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

Development of a dual-component biosensor for rapid and sensitive detection of influenza H7 and H5 subtypes

The outbreak of highly pathogenic influenza virus subtypes, such as H7 and H5, presents a significant global health challenge, necessitating the development of rapid and sensitive diagnostic methods. In this study, we have developed a novel dual-component biosensor assembly, each component of which incorporates an antibody fused with a nano-luciferase subunit. Our results demonstrate the effectiveness of this biosensor in enabling the rapid and sensitive detection of influenza H7 and other subtypes. Additionally, we successfully applied the biosensor in paper-based assay and lateral flow assay formats, expanding its versatility and potential for field-deployable applications. Notably, we achieved effective detection of the H7N9 virus using this biosensor. Furthermore, we designed and optimized a dedicated biosensor to the sensitive detection of the influenza H5 subtype. Collectively, our findings underscore the significant potential of this dual-component biosensor assembly as a valuable and versatile tool for accurate and timely diagnosis of influenza virus infections, promising to advance the field of influenza diagnostics and contribute to outbreak management and surveillance efforts.

Nanomaterials-based immunosensors for avian influenza virus detection

Avian influenza viruses (AIV) are capable of infecting a considerable proportion of the world's population each year, leading to severe epidemics with high rates of morbidity and mortality. The methods now used to diagnose influenza virus A include the Western blot test (WB), hemagglutination inhibition (HI), and enzyme-linked immunosorbent assays (ELISAs). But because of their labor-intensiveness, lengthy procedures, need for costly equipment, and inexperienced staff, these approaches are considered inappropriate. The present review elucidates the recent advancements in the field of avian influenza detection through the utilization of nanomaterials-based immunosensors between 2014 and 2024. The classification of detection techniques has been taken into account to provide a comprehensive overview of the literature. The review encompasses a detailed illustration of the commonly employed detection mechanisms in immunosensors, namely, colorimetry, fluorescence assay, surface plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS), electrochemical detection, quartz crystal microbalance (QCM) piezoelectric, and field-effect transistor (FET). Furthermore, the challenges and future prospects for the immunosensors have been deliberated upon. The present review aims to enhance the understanding of immunosensors-based sensing platforms for virus detection and to stimulate the development of novel immunosensors by providing novel ideas and inspirations. Therefore, the aim of this paper is to provide an updated information about biosensors, as a recent detection technique of influenza with its details regarding the various types of biosensors, which can be used for this review.

Advances in Aptamer-Based Biosensors for the Detection of Foodborne Mycotoxins

Foodborne mycotoxins (FBMTs) are toxins produced by food itself or during processing and transportation that pose an enormous threat to public health security. However, traditional instrumental and chemical methods for detecting toxins have shortcomings, such as high operational difficulty, time consumption, and high cost, that limit their large-scale applications. In recent years, aptamer-based biosensors have become a new tool for food safety risk assessment and monitoring due to their high affinity, good specificity, and fast response. In this review, we focus on the progress of single-mode and dual-mode aptasensors in basic research and device applications over recent years. Furthermore, we also point out some problems in the current detection strategies, with the aim of stimulating future toxin detection systems for a transition toward ease of operation and rapid detection.

The significance of antigen-antibody-binding avidity in clinical diagnosis

Immunoglobulin G (IgG) and immunoglobulin M (IgM) testing are commonly used to determine infection status. Typically, the detection of IgM indicates an acute or recent infection, while the presence of IgG alone suggests a chronic or past infection. However, relying solely on IgG and IgM antibody positivity may not be sufficient to differentiate acute from chronic infections. This limitation arises from several factors. The prolonged presence of IgM can complicate diagnostic interpretations, and false positive IgM results often arise from antibody cross-reactivity with various antigens. Additionally, IgM may remain undetectable in prematurely collected samples or in individuals who are immunocompromised, further complicating accurate diagnosis. As a result, additional diagnostic tools are required to confirm infection status. Avidity is a measure of the strength of the binding between an antigen and antibody. Avidity-based assays have been developed for various infectious agents, including toxoplasma, cytomegalovirus (CMV), SARS-CoV-2, and avian influenza, and are promising tools in clinical diagnostics. By measuring the strength of antibody binding, they offer critical insights into the maturity of the immune response. These assays are instrumental in distinguishing between acute and chronic or past infections, monitoring disease progression, and guiding treatment decisions. The development of automated platforms has optimized the testing process by enhancing efficiency and minimizing the risk of manual errors. Additionally, the recent advent of real-time biosensor immunoassays, including the label-free immunoassays (LFIA), has further amplified the capabilities of these assays. These advances have expanded the clinical applications of avidity-based assays, making them useful tools for the diagnosis and management of various infectious diseases. This review is structured around several key aspects of IgG avidity in clinical diagnosis, including: (i) a detailed exposition of the IgG affinity maturation process; (ii) a thorough discussion of the IgG avidity assays, including the recently emerged biosensor-based approaches; and (iii) an examination of the applications of IgG avidity in clinical diagnosis. This review is intended to contribute toward the development of enhanced diagnostic tools through critical assessment of the present landscape of avidity-based testing, which allows us to identify the existing knowledge gaps and highlight areas for future investigation.

Advancing Microfluidic Immunity Testing Systems: New Trends for Microbial Pathogen Detection

Pathogenic microorganisms play a crucial role in the global disease burden due to their ability to cause various diseases and spread through multiple transmission routes. Immunity tests identify antigens related to these pathogens, thereby confirming past infections and monitoring the host's immune response. Traditional pathogen detection methods, including enzyme-linked immunosorbent assays (ELISAs) and chemiluminescent immunoassays (CLIAs), are often labor-intensive, slow, and reliant on sophisticated equipment and skilled personnel, which can be limiting in resource-poor settings. In contrast, the development of microfluidic technologies presents a promising alternative, offering automation, miniaturization, and cost efficiency. These advanced methods are poised to replace traditional assays by streamlining processes and enabling rapid, high-throughput immunity testing for pathogens. This review highlights the latest advancements in microfluidic systems designed for rapid and high-throughput immunity testing, incorporating immunosensors, single molecule arrays (Simoas), a lateral flow assay (LFA), and smartphone integration. It focuses on key pathogenic microorganisms such as SARS-CoV-2, influenza, and the ZIKA virus (ZIKV). Additionally, the review discusses the challenges, commercialization prospects, and future directions to advance microfluidic systems for infectious disease detection.

Fluorescence Multi-Detection Device Using a Lensless Matrix Addressable microLED Array

A Point-of-Care system for molecular diagnosis (PoC-MD) is described, combining GaN and CMOS chips. The device is a micro-system for fluorescence measurements, capable of analyzing both intensity and lifetime. It consists of a hybrid micro-structure based on a 32 × 32 matrix addressable GaN microLED array, with square LEDs of 50 µm edge length and 100 µm pitch, with an underneath wire bonded custom chip integrating their drivers and placed face-to-face to an array of 16 × 16 single-photon avalanche diodes (SPADs) CMOS. This approach replaces instrumentation based on lasers, bulky optical components, and discrete electronics with a full hybrid micro-system, enabling measurements on 32 × 32 spots. The reported system is suitable for long lifetime (>10 ns) fluorophores with a limit of detection ~1/4 µM. Proof-of-concept measurements of streptavidin conjugate Qdot™ 605 and Amino PEG Qdot™ 705 are demonstrated, along with the device ability to detect both fluorophores in the same measurement.

Self-Assembled Block Copolymers as a Facile Pathway to Create Functional Nanobiosensor and Nanobiomaterial Surfaces

Block copolymer (BCP) surfaces permit an exquisite level of nanoscale control in biomolecular assemblies solely based on self-assembly. Owing to this, BCP-based biomolecular assembly represents a much-needed, new paradigm for creating nanobiosensors and nanobiomaterials without the need for costly and time-consuming fabrication steps. Research endeavors in the BCP nanobiotechnology field have led to stimulating results that can promote our current understanding of biomolecular interactions at a solid interface to the never-explored size regimes comparable to individual biomolecules. Encouraging research outcomes have also been reported for the stability and activity of biomolecules bound on BCP thin film surfaces. A wide range of single and multicomponent biomolecules and BCP systems has been assessed to substantiate the potential utility in practical applications as next-generation nanobiosensors, nanobiodevices, and biomaterials. To this end, this Review highlights pioneering research efforts made in the BCP nanobiotechnology area. The discussions will be focused on those works particularly pertaining to nanoscale surface assembly of functional biomolecules, biomolecular interaction properties unique to nanoscale polymer interfaces, functionality of nanoscale surface-bound biomolecules, and specific examples in biosensing. Systems involving the incorporation of biomolecules as one of the blocks in BCPs, i.e., DNA-BCP hybrids, protein-BCP conjugates, and isolated BCP micelles of bioligand carriers used in drug delivery, are outside of the scope of this Review. Looking ahead, there awaits plenty of exciting research opportunities to advance the research field of BCP nanobiotechnology by capitalizing on the fundamental groundwork laid so far for the biomolecular interactions on BCP surfaces. In order to better guide the path forward, key fundamental questions yet to be addressed by the field are identified. In addition, future research directions of BCP nanobiotechnology are contemplated in the concluding section of this Review.

Universal nanocomposite coating with antifouling and redox capabilities for electrochemical affinity biosensing in complex biological fluids

Electrochemical affinity biosensors have the potential to facilitate the development of multiplexed point-of-care diagnostics in complex biological fluids. However, their commercial viability has been hindered by challenges such as electrode biofouling and the lack of inherent redox properties. To address this unmet need, we have developed a universal nanocomposite coating which is unique in its ability to not only allow oriented conjugation of the biorecognition element but also specific detection directly in complex biological fluids like serum and urine owing to its built-in antifouling and redox capabilities, thus improving suitability for point of care testing. This multifunctional coating comprises a 3D porous crosslinked bovine serum albumin matrix for oriented conjugation and antifouling properties with embedded graphene nanosheets modified with amino-ferrocene for enhanced conductivity and mediator-free biosensing. The coating showed minimal signal degradation despite prolonged exposure to 1% bovine serum albumin, artificial urine and untreated human serum for up to 30 days. To demonstrate its utility, we fabricated and tested proof-of-concept electrochemical immunosensors for bladder cancer protein biomarkers, specifically interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF). The practical feasibility was highlighted by the excellent sensitivity and specificity observed for IL-8 and VEGF with a limit of detection of 41 pg mL-1 and 67 pg mL-1, respectively. Consequently, this universal nanocomposite-based electrochemical biosensing platform can be extended to the point of care testing of a broad spectrum of biomarkers present in complex biological fluids, thus enabling reliable and early diagnostics.

Trends and challenges in electroanalytical biosensing methodologies for infectious viral diseases

Viral pandemic diseases have disruptive global consequences leading to millions of deaths and a severe impact on the global economy. Inadequate preventative protocols have led to an overwhelming demand for intensive care leading to uncontrollable burdens and even breakdown of healthcare sectors across many countries. The rapid detection of viral disease helps in the understanding of the relevant intricacies, helping to tackle infection with improved guidelines. Portable biosensor devices offer promising solutions by facilitating on-site detection of viral pathogens. This review summarizes the latest innovative strategies reported using electroanalytical methods for the screening of viral antigens. The structural components of viruses and their categories are presented followed by the various recognition elements and transduction techniques involved in biosensors. Core sections focus on biosensors reported for viral genomic detection(DNA and RNA) and antigenic capsid protein. Strategies for addressing the challenges of electroanalytical biosensing of viral components are also presented. The advantages, and disadvantages of biorecognition elements and nanozymes for the detection of viral disease are highlighted. Such technical insights will help researchers working in chemistry, and biochemistry as well as clinicians working in medical diagnostics.

Biosensing Platforms for Cardiac Biomarker Detection

Myocardial infarction (MI) is a cardiovascular disease that occurs when there is an elevated demand for myocardial oxygen as a result of the rupture or erosion of atherosclerotic plaques. Globally, the mortality rates associated with MI are steadily on the rise. Traditional diagnostic biomarkers employed in clinical settings for MI diagnosis have various drawbacks, prompting researchers to investigate fast, precise, and highly sensitive biosensor platforms and technologies. Biosensors are analytical devices that combine biological elements with physicochemical transducers to detect and quantify specific compounds or analytes. These devices play a crucial role in various fields including healthcare, environmental monitoring, food safety, and biotechnology. Biosensors developed for the detection of cardiac biomarkers are typically electrochemical, mass, and optical biosensors. Nanomaterials have emerged as revolutionary components in the field of biosensing, offering unique properties that significantly enhance the sensitivity and specificity of the detection systems. This review provides a comprehensive overview of the advancements and applications of nanomaterial-based biosensing systems. Beginning with an exploration of the fundamental principles governing nanomaterials, we delve into their diverse properties, including but not limited to electrical, optical, magnetic, and thermal characteristics. The integration of these nanomaterials as transducers in biosensors has paved the way for unprecedented developments in analytical techniques. Moreover, the principles and types of biosensors and their applications in cardiovascular disease diagnosis are explained in detail. The current biosensors for cardiac biomarker detection are also discussed, with an elaboration of the pros and cons of existing platforms and concluding with future perspectives.

Hybrid Impedimetric Biosensors for Express Protein Markers Detection

Impedimetric biosensors represent a powerful and promising tool for studying and monitoring biological processes associated with proteins and can contribute to the development of new approaches in the diagnosis and treatment of diseases. The basic principles, analytical methods, and applications of hybrid impedimetric biosensors for express protein detection in biological fluids are described. The advantages of this type of biosensors, such as simplicity and speed of operation, sensitivity and selectivity of analysis, cost-effectiveness, and an ability to be integrated into hybrid microfluidic systems, are demonstrated. Current challenges and development prospects in this area are analyzed. They include (a) the selection of materials for electrodes and formation of nanostructures on their surface; (b) the development of efficient methods for biorecognition elements' deposition on the electrodes' surface, providing the specificity and sensitivity of biosensing; (c) the reducing of nonspecific binding and interference, which could affect specificity; (d) adapting biosensors to real samples and conditions of operation; (e) expanding the range of detected proteins; and, finally, (f) the development of biosensor integration into large microanalytical system technologies. This review could be useful for researchers working in the field of impedimetric biosensors for protein detection, as well as for those interested in the application of this type of biosensor in biomedical diagnostics.

Nanomaterials Connected to Bioreceptors to Introduce Efficient Biosensing Strategy for Diagnosis of the TORCH Infections: A Critical Review

TORCH infection is a significant risk factor for severe fetal damage, especially congenital malformations. Screening pregnant women for TORCH pathogens could reduce the incidence of adverse pregnancy outcomes and prevent birth defects. Hence, timely identification and inhibition of TORCH infections are effective ways to successfully prevent them in pregnant women. Recently, the superiority of biosensors in TORCH pathogen sensing has been emphasized due to their intrinsic benefits, such as rapid response time, portability, cost-effectiveness, much friendlier preparation and determination steps. With the introduction of advanced nanomaterials into biosensing, the diagnostic properties of biosensors have significantly improved. This study core presents and debates the current progress in biosensing systems for TORCH pathogens using various artificial and natural receptors. The incorporation of nanomaterials into various transduction systems can enhance diagnostic performance. The key performance characteristics of optical and electrochemical biosensors, such as response time, limit of detection (LOD), and linear detection range, are systematically discussed, along with the current TORCH pathogens used for constructing biosensors. Finally, the major problems that exist for converting scientific investigation into product development are also outlined.

Application of DNA-fueled molecular machines in food safety testing

Food is consumed by humans, which is indispensable to human life. Therefore, considerable attention of the whole society has been paid to food safety. Over the last few years, dramatic social development has brought new challenges to food safety, making developing new and quick methods for on-site food safety testing an important necessity. As a result, DNA-fueled molecular machines, characterized by high efficiency, accuracy, and sensitivity in testing, have come into the spotlight, based on which sensors can be constructed to detect toxic and harmful substances in food products. This study reviewed recent research on several DNA-fueled molecular machines, including DNA tweezers, DNA walkers, and DNA origami, for rapidly detecting toxic and harmful substances. Based on the above studies, the sensitivity and timeliness of several DNA molecular machines were summarized and compared, and the development prospect of DNA fuel molecular machines in the field of food safety detection was prospected.

Ultra-Sensitive Portable Visual Paper-Based Viral Molecularly Imprinted Sensor without Autofluorescence Interference

Detection of the virus is the primary factor to discover and block the occurrence and development of the virus epidemic. Here, an ultrasensitive paper-based virus molecular imprinting sensor is developed to detect two viruses simultaneously in which the detection limit of the influenza virus (H5N1) is 16.0 aM (9.63 × 103 particles/mL) while that of the Hepatitis B Virus (HBV) is 129 fM (7.77 × 107 particles/mL). This paper-based sensor is low cost and is easy to cut, store, and carry. In addition, the visual semiquantitative detection of two viruses is achieved by using two aptamer-functionalized persistent luminescent nanoparticles as signal probes. These probes and the imprinted cavities on the paper-based material formed sandwich-type double recognition of the target viruses. This sensor has extremely high sensitivity to the H5N1 virus, which is of great value to solve the influenza epidemic with the most outbreaks in history, and also opens up a new way for the prevention and control of other virus epidemics. This cheap and portable visual sensor provides the possibility for self-service detection and can greatly reduce the pressure on medical staff and reduce the risk of virus infection caused by the concentration of people to be tested.

Challenges and perspectives of multi-virus biosensing techniques: A review

In the context of globalization, individuals have an increased chance of being infected by multiple viruses simultaneously, thereby highlighting the importance of developing multiplexed devices. In addition to sufficient sensitivity and rapid response, multi-virus sensing techniques are expected to offer additional advantages including high throughput, one-time sampling for parallel analysis, and full automation with data visualization. In this paper, we review the optical, electrochemical, and mechanical platforms that enable multi-virus biosensing. The working mechanisms of each platform, including the detection principle, transducer configuration, bio-interface design, and detected signals, are reviewed. The advantages and limitations, as well as the challenges in implementing various detection strategies in real-life scenarios, were evaluated. Future perspectives on multiplexed biosensing techniques are critically discussed. Earlier access to multi-virus biosensors will efficiently serve for immediate pandemic control, such as in emerging SARS-CoV-2 and monkeypox cases.

Advances in immunoassay-based strategies for mycotoxin detection in food: From single-mode immunosensors to dual-mode immunosensors

Mycotoxin contamination in foods and other goods has become a broad issue owing to serious toxicity, tremendous threat to public safety, and terrible loss of resources. Herein, it is necessary to develop simple, sensitive, inexpensive, and rapid platforms for the detection of mycotoxins. Currently, the limitation of instrumental and chemical methods cannot be massively applied in practice. Immunoassays are considered one of the best candidates for toxin detection due to their simplicity, rapidness, and cost-effectiveness. Especially, the field of dual-mode immunosensors and corresponding assays is rapidly developing as an advanced and intersected technology. So, this review summarized the types and detection principles of single-mode immunosensors including optical and electrical immunosensors in recent years, then focused on developing dual-mode immunosensors including integrated immunosensors and combined immunosensors to detect mycotoxins, as well as the combination of dual-mode immunosensors with a portable device for point-of-care test. The remaining challenges were discussed with the aim of stimulating future development of dual-mode immunosensors to accelerate the transformation of scientific laboratory technologies into easy-to-operate and rapid detection platforms.

Compact Camera Fluorescence Detector for Parallel-Light Lens-Based Real-Time PCR System

The polymerase chain reaction is an important technique in biological research. However, it is time consuming and has a number of disadvantages. Therefore, real-time PCR technology that can be used in real-time monitoring has emerged, and many studies are being conducted regarding its use. Real-time PCR requires many optical components and imaging devices such as expensive, high-performance cameras. Therefore, its cost and assembly process are limitations to its use. Currently, due to the development of smart camera devices, small, inexpensive cameras and various lenses are being developed. In this paper, we present a Compact Camera Fluorescence Detector for use in parallel-light lens-based real-time PCR devices. The proposed system has a simple optical structure, the system cost can be reduced, and the size can be miniaturized. This system only incorporates Fresnel lenses without additional optics in order for the same field of view to be achieved for 25 tubes. In the center of the Fresnel lens, one LED and a complementary metal-oxide semiconductor camera were placed in directions that were as similar as possible. In addition, to achieve the accurate analysis of the results, image processing was used to correct them. As a result of an experiment using a reference fluorescent substance and double-distilled water, it was confirmed that stable fluorescence detection was possible.

Advances in Biosensing Technologies for Diagnosis of COVID-19

The COVID-19 pandemic has severely impacted normal human life worldwide. Due to its rapid community spread and high mortality statistics, the development of prompt diagnostic tests for a massive number of samples is essential. Currently used traditional methods are often expensive, time-consuming, laboratory-based, and unable to handle a large number of specimens in resource-limited settings. Because of its high contagiousness, efficient identification of SARS-CoV-2 carriers is crucial. As the advantages of adopting biosensors for efficient diagnosis of COVID-19 increase, this narrative review summarizes the recent advances and the respective reasons to consider applying biosensors. Biosensors are the most sensitive, specific, rapid, user-friendly tools having the potential to deliver point-of-care diagnostics beyond traditional standards. This review provides a brief introduction to conventional methods used for COVID-19 diagnosis and summarizes their advantages and disadvantages. It also discusses the pathogenesis of COVID-19, potential diagnostic biomarkers, and rapid diagnosis using biosensor technology. The current advancements in biosensing technologies, from academic research to commercial achievements, have been emphasized in recent publications. We covered a wide range of topics, including biomarker detection, viral genomes, viral proteins, immune responses to infection, and other potential proinflammatory biomolecules. Major challenges and prospects for future application in point-of-care settings are also highlighted.

Portable Electrochemical Biosensors Based on Microcontrollers for Detection of Viruses: A Review

With the rise of zoonotic diseases in recent years, there is an urgent need for improved and more accessible screening and diagnostic methods to mitigate future outbreaks. The recent COVID-19 pandemic revealed an over-reliance on RT-PCR, a slow, costly and lab-based method for diagnostics. To better manage the pandemic, a high-throughput, rapid point-of-care device is needed for early detection and isolation of patients. Electrochemical biosensors offer a promising solution, as they can be used to perform on-site tests without the need for centralized labs, producing high-throughput and accurate measurements compared to rapid test kits. In this work, we detail important considerations for the use of electrochemical biosensors for the detection of respiratory viruses. Methods of enhancing signal outputs via amplification of the analyte, biorecognition of elements and modification of the transducer are also explained. The use of portable potentiostats and microfluidics chambers that create a miniature lab are also discussed in detail as an alternative to centralized laboratory settings. The state-of-the-art usage of portable potentiostats for detection of viruses is also elaborated and categorized according to detection technique: amperometry, voltammetry and electrochemical impedance spectroscopy. In terms of integration with microfluidics, RT-LAMP is identified as the preferred method for DNA amplification virus detection. RT-LAMP methods have shorter turnaround times compared to RT-PCR and do not require thermal cycling. Current applications of RT-LAMP for virus detection are also elaborated upon.

Advances, limitations, and prospects of biosensing technology for detecting phytopathogenic bacteria

Phytopathogenic bacteria cause severe economic losses in agricultural production worldwide. The spread rates, severity, and emerging plant bacterial diseases have become serious threat to the sustainability of food sources and the fruit industry. Detection and diagnosis of plant diseases are imperative in order to manage plant diseases in field conditions, greenhouses, and food storage conditions as well as to maximize agricultural productivity and sustainability. To date, various techniques including, serological, observation-based, and molecular methods have been employed for plant disease detection. These methods are sensitive and specific for genetic identification of bacteria. However, these methods are specific for genetic identification of bacteria. Currently, the innovative biosensor-based disease detection technique is an attractive and promising alternative. A biosensor system involves biological recognition and transducer active receptors based on sensors used in plant-bacteria diagnosis. This system has been broadly used for the rapid diagnosis of plant bacterial pathogens. In the present review, we have discussed the conventional methods of bacterial-disease detection, however, the present review mainly focuses on the applications of different biosensor-based techniques along with point-of-care (POC), robotics, and cell phone-based systems. In addition, we have also discussed the challenges and limitations of these techniques.

Virus Detection: From State-of-the-Art Laboratories to Smartphone-Based Point-of-Care Testing

Infectious virus outbreaks pose a significant challenge to public healthcare systems. Early and accurate virus diagnosis is critical to prevent the spread of the virus, especially when no specific vaccine or effective medicine is available. In clinics, the most commonly used viral detection methods are molecular techniques that involve the measurement of nucleic acids or proteins biomarkers. However, most clinic-based methods require complex infrastructure and expensive equipment, which are not suitable for low-resource settings. Over the past years, smartphone-based point-of-care testing (POCT) has rapidly emerged as a potential alternative to laboratory-based clinical diagnosis. This review summarizes the latest development of virus detection. First, laboratory-based and POCT-based viral diagnostic techniques are compared, both of which rely on immunosensing and nucleic acid detection. Then, various smartphone-based POCT diagnostic techniques, including optical biosensors, electrochemical biosensors, and other types of biosensors are discussed. Moreover, this review covers the development of smartphone-based POCT diagnostics for various viruses including COVID-19, Ebola, influenza, Zika, HIV, et al. Finally, the prospects and challenges of smartphone-based POCT diagnostics are discussed. It is believed that this review will aid researchers better understand the current challenges and prospects for achieving the ultimate goal of containing disease-causing viruses worldwide.

Genosensors as an alternative diagnostic sensing approaches for specific detection of various certain viruses: a review of common techniques and outcomes

Viral infections are responsible for the deaths of millions of people throughout the world. Since outbreak of highly contagious and mutant viruses such as contemporary sars-cov-2 pandemic, has challenged the conventional diagnostic methods, the entity of a thoroughly sensitive, specific, rapid and inexpensive detecting technique with minimum level of false-positivity or -negativity, is desperately needed more than any time in the past decades. Biosensors as minimized devices could detect viruses in simple formats. So far, various nucleic acid, immune- and protein-based biosensors were designed and tested for recognizing the genome, antigen, or protein level of viruses, respectively; however, nucleic acid-based sensing techniques, which is the foundation of constructing genosensors, are preferred not only because of their ultra-sensitivity and applicability in the early stages of infections but also for their ability to differentiate various strains of the same virus. To date, the review articles related to genosensors are just confined to particular pathogenic diseases; In this regard, the present review covers comprehensive information of the research progress of the electrochemical, optical, and surface plasmon resonance (SPR) genosensors that applied for human viruses' diseases detection and also provides a well description of viruses' clinical importance, the conventional diagnosis approaches of viruses and their disadvantages. This review would address the limitations in the current developments as well as the future challenges involved in the successful construction of sensing approaches with the functionalized nanomaterials and also allow exploring into core-research works regarding this area.

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.

Cloud-Based Software Architecture for Fully Automated Point-of-Care Molecular Diagnostic Device

This paper proposes a cloud-based software architecture for fully automated point-of-care molecular diagnostic devices. The target system operates a cartridge consisting of an extraction body for DNA extraction and a PCR chip for amplification and fluorescence detection. To facilitate control and monitoring via the cloud, a socket server was employed for fundamental molecular diagnostic functions such as DNA extraction, amplification, and fluorescence detection. The user interface for experimental control and monitoring was constructed with the RESTful application programming interface, allowing access from the terminal device, edge, and cloud. Furthermore, it can also be accessed through any web-based user interface on smart computing devices such as smart phones or tablets. An emulator with the proposed software architecture was fabricated to validate successful operation.

Cost-Effective Multiplex Fluorescence Detection System for PCR Chip

The lack of portability and high cost of multiplex real-time PCR systems limits the device to be used in POC. To overcome this issue, this paper proposes a compact and cost-effective fluorescence detection system that can be integrated to a multiplex real-time PCR equipment. An open platform camera with embedded lens was used instead of photodiodes or an industrial camera. A compact filter wheel using a sliding tape is integrated, and the excitation LEDs are fixed at a 45° angle near the PCR chip, eliminating the need of additional filter wheels. The results show precise positioning of the filter wheel with an error less than 20 μm. Fluorescence detection results using a reference dye and standard DNA amplification showed comparable performance to that of the photodiode system.

Kinetic stability modulation of polymeric nanoparticles for enhanced detection of influenza virus via penetration of viral fusion peptides

Specific interactions between viruses and host cells provide essential insights into material science-based strategies to combat emerging viral diseases. pH-triggered viral fusion is ubiquitous to multiple viral families and is important for understanding the viral infection cycle. Inspired by this process, virus detection has been achieved using nanomaterials with host-mimetic membranes, enabling interactions with amphiphilic hemagglutinin fusion peptides of viruses. Most research has been on designing functional nanoparticles with fusogenic capability for virus detection, and there has been little exploitation of the kinetic stability to alter the ability of nanoparticles to interact with viral membranes and improve their sensing performance. In this study, a homogeneous fluorescent assay using self-assembled polymeric nanoparticles (PNPs) with tunable responsiveness to external stimuli is developed for rapid and straightforward detection of an activated influenza A virus. Dissociation of PNPs induced by virus insertion can be readily controlled by varying the fraction of hydrophilic segments in copolymers constituting PNPs, giving rise to fluorescence signals within 30 min and detection of various influenza viruses, including H9N2, CA04(H1N1), H4N6, and H6N8. Therefore, the designs demonstrated in this study propose underlying approaches for utilizing engineered PNPs through modulation of their kinetic stability for direct and sensitive identification of infectious viruses.

Self-Assembled Chromogenic Polymeric Nanoparticle-Laden Nanocarrier as a Signal Carrier for Derivative Binary Responsive Virus Detection

In the current biosensor, the signal generation is limited to single virus detection in the reaction chamber. An adaptive strategy is required to enable the recognition of multiple viruses for diagnostics and surveillance. In this work, a nanocarrier is deployed to bring specific signal amplification into the biosensor, depending on the target viruses. The nanocarrier is designed using pH-sensitive polymeric nanoparticle-laden nanocarriers (PNLNs) prepared by sequential nanoprecipitation. The nanoprecipitation of two chromogens, phenolphthalein (PP) and thymolphthalein (TP), is investigated in three different solvent systems in which PNLNs demonstrate a high loading of the chromogen up to 59.75% in dimethylformamide (DMF)/dimethyl sulfoxide (DMSO)/ethanol attributing to the coprecipitation degree of the chromogens and the polymer. The PP-encapsulated PNLNs (PP@PNLNs) and TP-encapsulated PNLNs (TP@PNLNs) are conjugated to antibodies specific to target viruses, influenza virus A subtype H1N1 (IV/A/H1N1) and H3N2 (IV/A/H3N2), respectively. After the addition of anti-IV/A antibody-conjugated magnetic nanoparticles (MNPs) and magnetic separation, the enriched PNLNs/virus/MNPs sandwich structure is treated in an alkaline solution. It demonstrates a synergy reaction in which the degradation of the polymeric boundary and the pH-induced colorimetric development of the chromogen occurred. The derivative binary biosensor shows feasible detection on IV/A with excellent specificities of PP@PNLNs on IV/A/H1N1 and TP@PNLNs on IV/A/H3N2 with LODs of 27.56 and 28.38 fg mL^-1, respectively. It intrigues the distinguished analytical signal in human serum with a variance coefficient of 25.8% and a recovery of 93.6-110.6% for one-step subtype influenza virus detection.

Electrochemical Affinity Assays/Sensors: Brief History and Current Status

The advent of electrochemical affinity assays and sensors evolved from pioneering efforts in the 1970s to broaden the field of analytes accessible to the selective and sensitive performance of electrochemical detection. The foundation of electrochemical affinity assays/sensors is the specific capture of an analyte by an affinity element and the subsequent transduction of this event into a measurable signal. This review briefly covers the early development of affinity assays and then focuses on advances in the past decade. During this time, progress on electroactive labels, including the use of nanoparticles, quantum dots, organic and organometallic redox compounds, and enzymes with amplification schemes, has led to significant improvements in sensitivity. The emergence of nanomaterials along with microfabrication and microfluidics technology enabled research pathways that couple the ease of use of electrochemical detection for the development of devices that are more user friendly, disposable, and employable, such as lab-on-a-chip, paper, and wearable sensors.

Advancements in electrochemical biosensing for respiratory virus detection: A review

Respiratory viruses are real menace for human health which result in devastating epidemic disease. Consequently, it is in urgent need of identifying and quantifying virus with a rapid, sensitive and precise approach. The study of electrochemical biosensors for respiratory virus detection has become one of the most rapidly developing scientific fields. Recent developments in electrochemical biosensors concerning respiratory virus detection are comprehensively reviewed in this paper. This review is structured along common detecting objects of respiratory viruses, electrochemical biosensors, electrochemical biosensors for respiratory virus detection and future challenges. The electrochemical biosensors for respiratory virus detection are introduced, including nucleic acids-based, immunosensors and other affinity biosensors. Lastly, for Coronavirus disease 2019 (COVID-19) diagnosis, the future challenges regarding developing electrochemical biosensor-based Point-of-Care Tests (POCTs) are summarized. This review is expected to provide a helpful guide for the researchers entering this interdisciplinary field and developing more novel electrochemical biosensors for respiratory virus detection.

Wastewater-Based Epidemiology as an Early Warning System for the Spreading of SARS-CoV-2 and Its Mutations in the Population

New methodologies based on the principle of "sewage epidemiology" have been successfully applied before in the detection of illegal drugs. The study describes the idea of early detection of a virus, e.g., SARS-CoV-2, in wastewater in order to focus on the area of virus occurrence and supplement the results obtained from clinical examination. By monitoring temporal variation in viral loads in wastewater in combination with other analysis, a virus outbreak can be detected and its spread can be suppressed early. The use of biosensors for virus detection also seems to be an interesting application. Biosensors are highly sensitive, selective, and portable and offer a way for fast analysis. This manuscript provides an overview of the current situation in the area of wastewater analysis, including genetic sequencing regarding viral detection and the technological solution of an early warning system for wastewater monitoring based on biosensors.

Indirect competitive-structured electrochemical immunosensor for tetrabromobisphenol A sensing using CTAB-MnO2 nanosheet hybrid as a label for signal amplification

Tetrabromobisphenol A (TBBPA) is a kind of brominated flame retardant that is usually added to products to reduce their flame retardancy. However, its extensive use has resulted in their residues being found in the environment, which is very harmful. Herein, an indirect competitive immunosensor has been established for TBBPA detection based on the signal amplification system. Pd nanospheres in situ reduced on the surface of MnO₂ nanosheet hybrid (MnO₂/Pd) was used as the label for the secondary antibody through the Pd-N bond, and gold-toluidine blue composite was loaded onto MWCNTs (MWCNTs/Au-TB), which functioned as the platform for the immunosensor. The spherical structure of Pd had abundant catalytic active sites, which enhanced the catalytic activity of MnO₂/Pd as the label, hence amplifying the signal response. Besides, MWCNTs/Au-TB improved electron transfer and produced a strong signaling pathway for immobilizing antigens through the Au-NH₂ bond, which can specifically recognize primary antibodies to improve sensitivity. The immunosensor had a linear concentration range of 0-81 ng/mL, a low detection limit of 0.17 ng/mL (S/N = 3), with good stability, selectivity, and reproducibility based on the above advantages. Additionally, the acceptable accuracy and recoveries (recoveries, 92-124%; CV, 3.3-8.8%) in the real water sample analysis indicated that this strategy is promising for emerging pollutant analysis.

Enhanced performance of a surface plasmon resonance-based immunosensor for the detection of glycocholic acid

The concentration of glycocholic acid (GCA) in urine and blood is an important biomarker for liver cancer. Monitoring of GCA depends to a large extent on the availability of appropriate analytical techniques. In this work, based on the immobilization of GCA-OVA onto the sensor chip surface, a label-free competitive inhibition immunoassay for the determination of GCA with the surface plasmon resonance (SPR) technique was developed. The proposed SPR immunosensor is simple to prepare, recyclable and exhibits excellent sensitivity to GCA (a linear range of 13.3-119.4 ng mL^-1 and a limit of detection (LOD) of 2.5 ng mL^-1), which was 14 times lower than that of the traditional immunoassay. Excellent recoveries and correlation between these two methods were observed (R² = 0.995). Hence, it can be proved that the SPR immunosensor could be used to achieve rapid and sensitive quantitative detection of GCA in real urine samples and meet clinical needs.

Advances in emergent biological recognition elements and bioelectronics for diagnosing COVID-19

Coronaviruses pose a serious threat to public health. Tremendous efforts are dedicated to advance reliable and effective detection of coronaviruses. Currently, the coronavirus disease 2019 (COVID-19) diagnosis mainly relies on the detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genetic materials by using reverse transcription-polymerase chain reaction (RT-PCR) assay. However, simpler and more rapid and reliable alternatives are needed to meet high demand during the pandemic. Biosensor-based diagnosis approaches become alternatives for selectively and rapidly detecting virus particles because of their biorecognition elements consisting of biomaterials that are specific to virus biomarkers. Here, we summarize biorecognition materials, including antibodies and antibody-like molecules, that are designed to recognize SARS-CoV-2 biomarkers and the advances of recently developed biosensors for COVID-19 diagnosis. The design of biorecognition materials or layers is crucial to maximize biosensing performances, such as high selectivity and sensitivity of virus detection. Additionally, the recent representative achievements in developing bioelectronics for sensing coronavirus are included. This review includes scholarly articles, mainly published in 2020 and early 2021. In addition to capturing the fast development in the fields of applied materials and biodiagnosis, the outlook of this rapidly evolving technology is summarized. Early diagnosis of COVID-19 could help prevent the spread of this contagious disease and provide significant information to medical teams to treat patients.

Earlier diagnoses of acute leukemia by a sandwich type of electrochemical aptasensor based on copper sulfide-graphene composite

Due to high affinity and specificity of aptamers, they are widely considered for construction of aptasensor to specific recognizing of analytes in biological complex matrix. So, in this work we design a high selective and sensitive aptasensor for leukemia cancer cells (CCRF-CEM) via superior catalytic effect of copper sulfide-graphene (CuS-GR) nanocomposite as label and Au-GR nanocomposite as sensing platform. The CuS-GR nano-composite (label component) is CuS nanoparticles that wrapping on graphene sheets. Its catalytic activity (CuS-GR) increases the current of sensor in parallel with adding of CCRF-CEM and provide sensitive detection of analytes. The detailed of signal amplification and effect on the aptasensor performance completely discussed. This sensor has a linear range of 50-1 × 10⁶ cell mL^-1, with a limit of detection of 18 cell mL^-1. Also, the developed aptasensor has a significance specificity, high sensitivity and accuracy. It was used for the identification of CCRF-CEM cells in blood samples.

Biosensors for the detection of respiratory viruses: A review

The recent events of outbreaks related to different respiratory viruses in the past few years, exponentiated by the pandemic caused by the coronavirus disease 2019 (COVID-19), reported worldwide caused by SARS-CoV-2, raised a concern and increased the search for more information on viruses-based diseases. The detection of the virus with high specificity and sensitivity plays an important role for an accurate diagnosis. Despite the many efforts to identify the SARS-CoV-2, the diagnosis still relays on expensive and time-consuming analysis. A fast and reliable alternative is the use of low-cost biosensor for in loco detection. This review gathers important contributions in the biosensor area regarding the most current respiratory viruses, presents the advances in the assembly of the devices and figures of merit. All information is useful for further biosensor development for the detection of respiratory viruses, such as for the new coronavirus.

Nanobiosensors for the Detection of Novel Coronavirus 2019-nCoV and Other Pandemic/Epidemic Respiratory Viruses: A Review

The coronavirus disease 2019 (COVID-19) pandemic is considered a public health emergency of international concern. The 2019 novel coronavirus (2019-nCoV) or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that caused this pandemic has spread rapidly to over 200 countries, and has drastically affected public health and the economies of states at unprecedented levels. In this context, efforts around the world are focusing on solving this problem in several directions of research, by: (i) exploring the origin and evolution of the phylogeny of the SARS-CoV-2 viral genome; (ii) developing nanobiosensors that could be highly effective in detecting the new coronavirus; (iii) finding effective treatments for COVID-19; and (iv) working on vaccine development. In this paper, an overview of the progress made in the development of nanobiosensors for the detection of human coronaviruses (SARS-CoV, SARS-CoV-2, and Middle East respiratory syndrome coronavirus (MERS-CoV) is presented, along with specific techniques for modifying the surface of nanobiosensors. The newest detection methods of the influenza virus responsible for acute respiratory syndrome were compared with conventional methods, highlighting the newest trends in diagnostics, applications, and challenges of SARS-CoV-2 (COVID-19 causative virus) nanobiosensors.

Recent Development of Aptasensor for Influenza Virus Detection

In nowadays, we have entered the new era of pandemics and the significance of virus detection deeply impacts human society. Viruses with genetic mutations are reported nearly every year, and people have prepared tools to detect the virus and vaccines to ensure proper treatments. Influenza virus (IV) is one of the most harmful viruses reporting various mutations, sub-types, and rapid infection speed for humans and animals including swine and poultry. Moreover, IV infection presents several harmful symptoms including cough, fever, diarrhea, chills, even causing death. To reduce the IV-induced harm, its proper and rapid detection is highly required. Conventional techniques were used against various IV sub-types including H1N1, H3N2, and H5N1. However, some of the techniques are time-consuming, expensive, or labor-intensive for detecting IV. Recently, the nucleic acid-based aptamer has gained attention as a novel bioprobe for constructing a biosensor. In this review, the authors discuss the recent progress in aptasensors for detecting IV in terms of an electrochemical and an optical biosensor.

Detection of COVID-19: A review of the current literature and future perspectives

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the coronavirus disease 2019 (COVID-19) worldwide pandemic. This unprecedented situation has garnered worldwide attention. An effective strategy for controlling the COVID-19 pandemic is to develop highly accurate methods for the rapid identification and isolation of SARS-CoV-2 infected patients. Many companies and institutes are therefore striving to develop effective methods for the rapid detection of SARS-CoV-2 ribonucleic acid (RNA), antibodies, antigens, and the virus. In this review, we summarize the structure of the SARS-CoV-2 virus, its genome and gene expression characteristics, and the current progression of SARS-CoV-2 RNA, antibodies, antigens, and virus detection. Further, we discuss the reasons for the observed false-negative and false-positive RNA and antibody detection results in practical clinical applications. Finally, we provide a review of the biosensors which hold promising potential for point-of-care detection of COVID-19 patients. This review thereby provides general guidelines for both scientists in the biosensing research community and for those in the biosensor industry to develop a highly sensitive and accurate point-of-care COVID-19 detection system, which would be of enormous benefit for controlling the current COVID-19 pandemic.

A Stable Biotin-Streptavidin Surface Enables Multiplex, Label-Free Protein Detection by Aptamer and Aptamer-Protein Arrays Using Arrayed Imaging Reflectometry

While label-free multiplex sensor technology enables "mixing and matching" of different capture molecules in principle, in practice this has been rarely (if ever) demonstrated. To fill this gap, we developed protocols for the preparation of mixed aptamer-protein arrays on the arrayed imaging reflectometry (AIR) sensing platform using streptavidin as a common attachment point for both biotinylated proteins and aptamers. Doing so required overcoming the noted instability of dried streptavidin monolayers on surfaces. After characterizing this degradation, stable surfaces were obtained using a commercial microarray product. Microarraying through the layer of stabilizer then provided mixed aptamer-antibody arrays. We demonstrate that sensor arrays prepared in this manner are suitable for several probes (thrombin and TGF-β1 aptamers; avi-tagged protein) and targets.

How Nanophotonic Label-Free Biosensors Can Contribute to Rapid and Massive Diagnostics of Respiratory Virus Infections: COVID-19 Case

The global sanitary crisis caused by the emergence of the respiratory virus SARS-CoV-2 and the COVID-19 outbreak has revealed the urgent need for rapid, accurate, and affordable diagnostic tests to broadly and massively monitor the population in order to properly manage and control the spread of the pandemic. Current diagnostic techniques essentially rely on polymerase chain reaction (PCR) tests, which provide the required sensitivity and specificity. However, its relatively long time-to-result, including sample transport to a specialized laboratory, delays massive detection. Rapid lateral flow tests (both antigen and serological tests) are a remarkable alternative for rapid point-of-care diagnostics, but they exhibit critical limitations as they do not always achieve the required sensitivity for reliable diagnostics and surveillance. Next-generation diagnostic tools capable of overcoming all the above limitations are in demand, and optical biosensors are an excellent option to surpass such critical issues. Label-free nanophotonic biosensors offer high sensitivity and operational robustness with an enormous potential for integration in compact autonomous devices to be delivered out-of-the-lab at the point-of-care (POC). Taking the current COVID-19 pandemic as a critical case scenario, we provide an overview of the diagnostic techniques for respiratory viruses and analyze how nanophotonic biosensors can contribute to improving such diagnostics. We review the ongoing published work using this biosensor technology for intact virus detection, nucleic acid detection or serological tests, and the key factors for bringing nanophotonic POC biosensors to accurate and effective COVID-19 diagnosis on the short term.

Plasmon-enhanced quantum dots electrochemiluminescence aptasensor for selective and sensitive detection of cardiac troponin I

The development of highly sensitive electrochemiluminescence (ECL) immunosensors by using functional nanoparticles as signal amplifiers is a solution towards sensitive determination of many low concentration disease biomarkers. Herein, a sensitive aptamer-based, sandwich-type surface plasmon enhanced electrochemiluminescence (SPEECL) immunosensor was demonstrated for the detection of cardiac troponin I (cTnI), by means of aptamer conjugated CdS QDs and AuNPs as ECL luminophores and plasmon sources, respectively, in which Tro4 aptamer was used as a capture probe for cTnI and Tro6 aptamer as a detecting probe. The signal of the developed SPEECL system showed ~ 5-fold increment as compared to that of without AuNPs. Using this ECL platform for the detection of cTnI, a linear range and the limit of detection (LOD) were found to be 1 fg/mL - 10 ng/mL and 0.75 fg/mL, respectively.

Engineering photonics solutions for COVID-19

As the impact of COVID-19 on society became apparent, the engineering and scientific community recognized the need for innovative solutions. Two potential roadmaps emerged: developing short-term solutions to address the immediate needs of the healthcare communities and developing mid/long-term solutions to eliminate the over-arching threat. However, in a truly global effort, researchers from all backgrounds came together in tackling this challenge. Short-term efforts have focused on re-purposing existing technologies and leveraging additive manufacturing techniques to address shortages in personal protective equipment and disinfection. More basic research efforts with mid-term and long-term impact have emphasized developing novel diagnostics and accelerating vaccines. As a foundational technology, photonics has contributed directly and indirectly to all efforts. This perspective will provide an overview of the critical role that the photonics field has played in efforts to combat the immediate COVID-19 pandemic as well as how the photonics community could anticipate contributing to future pandemics of this nature.

Advanced "lab-on-a-chip" to detect viruses - Current challenges and future perspectives

Massive viral outbreaks draw attention to viruses that have not been thoroughly studied or understood. In recent decades, microfluidic chips, known as "lab-on-a-chip", appears as a promising tool for the detection of viruses. Here, we review the development of microfluidic chips that could be used in response to viral detection, specifically for viruses involved in more recent outbreaks. The advantages as well as the disadvantages of microfluidic systems are discussed and analyzed. We also propose ideas for future development of these microfluidic chips and we expect this advanced technology to be used in the future for viral outbreaks.

Design of engineered surfaces for prospective detection of SARS-CoV-2 using quartz crystal microbalance-based techniques

INTRODUCTION

Rapid transmission of the severe acute respiratory syndrome coronavirus 2 has affected the whole world and forced it to a halt (lockdown). A fast and label-free detection method for the novel coronavirus needs to be developed along with the existing enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR)-based methods.

AREAS COVERED

In this report, biophysical aspects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein are outlined based on its recent reported electron microscopy structure. Protein binding sites are analyzed theoretically, which consisted of hydrophobic and positive charged amino acid residues. Different strategies to form mixed self-assembled monolayers (SAMs) of hydrophobic (CH₃) and negatively charged (COOH) groups are discussed to be used for the specific and strong interactions with spike protein. Bio-interfacial interactions between the spike protein and device (sensor) surface and its implications toward designing suitable engineered surfaces are summarized.

EXPERT OPINION

Implementation of the engineered surfaces in quartz crystal microbalance (QCM)-based detection techniques for the diagnosis of the novel coronavirus from oral swab samples is highlighted. The proposed strategy can be explored for the label-free and real-time detection with sensitivity up to ng level. These engineered surfaces can be reused after desorption.