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An Intelligent Face Mask Integrated with High Density Conductive Nanowire Array for Directly Exhaled Coronavirus Aerosols Screening

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An Intelligent Face Mask Integrated with High Density Conductive Nanowire Array for Directly Exhaled Coronavirus Aerosols Screening

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Abstract

The current ongoing outbreak of Coronavirus Disease 2019 (COVID-19) has globally affected the lives of more than one hundred million people. RT-PCR based molecular test is recommended as the gold standard method for diagnosing current infections. However, transportation and processing of the clinical sample for detecting virus require an expert operator and long processing time. Testing device enables on-site virus detection could reduce the sample-to-answer time, which plays a central role in containing the pandemic. In this work, we proposed an intelligent face mask, where a flexible immunosensor based on high density conductive nanowire array, a miniaturized impedance circuit, and wireless communication units were embedded. The sub-100 nm size and the gap between the neighbored nanowires facilitate the locking of nanoscale virus particles by the nanowire arrays and greatly improve the detection efficiency. Such a point-of-care (POC) system was demonstrated for coronavirus ‘spike’ protein and whole virus aerosol detection in simulated human breath. Detection of viral concentration as low as 7 pfu/mL from the atomized sample of coronavirus aerosol mimic was achieved in only 5 mins. The POC systems can be readily applied for preliminary screening of coronavirus infections on-site and may help to understand the COVID-19 progression while a patient is under prescribed therapy.

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... In approximately 5 min, viral concentrations as low as 7 pfu/mL were detected from an atomized sample of coronavirus aerosol mimic. The POC systems can be used on-site for basic screening of coronavirus infections and may aid in understanding the course of COVID-19 while a patient is on treatment [90]. A cotton-tipped electrochemical immunosensor for detecting the virus antigen of the SARS-CoV-2 was developed by Eissa et al. [90]. ...
... The POC systems can be used on-site for basic screening of coronavirus infections and may aid in understanding the course of COVID-19 while a patient is on treatment [90]. A cotton-tipped electrochemical immunosensor for detecting the virus antigen of the SARS-CoV-2 was developed by Eissa et al. [90]. Unlike previously described methods, we combined sample collection and detection instruments on a single platform by coating screen-printed electrodes with absorbent cotton padding. ...
... D The setup of the breath simulation experiment. Reproduced with permission from [90] of the virus antigen. Our electrochemical immunosensor is therefore a promising diagnostic instrument to detect the COVID-19 virus directly and quickly and does not require any transfer of samples or pretreatment [91]. ...
Article
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A new epidemic of acute respiratory viral pneumonia was discovered in central China at the end of 2019. The disease was given the name coronavirus disease 2019 (COVID-19), and the virus that caused this disease was known as severe acute respiratory syndrome coronavirus (SARS-CoV-2). So far, diagnostic methods have been focused on (a) human antibody detection, (b) viral antigen detection and (c) viral gene detection, the latter using RT-PCR being the most accurate approach. In this paper, we present a summary of the COVID-19 pandemic, clinical features and epidemiology and pathogenesis. Also, we focus on the recent advances in bioanalytical diagnostic methods based on various techniques for SARS-CoV-2 sensing that have recently been published (2020–2021). Furthermore, we present the mechanisms, advantages and disadvantages of the most common biosensors for COVID-19 detection, which include optical, electrochemical and piezoelectric biosensors as well as wearable and smart nanobiosensors, immunosensors, aptasensors and genosensors.
... The only completed sensor embedded in a face mask for antigen detection was reported by Xue et al. [47]. These authors were the first to develop an immunosensor for the detection of SARS-CoV-2 in droplets by exploiting the surface of the face mask to collect and enrich the respiratory droplets ( Figure 5B). ...
... The developed sensing system was able to detect the S protein and whole virus in simulated human breath, with a detection limit as low as 7 pfu/mL from an atomized sample of a coronavirus aerosol mimic and a measurement time of only 5 min. The only completed sensor embedded in a face mask for antigen detection was reported by Xue et al. [47]. These authors were the first to develop an immunosensor for the detection of SARS-CoV-2 in droplets by exploiting the surface of the face mask to collect and enrich the respiratory droplets ( Figure 5B). ...
... To boost the applicability of saliva-based biosensors, which are less invasive and still highly sensitive, and enable them to reach market, several challenges remain to be addressed, including scalable manufacturing and storage stability, which are primary issues for any successful commercially available point-of-care device. Nasopharyngeal swab Nasopharyngeal swabs were suspended in a universal transport medium [26] Nasopharyngeal swab Nasopharyngeal swabs were suspended in a viral transport medium [32] Nasopharyngeal and throat swabs Nasopharyngeal and throat swabs were mixed in a viral transport medium [33] Nasopharyngeal swab Not reported [34] Nasopharyngeal swab Nasopharyngeal specimens were vortexed in a universal transport medium [35] Saliva No treatment [38] Saliva No treatment [39] Saliva No treatment [40] Saliva No treatment [41] Serum Whole and 5× diluted [43] Droplets No treatment [47] ...
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The recent global events of COVID-19 in 2020 have alerted the world to the risk of viruses and their impacts on human health, including their impacts in the social and economic sectors. Rapid tests are urgently required to enable antigen detection and thus to facilitate rapid and simple evaluations of contagious individuals, with the overriding goal to delimitate spread of the virus among the population. Many efforts have been achieved in recent months through the realization of novel diagnostic tools for rapid, affordable, and accurate analysis, thereby enabling prompt responses to the pandemic infection. This review reports the latest results on electrochemical and optical biosensors realized for the specific detection of SARS-CoV-2 antigens, thus providing an overview of the available diagnostics tested and marketed for SARS-CoV-2 antigens as well as their pros and cons.
... This mask can be instantly utilized for primary diagnosis of coronavirus infections on-site and may help to reduce the time and clinical hassle of detecting the virus. [105] Daniels et al. reported a point-of-care diagnosis of SARS-CoV-2 based on a facemask-centered diagnostic platform, where an electrochemical biosensor analyzes the exhaled breath condensate within the mask. [106] During shortages of standard MAR, cloth masks are a potential alternative. ...
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The unprecedented threat of COVID‐19 and the likelihood of other emerging infectious diseases have accentuated the need for sustainable and effective masks and respirators (MAR). MAR assists in minimizing the risk of infection and controlling the spread of pathogens. However, during the COVID‐19 pandemic, there was a worldwide scarcity of MAR due to unprecedented global demand. There are also notable limitations in commonly used MAR, such as low filtration efficiency, poor fit, non‐reusability, physiological impact, lack of biocompatibility and non‐biodegradability, and inability to kill pathogens. Therefore, there remains an unmet need for a comprehensive study focusing on potential materials and new technologies for MAR. Here we outline a comprehensive overview of the limitations of conventional MAR followed by required potential solutions (such as using nanofibers/graphene base filters/metal‐organic framework as filter media, laser scanning and 3D printing for fit and seal, applying antimicrobial nanomaterials coating on filter media, using reusable and biodegradable materials, developing high‐performing cloth masks, improving hydrophobicity, etc.). The information on potential materials and new technologies of MAR and research evidence outlined here can inform further research and development of high‐performing and sustainable respiratory protection technologies to improve the health and safety of the first responders and the community. The shortcomings of the commonly used conventional facemasks/respirators are pointed out, followed by the outline of potential materials and technologies that can inform the development of more effective technologies for respiratory protection.
... Based on micro/nano technologies and the principle of immunoassay, some POCT platforms are constructed directly for detection of infectious pathogens waiving nucleic acid amplifications. Integrating the detection devices into wearables can expand opportunities for long-term and noninvasive monitoring of infections [158,159]. Xue et al. reported an intelligent wearable face mask integrated with a flexible immunosensor for highly sensitive screening of exhaled coronavirus aerosols. In addition, some other kinds of on-site detection devices, such as the electrochemical biosensors, allow detection of multiple kinds of molecules, including antigens and antibodies with high sensitivity and specificity [160,161,162,163]. ...
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Corona Virus Disease 2019 (COVID-19) has developed into a global pandemic in the last two years, causing significant impacts on our daily life in many countries. Rapid and accurate detection of COVID-19 is of great importance to both treatments and pandemic management. Till now, a variety of point-of-care testing (POCT) approaches devices, including nucleic acid-based test and immunological detection, have been developed and some of them has been rapidly ruled out for clinical diagnosis of COVID-19 due to the requirement of mass testing. In this review, we provide a summary and commentary on the methods and biomedical devices innovated or renovated for the quick and early diagnosis of COVID-19. In particular, some of micro and nano devices with miniaturized structures, showing outstanding analytical performances such as ultra-sensitivity, rapidness, accuracy and low cost, are discussed in this paper. We also provide our insights on the further implementation of biomedical devices using advanced micro and nano technologies to meet the demand of point-of-care diagnosis and home testing to facilitate pandemic management. In general, our paper provides a comprehensive overview of the latest advances on the POCT device for diagnosis of COVID-19, which may provide insightful knowledge for researcher to further develop novel diagnostic technologies for rapid and on-site detection of pathogens including SARS-CoV-2.
... With the use of nanowires, there are advantages such as ultra-low power consumption; small size; rapid response; high sensitivity; and being non-hazardous, easy to use, non-invasive, stored well and not that costly. For the management and detection of respiratory infections, a sensitive and affordable POC tool was provided as a combination of nanoscale sensors and a face mask [157]. ...
Article
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Selective, sensitive and affordable techniques to detect disease and underlying health issues have been developed recently. Biosensors as nanoanalytical tools have taken a front seat in this context. Nanotechnology-enabled progress in the health sector has aided in disease and pandemic management at a very early stage efficiently. This report reflects the state-of-the-art of nanobiosensor-based virus detection technology in terms of their detection methods, targets, limits of detection, range, sensitivity, assay time, etc. The article effectively summarizes the challenges with traditional technologies and newly emerging biosensors, including the nanotechnology-based detection kit for COVID-19; optically enhanced technology; and electrochemical, smart and wearable enabled nanobiosensors. The less explored but crucial piezoelectric nanobiosensor and the reverse transcription-loop mediated isothermal amplification (RT-LAMP)-based biosensor are also discussed here. The article could be of significance to researchers and doctors dedicated to developing potent, versatile biosensors for the rapid identification of COVID-19. This kind of report is needed for selecting suitable treatments and to avert epidemics.
... Especially, the constitution and concentration of volatiles in the exhaled breath differ markedly between healthy people and those with specific kinds and stages of diseases [14][15][16]. Therefore, abnormal changes in the composition and concentration of gas coming from the human body indicate a potential disease [17,18]. As long as the disease-specific gas is found, the disease can be diagnosed by monitoring gas variations. ...
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With the progress of intelligent and digital healthcare, wearable sensors are attracting considerable attention due to their portable and real-time monitoring capabilities. Among them, wearable gas sensors, which can detect both gas markers from the human body and hazardous gas from the environment, are particularly gaining tremendous interest. To ensure the gas sensors can be worn and carried easily, most of them were fabricated on flexible substrates. However, some traditional fabrication techniques of gas sensors such as lithography and chemical vapor deposited, are incompatible with most flexible substrates due to the flexible substrates cannot endure the harsh fabricated conditions, for instance, high temperature. Therefore, fabrication techniques for wearable gas sensors are extremely limited, thus a summary of which is necessary. Here, recent advances in the fabrication techniques of wearable gas sensors are presented. Fabrication techniques included coating techniques, printing techniques, spinning techniques, and transferring techniques are discussed in detail, respectively.
... With these AI-assisted technologies, scientists have invented state-of-the-art technology-embedded products and systems for dentistry. These include (1) smart goggles with LED illumination and eyesight corrections resulting in reduced eye strain, improved productivity, less time taken for patient observation (Chandrasekaran et al., 2021), (2) smart facemasks with inbuilt viral load detection facility enabling identification of COVID-19 infectious people visiting clinics (Hyysalo et al., 2021;Xue et al., 2021), (3) intelligent robotics with improved services for telemedicine, cleaning, assistance rendered in dental equipment mobility, data recording, and medicine dispatching (Khan et al., 2020), (4) 3-D printing for improved production of physical models for implants, the manufacture of dental, craniomaxillofacial, and orthopedic implants, and the fabrication of copings and frameworks for an implant and dental restorations (Jain et al., 2016), (5) intraoral cameras fitted with LIDAR sensors with improved data acquisition rate, accuracy, signal to noise ratio, and dynamic depth resolution in imaging systems, and automatic Lux level adjustments (Sandborn, 2017), (6) Convolutional Neural Networkassisted software enabling the preliminary and cost-effective screening of dental caries (Zhang et al., 2020), (7) big data handling repositories for storing patient's information and data for easy clinical decision-making, monitoring the progression of oral diseases, and pattern recognition (Nanayakkara et al., 2019) and (8) Intelligent systems for the diagnosis for oral medicines (Ehtesham et al., 2019). ...
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Zika virus (ZIKV) infection is an emerging pandemic threat to humans that can be fatal in newborns. Advances in digital health systems and nanoparticles can facilitate the development of sensitive and portable detection technologies for timely management of emerging viral infections. Here we report a nanomotor-based bead-motion cellphone (NBC) system for the immunological detection of ZIKV. The presence of virus in a testing sample results in the accumulation of platinum (Pt)-nanomotors on the surface of beads, causing their motion in H2O2 solution. Then the virus concentration is detected in correlation with the change in beads motion. The developed NBC system was capable of detecting ZIKV in samples with virus concentrations as low as 1 particle/μL. The NBC system allowed a highly specific detection of ZIKV in the presence of the closely related dengue virus and other neurotropic viruses, such as herpes simplex virus type 1 and human cytomegalovirus. The NBC platform technology has the potential to be used in the development of point-of-care diagnostics for pathogen detection and disease management in developed and developing countries.
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A wearable skin hydration sensor in the form of a capacitor is demonstrated based on skin impedance measurement. The capacitor consists of two interdigitated or parallel electrodes that are made of silver nanowires (AgNWs) in a polydimethylsiloxane (PDMS) matrix. The flexible and stretchable nature of the AgNW/PDMS electrode allows conformal contact to the skin. The hydration sensor is insensitive to the external humidity change and is calibrated against a commercial skin hydration system on an artificial skin over a wide hydration range. The hydration sensor is packaged into a flexible wristband, together with a network analyzer chip, a button cell battery, and an ultralow power microprocessor with Bluetooth. In addition, a chest patch consisting of a strain sensor, three electrocardiography electrodes, and a skin hydration sensor is developed for multimodal sensing. The wearable wristband and chest patch may be used for low-cost, wireless, and continuous monitoring of skin hydration and other health parameters.
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Viral infectious diseases can erupt unpredictably, spread rapidly, and ravage mass populations. Although established methods, such as polymerase chain reaction, virus isolation, and next-generation sequencing have been used to detect viruses, field samples with low virus count pose major challenges in virus surveillance and discovery. We report a unique carbon nanotube size-tunable enrichment microdevice (CNT-STEM) that efficiently enriches and concentrates viruses collected from field samples. The channel sidewall in the microdevice was made by growing arrays of vertically aligned nitrogen-doped multiwalled CNTs, where the intertubular distance between CNTs could be engineered in the range of 17 to 325 nm to accurately match the size of different viruses. The CNT-STEM significantly improves detection limits and virus isolation rates by at least 100 times. Using this device, we successfully identified an emerging avian influenza virus strain [A/duck/PA/02099/2012(H11N9)] and a novel virus strain (IBDV/turkey/PA/00924/14). Our unique method demonstrates the early detection of emerging viruses and the discovery of new viruses directly from field samples, thus creating a universal platform for effectively remediating viral infectious diseases.
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Suspensions of transmissible gastroenteritis virus (TGEV), a porcine coronavirus, were nebulized at rates of 0.1–0.2ml/min into moving air using a Collison nebulizer or a plastic medical nebulizer operating at pressures ranging from 7 to 15psi. The airborne viruses were collected on heating, ventilating, and air conditioning (HVAC) filters in an experimental apparatus and also sampled upstream of these test filters using AGI-30 and BioSampler impinger samplers. To study the effects of relative humidity (RH) on TGEV collection by the filters and samplers, the virus was nebulized into air at 30, 50, 70, and 90% RH. There were no significant changes in virus titer in the nebulizer suspension before and after nebulization for either nebulizer at any of the pressures utilized. Aerosolization efficiency – the ratio of viable virus sampled with impingers to the quantity of viable virus nebulized – decreased with increasing humidity. BioSamplers detected more airborne virus than AGI-30 samplers at all RH levels. This difference was statistically significant at 30 and 50% RH. Nebulizer type and pressure did not significantly affect the viability of the airborne virus. Virus recovery from test filters relative to the concentration of virus in the nebulizer suspension was less than 10%. The most and the least virus were recovered from filter media at 30% and 90% RH, respectively. The results suggest that TGEV, and perhaps other coronaviruses, remain viable longer in an airborne state and are sampled more effectively at low RH than at high humidity.
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Avian influenza virus (AIV) subtype H5N1 was first discovered in the 1990 s and since then its emergence has become a likely source of a global pandemic and economic loss. Currently accepted gold standard methods of influenza detection, viral culture and rRT-PCR, are time consuming, expensive and require special training and laboratory facilities. A rapid, sensitive, and specific screening method is needed for in-field or bedside testing of AI virus to effectively implement quarantines and medications. Therefore, the objective of this study was to improve the specificity and sensitivity of an impedance biosensor that has been developed for the screening of AIV H5. Three major components of the developed biosensor are immunomagnetic nanoparticles for the separation of AI virus, a microfluidic chip for sample control and an interdigitated microelectrode for impedance measurement. In this study polyclonal antibody against N1 subtype was immobilized on the surface of the microelectrode to specifically bind AIV H5N1 to generate more specific impedance signal and chicken red blood cells (RBC) were used as biolabels to attach to AIV H5N1 captured on the microelectrode to amplify impedance signal. RBC amplification was shown to increase the impedance signal change by more than 100% compared to the protocol without RBC biolabels, and was necessary for forming a linear calibration curve for the biosensor. The use of a second antibody against N1 offered much greater specificity and reliability than the previous biosensor protocol. The biosensor was able to detect AIV H5N1 at concentrations down to 10(3) EID(50)ml(-1) in less than 2h.
Article
Airborne pathogens causing infectious diseases are often highly transmittable between humans. Therefore, an airborne pathogen-monitoring system capable of on-site detection and identification would aid tremendously in preventing and controlling the early stages of pathogen spread. Here, we describe an integrated sampling/monitoring platform for on-site and real-time detection of airborne viruses. We used MS2 bacteriophage and avian influenza virus (AIV) H1N1 to evaluate bioaerosol sampling and detection performance of the platform. Our results show that, within 20 min, aerosolized viruses can be detected using the signal of near-infrared (NIR)-to-NIR nanoprobes. The pretreatment of the sampling pad improved the transfer efficiency of MS2 viruses to the detection zone, compared to an untreated pad. Our platform could detect concentrations as low as 104.294 50% egg infectious dose (EID50)/m3 AIVs collected from a cloacal swab sample (104.838 EID50/mL). These results indicate that our sampling/monitoring platform could be applied for the early detection of biological hazards in various fields.
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To manage the COVID-19 pandemic, development of rapid, selective, sensitive diagnostic systems for early stage β-coronavirus severe acute respiratory syndrome (SARS-CoV-2) virus protein detection is emerging as a necessary response to generate the bioinformatics needed for efficient smart diagnostics, optimization of therapy, and investigation of therapies of higher efficacy. The urgent need for such diagnostic systems is recommended by experts in order to achieve the mass and targeted SARS-CoV-2 detection required to manage the COVID-19 pandemic through the understanding of infection progression and timely therapy decisions. To achieve these tasks, there is a scope for developing smart sensors to rapidly and selectively detect SARS-CoV-2 protein at the picomolar level. COVID-19 infection, due to human-to-human transmission, demands diagnostics at the point-of-care (POC) without the need of experienced labor and sophisticated laboratories. Keeping the above-mentioned considerations, we propose to explore the compartmentalization approach by designing and developing nanoenabled miniaturized electrochemical biosensors to detect SARS-CoV-2 virus at the site of the epidemic as the best way to manage the pandemic. Such COVID-19 diagnostics approach based on a POC sensing technology can be interfaced with the Internet of things and artificial intelligence (AI) techniques (such as machine learning and deep learning for diagnostics) for investigating useful informatics via data storage, sharing, and analytics. Keeping COVID-19 management related challenges and aspects under consideration, our work in this review presents a collective approach involving electrochemical SARS-CoV-2 biosensing supported by AI to generate the bioinformatics needed for early stage COVID-19 diagnosis, correlation of viral load with pathogenesis, understanding of pandemic progression, therapy optimization, POC diagnostics, and diseases management in a personalized manner.
Article
From 2002 to 2019, three deadly human coronaviruses (hCoVs), severe acute respiratory syndrome coronavirus (SARS‐CoV), Middle Eastern respiratory syndrome coronavirus (MERS‐CoV) and severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) emerged to produce outbreaks of SARS, MERS and coronavirus disease 2019 (Covid‐19), respectively. All three hCoVs are members of the Betacoronavirus genus in the subfamily Orthocoronavirinae and share many similarities in virology and epidemiology. However, the pattern and scale of Covid‐19 global spread is similar to 2009 pandemic H1N1 influenza (H1N1pdm09), rather than SARS or MERS. Covid‐19 exhibits high viral shedding in the upper respiratory tract at an early stage of infection, and has a high proportion of transmission competent individuals that are pre‐symptomatic, asymptomatic and mildly symptomatic, characteristics seen in H1N1pdm09 but not in SARS or MERS. These two traits of Covid‐19 and H1N1pdm09 result in reduced efficiency in identification of transmission sources by symptomatic screening and play important roles in their ability to spread unchecked to cause pandemics. To overcome these attributes of Covid‐19 in community transmission, identifying the transmission source by testing for virus shedding and interrupting chains of transmission by social distancing and public masking are required.
Article
Sensitive virus detection method applicable for an early stage increases the probability of survival. Here, we develop a simple and rapid detection strategy for the detection of Hepatitis E virus (HEV) by an electrocatalytic water oxidation reaction (WOR) using Platinum (Pt)-incorporated cobalt (Co)-based zeolite imidazole framework (ZIF-67). The surface cavity of ZIF-67 enables the rich-loading of Pt NPs, and subsequent calcination etches the cavity, promoting the electrocatalytic activity of Pt-Co3O4 HCs. The Pt-Co3O4 HCs shows an excellent behavior for WOR due to the synergistic interaction of Pt and Co3O4, evaluated by voltammetry and chronoamperometry. The synthesized Pt-Co3O4 HCs are conjugated with Anti-HEV antibody (Ab@Pt-Co3O4 HCs), the electrocatalytic activity of Ab@Pt-Co3O4 HCs is combined with antibody-conjugated magnetic nanoparticles (MNPs) for HEV detection by magneto-and-nanocomposite sandwich immunoassay. The sensor is challenged to detect the HEV in spiked serum samples and HEV G7 genotypes collected from the cell culture supernatant, reaching a low limit of detection down to 61 RNA copies mL-1. This work establishes a free-indicator one-step approach with the controlled design of Pt-Co3O4 HCs, which presents an effective WOR technique for virus detection in neutral pH solution, extending the electrocatalytic study in the future integrated biosensing systems.
Article
In March of 2020, the World Health Organization declared a pandemic of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The pandemic led to a shortage of N95-grade filtering facepiece respirators (FFRs), especially surgical-grade N95 FFRs for protection of healthcare professionals against airborne transmission of SARS-CoV-2. We and others have previously reported promising decontamination methods that may be applied to the recycling and reuse of FFRs. In this study we tested disinfection of three viruses including SARS-CoV-2, dried on a piece of meltblown fabric, the principal component responsible for filtering of fine particles in N95-level FFRs, under a range of temperatures (60-95˚C) at ambient or 100% relative humidity (RH) in conjunction with filtration efficiency testing. We found that heat treatments of 75˚C for 30 min or 85˚C for 20 min at 100% RH resulted in efficient decontamination from the fabric of SARS-CoV-2, human coronavirus NL63 (HCoV-NL63), and another enveloped RNA virus, chikungunya virus vaccine strain 181/25 (CHIKV-181/25), without lowering the meltblown fabric's filtration efficiency.
Article
Since its emergence late in 2019, the COVID-19 pandemic continues to exude major public health and socio-economic burden globally. South Africa is currently the epicenter for the pandemic in Africa. This study is based on the use of a compartmental model to analyse the transmission dynamics of the disease in South Africa. A notable feature of the model is the incorporation of the role of environmental contamination by COVID-infected individuals. The model, which is fitted and parametrized using cumulative mortality data from South Africa, is used to assess the impact of various control and mitigation strategies. Rigorous analysis of the model reveals that its associated continuum of disease-free equilibria is globally-asymptotically stable whenever the control reproduction number is less than unity. The epidemiological implication of this result is that the disease will eventually die out, particularly if control measures are implemented early and for a sustainable period of time. For instance, numerical simulations suggest that if the lockdown measures in South Africa were implemented a week later than the 26 March, 2020 date it was implemented, this will result in the extension of the predicted peak time of the pandemic, and causing about 10% more cumulative deaths. In addition to illustrating the effectiveness of self-isolation in reducing the number of cases, our study emphasizes the importance of surveillance testing and contact tracing of the contacts and confirmed cases in curtailing the pandemic in South Africa.
Article
The novel coronavirus (COVID-19), average size 100nm (nano-aerosol), can be aerosolized by coughing, sneezing, and breathing from infected persons. The airborne carrier for the COVID-19 can be tiny droplets and particulates from infected person, fine suspended mists (humidity) in air, or ambient aerosols in air. To-date, unfortunately there are no test standards for nano-aerosols. A goal in our study is to develop a filter with 90% capture on 100nm COVID-19 with pressure drop of less than 30Pa (3.1mm water). There are two challenges. First, this airborne bio-nanoaerosol (combined virus and carrier) is amorphous. Second, unlike standard laboratory tests on NaCl crystals and test oil (DOP) droplets, these polydispersed aerosols are of different sizes and can interact among themselves before simultaneously challenging the filter, e.g. facemask. For the first time, we have studied these two effects using ambient aerosols (simulating the bio-nanoaerosols of coronavirus plus carrier of different shapes and sizes) to challenge electrostatically charged multilayer nanofiber filters. This problem is fundamentally complicated due to mechanical and electrostatic interactions among aerosols of different sizes with induced charges of different magnitudes. The test filters were arranged in 2, 4, and 6 multiple-modules stack-up with each module having 0.765 g/m² of charged PVDF nanofibers (mean diameter 525±191nm). This configuration minimized electrical interference among neighboring charged nanofibers and reduced flow resistance in the filter. For ambient aerosol size greater than 80nm (applicable to the smallest COVID-19), the electrostatic effect contributes 100 - 180% more efficiency to the existing mechanical efficiency (due to diffusion and interception) depending on the number of modules in the filter. By stacking-up modules to increase fiber basis weight in the filter, a 6-layer charged nanofiber filter achieved 88%, 88% and 96% filtration efficiency for, respectively, 55nm, 100nm and 300nm ambient aerosol. This is very close to attaining our set goal of 90%-efficiency on the 100nm ambient aerosol. The pressure drop for the 6-layer nanofiber filter was only 26Pa (2.65 mm water column) which was below our goal of 30Pa (3.1mm water). For the test multi-module filters, a high ‘quality factor’ (efficiency-to-pressure-drop ratio) of about 0.1 to 0.13Pa⁻¹ can be consistently maintained, which was far better than conventional filters. Using the same PVDF 6-layer charged nanofiber filter, laboratory tests results using monodispersed NaCl aerosols of 50, 100, and 300nm yielded filtration efficiency, respectively, 92%, 94% and 98% (qualified for N98 standard) with same pressure drop of 26Pa. The 2-6% discrepancy in efficiency for the NaCl aerosols was primarily attributed to the absence of interaction among aerosols of different sizes. This discrepancy can be further reduced with increase number of modules in the filter and for larger 300nm aerosol. The 6-layer charged nanofiber filter was qualified as a N98 respirator (98% efficiency for 300nm NaCl aerosols) but with pressure drop of only 2.65-mm water which was 1/10 below conventional N95 with 25-mm (exhaling) to 35-mm (inhaling) water column, and also far below that of conventional N98! The 6-layer charged PVDF nanofiber filter provides good personal protection against airborne COVID-19 virus and nano-aerosols from pollution based on the N98 standard, yet it is at least 10X more breathable than a conventional N98 respirator.
Article
Development of wearable devices for continuous respiration monitoring is of great importance for evaluating human health. Here, we propose a new strategy to achieve rapid respiration response by confining conductive polymers into 1D nanowires which facilitates the water molecules absorption/desorption and maximizes the sensor response to moisture. The nanowires arrays were fabricated through a low-cost nanoscale printing approach on flexible substrate. The nanoscale humidity sensor shows a high sensitivity (5.46%) and ultrafast response (0.63 s) when changing humidity between 0 and 13% and can tolerate 1000 repetitions of bending to a curvature radius of 10 mm without influencing its performance. Benefited by its fast response and low power assumption, the humidity sensor was demonstrated to monitor human respiration in real time. Different respiration patterns including normal, fast and deep respiration can be distinguished accurately.
Article
Viruses pose serious infectious diseases threats to human and animals. To significantly decrease the mortality and morbidity caused by virus infection, there is an urgent need of sensitive and rapid point-of-care platforms for virus detection, especially in low-resource settings. Herein, we developed a smartphone-based point-of-care platform for highly sensitive and selective detecting of avian influenza virus based on nanomaterial-enabled colorimetric detection. The 3D nano-structures, which serve as scaffold for antibody conjugation to capture avian influenza virus, are made on PDMS herringbone structures with a ZnO nanorods template. After virus capture, on-chip gold nanoparticles-based colorimetric reaction allows virus detection by naked eyes with a detection limit of 2.7×104 EID50/ml, which is one order of magnitude better than that of conventional fluorescence-based ELISA. Furthermore, a smartphone imaging system with data processing capability further improves the detection limit, reaching down to 8 ×103 EID50/ml. The entire virus capture and detection process can be completed in 1.5 hours. We envision that this point-of-care microfluidic system integrated with smartphone imaging and colorimetric detection would provide a fast, cheap, sensitive and user-friendly platform for virus detection in low-resource settings.
Article
The deposition of micro- and nanolitre volumes is crucial in sessile droplet microfluidic systems. Several techniques exist for the fabrication of surfaces with patterned wettabilities; however, many of these fabrication techniques are time-consuming and complex. Here, we present a device that allows for deposition of multiple droplets within seconds followed by directed evaporative preconcentration. Hydrophobic-coated glass substrates are fashioned with hydrophilic surface energy traps (SETs) using picosecond laser micromachining. SETs can capture nanolitre volumed droplets of both aqueous and organic liquids through discontinuous dewetting. Modification of the machined hydrophilic shape yields a passive mechanism that preconcentrates analyte through evaporation. Studies and optimizations of SET parameters/dimensions (laser power, laser passes, ring/patch diameter) and their effect on patch wettability and degree of preconcentration are presented. As a demonstration, the optimized platform was used to improve the colourimetric detection of cadmium-containing aqueous samples. The optimized SET design demonstrated an 18-fold increase in colourimetric sensitivity compared to conventional milled SETs, suggesting the design would be well-suited for trace analysis. The evaporative preconcentration was also applied to MALDI-IMS analysis of peptides where it resulted in improved uniformity of deposited analyte and decreased analysis times. The rapid droplet deposition and directed evaporative approach can be tailored to provide different concentration factors and is compatible with a wide variety of detection schemes.
Article
The demand for fast and ultratrace biomarkers detection is increasing in bioanalytical chemistry. In this work, highly ordered nanowires array and sensor integration are achieved with nanoscale printing approach. Negatively charged poly(3,4‐ethylenedioxythiophene)–poly(styrenesulfonate) doped with positively charged PEGylated biotin‐derivatized polyelectrolytes results a direct biofunctionalization on the nanowire surface without multiple postmodification steps. It provides homogeneous dispersed biofunctional sites and nonfouling surface on the nanowires. The ordered nanowires array enables the immunosensor to detect biotargets quickly and ultrasensitively. The nanowires impedimetric immunosensor is demonstrated for specific biomarkers detection and achieved a minimum responsive concentration as low as 10 pg mL−1 for protein biomarker and 10 CFU mL−1 for pathogen. A kind of biotin functionalization ink is achieved by doping with PEGylated biotin‐derivatized polyelectrolytes which enables a direct biofunctionalization on the nanowire surface. Then an immunosensor based on highly ordered nanowires array is fabricated by nanoscale printing approach. This sensor can be a general platform for different materials and various bioanalytical applications with ultrahigh sensitivity, trace detection, and fast response.
Article
Flexible ammonia (NH3) sensors based on one-dimensional nanostructures have attracted great attention due to their high flexibility and low-power consumption. However, it is still challenging to reliably and cost-effectively fabricate ordered nanostructure-based flexible sensors. Herein, a smartphone-enabled fully integrated system based on a flexible nanowire sensor was developed for real-time NH3 monitoring. Highly aligned, sub-100 nm nanowires on a flexible substrate fabricated by facile and low-cost soft lithography were used as sensitive elements to produce impedance response. The detection signals were sent to a smartphone and displayed on the screen in real time. This nanowire-based sensor exhibited robust flexibility and mechanical durability. Moreover, the integrated NH3 sensing system presented enhanced performance with a detection limit of 100 ppb, as well as high selectivity and reproducibility. The power consumption of the flexible nanowire sensor was as low as 3 μW. By using this system, measurements were carried out to obtain reliable information about the spoilage of foods. This smartphone-enabled integrated system based on a flexible nanowire sensor provided a portable and efficient way to detect NH3 in daily life.
Article
A mathematical model is developed for the impedance response of immobilized glucose oxidase electrochemical biosensors. The coupling between the homogeneous reactions and heterogeneous reactions considered in the model included anomerization between α-d-glucose and β-d-glucose and four reversible enzymatic catalytic reactions transforming β-d-glucose and oxygen into gluconic acid and hydrogen peroxide. The electroactive hydrogen peroxide was considered to be reversibly oxidized or reduced at the electrode. The electrochemical system was modeled mathematically as a one-dimensional boundary-value problem and solved by use of Newman's BAND algorithm. The corresponding impedance was calculated for each specified frequency. The resulted limiting current, reaction profiles, and impedance response provide insights into the influence of system parameters such as interstitial glucose concentration and enzymatic rate constants. This model has a potential application in predicting sensor design and diagnosing sensor failure mechanisms.
Article
The extraordinary electronic and photonic features render black phosphorus (BP) an important material for the development of novel electronics and optoelectronics. Despite the recent progress in the preparation of few-layered BP flakes, scalable synthesis of large-size, pristine BP flakes represents one of the main challenges. Here we demonstrate an electrochemical delamination strategy, based on the intercalation of diverse cations in non-aqueous electrolytes, to peel off bulk BP crystals into few-layer, defect-free flakes. The interplay between tetra-n-butyl-ammonium cations and bisulfate anions promotes high exfoliation yield up to 78 % and large BP flakes up to 20.6 µm. Bottom-gate and bottom-contact field effect transistors based on few-layered single BP flakes exhibit high hole mobility of 252±18 cm2 V-1 s-1 and remarkable on/off ratio of (1.2±0.15)×105 at 143 K under vacuum. This efficient and scalable delamination method holds great promise in the future development of BP-based composites and optoelectronic devices.
Book
Principles of Bacterial Detection: Biosensors, Recognition Receptors and Microsystems presents a significant and up-to-date review of various integrated approaches for bacterial detection. Distinguished engineers and scientists from key institutions worldwide have contributed chapters that provide a deep analysis of their particular subject; at the same time, each topic is framed within the context of this integrated approach. This work is a comprehensive approach to bacterial detection requiring a thorough knowledge of the subject and an effective integration of other disciplines in order to appropriately convey the state-of-the-art fundamentals and applications of the involved disciplines. The book consists of four parts: The first part provides an introduction to pathogenic bacteria and sampling techniques and an overview of the rapid microbiological methods. The second part describes the different transducers used for the detection of bacteria. It covers the theory behind each technique and provides a state-of-the-art review of all the new technologies used for the detection of bacteria in detail. Strategies and future prospects are suggested at the end of each chapter for developing future technologies to achieve a better sensitivity and swifter detection of bacteria. The third part gives an account of the different recognition receptors used in the various methods for the detection of bacteria. It describes in detail the use of immunoassays, nucleic acids, oligonucleotide microarrays, carbohydrates, aptamers, protein microarrays, bacteriophages, phage displays and molecular imprinted polymers as recognition elements. The fourth part covers the microsystems used for detection/identification and bacterial manipulation such as bacteria lysis and PCR in microfluidics, dielectrophoresis, ultrasonic manipulation techniques and mass spectrometry techniques. Students and researchers who need a solid foundation or reference and practitioners interested in discovering more about the state-of-the-art methods of bacterial detection will find this book invaluable. This book is directed at academics and undergraduate and postgraduate students who work in areas related to bacterial detection. It may also serve as an important reference for professionals working in different fields, including biomedical science, physical science, microsystems engineering, nanotechnology, veterinary science, food quality assurance, bioterrorism and security as well as health surveillance.
Article
Exhaled breath collection has long been recognized as requiring the least invasive methods of the biological fluids and so is preferred for environmental and public health studies. This commentary describes how breath biomonitoring is generally preferred for certain logistical reasons in public health and occupational biomonitoring. Three different fractions of exhaled breath are considered: gas-phase, liquid condensate, and aerosols. The focus is on the exhaled breath aerosol (EBA) fraction and the development of targeted sampling and analysis methods. Specifically, the biological constituents found in dried aerosols are wiped or extracted from respiratory masks or surfaces and subsequently reconstituted in the laboratory for immunochemical or mass spectrometric analysis. This avoids logistical issues in the field regarding whole-breath or condensed liquid sampling and transport and represents the simplest non-invasive medium for biological assessment.
Article
Metal and metal oxides with various nanostructures have been widely studied in non-enzymatic glucose sensing. In this work, we report an efficient catalyst platform, which is made of three-dimensional copper foam (CF) skeleton and copper oxide nanowire arrays (CuONWA), is used to construct glucose sensor. The three-dimensional CuONWA/CF was synthesized via a facile wet-chemical method and subsequent annealing. The CuONWA is evenly covered by CuO nanoflowers. The morphology and composition of the platform were characterized. The nanowire arrays and nanoflowers both enhanced the electrocatalytic performance of the integrated electrode via greatly increasing the surface area of the CF substrate. The electrocatalytic properties of the non-enzymatic glucose sensor were characterized by a series of electrochemical measurements. The sensor exhibits excellent performance, with a linear range of 0.10 μM ∼ 0.50 mM, a sensitivity of 32330 μA mM⁻¹ cm⁻², a low limit of detection of 20 nM (S/N = 3), excellent selectivity, reproducibility, and stability. The sensor was also used for glucose sensing in human serum and Wahaha ice black tea, with relative standard deviations (for n = 6) of 3.15% and 2.43%, respectively.
Article
It is well known, that bioaerosols possess hazard to human health. Bioaerosols could be a cause of various severe diseases. Rapid and precise detection of airborne pathogens in different environments has received considerable attention in recent years. Earlier, we explored a Surface Plasmon Resonance (SPR) protocol in conjunction with our recently developed personal bioaerosol sampler for rapid detection of airborne viruses. The developed label-free approach has been verified under controlled laboratory conditions. The immunosensor based technique was capable of detecting airborne virus in a broad range of concentrations within minutes with high accuracy and specificity. This project is a logical continuation of our previous study where we describe the performance evaluation study of two immunosensor types (differed in surface chemistry) for direct viral detection. Common viral surrogate MS2 bacteriophage was employed as a model organism. The detection limits of developed SPR techniques were found to be 1.12×106 PFU/mL and 2.2×107 PFU/mL for the COOH1 and COOH5 sensor types respectively. Our data confirmed that COOH1 based sensor is more sensitive and robust regarding detection of small viral objects like MS2 phage. The combination of SPR procedure with the bioaerosol sampler allowed detecting virus in the air within less than two minutes. The minimal detectable viral concentration in the air for 1 minute of sampling time was found to be 1.9×107 PFU per litre. Our findings justify that the SPR technique is fully suitable for the bioaerosol monitoring applications. The proposed technology, based on the direct detection of viral aerosols, could be applied to various viral pathogens infectious to animals or humans, and be further realised in a concept of portable real-time bioaerosol monitor.
Article
Antibody mimic proteins (AMPs) are polypeptides that bind to their target analytes with high affinity and specificity, just like conventional antibodies, but are much smaller in size (2-5 nm, less than 10 kDa). In this report, we describe the first application of AMP in the field of nanobiosensors. In(2)O(3) nanowire based biosensors have been configured with an AMP (Fibronectin, Fn) to detect nucleocapsid (N) protein, a biomarker for severe acute respiratory syndrome (SARS). Using these devices, N protein was detected at subnanomolar concentration in the presence of 44 microM bovine serum albumin as a background. Furthermore, the binding constant of the AMP to Fn was determined from the concentration dependence of the response of our biosensors.
American journal of respiratory and critical care medicine
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Reviews in Medical Virology 31, e2171
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