Micro- and nanosystems for the detection of hemorrhagic fever viruses

Hemorrhagic fever viruses (HFVs) are virulent pathogens that can cause severe and often fatal illnesses in humans. Timely and accurate detection of HFVs is critical for effective disease management and prevention. In recent years, micro- and nano-technologies have emerged as promising approaches for the detection of HFVs. This paper provides an overview of the current state-of-the-art systems for micro- and nano-scale approaches to detect HFVs. It covers various aspects of these technologies, including the principles behind their sensing assays, as well as the different types of diagnostic strategies that have been developed. This paper also explores future possibilities of employing micro- and nano-systems for the development of HFV diagnostic tools that meet the practical demands of clinical settings.

TiO2-guanine as a new amalgamation compound for fabrication of a disposable biosensor with high sensitivity and rapid detection of H1N1 swine flu virus

A TiO2-guanine nanocomposite (TG NC)-based electrochemical biosensor was immobilized with hemagglutinin (HA) gene specific probe with 5' NH2 group on screen-printed gold electrode (probe(ss)DNA-TG-SPGE). The modified biosensor was examined for H1N1 swine flu virus. TG NCs along with precursors were characterized spectroscopically and morphologically by employing several approaches. Electrochemical investigations were performed with the help of cyclic voltammetric (CV) and electrochemical impedance spectroscopy (EIS) in 0.1 M phosphate buffer saline (PBS; pH 7.4) with 1 µM methylene blue (MB) redox indicator. For better detection of single-stranded virus DNA, the modified electrode was optimized at various concentrations, pH, and scan rates. The modified biosensor showed high sensitivity (40.32 μA/ng.cm2), low LOD (0.00024 ng/6 µL), and broad linear range 0.0002-20 ng/6µL with coefficient of determination of R2=0.9981 for H1N1 virus detection. The HA gene-modified biosensor presented decent stability and specificity against different infectious pathogens including H3N2 virus and human DNA with negative response. Furthermore, the modified biosensor also responded well for real sample target DNA detection with a recovery of >96%. The simply designed HA gene-modified biosensor transduces decreased current response towards target-specific (ss)DNA binding and could be used as a rapid detection tool for H1N1 swine flu virus diagnosis.

Recent Advances in Colorimetric Tests for the Detection of Infectious Diseases and Antimicrobial Resistance

Diagnosis of infection-causing microorganisms with sensitive, rapid, selective and economical diagnostic tests is critical to start the right treatment. With these tests, the spread of infections can be prevented. In addition to that, the detection of antimicrobial resistance also makes a significant contribution to public health. In recent years, different types of diagnostic tests have been developed as alternatives to traditional diagnostic tests used in clinics. In particular, colorimetric tests, which minimize the need for an instrument, have advantages owing to their cost effectiveness, rapid response and naked-eye detection and practical use. In this review, we especially focused on pH indicators and nanomaterial-based colorimetric tests in detection of infection-causing microorganisms and antimicrobial resistance.

Recent Advances in Conjugated Polymer-Based Biosensors for Virus Detection

Nowadays, virus pandemics have become a major burden seriously affecting human health and social and economic development. Thus, the design and fabrication of effective and low-cost techniques for early and accurate virus detection have been given priority for prevention and control of such pandemics. Biosensors and bioelectronic devices have been demonstrated as promising technology to resolve the major drawbacks and problems of the current detection methods. Discovering and applying advanced materials have offered opportunities to develop and commercialize biosensor devices for effectively controlling pandemics. Along with various well-known materials such as gold and silver nanoparticles, carbon-based materials, metal oxide-based materials, and graphene, conjugated polymer (CPs) have become one of the most promising candidates for preparation and construction of excellent biosensors with high sensitivity and specificity to different virus analytes owing to their unique π orbital structure and chain conformation alterations, solution processability, and flexibility. Therefore, CP-based biosensors have been regarded as innovative technologies attracting great interest from the community for early diagnosis of COVID-19 as well as other virus pandemics. For providing precious scientific evidence of CP-based biosensor technologies in virus detection, this review aims to give a critical overview of the recent research related to use of CPs in fabrication of virus biosensors. We emphasize structures and interesting characteristics of different CPs and discuss the state-of-the-art applications of CP-based biosensors as well. In addition, different types of biosensors such as optical biosensors, organic thin film transistors (OTFT), and conjugated polymer hydrogels (CPHs) based on CPs are also summarized and presented.

Conductive Thread-Based Immunosensor for Pandemic Influenza A (H1N1) Virus Detection

Infectious agents such as viruses pose significant threats to human health, being transmitted via direct contact as well as airborne transmission without direct contact, thus requiring rapid detection to prevent the spread of infectious diseases. In this study, we developed a conductive thread-based immunosensor (CT-IS), a biosensor to easily detect the presence of airborne viruses. CT-IS utilizes an antibody that specifically recognizes the HA protein of the pandemic influenza A (pH1N1) virus, which is incorporated into the conductive thread. The antigen-antibody interaction results in increased strain on the conductive thread in the presence of the pH1N1 virus, resulting in increased electrical resistance of the CT-IS. We evaluated the performance of this sensor using the HA protein and the pH1N1 virus, in addition to samples from patients infected with the pH1N1 virus. We observed a significant change in resistance in the pH1N1-infected patient samples (positive: n = 11, negative: n = 9), whereas negligible change was observed in the control samples (patients not infected with the pH1N1 virus; negative). Hence, the CT-IS is a lightweight fiber-type sensor that can be used as a wearable biosensor by combining it with textiles, to detect the pH1N1 virus in a person's vicinity.

Recent advances in airborne pathogen detection using optical and electrochemical biosensors

The world is currently facing an adverse condition due to the pandemic of airborne pathogen SARS-CoV-2. Prevention is better than cure; thus, the rapid detection of airborne pathogens is necessary because it can reduce outbreaks and save many lives. Considering the immense role of diverse detection techniques for airborne pathogens, proper summarization of these techniques would be beneficial for humans. Hence, this review explores and summarizes emerging techniques, such as optical and electrochemical biosensors used for detecting airborne bacteria (Bacillus anthracis, Mycobacterium tuberculosis, Staphylococcus aureus, and Streptococcus pneumoniae) and viruses (Influenza A, Avian influenza, Norovirus, and SARS-CoV-2). Significantly, the first section briefly focuses on various diagnostic modalities applied toward airborne pathogen detection. Next, the fabricated optical biosensors using various transducer materials involved in colorimetric and fluorescence strategies for infectious pathogen detection are extensively discussed. The third section is well documented based on electrochemical biosensors for airborne pathogen detection by differential pulse voltammetry, cyclic voltammetry, square-wave voltammetry, amperometry, and impedance spectroscopy. The unique pros and cons of these modalities and their future perspectives are addressed in the fourth and fifth sections. Overall, this review inspected 171 research articles published in the last decade and persuaded the importance of optical and electrochemical biosensors for airborne pathogen detection.

A novel colorimetric biosensor for detecting SARS-CoV-2 by utilizing the interaction between nucleocapsid antibody and spike proteins

SARS-CoV-2 is a pandemic coronavirus that causes severe respiratory disease (COVID-19) in humans and is responsible for millions of deaths around the world since early 2020. The virus affects the human respiratory cells through its spike (S) proteins located at the outer shell. To monitor the rapid spreading of SARS-CoV-2 and to reduce the deaths from the COVID-19, early detection of SARS-CoV-2 is of utmost necessity. This report describes a flexible colorimetric biosensor capable of detecting the S protein of SARS-CoV-2. The colorimetric biosensor is made of polyurethane (PU)-polydiacetylene (PDA) nanofiber composite that was chemically functionalized to create a binding site for the receptor molecule-nucleocapsid antibody (anti-N) protein of SARS-CoV-2. After the anti-N protein conjugation to the functionalized PDA fibers, the PU-PDA-NHS-anti fiber was able to detect the S protein of SARS-CoV-2 at room temperature via a colorimetric transition from blue to red. The PU-PDA nanofiber-based biosensors are flexible and lightweight and do not require a power supply such as a battery when the colorimetric detection to S protein occurs, suggesting a sensing platform of wearable devices and personal protective equipment such as face masks and medical gowns for real-time monitoring of virus contraction and contamination. The wearable biosensors could significantly power mass surveillance technologies to fight against the COVID-19 pandemic.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s44164-022-00022-z.

Dual synergistic response for the electrochemical detection of H1N1 virus and viral proteins using high affinity peptide receptors

Identifying alternatives to antibodies as bioreceptors to test samples feasibly is crucial for developing next-generation in vitro diagnostic methods. Here, we aimed to devise an analytical method for detecting H1N1 viral proteins (hemagglutinin [HA] and neuraminidase [NA]) as well as the complete H1N1 virus with high sensitivity and selectivity. By applying biopanning of M13 peptide libraries, high affinity peptides specific for HA or NA were successfully identified. After selection, three different synthetic peptides that incorporated gold-binding motifs were designed and chemically synthesized on the basis of the original sequence identified phage display technique with or without two repeat. Their binding interactions were characterized by enzyme-linked immunosorbent assay (ELISA), square wave voltammetry (SWV), Time of flight-secondary ion mass spectroscopy (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). The binding constants (K_d) of HA BP1, HA BP2 and NA BP1 peptides were found to be 169.72 nM, 70.02 nM and 224.49 nM for HA or NA proteins by electrochemical measurements (SWV). The single use of HA BP2 peptide enabled the detection of either H1N1 viral proteins or the actual H1N1 virus, while NA BP1 peptide exhibited lower binding for real H1N1 virus particles. Moreover, the use of both HA BP1 and BP2 as a divalent capturing reagent improved sensor performance as well as the strength of the electrochemical signal, thereby exhibiting a dual synergistic effect for the electrochemical detection of H1N1 antigens with satisfactory specificity and sensitivity (limit of detection of 1.52 PFU/mL).

Veni, Vidi, Vici: Immobilized Peptide-Based Conjugates as Tools for Capture, Analysis, and Transformation

Analysis of peptide biomarkers of pathological states of the organism is often a serious challenge, due to a very complex composition of the cell and insufficient sensitivity of the current analytical methods (including mass spectrometry). One of the possible ways to overcome this problem is sample enrichment by capturing the selected components using a specific solid support. Another option is increasing the detectability of the desired compound by its selective tagging. Appropriately modified and immobilized peptides can be used for these purposes. In addition, they find application in studying the specificity and activity of proteolytic enzymes. Immobilized heterocyclic peptide conjugates may serve as metal ligands, to form complexes used as catalysts or analytical markers. In this review, we describe various applications of immobilized peptides, including selective capturing of cysteine-containing peptides, tagging of the carbonyl compounds to increase the sensitivity of their detection, enrichment of biological samples in deoxyfructosylated peptides, and fishing out of tyrosine–containing peptides by the formation of azo bond. Moreover, the use of the one-bead-one-compound peptide library for the analysis of substrate specificity and activity of caspases is described. Furthermore, the evolution of immobilization from the solid support used in peptide synthesis to nanocarriers is presented. Taken together, the examples presented here demonstrate immobilized peptides as a multifunctional tool, which can be successfully used to solve multiple analytical problems.

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

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

Rapid diagnosis of COVID-19 via nano-biosensor-implemented biomedical utilization: a systematic review

The novel human coronavirus pandemic is one of the most significant occurrences in human civilization. The rapid proliferation and mutation of Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2) have created an exceedingly challenging situation throughout the world's healthcare systems ranging from underdeveloped countries to super-developed countries. The disease is generally recognized as coronavirus disease 2019 (COVID-19), and it is caused by a new human CoV, which has put mankind in jeopardy. COVID-19 is death-dealing and affects people of all ages, including the elderly and middle-aged people, children, infants, persons with co-morbidities, and immunocompromised patients. Moreover, multiple SARS-CoV-2 variants have evolved as a result of genetic alteration. Some variants cause severe symptoms in patients, while others cause an unusually high infection rate, and yet others cause extremely severe symptoms as well as a high infection rate. Contrasting with a previous epidemic, COVID-19 is more contagious since the spike protein of SARS-CoV-2 demonstrates profuse affection to angiotensin-converting enzyme II (ACE2) that is copiously expressed on the surface of human lung cells. Since the estimation and tracking of viral loads are essential for determining the infection stage and recovery duration, a quick, accurate, easy, cheap, and versatile diagnostic tool is critical for managing COVID-19, as well as for outbreak control. Currently, Reverse Transcription Polymerase Chain Reaction (RT-PCR) testing is the most often utilized approach for COVID-19 diagnosis, while Computed Tomography (CT) scans of the chest are used to assess the disease's stages. However, the RT-PCR method is non-portable, tedious, and laborious, and the latter is not capable of detecting the preliminary stage of infection. In these circumstances, nano-biosensors can play an important role to deliver point-of-care diagnosis for a variety of disorders including a wide variety of viral infections rapidly, economically, precisely, and accurately. New technologies are being developed to overcome the drawbacks of the current methods. Nano-biosensors comprise bioreceptors with electrochemical, optical, or FET-based transduction for the specific detection of biomarkers. Different types of organic–inorganic nanomaterials have been incorporated for designing, fabricating, and improving the performance and analytical ability of sensors by increasing sensitivity, adsorption, and biocompatibility. The particular focus of this review is to carry out a systematic study of the status and perspectives of synthetic routes for nano-biosensors, including their background, composition, fabrication processes, and prospective applications in the diagnosis of COVID-19.

This review will focus on the rapid, selective, accurate, easy, affordable, versatile, and point-of-care diagnosis of COVID-19 using electrochemical, optical, magnetic, aptameric, and plasmonic nano-biosensors.

Self-Assembled Peptide-Labeled Probes for Agglutination-Based Sensing

The use of polydiacetylene (PDA) vesicles in sensing systems are wide-spread due to the interesting optical properties of this stimuli-responsive material; however, agglutination based sensing with PDA have been relatively underutilized. To demonstrate the means for rapidly generating an agglutination probe based on peptide-displaying polydiacetylene vesicles, we implement here the use of a biotin mimetic peptide functionalized to a diacetylene amphiphile for proof-of-concept detection of a multivalent target, specifically streptavidin. Tuning of the vesicle composition revealed a distinct limit in the surface density of peptide amphiphile that could be displayed for this particular peptide sequence. A wide operational detection range was demonstrated, and the result also revealed an effective agglutination response of the PDA-based probe to streptavidin suggesting possible use of future formulations in profiling other multivalent targets.

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.

Application of Nanomaterials as an Advanced Strategy for the Diagnosis, Prevention, and Treatment of Viral Diseases

The coronavirus disease (COVID-19) pandemic poses serious global health concerns with the continued emergence of new variants. The periodic outbreak of novel emerging and re-emerging infectious pathogens has elevated concerns and challenges for the future. To develop mitigation strategies against infectious diseases, nano-based approaches are being increasingly applied in diagnostic systems, prophylactic vaccines, and therapeutics. This review presents the properties of various nanoplatforms and discusses their role in the development of sensors, vectors, delivery agents, intrinsic immunostimulants, and viral inhibitors. Advanced nanomedical applications for infectious diseases have been highlighted. Moreover, physicochemical properties that confer physiological advantages and contribute to the control and inhibition of infectious diseases have been discussed. Safety concerns limit the commercial production and clinical use of these technologies in humans; however, overcoming these limitations may enable the use of nanomaterials to resolve current infection control issues via application of nanomaterials as a platform for the diagnosis, prevention, and treatment of viral diseases.

Rapid detection of influenza A (H1N1) virus by conductive polymer-based nanoparticle via optical response to virus-specific binding

A recurrent pandemic with unpredictable viral nature has implied the need for a rapid diagnostic technology to facilitate timely and appropriate countermeasures against viral infections. In this study, conductive polymer-based nanoparticles have been developed as a tool for rapid diagnosis of influenza A (H1N1) virus. The distinctive property of a conductive polymer that transduces stimulus to respond, enabled immediate optical signal processing for the specific recognition of H1N1 virus. Conductive poly(aniline-co-pyrrole)-encapsulated polymeric vesicles, functionalized with peptides, were fabricated for the specific recognition of H1N1 virus. The low solubility of conductive polymers was successfully improved by employing vesicles consisting of amphiphilic copolymers, facilitating the viral titer-dependent production of the optical response. The optical response of the detection system to the binding event with H1N1, a mechanical stimulation, was extensively analyzed and provided concordant information on viral titers of H1N1 virus in 15 min. The specificity toward the H1N1 virus was experimentally demonstrated via a negative optical response against the control group, H3N2. Therefore, the designed system that transduces the optical response to the target-specific binding can be a rapid tool for the diagnosis of H1N1.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (Table S1 and Figs. S1-S8) is available in the online version of this article at 10.1007/s12274-021-3772-6.

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.

Nanobiosensor-based diagnostic tools in viral infections: Special emphasis on Covid-19

The rapid propagation of novel human coronavirus 2019 and its emergence as a pandemic raising morbidity calls for taking more appropriate measures for rapid improvement of present diagnostic techniques which are time‐consuming, labour‐intensive and non‐portable. In this scenario, biosensors can be considered as a means to outmatch customary techniques and deliver point‐of‐care diagnostics for many diseases in a much better way owing to their speed, cost‐effectiveness, accuracy, sensitivity and selectivity. Besides this, these biosensors have been aptly used to detect a wide spectrum of viruses thus facilitating timely delivery of correct therapy. The present review is an attempt to analyse such different kinds of biosensors that have been implemented for virus detection. Recently, the field of nanotechnology has given a great push to diagnostic techniques by the development of smart and miniaturised nanobiosensors which have enhanced the diagnostic procedure and taken it to a new level. The portability, hardiness and affordability of nanobiosensor make them an apt diagnostic agent for different kinds of viruses including SARS‐CoV‐2. The role of such novel nanobiosensors in the diagnosis of SARS‐CoV‐2 has also been addressed comprehensively in the present review. Along with this, the challenges and future position of developing such ultrasensitive nanobiosensors which should be taken into consideration before declaring these nano‐weapons as the ideal futuristic gold standard of diagnosis has also been accounted for here.

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.

Rapid diagnostics of coronavirus disease 2019 in early stages using nanobiosensors: Challenges and opportunities

The rapid outbreak of coronavirus disease 2019 (COVID-19) around the world is a tragic and shocking event that demonstrates the unpreparedness of humans to develop quick diagnostic platforms for novel infectious diseases. In fact, statistical reports of diagnostic tools show that their accuracy, specificity and sensitivity in the detection of COVID hampered by some challenges that can be eliminated by using nanoparticles (NPs). In this study, we aimed to present an overview on the most important ways to diagnose different kinds of viruses followed by the introduction of nanobiosensors. Afterward, some methods of COVID-19 detection such as imaging, laboratory and kit-based diagnostic tests are surveyed. Furthermore, nucleic acids/protein- and immunoglobulin (Ig)-based nanobiosensors for the COVID-19 detection infection are reviewed. Finally, current challenges and future perspective for the development of diagnostic or monitoring technologies in the control of COVID-19 are discussed to persuade the scientists in advancing their technologies beyond imagination. In conclusion, it can be deduced that as rapid COVID-19 detection infection can play a vital role in disease control and treatment, this review may be of great help for controlling the COVID-19 outbreak by providing some necessary information for the development of portable, accurate, selectable and simple nanobiosensors.

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 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.

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

We have developed a novel oseltamivir derivative (oseltamivir hexylthiol; OHT) that exhibits a higher binding affinity for Tamiflu-resistant virus (Tamiflu resistance) than for the wild-type virus (Tamiflu-susceptible virus; WT) as an antibody. First, OHT-modified gold nanoparticles (OHT-GNPs) are used in a simple colorimetric assay as nanoprobes for the Tamiflu-resistant virus. In the presence of Tamiflu-resistant virus, they show a colorimetric change from deep red to purple because of the OHT-GNP aggregation driven by strong interactions between OHT and neuraminidase (NA) on the surface of the Tamiflu-resistance. Moreover, the color gradually turns purple as the concentration of the Tamiflu-resistant virus increases, allowing the determination of the presence of the virus with the naked eye. Furthermore, an OHT-based lateral flow assay (LFA) has been developed as a rapid and easy detection device for Tamiflu resistance. It shows detection specificity for various virus concentrations of Tamiflu-resistant virus even for the mixture of WT and Tamiflu-resistant viruses, where the limit of detection (LOD) is 5 × 10² ~ 10³ PFU per test (=1 × 10⁴ PFU/mL). It has been confirmed that this platform can provide accurate information on whether a virus exhibits Tamiflu resistance, thus supporting the selection of appropriate treatments using point-of-care (POC) diagnostics.

Recent Trends in Nanomaterials-Based Colorimetric Detection of Pathogenic Bacteria and Viruses

Rapid, sensitive, selective, convenient, and cost-effective pathogen diagnosis is important to prevent further spread of pandemic diseases, minimize social and economic losses, and to facilitate right clinical therapy. Over the past few years, various sensor-based diagnostic systems outperforming conventional pathogenic diagnostic assays have been developed. Among them, colorimetric biosensors detecting target molecules by the naked eye have attracted much attention due to their simplicity, practicality, and cost-effectiveness. Recently, nanomaterials have been adopted as a versatile signal transduction and amplification tool for rapid and sensitive detection of pathogenic bacteria and viruses. Here, recent trends and advances are reviewed in detecting and diagnosing pathogenic bacteria and viruses using colorimetric biosensors employing various nanomaterials. In addition, it is discussed how nanomaterials and bioreceptors can be better integrated together to develop rapid and sensitive colorimetric detection system in the future.

Responsive Polydiacetylene Vesicles for Biosensing Microorganisms

Polydiacetylene (PDA) inserted in films or in vesicles has received increasing attention due to its property to undergo a blue-to-red colorimetric transition along with a change from non-fluorescent to fluorescent upon application of various stimuli. In this review paper, the principle for the detection of various microorganisms (bacteria, directly detected or detected through the emitted toxins or through their DNA, and viruses) and of antibacterial and antiviral peptides based on these responsive PDA vesicles are detailed. The analytical performances obtained, when vesicles are in suspension or immobilized, are given and compared to those of the responsive vesicles mainly based on the vesicle encapsulation method. Many future challenges are then discussed.

Biomolecule-Functionalized Smart Polydiacetylene for Biomedical and Environmental Sensing

Polydiacetylene (PDA) has attracted interest for use as a sensing platform in biomedical, environmental, and chemical engineering applications owing to its capacity for colorimetric and fluorescent transition in response to external stimuli. Many researchers have attempted to develop a tailor-made PDA sensor via conjugation of chemical or biological substances to PDA. Here, we review smart bio-conjugates of PDA with various biomolecules such as carbohydrates, lipids, nucleic acids, and proteins. In addition, materialization and signal amplification strategies to improve handling and sensitivity are described.