Rapid and simple detection of Tamiflu-resistant influenza virus: Development of oseltamivir derivative-based lateral flow biosensor for point-of-care (POC) diagnostics

Microfluidic paper-based device coupled with 3D printed imaging box for colorimetric detection in resource-limited settings

Rapid and effective methods for the detection of analytes such as water contaminants, food adulterants and biomolecules are essential for the protection of public health and environmental protection. Most of the currently established analytical techniques need sophisticated equipment, centralized testing facilities, costly operations, and trained personnel. Such limitations make them inaccessible to the general populace, particularly in regions with limited resources. The emergence of microfluidic devices offers a promising alternative to overcome several such constraints. This work describes a protocol for fabricating a low-cost, open-source paper-based microfluidic device using easily available tools and materials for colorimetric detection of analytes. The ease and simplicity of fabrication allow users to design customized devices. The device is coupled with an imaging box assembled from 3D printed parts to maintain uniform lighting conditions during analytical testing. The platform allows digital imaging using smartphones or cameras to instantaneously capture images of reaction zones on the device for quantitative analysis. The system is demonstrated for detecting hexavalent chromium, a toxic water contaminant. The image analysis is performed using open-source ImageJ for quantification of results. The approach demonstrated in this work can be readily adopted for a wide range of sensing applications.

Recent Advances in Molecular and Immunological Diagnostic Platform for Virus Detection: A Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused an ongoing coronavirus disease (COVID-19) outbreak and a rising demand for the development of accurate, timely, and cost-effective diagnostic tests for SARS-CoV-2 as well as other viral infections in general. Currently, traditional virus screening methods such as plate culturing and real-time PCR are considered the gold standard with accurate and sensitive results. However, these methods still require sophisticated equipment, trained personnel, and a long analysis time. Alternatively, with the integration of microfluidic and biosensor technologies, microfluidic-based biosensors offer the ability to perform sample preparation and simultaneous detection of many analyses in one platform. High sensitivity, accuracy, portability, low cost, high throughput, and real-time detection can be achieved using a single platform. This review presents recent advances in microfluidic-based biosensors from many works to demonstrate the advantages of merging the two technologies for sensing viruses. Different platforms for virus detection are classified into two main sections: immunoassays and molecular assays. Moreover, available commercial sensing tests are analyzed.

Nanomaterials for virus sensing and tracking

The effect of the on-going COVID-19 pandemic on global healthcare systems has underlined the importance of timely and cost-effective point-of-care diagnosis of viruses. The need for ultrasensitive easy-to-use platforms has culminated in an increased interest for rapid response equipment-free alternatives to conventional diagnostic methods such as polymerase chain reaction, western-blot assay, etc. Furthermore, the poor stability and the bleaching behavior of several contemporary fluorescent reporters is a major obstacle in understanding the mechanism of viral infection thus retarding drug screening and development. Owing to their extraordinary surface-to-volume ratio as well as their quantum confinement and charge transfer properties, nanomaterials are desirable additives to sensing and imaging systems to amplify their signal response as well as temporal resolution. Their large surface area promotes biomolecular integration as well as efficacious signal transduction. Due to their hole mobility, photostability, resistance to photobleaching, and intense brightness, nanomaterials have a considerable edge over organic dyes for single virus tracking. This paper reviews the state-of-the-art of combining carbon-allotrope, inorganic and organic-based nanomaterials with virus sensing and tracking methods, starting with the impact of human pathogenic viruses on the society. We address how different nanomaterials can be used in various virus sensing platforms (e.g. lab-on-a-chip, paper, and smartphone-based point-of-care systems) as well as in virus tracking applications. We discuss the enormous potential for the use of nanomaterials as simple, versatile, and affordable tools for detecting and tracing viruses infectious to humans, animals, plants as well as bacteria. We present latest examples in this direction by emphasizing major advantages and limitations.

A Therapeutically Active Minibody Exhibits an Antiviral Activity in Oseltamivir-Resistant Influenza-Infected Mice via Direct Hydrolysis of Viral RNAs

Emerging Oseltamivir-resistant influenza strains pose a critical public health threat due to antigenic shifts and drifts. We report an innovative strategy for controlling influenza A infections by use of a novel minibody of the 3D8 single chain variable fragment (scFv) showing intrinsic viral RNA hydrolyzing activity, cell penetration activity, and epidermal cell penetration ability. In this study, we examined 3D8 scFv’s antiviral activity in vitro on three different H1N1 influenza strains, one Oseltamivir-resistant (A/Korea/2785/2009pdm) strain, and two Oseltamivir-sensitive (A/PuertoRico/8/1934 and A/X-31) strains. Interestingly, the 3D8 scFv directly digested viral RNAs in the ribonucleoprotein complex. scFv’s reduction of influenza viral RNA including viral genomic RNA, complementary RNA, and messenger RNA during influenza A infection cycles indicated that this minibody targets all types of viral RNAs during the early, intermediate, and late stages of the virus’s life cycle. Moreover, we further addressed the antiviral effects of 3D8 scFv to investigate in vivo clinical outcomes of influenza-infected mice. Using both prophylactic and therapeutic treatments of intranasal administered 3D8 scFv, we found that Oseltamivir-resistant H1N1-infected mice showed 90% (prophylactic effects) and 40% (therapeutic effects) increased survival rates, respectively, compared to the control group. The pathological signs of influenza A in the lung tissues, and quantitative analyses of the virus proliferations supported the antiviral activity of the 3D8 single chain variable fragment. Taken together, these results demonstrate that 3D8 scFv has antiviral therapeutic potentials against a wide range of influenza A viruses via the direct viral RNA hydrolyzing activity.

Gold nanoparticle-based optical nanosensors for food and health safety monitoring: recent advances and future perspectives

Modern society has been facing serious health-related problems including food safety, diseases and illness. Hence, it is urgent to develop analysis methods for the detection and control of food contaminants, disease biomarkers and pathogens. As the traditional instrumental methods have several disadvantages, including being time consuming, and having high cost and laborious procedures, optical nanosensors have emerged as promising alternative or complementary approaches to those traditional ones. With the advantages of simple preparation, high surface-to-volume ratio, excellent biocompatibility, and especially, unique optical properties, gold nanoparticles (AuNPs) have been demonstrated as excellent transducers for optical sensing systems. Herein, we provide an overview of the synthesis of AuNPs and their excellent optical properties that are ideal for the development of optical nanosensors based on local surface plasmon resonance (LSPR), colorimetry, fluorescence resonance energy transfer (FRET), and surface-enhanced Raman scattering (SERS) phenomena. We also review the sensing strategies and their mechanisms, as well as summarizing the recent advances in the monitoring of food contaminants, disease biomarkers and pathogens using developed AuNP-based optical nanosensors in the past seven years (2015-now). Furthermore, trends and challenges in the application of these nanosensors in the determination of those analytes are discussed to suggest possible directions for future developments.

Thermally Responsive Alkane Partitions for Assay Automation

For point-of-care diagnostic tools to be impactful, they must be inexpensive, equipment-free, and sample-to-answer (i.e., require no user intervention). Here, we report a new approach to enable sample-to-answer diagnostics that utilizes thermally responsive alkane partitions (TRAPs) as automated pseudo-valves. When combined with the magnetic manipulation of microbeads, TRAPs enable the pumpless automation of all steps in complex assays. We demonstrate that in relatively narrow channel geometries, liquified alkane partitions continue to separate reagents on each side of the partition while enabling the transition of magnetic beads from one reagent to the next, replacing manual pipetting steps in conventional assays. In addition, we show that in relatively broader geometries, liquified partitions breach, enabling the addition/mixing of preloaded reagents. Through calculation and experimentation, we determine the geometric design rules for implementing the stationary and removable partitions in fluidic channels. In addition, we demonstrate that magnetic microbeads can be pulled through liquified stationary TRAPs without disrupting partition integrity and without disrupting bound protein complexes attached at the microbead surface. The TRAP technology introduced here can enable a new low-cost and equipment-free approach for fully automated sample-to-answer diagnostics.

Advances in the Rapid Diagnostic of Viral Respiratory Tract Infections

Viral infections are a significant public health problem, primarily due to their high transmission rate, various pathological manifestations, ranging from mild to severe symptoms and subclinical onset. Laboratory diagnostic tests for infectious diseases, with a short enough turnaround time, are promising tools to improve patient care, antiviral therapeutic decisions, and infection prevention. Numerous microbiological molecular and serological diagnostic testing devices have been developed and authorised as benchtop systems, and only a few as rapid miniaturised, fully automated, portable digital platforms. Their successful implementation in virology relies on their performance and impact on patient management. This review describes the current progress and perspectives in developing micro- and nanotechnology-based solutions for rapidly detecting human viral respiratory infectious diseases. It provides a nonexhaustive overview of currently commercially available and under-study diagnostic testing methods and discusses the sampling and viral genetic trends as preanalytical components influencing the results. We describe the clinical performance of tests, focusing on alternatives such as microfluidics-, biosensors-, Internet-of-Things (IoT)-based devices for rapid and accurate viral loads and immunological responses detection. The conclusions highlight the potential impact of the newly developed devices on laboratory diagnostic and clinical outcomes.

Ultrasensitive chemiluminescent neuraminidase probe for rapid screening and identification of small-molecules with antiviral activity against influenza A virus in mammalian cells

Influenza A virus is the most virulent influenza subtype and is associated with large-scale global pandemics characterized by high levels of morbidity and mortality. Developing simple and sensitive molecular methods for detecting influenza viruses is critical. Neuraminidase, an exo-glycosidase displayed on the surface of influenza virions, is responsible for the release of the virions and their spread in the infected host. Here, we present a new phenoxy-dioxetane chemiluminescent probe (CLNA) that can directly detect neuraminidase activity. The probe exhibits an effective turn-on response upon reaction with neuraminidase and produces a strong emission signal at 515 nm with an extremely high signal-to-noise ratio. Comparison measurements of our new probe with previously reported analogous neuraminidase optical probes showed superior detection capability in terms of response time and sensitivity. Thus, as far as we know, our probe is the most sensitive neuraminidase probe known to date. The chemiluminescence turn-on response produced by our neuraminidase probe enables rapid screening for small molecules that inhibit viral replication through different mechanisms as validated directly in influenza A-infected mammalian cells using the known inhibitors oseltamivir and amantadine. We expect that our new chemiluminescent neuraminidase probe will prove useful for various applications requiring neuraminidase detection including drug discovery assays against various influenza virus strains in mammalian cells.

A new chemiluminescence neuraminidase probe enables rapid screening of small molecules that inhibit viral replication, directly in influenza A-infected mammalian cells.

Development of antibody against drug-resistant respiratory syncytial virus: Rapid detection of mutant virus using split superfolder green fluorescent protein-antibody system

Respiratory syncytial virus (RSV) infections are associated with severe bronchiolitis or pneumonia. Although palivizumab is used to prevent RSV infections, the occurrence of palivizumab-resistant RSV strains is increasing, and these strains pose a threat to public health. Herein, we report an antibody with affinity to the S275F RSV antigen, enabling the specific detection of palivizumab-resistant RSV strains. Experimental and simulation results confirmed the affinity of the antibody to the S275F RSV antigen. Furthermore, we developed a rapid S275F RSV antigen detection method using a split superfolder green fluorescent protein (ssGFP) that can interact with the antibody. In the presence of the mutant virus antigen, ssGFP emitted fluorescence within 1 min, allowing the rapid identification of S275F RSV. We anticipate that the developed antibody would be useful for the precise diagnosis of antiviral drug-resistant RSV strains and help treat patients with RSV infections.

Advanced Nanomaterials for Preparedness Against (Re-)Emerging Viral Diseases

While the coronavirus disease (COVID-19) accounts for the current global pandemic, the emergence of other unknown pathogens, named "Disease X," remains a serious concern in the future. Emerging or re-emerging pathogens continue to pose significant challenges to global public health. In response, the scientific community has been urged to create advanced platform technologies to meet the ever-increasing needs presented by these devastating diseases with pandemic potential. This review aims to bring new insights to allow for the application of advanced nanomaterials in future diagnostics, vaccines, and antiviral therapies, thereby addressing the challenges associated with the current preparedness strategies in clinical settings against viruses. The application of nanomaterials has advanced medicine and provided cutting-edge solutions for unmet needs. Herein, an overview of the currently available nanotechnologies is presented, highlighting the significant features that enable them to control infectious diseases, and identifying the challenges that remain to be addressed for the commercial production of nano-based products is presented. Finally, to conclude, the development of a nanomaterial-based system using a "One Health" approach is suggested. This strategy would require a transdisciplinary collaboration and communication between all stakeholders throughout the entire process spanning across research and development, as well as the preclinical, clinical, and manufacturing phases.

Nanotechnology-based Colorimetric Approaches for Pathogenic Virus Sensing: A review

Fast and inexpensive virus identification protocols are paramount to hinder the further extent of pandemic diseases, minimize economic and social damages, and expedite proper clinical rehabilitation. Until now, various biosensors have been fabricated for the identification of pathogenic particles. But, they offer many difficulties. Nanotechnology resolves these difficulties and offers direct identification of pathogenic species in real-time. Among them, nanomaterial based-colorimetric sensing approach of pathogenic viruses by the naked eye has attracted much awareness because of their simplicity, speed, and low cost. In this review, the latest tendencies and advancements are overviewed in detecting pathogenic viruses using colorimetric concepts. We focus on and reconsider the use of distinctive nanomaterials such as metal nanoparticles, carbon nanotubes, graphene oxide, and conducting polymer to form colorimetric pathogenic virus sensors.

A simple fluorescence-based lateral flow test platform for rapid influenza B virus screening

A simple fluorescence-based lateral flow test platform for rapid influenza B virus screening as a model target molecule was successfully developed. In this work, Cy5-loaded silica nanoparticles were directly conjugated to monoclonal antibodies, specific to the influenza B nucleoprotein, via a direct physisorption method and used as detector probes. Using this approach, the signal response to the detection was further determined using a fluorescent signal intensity measurement method via a portable reader, in combination with fluorescence imaging analysis. The degree to which the fluorescence signal response is detected is proportional to the amount of the target virus protein present in the system, reflected by the accumulation of the formed particle-antibody conjugates within the test system. Under optimized conditions, the system is capable of detecting the influenza B virus protein at a level of 0.55 μg per test within 30 min, using small sample volumes as low as 100 μL (R² = 0.9544). In addition to its simplicity, further application of the system in detecting the influenza B virus protein was demonstrated using the viral transport media as specimen matrices. It was also shown that the system can perform the detection without cross-reactivity to other closely related respiratory viruses.

Optical Biosensors for Virus Detection: Prospects for SARS-CoV-2/COVID-19

The recent pandemic of the novel coronavirus disease 2019 (COVID-19) has caused huge worldwide disruption due to the lack of available testing locations and equipment. The use of optical techniques for viral detection has flourished in the past 15 years, providing more reliable, inexpensive, and accurate detection methods. In the current minireview, optical phenomena including fluorescence, surface plasmons, surface-enhanced Raman scattering (SERS), and colorimetry are discussed in the context of detecting virus pathogens. The sensitivity of a viral detection method can be dramatically improved by using materials that exhibit surface plasmons or SERS, but often this requires advanced instrumentation for detection. Although fluorescence and colorimetry lack high sensitivity, they show promise as point-of-care diagnostics because of their relatively less complicated instrumentation, ease of use, lower costs, and the fact that they do not require nucleic acid amplification. The advantages and disadvantages of each optical detection method are presented, and prospects for applying optical biosensors in COVID-19 detection are discussed.

Development of a Low-Cost Cotton-Tipped Electrochemical Immunosensor for the Detection of SARS-CoV-2

Collection of nasopharyngeal samples using swabs followed by the transfer of the virus into a solution and an RNA extraction step to perform reverse transcription polymerase chain reaction (PCR) is the primary method currently used for the diagnosis of COVID-19. However, the need for several reagents and steps and the high cost of PCR hinder its worldwide implementation to contain the outbreak. Here, we report a cotton-tipped electrochemical immunosensor for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus antigen. Unlike the reported approaches, we integrated the sample collection and detection tools into a single platform by coating screen-printed electrodes with absorbing cotton padding. The immunosensor was fabricated by immobilizing the virus nucleocapsid (N) protein on carbon nanofiber-modified screen-printed electrodes which were functionalized by diazonium electrografting. The detection of the virus antigen was achieved via swabbing followed by competitive assay using a fixed amount of N protein antibody in the solution. A square wave voltammetric technique was used for the detection. The limit of detection for our electrochemical biosensor was 0.8 pg/mL for SARS-CoV-2, indicating very good sensitivity for the sensor. The biosensor did not show significant cross-reactivity with other virus antigens such as influenza A and HCoV, indicating high selectivity of the method. Moreover, the biosensor was successfully applied for the detection of the virus antigen in spiked nasal samples showing excellent recovery percentages. Thus, our electrochemical immunosensor is a promising diagnostic tool for the direct rapid detection of the COVID-19 virus that requires no sample transfer or pretreatment.

Biomimetic Nanopillar-Based Biosensor for Label-Free Detection of Influenza A Virus

Since the first emergence of influenza viruses, they have caused the flu seasonally worldwide. Precise detection of influenza viruses is required to prevent the spreading of the disease. Herein, we developed an optical biosensor using peptide-immobilized nanopillar structures for the label-free detection of influenza viruses. The spin-on-glass nanopillar structures were fabricated by nanoimprint lithography. A sialic acid-mimic peptide, which can specifically bind to hemagglutinin on the surface of the influenza virus, was immobilized onto the nanopillars via polymerized dopamine. The constructed nanopillar sensor enabled us to detect influenza A viruses in the range of 10³-10⁵ plaque-forming units through simple measurements of reflectance. Our findings suggest that biomimetic modification of nanopillar structures can be an alternative method for the immunodiagnosis of influenza viruses.

Colorimetric Detection of SARS-CoV-2 and Drug-Resistant pH1N1 Using CRISPR/dCas9

Viruses have been a continuous threat to human beings. The coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to a pandemic that is still ongoing worldwide. Previous pandemic influenza A virus (pH1N1) might be re-emerging through a drug-resistant mutation. We report a colorimetric viral detection method based on the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 endonuclease dead (dCas9) system. In this method, RNA in the viral lysate was directly recognized by the CRISPR/dCas9 system with biotin-protospacer adjacent motif (PAM)-presenting oligonucleotide (PAMmer). Streptavidin-horseradish peroxidase then bound to biotin-PAMmer, inducing a color change through the oxidation of 3,3',5,5'-tetramethylbenzidine. Using the developed method, we successfully identified SARS-CoV-2, pH1N1, and pH1N1/H275Y viruses by the naked eye. Moreover, the detection of viruses in human nasopharyngeal aspirates and sputum was demonstrated. Finally, clinical samples from COVID-19 patients led to a successful diagnosis. We anticipate that the current method can be employed for simple and accurate diagnosis of viruses.

Colorimetric Detection of SARS-CoV-2 and Drug-Resistant pH1N1 Using CRISPR/dCas9

Viruses have been a continuous threat to human beings. The coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to a pandemic that is still ongoing worldwide. Previous pandemic influenza A virus (pH1N1) might be re-emerging through a drug-resistant mutation. We report a colorimetric viral detection method based on the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 endonuclease dead (dCas9) system. In this method, RNA in the viral lysate was directly recognized by the CRISPR/dCas9 system with biotin-protospacer adjacent motif (PAM)-presenting oligonucleotide (PAMmer). Streptavidin-horseradish peroxidase then bound to biotin-PAMmer, inducing a color change through the oxidation of 3,3',5,5'-tetramethylbenzidine. Using the developed method, we successfully identified SARS-CoV-2, pH1N1, and pH1N1/H275Y viruses by the naked eye. Moreover, the detection of viruses in human nasopharyngeal aspirates and sputum was demonstrated. Finally, clinical samples from COVID-19 patients led to a successful diagnosis. We anticipate that the current method can be employed for simple and accurate diagnosis of viruses.

A critical review of point-of-care diagnostic technologies to combat viral pandemics

The COVID-19 global pandemic of 2019-2020 pointedly revealed the lack of diagnostic solutions that are able to keep pace with the rapid spread of the virus. Despite the promise of decades of lab-on-a-chip research, no commercial products were available to deliver rapid results or enable testing in the field at the onset of the pandemic. In this critical review, we assess the current state of progress on the development of point-of-care technologies for the diagnosis of viral diseases that cause pandemics. While many previous reviews have reported on progress in various lab-on-a-chip technologies, here we address the literature from the perspective of the testing needs of a rapidly expanding pandemic. First, we recommend a set of requirements to heed when designing point-of-care diagnostic technologies to address the testing needs of a pandemic. We then review the current state of assay technologies with a focus on isothermal amplification and lateral-flow immunoassays. Though there is much progress on assay development, we argue that the largest roadblock to deployment exists in sample preparation. We summarize current approaches to automate sample preparation and discuss both the progress and shortcomings of these developments. Finally, we provide our recommendations to the field of specific challenges to address in order to prepare for the next pandemic.

Point-of-Use Rapid Detection of SARS-CoV-2: Nanotechnology-Enabled Solutions for the COVID-19 Pandemic

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the COVID-19 pandemic that has been spreading around the world since December 2019. More than 10 million affected cases and more than half a million deaths have been reported so far, while no vaccine is yet available as a treatment. Considering the global healthcare urgency, several techniques, including whole genome sequencing and computed tomography imaging have been employed for diagnosing infected people. Considerable efforts are also directed at detecting and preventing different modes of community transmission. Among them is the rapid detection of virus presence on different surfaces with which people may come in contact. Detection based on non-contact optical techniques is very helpful in managing the spread of the virus, and to aid in the disinfection of surfaces. Nanomaterial-based methods are proven suitable for rapid detection. Given the immense need for science led innovative solutions, this manuscript critically reviews recent literature to specifically illustrate nano-engineered effective and rapid solutions. In addition, all the different techniques are critically analyzed, compared, and contrasted to identify the most promising methods. Moreover, promising research ideas for high accuracy of detection in trace concentrations, via color change and light-sensitive nanostructures, to assist fingerprint techniques (to identify the virus at the contact surface of the gas and solid phase) are also presented.

Colorimetric biosensors for point-of-care virus detections

Colorimetric biosensors can be used to detect a particular analyte through color changes easily by naked eyes or simple portable optical detectors for quantitative measurement. Thus, it is highly attractive for point-of-care detections of harmful viruses to prevent potential pandemic outbreak, as antiviral medication must be administered in a timely fashion. This review paper summaries existing and emerging techniques that can be employed to detect viruses through colorimetric assay design with detailed discussion of their sensing principles, performances as well as pros and cons, with an aim to provide guideline on the selection of suitable colorimetric biosensors for detecting different species of viruses. Among the colorimetric methods for virus detections, loop-mediated isothermal amplification (LAMP) method is more favourable for its faster detection, high efficiency, cheaper cost, and more reliable with high reproducible assay results. Nanoparticle-based colorimetric biosensors, on the other hand, are most suitable to be fabricated into lateral flow or lab-on-a-chip devices, and can be coupled with LAMP or portable PCR systems for highly sensitive on-site detection of viruses, which is very critical for early diagnosis of virus infections and to prevent outbreak in a swift and controlled manner.

Colorimetric detection of creatinine using its specific binding peptides and gold nanoparticles

A new selective detection method was developed for creatinine by combining gold nanoparticles (GNPs) and peptide probes which were screened and selected using phage-display technology.

Fluorescent fullerene nanoparticle-based lateral flow immunochromatographic assay for rapid quantitative detection of C-reactive protein

A fluorescent fullerene nanoparticle (NP)-based lateral flow immunochromatographic assay (LFIA) was developed for the rapid and quantitative detection of C-reactive protein (CRP) in serum. The polyclonal CRP-antibody-conjugated fullerene NPs were simply prepared by 1-ethyl-3-(3-dimethyllaminopropyl)-carbodiimide hydrochloride coupling after carboxylation of fluorescent fullerene NPs. By applying the CRP-antibody-conjugated fullerene NPs to a lateral flow test strip, quantitative analysis of CRP in serum was possible at a concentration range of 0.1-10 ng/ml within 15 min. We anticipate that this novel fluorescent fullerene NP-based LFIA can be useful for the rapid and accurate sensing of biological and chemical species, contributing to the disease diagnosis and prognosis, environmental monitoring, and food safety.

Diagnosis of Tamiflu-Resistant Influenza Virus in Human Nasal Fluid and Saliva Using Surface-Enhanced Raman Scattering

Influenza viruses cause respiratory infection, spread through respiratory secretions, and are shed into the nasal secretion and saliva specimens. Therefore, nasal fluid and saliva are effective clinical samples for the diagnosis of influenza virus-infected patients. Although several methods have been developed to detect various types of influenza viruses, approaches for detecting mutant influenza viruses in clinical samples are rarely reported. Herein, we report for the first time a surface-enhanced Raman scattering (SERS)-based sensing platform for oseltamivir-resistant pandemic H1N1 (pH1N1) virus detection in human nasal fluid and saliva. By combining SERS-active urchin Au nanoparticles and oseltamivir hexylthiol, an excellent receptor for the pH1N1/H275Y mutant virus, we detected the pH1N1/H275Y virus specifically and sensitively in human saliva and nasal fluid samples. Considering that the current influenza virus infection testing methods do not provide information on the antiviral drug resistance of the virus, the proposed SERS-based diagnostic test for the oseltamivir-resistant virus will inform clinical decisions about the treatment of influenza virus infections, avoiding the unnecessary prescription of ineffective drugs and greatly improving therapy.

Immunosensor-based label-free and multiplex detection of influenza viruses: State of the art

The ability of influenza viruses to rapidly evolve has caused significant challenges in viral surveillance, diagnosis, and therapeutic development. Molecular sequencing methods, though powerful tools for monitoring influenza evolution at the genetic level, are not able to fully characterize the antigenic properties of influenza viruses. Understanding influenza virus antigenicity is critical to vaccine development and disease prevention. Traditional immunoassays which have been widely used for evaluating influenza antigenicity have limited throughput. To alleviate these problems, new bioanalytical tools to investigate influenza antigenicity by measuring antibody-antigen binding are an active area of research. Herein, we review immunosensor technologies from the aspects of various sensing principles, while highlighting recent developments in multiplex, label-free detection strategies. Highlighted technologies include electrochemical immunosensors relying on impedimetric detection; these demonstrate simple design and cost effectiveness for mass production. Antibody arrays implemented on an optical interferometric sensor system allow systematic characterization of influenza antigenicity. Quartz microbalance immunosensors are highly sensitive but have yet to be explored for multiplex sensing. Immunosensors made on lateral flow strips have shown promise in rapid diagnosis of influenza subtypes. We anticipate that these and other technologies discussed in the review will facilitate advances in the study of influenza, and other viral pathogens.

Magnetic Focus Lateral Flow Sensor for Detection of Cervical Cancer Biomarkers

We report on a magnetic focus lateral flow biosensor (mLFS) for ultrasensitive detection of protein biomarkers in a practical format. With valosin-containing protein as a target protein, we show that the developed mLFS concept could detect as low as 25 fg/mL with magnetic focus to enhance target capture efficiency to deliver a 10⁶-fold improvement in sensitivity compared to that of conventional lateral flow (LF) systems. The conceptualized strategy utilizes a simple magnet placed beneath the three-dimensional printed LF device to concentrate the targets at the signal zone without any additional instrumentation. In addition, protein mixtures extracted from the tissue of cervical cancer patients was also utilized to validate the sensor. To investigate the effect of magnetic focus on sensitivity, surface-enhanced Raman spectroscopy and dark-field imaging was utilized to characterize the distribution and movement of Fe₃O₄ core-Au shell nanoprobes in a model LF strip. Our experiments show that the magnetic focus results in an increased interaction time between the magnetic probe-labeled targets and the capture antibody, yielding a higher capture efficiency, allowing for ultrasensitive detection of the target not possible before with LF. The proposed mLFS can be utilized to detect a range of trace protein biomarkers for early diagnosis and can be combined with diverse pretreatment and signal amplification steps to query complex samples.

Mannitol-induced gold nanoparticle aggregation for the ligand-free detection of viral particles

Addition of osmolytes causes viruses-coated AuNPs to aggregate and not protein-coated AuNPs. Ligand-free detection of virus was developed without the need for prior knowledge of the specific virus target.

Recent Advances in AIV Biosensors Composed of Nanobio Hybrid Material

Since the beginning of the 2000s, globalization has accelerated because of the development of transportation systems that allow for human and material exchanges throughout the world. However, this globalization has brought with it the rise of various pathogenic viral agents, such as Middle East respiratory syndrome coronavirus (MERS-CoV), severe acute respiratory syndrome coronavirus (SARS-CoV), Zika virus, and Dengue virus. In particular, avian influenza virus (AIV) is highly infectious and causes economic, health, ethnical, and social problems to human beings, which has necessitated the development of an ultrasensitive and selective rapid-detection system of AIV. To prevent the damage associated with the spread of AIV, early detection and adequate treatment of AIV is key. There are traditional techniques that have been used to detect AIV in chickens, ducks, humans, and other living organisms. However, the development of a technique that allows for the more rapid diagnosis of AIV is still necessary. To achieve this goal, the present article reviews the use of an AIV biosensor employing nanobio hybrid materials to enhance the sensitivity and selectivity of the technique while also reducing the detection time and high-throughput process time. This review mainly focused on four techniques: the electrochemical detection system, electrical detection method, optical detection methods based on localized surface plasmon resonance, and fluorescence.