flu A detection were designed according to the Flu A gene sequence of matrix proteins. Finally, we evaluated the detection spectra, sensitivity, specificity, and diagnostic performance of the assay.

RESULTS

The TD-01 was able to successfully automatically detect Flu A RNA within 30 min. Results for serially diluted viruses indicated that the lower limit of detection for Flu A was 0.1 TCID₅₀/ml (50% tissue culture infective dose). After evaluating known virus stocks, including 15 strains of Flu A, four strains of Flu B, and two strains of respiratory syncytial virus (RSV), the assay had a favorable detection spectrum and no obvious cross-reactivity. Method verification based on 554 clinical samples indicated that the sensitivity and specificity of TD-01 were 98.30% (231/235) and 98.75% (315/319), respectively.

CONCLUSIONS

The results indicate that Flu A detection by TD-01 is particularly suitable for on-site testing and has the potential for application in point-of-care testing.

Blueprints for Biosensors: Design, Limitations, and Applications

Biosensors are enabling major advances in the field of analytics that are both facilitating and being facilitated by advances in synthetic biology. The ability of biosensors to rapidly and specifically detect a wide range of molecules makes them highly relevant to a range of industrial, medical, ecological, and scientific applications. Approaches to biosensor design are as diverse as their applications, with major biosensor classes including nucleic acids, proteins, and transcription factors. Each of these biosensor types has advantages and limitations based on the intended application, and the parameters that are required for optimal performance. Specifically, the choice of biosensor design must consider factors such as the ligand specificity, sensitivity, dynamic range, functional range, mode of output, time of activation, ease of use, and ease of engineering. This review discusses the rationale for designing the major classes of biosensor in the context of their limitations and assesses their suitability to different areas of biotechnological application.

Portable GMR Handheld Platform for the Detection of Influenza A Virus

Influenza A virus (IAV) is a common respiratory pathogen infecting many hosts including humans, pigs (swine influenza virus or SIV), and birds (avian influenza virus or AIV). Monitoring swine and avian influenza viruses in the wild, farms, and live poultry markets is of great significance for human and veterinary public health. A portable, sensitive, and quantitative immunoassay device will be of high demand especially in the rural and resource-limited areas. We report herein our Z-Lab point-of-care (POC) device for sensitive and specific detection of swine influenza viruses with minimum sample handling and laboratory skill requirements. In the present study, a portable and quantitative immunoassay platform based on giant magnetoresistive (GMR) technology is used for the detection of IAV nucleoprotein (NP) and purified H3N2v. Z-Lab displays quantitative results in less than 10 min with sensitivities down to 15 ng/mL and 125 TCID₅₀/mL for IAV nucleoprotein and purified H3N2v, respectively. This platform allows lab-testing to be performed outdoors and opens up the applications of immunoassays in nonclinical settings.

Utilization of chromic polydiacetylene assemblies as a platform to probe specific binding between drug and RNA

Recognition of nucleic acids remains an important endeavor in biology. Nucleic acids adopt shapes ranging from A-form (RNA and GC rich DNA) to B-form (AT rich DNA). We show, in this contribution, shape-specific recognition of A-U rich RNA duplex by a neomycin (Neo)-polydiacetylene (PDA) complex. PDA assemblies are fabricated by using a well-known diacetylene (DA) monomer, 10,12-pentacosadiynoic acid (PCDA). The response of poly(PCDA) assemblies is generated by mixing with a modified neomycin-PCDA monomer (Neo-PCDA). The functionalization by neomycin moiety provides specific binding with homopolyribonucleotide poly (rA) - poly (rU) stimulus. Various types of alcohols are utilized as additives to enhance the sensitivity of poly(PCDA)/Neo-PCDA assemblies. A change of absorption spectra is clearly observed when a relatively low concentration of poly (rA)-poly (rU) is added into the system. Furthermore, poly(PCDA)/Neo-PCDA shows a clear specificity for poly (rA)-poly (rU) over the corresponding DNA duplex. The variation of linker between neomycin moiety and conjugated PDA backbone is found to significantly affect its sensitivity. We also investigate other parameters including the concentration of Neo-PCDA and the DA monomer structure. Our results provide here preliminary data for an alternative approach to improve the sensitivity of PDA utilized in biosensing and diagnostic applications.

Detection of rotavirus in clinical specimens using an immunosensor prototype based on the photon burst counting technique

In this study, a sensitive fluorescence sensor was developed for the detection of small, fluorescence-labeled particles dispersed in a solution. The prototype system comprises of a laser confocal optical system and a mechanical sample stage to detect photon bursting of fluorescence-labeled small particles in sample volumes less than 5 μL within 3 minutes. To examine the feasibility of the prototype system as a diagnostic tool, assemblages of rotavirus and fluorescence-labeled antibody were analyzed. The detection sensitivity for rotavirus was 1 × 10⁴ pfu/mL. Rotavirus in stool samples from patients with acute gastroenteritis was also detected. The advantages and disadvantages of this immunosensor with respect to ELISA and RT-PCR, the current gold standards for virus detection, are discussed.

Evaluating the immunogenicity and safety of a BiondVax-developed universal influenza vaccine (Multimeric-001) either as a standalone vaccine or as a primer to H5N1 influenza vaccine: Phase IIb study protocol

INTRODUCTION

Influenza is a major respiratory viral infection of humans with high mortality and morbidity rates and profound economic impact. Although influenza vaccines are generally updated yearly to match the viruses expected in the coming season, genetic mutation and reassortment can result in unexpected novel strains. Therefore, it is important to develop universal vaccines inducing protective immunity to such strains before they appear. This clinical trial is designed to evaluate the safety and immunogenicity of Multimeric-001 (M-001), which contains conserved epitopes of influenza A and B. M-001 is able to induce both humoral and cellular immunity and provides broad strain coverage.

METHODS

In a multicenter, randomized, double-blind, and controlled phase IIb trial, 222 healthy volunteers aged 18 to 60 years will be randomized into 3 groups (1:1:1) to receive either 2 intramuscular injections of 0.5 mg M-001 (arm 1), 1.0 mg M-001 (arm 2), or saline (arm 3-placebo), before receiving an investigational (whole virus, inactivated, aluminum phosphate gel [AlPO4]-adjuvanted) prepandemic influenza vaccine (H5N1). Primary outcomes are safety and cellular immune responses (cell-mediated immunity [CMI]) induced by M-001, evaluated by multiparametric flow cytometry of intracellular cytokines. The secondary outcome is the serum hemagglutination inhibition (HAI) titer toward the H5N1 vaccine strain. Additionally, exploratory outcomes include evaluation of CMI by quantitative reverse transcription polymerase chain reaction of cytokine mRNA, HAI titers toward H5-drifted strains, serum single radial hemolysis titers toward the H5N1 study vaccine, and the association between CMI markers and antibody response.

DISCUSSION

There is a need for influenza vaccines that give the population a broader protection against multiple strains of influenza virus. M-001 might be such vaccine which will be tested in this current trial as a standalone vaccine and as a pandemic primer. Both cellular and humoral immune responses will be evaluated.

TRIAL REGISTRATION

EudraCT number: 2015-001979-46.

Label-free Detection of Influenza Viruses using a Reduced Graphene Oxide-based Electrochemical Immunosensor Integrated with a Microfluidic Platform

Reduced graphene oxide (RGO) has recently gained considerable attention for use in electrochemical biosensing applications due to its outstanding conducting properties and large surface area. This report presents a novel microfluidic chip integrated with an RGO-based electrochemical immunosensor for label-free detection of an influenza virus, H1N1. Three microelectrodes were fabricated on a glass substrate using the photolithographic technique, and the working electrode was functionalized using RGO and monoclonal antibodies specific to the virus. These chips were integrated with polydimethylsiloxane microchannels. Structural and morphological characterizations were performed using X-ray photoelectron spectroscopy and scanning electron microscopy. Electrochemical studies revealed good selectivity and an enhanced detection limit of 0.5 PFU mL-1, where the chronoamperometric current increased linearly with H1N1 virus concentration within the range of 1 to 104 PFU mL-1 (R2 = 0.99). This microfluidic immunosensor can provide a promising platform for effective detection of biomolecules using minute samples.

A promising magnetic SERS immunosensor for sensitive detection of avian influenza virus

Avian influenza viruses infect a great number of global populations every year and can lead to severe epidemics with high morbidity and mortality. Facile, rapid and sensitive detection of viruses is very crucial to control the viral spread at its early stage. In this work, we developed a novel magnetic immunosensor based on surface enhanced Raman scattering (SERS) spectroscopy to detect intact but inactivated influenza virus H3N2 (A/Shanghai/4084T/2012) by constructing a sandwich complex consisting of SERS tags, target influenza viruses and highly SERS-active magnetic supporting substrates. The procedure of sample pretreatment could be significantly simplified since the magnetic supporting substrates allowed the enrichment and separation of viruses from a complex matrix. With a portable Raman spectrometer, the immunosensor could detect H3N2 down to 10²TCID₅₀/mL (TCID₅₀ refers to tissue culture infection dose at 50% end point), with a good linear relationship from 10² to 5×10³ TCID₅₀/mL. Considering its time efficiency, portability and sensitivity, the proposed SERS-based magnetic immunoassay is very promising for a point-of-care (POC) test in clinical and diagnostic praxis.

Ultrasensitive detection of influenza viruses with a glycan-based impedimetric biosensor

An ultrasensitive impedimetric glycan-based biosensor for reliable and selective detection of inactivated, but intact influenza viruses H3N2 was developed. Such glycan-based approach has a distinct advantage over antibody-based detection of influenza viruses since glycans are natural viral receptors with a possibility to selectively distinguish between potentially pathogenic influenza subtypes by the glycan-based biosensors. Build-up of the biosensor was carefully optimized with atomic force microscopy applied for visualization of the biosensor surface after binding of viruses with the topology of an individual viral particle H3N2 analyzed. The glycan biosensor could detect a glycan binding lectin with a limit of detection (LOD) of 5 aM. The biosensor was finally applied for analysis of influenza viruses H3N2 with LOD of 13 viral particles in 1 μl, what is the lowest LOD for analysis of influenza viral particles by the glycan-based device achieved so far. The biosensor could detect H3N2 viruses selectively with a sensitivity ratio of 30 over influenza viruses H7N7. The impedimetric biosensor presented here is the most sensitive glycan-based device for detection of influenza viruses and among the most sensitive antibody or aptamer based biosensor devices.

Giant Magnetoresistance-based Biosensor for Detection of Influenza A Virus

We have developed a simple and sensitive method for the detection of influenza A virus based on giant magnetoresistance (GMR) biosensor. This assay employs monoclonal antibodies to viral nucleoprotein (NP) in combination with magnetic nanoparticles (MNPs). Presence of influenza virus allows the binding of MNPs to the GMR sensor and the binding is proportional to the concentration of virus. Binding of MNPs onto the GMR sensor causes change in the resistance of sensor, which is measured in a real time electrical readout. GMR biosensor detected as low as 1.5 × 10(2) TCID50/mL virus and the signal intensity increased with increasing concentration of virus up to 1.0 × 10(5) TCID50/mL. This study showed that the GMR biosensor assay is relevant for diagnostic application since the virus concentration in nasal samples of influenza virus infected swine was reported to be in the range of 10(3) to 10(5) TCID50/mL.

Impedance Analysis of Colloidal Gold Nanoparticles in Chromatography Paper for Quantitation of an Immunochromatographic Assay

A detection method of gold nanoparticles in chromatography paper has been developed for a simple, cost-effective and reliable quantitation of immunochromatographic strip test. The time courses of the solution resistance in chromatography paper with the gold nanoparticles solution are electrochemically measured by chrono-impedimetry. The dependence of the solution resistance on the concentration of gold nanoparticles has been successfully observed. The main factor to increase the solution resistance may be obstruction of the ion transport due to the presence of gold nanoparticles. The existence of gold nanoparticles with 1.92 × 10(9) particles/mL in an indistinctly-colored chromatography paper is also identified by a solution resistance measurement. This indicates that the solution resistance assay has the potential to lower the detection limit of the conventional qualitative assay.

Quartz-Crystal Microbalance (QCM) for Public Health: An Overview of Its Applications

Nanobiotechnologies, from the convergence of nanotechnology and molecular biology and postgenomics medicine, play a major role in the field of public health. This overview summarizes the potentiality of piezoelectric sensors, and in particular, of quartz-crystal microbalance (QCM), a physical nanogram-sensitive device. QCM enables the rapid, real time, on-site detection of pathogens with an enormous burden in public health, such as influenza and other respiratory viruses, hepatitis B virus (HBV), and drug-resistant bacteria, among others. Further, it allows to detect food allergens, food-borne pathogens, such as Escherichia coli and Salmonella typhimurium, and food chemical contaminants, as well as water-borne microorganisms and environmental contaminants. Moreover, QCM holds promises in early cancer detection and screening of new antiblastic drugs. Applications for monitoring biohazards, for assuring homeland security, and preventing bioterrorism are also discussed.

Electrical immunosensor based on dielectrophoretically-deposited carbon nanotubes for detection of influenza virus H1N1

The influenza virus has received extensive attention due to the recent H1N1 pandemics originating from swine. This study reports a label-free, highly sensitive, and selective electrical immunosensor for the detection of influenza virus H1N1 based on dielectrophoretically deposited single-walled carbon nanotubes (SWCNTs). COOH-functionalized SWCNTs were deposited on a self-assembled monolayer of polyelectrolyte polydiallyldimethyl-ammonium chloride (PDDA) between two gold electrodes by dielectrophoretic and electrostatic forces, which resulted in reproducible, uniform, aligned, and aggregation-free SWCNT channels (2-10 μm in length). Avidin was immobilized onto the PDDA-SWCNT channels, and viral antibodies were immobilized using biotin-avidin coupling. The resistance of the channels increased with the binding of the influenza viruses to the antibodies. These immunosensors showed linear behavior as the virus concentration was varied from 1 to 10(4) PFU ml(-1) along with a detection time of 30 min. The immunosensors with a 2 μm channel length detected 1 PFU ml(-1) of the influenza virus accurately (R(2) = 0.99) and selectively from MS2 bacteriophages. These immunosensors have the potential to become an important component of a point-of-care test kit that will enable a rapid clinical diagnosis.

Electrochemical DNA Biosensor Based on a Tetrahedral Nanostructure Probe for the Detection of Avian Influenza A (H7N9) Virus

A DNA tetrahedral nanostructure-based electrochemical biosensor was developed to detect avian influenza A (H7N9) virus through recognizing a fragment of the hemagglutinin gene sequence. The DNA tetrahedral probe was immobilized onto a gold electrode surface based on self-assembly between three thiolated nucleotide sequences and a longer nucleotide sequence containing complementary DNA to hybridize with the target single-stranded (ss)DNA. The captured target sequence was hybridized with a biotinylated-ssDNA oligonucleotide as a detection probe, and then avidin-horseradish peroxidase was introduced to produce an amperometric signal through the interaction with 3,3',5,5'-tetramethylbenzidine substrate. The target ssDNA was obtained by asymmetric polymerase chain reaction (PCR) of the cDNA template, reversely transcribed from the viral lysate of influenza A (H7N9) virus in throat swabs. The results showed that this electrochemical biosensor could specifically recognize the target DNA fragment of influenza A (H7N9) virus from other types of influenza viruses, such as influenza A (H1N1) and (H3N2) viruses, and even from single-base mismatches of oligonucleotides. Its detection limit could reach a magnitude of 100 fM for target nucleotide sequences. Moreover, the cycle number of the asymmetric PCR could be reduced below three with the electrochemical biosensor still distinguishing the target sequence from the negative control. To the best of our knowledge, this is the first report of the detection of target DNA from clinical samples using a tetrahedral DNA probe functionalized electrochemical biosensor. It displays that the DNA tetrahedra has a great potential application as a probe of the electrochemical biosensor to detect avian influenza A (H7N9) virus and other pathogens at the gene level, which will potentially aid the prevention and control of the disease caused by such pathogens.

A homogenous fluorescence quenching based assay for specific and sensitive detection of influenza virus A hemagglutinin antigen

Influenza pandemics cause millions of deaths worldwide. Effective surveillance is required to prevent their spread and facilitate the development of appropriate vaccines. In this study, we report the fabrication of a homogenous fluorescence-quenching-based assay for specific and sensitive detection of influenza virus surface antigen hemagglutinins (HAs). The core of the assay is composed of two nanoprobes namely the glycan-conjugated highly luminescent quantum dots (Gly-QDs), and the HA-specific antibody-modified gold nanoparticle (Ab-Au NPs). When exposed to strain-specific HA, a binding event between the HA and the two nanoprobes takes place, resulting in the formation of a sandwich complex which subsequently brings the two nanoprobes closer together. This causes a decrease in QDs fluorescence intensity due to a non-radiative energy transfer from QDs to Au NPs. A resulting correlation between the targets HA concentrations and fluorescence changes can be observed. Furthermore, by utilizing the specific interaction between HA and glycan with sialic acid residues, the assay is able to distinguish HAs originated from viral subtypes H1 (human) and H5 (avian). The detection limits in solution are found to be low nanomolar and picomolar level for sensing H1-HA and H5-HA, respectively. Slight increase in assay sensitivity was found in terms of detection limit while exposing the assay in the HA spiked in human sera solution. We believe that the developed assay could serve as a feasible and sensitive diagnostic tool for influenza virus detection and discrimination, with further improvement on the architectures.

A surface plasmon resonance assay for measurement of neuraminidase inhibition, sensitivity of wild-type influenza neuraminidase and its H274Y mutant to the antiviral drugs zanamivir and oseltamivir

Antiviral resistance is currently monitored by a labelled enzymatic assay, which can give inconsistent results because of the short half-life of the labelled product, and variations in assay conditions. In this paper, we describe a competitive surface plasmon resonance (SPR) inhibition assay for measuring the sensitivities of wild-type neuraminidase (WT NA) and the H274Y (histidine 274 tyrosine) NA mutant to antiviral drugs. The two NA isoforms were expressed in High-five™ (Trichoplusia ni) insect cells. A spacer molecule (1,6-hexanediamine (HDA)) was conjugated to the 7-hydroxyl group of zanamivir, and the construct (HDA-zanamivir) was immobilized onto a SPR sensor chip to obtain a final immobilization response of 431 response units. The immobilized HDA-zanamivir comprised a bio-specific ligand for the WT and mutant proteins. The effects of the natural substrate (sialic acid) and two inhibitors (zanamivir and oseltamivir) on NA binding to the immobilized ligand were studied. The processed SPR data was analysed to determine 50% inhibitory concentrations (IC50-spr ), using a log dose-response curve fit. Although both NA isoforms had almost identical IC50-spr values for sialic acid (WT = 5.5 nM; H274Y mutant = 3.25 nM) and zanamivir (WT = 2.16 nM; H274Y mutant = 2.42 nM), there were significant differences between the IC50-spr values obtained for the WT (7.7 nM) and H274Y mutant (256 nM) NA in the presence of oseltamivir, indicating that oseltamivir has a reduced affinity for the H274Y mutant. The SPR inhibition assay strategy presented in this work could be applied for the rapid screening of newly emerging variants of NA for their sensitivity to antiviral drugs.

Immunological characterization of monoclonal antibodies used in rapid influenza diagnostic test for detection of the 2009 pandemic influenza A(H1N1)pdm09 infection

Since the 2009 pandemic, monoclonal antibodies (mAbs) for rapid influenza diagnostic tests (RIDT) have been developed for specific diagnostics of pandemic viral infection. Most of the mAbs were poorly characterized because of urgency during the pandemic. Further characterization of the mAbs for RIDTs would be beneficial for understanding the immunological properties of the pandemic virus and utilizing the mAbs for other research purposes. In this study, it was confirmed that two mAbs (I38 and D383) in an RIDT for H1N1pdm09 diagnostics were able to detect H1N1pdm09 virus through enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay (IFA). Also, the two mAbs exhibited reactivity to hemagglutinins (HAs) of both the H1N1pdm09 and 1918 H1N1 viruses; therefore, the RIDT using the mAbs could detect HAs of H1N1pdm09 and also HAs of 1918 H1N1-like strains. In an extension to our previous study, the epitopes (Sa antigenic site and the interface area of F' and vestigial esterase subdomains on the HA1 domain of HA of H1N1pdm09) recognized by the mAbs were corroborated in depth by IFA with escape-mutants from the mAbs and mapping of the epitopes on the crystal structure of human H1N1 viral HAs. Collectively, these results imply that the mAbs for the RIDT may be suitable for use in studying the immunological properties of H1N1pdm09 viruses and that the Sa antigenic site and the interface area between F' and vestigial esterase subdomains on influenza viral HA recognized by the mAbs are immunologically conserved regions between H1N1pdm09 and 1918 H1N1.

Development of a surface plasmon resonance assay to measure the binding affinity of wild-type influenza neuraminidase and its H274Y mutant to the antiviral drug zanamivir

Influenza is one of the most common infections of the upper respiratory tract. Antiviral drugs that are currently used to treat influenza, such as oseltamivir and zanamivir, are neuraminidase (NA) inhibitors. However, the virus may develop resistance through single-point mutations of NA. Antiviral resistance is currently monitored by a labelled enzymatic assay, which can be inconsistent because of the short half-life of the labelled product and variations in the assay conditions. In this paper, we describe a label-free surface plasmon resonance (SPR) assay for measuring the binding affinity of NA-drug interactions. Wild-type (WT) NA and a histidine 274 tyrosine (H274Y) mutant were expressed in High Five™ (Trichoplusia ni) insect cells. A spacer molecule (1,6-hexanediamine) was site-specifically conjugated to the 7-hydroxyl group of zanamivir, which is not involved in binding to NA, and the construct was immobilized onto a SPR sensor Chip to obtain a final immobilization response of 431 response units. Binding responses obtained for WT and H274Y mutant NAs were fitted to a simple Langmuir 1:1 model with drift to obtain the association (ka ) and dissociation (kd ) rate constants. The ratio between the binding affinities for the two isoforms was comparable to literature values obtained using labelled enzyme assays. Significant potential exists for an extension of this approach to test for drug resistance of further NA mutants against zanamivir and other antiviral drugs, perhaps paving the way for a reliable SPR biosensor assay that may replace labelled enzymatic assays.

Fast high-throughput screening of H1N1 virus by parallel detection with multichannel microchip electrophoresis

Influenza is one of the acute respiratory diseases of human caused by the influenza A (H1N1) virus and accounted for major public health concerns worldwide. The polymerase chain reaction (PCR) methods are the most popular tools for clinical diagnosis of influenza A virus. Microchip electrophoresis is a widely used method for DNA molecules separation. Herein, we describe the fast and high-throughput separation of hemagglutinin (HA) and nucleocapsid protein (NP) gene PCR products (116 bp and 195 bp, respectively) by parallel detection with multichannel microchip electrophoresis and programmed step electric field strength (PSEFS).