Point-of-Care Diagnostics: Recent Developments in a Connected Age

MeCas12a, a Highly Sensitive and Specific System for COVID-19 Detection

Cas12a-based systems, which detect specific nucleic acids via collateral cleavage of reporter DNA, display huge potentials for rapid diagnosis of infectious diseases. Here, the Manganese-enhanced Cas12a (MeCas12a) system is described, where manganese is used to increase the detection sensitivity up to 13-fold, enabling the detection of target RNAs as low as five copies. MeCas12a is also highly specific, and is able to distinguish between single nucleotide polymorphisms (SNPs) differing by a single nucleotide. MeCas12a can detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in clinical samples and distinguish between SARS-CoV-2 and Middle East respiratory syndrome coronavirus (MERS-CoV) RNA in simulated samples, thus offering an attractive alternative to other methods for the diagnosis of infectious diseases including COVID-19 and MERS.

Enzyme-Assisted Nucleic Acid Detection for Infectious Disease Diagnostics: Moving toward the Point-of-Care

Driven by complex and interconnected factors, including population growth, climate change, and geopolitics, infectious diseases represent one of the greatest healthcare challenges of the 21st century. Diagnostic technologies are the first line of defense in the fight against infectious disease, providing critical information to inform epidemiological models, track diseases, decide treatment choices, and ultimately prevent epidemics. The diagnosis of infectious disease at the genomic level using nucleic acid disease biomarkers has proven to be the most effective approach to date. Such methods rely heavily on enzymes to specifically amplify or detect nucleic acids in complex samples, and significant effort has been exerted to harness the power of enzymes for in vitro nucleic acid diagnostics. Unfortunately, significant challenges limit the potential of enzyme-assisted nucleic acid diagnostics, particularly when translating diagnostic technologies from the lab toward the point-of-use or point-of-care. Herein, we discuss the current state of the field and highlight cross-disciplinary efforts to solve the challenges associated with the successful deployment of this important class of diagnostics at or near the point-of-care.

Biofilm formation and extracellular microvesicles-The way of foodborne pathogens toward resistance

Almost all known foodborne pathogens are able to form biofilms as one of the strategies for survival under harsh living conditions, to ward off the inhibition and the disinfection during food production, transport and storage, as well as during cleaning and sanitation of corresponding facilities. Biofilms are communities where microbial cells live under constant intracellular interaction and communication. Members of the biofilm community are embedded into extracellular matrix that contains polysaccharides, DNA, lipids, proteins, and small molecules that protect microorganisms and enable their intercellular communication under stress conditions. Membrane vesicles (MVs) are produced by both Gram positive and Gram negative bacteria. These lipid membrane-enveloped nanoparticles play an important role in biofilm genesis and in communication between different biofilm members. Furthermore, MVs are involved in other important steps of bacterial life like cell wall modeling, cellular division, and intercellular communication. They also carry toxins and virulence factors, as well as nucleic acids and different metabolites, and play a key role in host infections. After entering host cells, MVs can start many pathologic processes and cause serious harm and cell death. Prevention and inhibition of both biofilm formation and shedding of MVs by foodborne pathogens has a very important role in food production, storage, and food safety in general. Better knowledge of biofilm formation and maintaining, as well as the role of microbial vesicles in this process and in the process of host cells' infection is essential for food safety and prevention of both food spoilage and host infection.

Development of a portable lab-on-a-valve device for making primary diagnoses based on gold-nanoparticle aggregation induced by a switchable linker

We have developed a low-cost, portable lab-on-a-valve (LOV) integrated microdevice for the detection of pathogens in primary-diagnosis settings. This system was designed for field-based pathogen detection based on the aggregation of gold nanoparticles induced by a switchable linker. A three-way valve, which has attracted much attention as a functional mesofluidic platform for pressure-driven flow, has been designed as a universal reaction platform that combines the functions of fluid flow and a reaction chamber. In addition, we obtain rapid and enhanced visual signals by the use of a syringe filter to remove gold nano-aggregates (Au NAs). Using this device, Salmonella Typhimurium down to 101 CFU mL-1 can be visually detected within 30 min by performing a simple operation that requires no complex equipment. This prototype device has great potential for use in the semi-quantitative and qualitative identification of pathogens in on-site primary diagnoses.

A Comparative Assessment of the Nova Stat Profile Prime Plus® Critical Care Analyzer

BACKGROUND

Point-of-care testing (POCT) plays an integral role in the management of acutely ill patients presenting to the emergency department (ED). Due to its rapid turnaround time, POCT has been shown to improve ED workflow, reduce unnecessary admissions and lessen the burden on ED staff. The aim of the study was to compare the accuracy, precision and linearity of the Nova Stat Profile Prime Plus^® (Nova Biomedical, Waltham, MA, USA) to the Radiometer ABL800 FLEX^® (Radiometer South Africa Pty Ltd, Gauteng) and the Abbott i-stat Chem8+^® (Abbott, Princeton, NJ, USA) POCT analyzers.

METHODS

A convenience sample of 150 discarded whole blood specimens was obtained and analyzed. Paired test measurements were conducted for method comparison. Accuracy was measured by pairing individual results from the Nova Stat Profile Prime Plus^® with either the Radiometer ABL800 FLEX^® or the Abbot i-stat Chem8+^® analyzers by calculating the differences.

RESULTS

The with-in run percentage coefficient of variation (%CV) was below 2.4% for pH, carboxyhemoglobin (COHb), deoxyhemoglobin (HHb), total hemoglobin (tHb), total bilirubin (tBil), sodium (Na), potassium (K), chloride (Cl), ionized calcium (iCa), urea, glucose and lactate, and was below 5.1% for all other analytes. The day-to-day %CV was below 1.6% for pH, COHb, HHb, tHb, tBil, Na, K, Cl, iCa, urea, glucose and lactate, and below 6.10% for all other analytes. The correlation coefficient (r) was 0.351 and ranged from 0.897 to 0.998 for all analytes. The mean bias was minimal for all analytes.

CONCLUSION

There was a good correlation between the Nova Stat Profile Prime Plus^® and the Radiometer ABL800 FLEX^®/Abbott i-STAT Chem8+^® POCT analyzers. The Stat Profile Prime Plus^® exhibited good precision both within-run and day-to-day.

Precipitation-based colorimetric multiplex immunoassay in hydrogel particles

Despite a growing demand for more accessible diagnostic technologies, current methods struggle to simultaneously detect multiple analytes with acceptable sensitivity and portability. Colorimetric assays have been widely used due to their simplicity of signal readout, but the lack of multiplexibility has been a perpetual constraint. Meanwhile, particle-based assays offer multiplex detection by assigning an identity code to each analyte, but they often require lab-based equipment unsuitable for portable diagnostics. Here, by merging the two approaches, this paper reports a colorimetric multiplex immunoassay based on hydrogel microparticles that achieves the best of both worlds. The low-cost portable multiplex assay demonstrates sensitivities as high as and dynamic ranges greater than the lab-based enzyme-linked immunosorbent assay (ELISA). These critical advances are made possible by local precipitation and amplification of insoluble colour dyes inside the hydrogel networks. For the first time, enzymatic accumulation of colour dyes in hydrogel particles is reported and the kinetics of colour development is characterized in this work. By taking advantage of the colour signals in the visible spectrum, the hydrogel microparticles were imaged and analysed using low-cost portable devices. The colorimetric multiplex immunoassay was used to successfully detect three target biomarkers of preeclampsia and validated clinically using healthy and patient-derived plasma samples.

A Systematic Review of Smartphone Applications Available for Corona Virus Disease 2019 (COVID19) and the Assessment of their Quality Using the Mobile Application Rating Scale (MARS)

The global impact of COVID-19 pandemic has led to a rapid development and utilization of mobile health applications. These are addressing the unmet needs of healthcare and public health system including contact tracing, health information dissemination, symptom checking and providing tools for training healthcare providers. Here we provide an overview of mobile applications being currently utilized for COVID-19 and their assessment using the Mobile Application Rating Scale. We performed a systematic review of the literature and mobile platforms to assess mobile applications currently utilized for COVID-19, and a quality assessment of these applications using the Mobile Application Rating Scale (MARS) for overall quality, Engagement, Functionality, Aesthetics, and Information. Finally, we provide an overview of the key salient features that should be included in mobile applications being developed for future use. Our search identified 63 apps that are currently being used for COVID-19. Of these, 25 were selected from the Google play store and Apple App store in India, and 19 each from the UK and US. 18 apps were developed for sharing up to date information on COVID-19, and 8 were used for contact tracing while 9 apps showed features of both. On MARS Scale, overall scores ranged from 2.4 to 4.8 with apps scoring high in areas of functionality and lower in Engagement. Future steps should involve developing and testing of mobile applications using assessment tools like the MARS scale and the study of their impact on health behaviours and outcomes.

"Tomorrow Never Dies": Recent Advances in Diagnosis, Treatment, and Prevention Modalities against Coronavirus (COVID-19) amid Controversies

The outbreak of novel coronavirus disease (2019-nCoV or COVID-19) is responsible for severe health emergency throughout the world. The attack of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is found to be responsible for COVID-19. The World Health Organization has declared the ongoing global public health emergency as a pandemic. The whole world fights against this invincible enemy in various capacities to restore economy, lifestyle, and safe life. Enormous amount of scientific research work(s), administrative strategies, and economic measurements are in place to create a successful step against COVID-19. Furthermore, differences in opinion, facts, and implementation methods laid additional layers of complexities in this battle against survival. Thus, a timely overview of the recent, important, and overall inclusive developments against this pandemic is a pressing need for better understanding and dealing with COVID-19. In this review, we have systematically summarized the epidemiological studies, clinical features, biological properties, diagnostic methods, treatment modalities, and preventive measurements related to COVID-19.

Paper/Soluble Polymer Hybrid-Based Lateral Flow Biosensing Platform for High-Performance Point-of-Care Testing

As a global shift continues to occur in high burden diseases toward developing countries, the importance of medical diagnostics based on point-of-care testing (POCT) is rapidly increasing. However, most diagnostic tests that meet clinical standards rely on high-end analyzers in central hospitals. Here, we report the development of a simple, low-cost, mass-producible, highly sensitive/quantitative, automated, and robust paper/soluble polymer hybrid-based lateral flow biosensing platform, paired with a smartphone-based reader, for high-performance POCT. The testing architecture incorporates a polymeric barrier that programs/automates sequential reactions via a polymer dissolving mechanism. The smartphone-based reader with simple opto-mechanical parts offers a stable framework for accurate quantification. Analytical performance of this platform was evaluated by testing human cardiac troponin I (cTnI), a preferred biomarker for the diagnosis of myocardial infarction, in serum/plasma samples. Coupled with catalytic/colorimetric gold-ion amplification, this platform produced results within 20 min with a detection limit of 0.92 pg mL^-1 and a coefficient of variation <10%, which is equivalent to the performance of a high-sensitivity standard analyzer, and operated within acceptable levels stipulated by clinical guidelines. Moreover, cTnI clinical sample tests indicate a high correlation (r = 0.981) with the contemporary analyzers, demonstrating the clinical utility of this platform in high-performance POCT.

Development of Solid-Phase RPA on a Lateral Flow Device for the Detection of Pathogens Related to Sepsis

Population extended life expectancy has significantly increased the risk of septic shock in an ageing population. Sepsis affects roughly 20 million people every year, resulting in over 11 million deaths. The need for faster more accurate diagnostics and better management is therefore paramount in the fight to prevent these avoidable deaths. Here we report the development of a POC device with the ability to identify a broad range of pathogens on a lateral flow platform. Namely Gram-positive and Gram-negative bacteria. The simple to use laboratory device has the potential to be automated, thus enabling an operator to carry out solid-phase lysis and room temperature RPA in situ, providing accurate results in hours rather than days. Results show there is a potential for a fully automated device in which concepts described in this paper can be integrated into a lateral flow device.

Laser-Induced Direct Patterning of Free-standing Ti3C2-MXene Films for Skin Conformal Tattoo Sensors

The discovery of stable two-dimensional (2D) materials has effectuated a rapid evolution of skin conformal sensors for health monitoring via epidermal electronics. Among the newly discovered 2D materials, MXene stands out as a solution-processable 2D material allowing easy fabrication of highly conductive thin films with the potential to realize flexible skin conformal sensors. Here, we present a successful demonstration of a Ti₃C₂-MXene resistor as an extremely sensitive strain sensor in the form an ultrathin skin mountable temporary tattoo. The skin conformability and form factor afforded by the sensor promises inconspicuous and continuous monitoring of vital health parameters of an individual, like the pulse rate, respiration rate, and surface electromyography. The sensor serves as a single conduit for sensing the respiration rate and pulse, dispensing with the need of mounting multiple sensors. Its remarkably high sensitivity with a gauge factor of ∼7400 has been ascribed to development of nanocracks and their propagation through the film upon application of strain. The fast response and highly repeatable sensor follows easy fabrication steps and can be patterned into any shape and size using a laser.

Colorimetric Urinalysis for On-Site Detection of Metabolic Biomarkers

Over the past few decades, colorimetric assays have been developed for cost-effective and rapid on-site urinalysis. Most of these assays were employed for detection of biomarkers such as glucose, uric acid, ions, and albumin that are abundant in urine at micromolar to millimolar levels. In contrast, direct assaying of urinary biomarkers such as glycated proteins, low-molecular-weight reactive oxygen species, and nucleic acids that are present at significantly lower levels (nanomolar to picomolar) remain challenging due to the interferences from the urine sample matrix. State-of-the-art assays for detection of trace amounts of urinary biomarkers typically utilize time-consuming and equipment-dependent sample pretreatment or clean-up protocols prior to assaying, which limits their applicability for on-site analysis. Herein, we report a colorimetric assay for on-site detection of trace amount of generic biomarkers in urine without involving tedious sample pretreatment protocols. The detection strategy is based on monitoring the changes in optical properties of poly(3-(4-methyl-3'-thienyloxy)propyltriethylammonium bromide) upon interacting with an aptamer or a peptide nucleic acid in the presence and absence of target biomarkers of relevance for the diagnosis of metabolic complications and diabetes. As a proof of concept, this study demonstrates facile assaying of advanced glycation end products, 8-hydroxy-2'-deoxyguanosine and hepatitis B virus DNA in urine samples at clinically relevant concentrations, with limits of detection of ∼850 pM, ∼650 pM, and ∼ 1 nM, respectively. These analytes represent three distinct classes of biomarkers: (i) glycated proteins, (ii) low-molecular-weight reactive oxygen species, and (iii) nucleic acids. Hence, the proposed methodology is applicable for rapid detection of generic biomarkers in urine, without involving sophisticated equipment and skilled personnel, thereby enabling on-site urinalysis. At the end of the contribution, we discuss the opportunity to translate the homogeneous assay into a paper-based format.

Reusable optofluidic point-of-care testing platform with lyophilized specific antibody for fluorescence detection of cholylglycine in serum

A reusable optofluidic point-of-care testing platform (OPOCT) was successfully constructed through integrating evanescent wave fluorescence technology into an all-fiber-based optofluidic system. The compact design of the OPOCT allows it to be portable and suitable for on-site sensitive determination of biomarkers in serum without complicated and costly procedures. The sensitivity of 90.9 pM for antibody determination is observed thanks to the high transmission efficiency of excitation light and fluorescence in the OPOCT. The affinity constant between cholylglycine (CG) and anti-CG antibody was quantified using this platform based on the proposed theory. Using the lyophilized fluorescence-labeled specific antibody and reusable fiber optic biosensor, the OPOCT is applied to the one-step sensitive determination of CG in serum, which eliminates the dearth associated with liquid reagent handling, disposable biosensors, and user intervention. A limit of detection of 0.025 μg/mL for CG is obtained, which is far more than adequate for meeting diagnostic requirements. The matrix effect of serum samples on the evanescent wave-based optofluidic biosensor can be effectively reduced by simple dilution of serum samples. The performance of the OPOCT also compared favorably with that of a commercial turbidimetric inhibition immunoassay through analyzing multiple serum samples. This platform is ready to expand to measure any other biomarker by using its specific antibody. The simplicity, sensitivity, cost-effectiveness, and robustness of the OPOCT enable the early diagnosis of disease and making a timely clinical decision. Graphical abstract .

Enhancement of mixing in a viscous, non-volatile droplet using a contact-free vapor-mediated interaction

Mixing at small fluidic length scales is especially challenging in viscous and non-volatile droplets frequently encountered in bio-chemical assays. In situ methods of mixing, which depend on diffusion or evaporation-driven capillary flow, are typically slow and inefficient, while thermal or electro-capillary methods that are either complicated to implement or may cause sample denaturing. This article demonstrates an enhanced mixing timescale in a sessile droplet of glycerol by simply introducing a droplet of ethanol in its near vicinity. The fast evaporation of ethanol introduces molecules in the proximity of the glycerol droplet, which are preferentially adsorbed (more on the side closer to ethanol) creating a gradient of surface tension driving the Marangoni convection in the droplet. We conclusively show that for the given volume of the droplet, the mixing time reduces by ∼10 hours due to the vapour-mediated Marangoni convection. Simple scaling arguments are used to predict the enhancement of the mixing timescale. Experimental evidence obtained from fluorescence imaging is used to quantify mixing and validate the analytical results. This is the first proof of concept of enhanced mixing in a viscous, sessile droplet using the vapour mediation technique.

A systematic review of the smartphone applications available for coronavirus disease 2019 (COVID19) and their assessment using the mobile app rating scale (MARS)

The global impact of COVID-19 pandemic has increased the need to rapidly develop and improve utilization of mobile applications across the healthcare continuum to address rising barriers of access to care due to social distancing challenges and allow continuity in sharing of health information, assist with COVID-19 activities including contact tracing, and providing useful information as needed. Here we provide an overview of mobile applications being currently utilized for COVID-19 related activities. We performed a systematic review of the literature and mobile platforms to assess mobile applications been currently utilized for COVID-19, and quality assessment of these applications using the Mobile Application Rating Scale (MARS) for overall quality, Engagement, Functionality, Aesthetics, and Information. Finally, we provide an overview of the key salient features that should be included in mobile applications being developed for future use. Our search identified 63 apps that are currently being used for COVID-19. Of these, 25 were selected from the Google play store and Apple App store in India, and 19 each from the UK and US. 18 apps were developed for sharing up to date information on COVID-19, and 8 were used for contact tracing while 9 apps showed features of both. On MARS Scale, overall scores ranged from 2.4 to 4.8 with apps scoring high in areas of functionality and lower in Engagement. Future steps should involve developing and testing of mobile applications using assessment tools like the MARS scale and the study of their impact on health behaviors and outcomes.

Circulating tumour cells: a broad perspective

Circulating tumour cells (CTCs) have recently been identified as valuable biomarkers for diagnostic and prognostic evaluations, as well for monitoring therapeutic responses to treatments. CTCs are rare cells which may be present as one CTC surrounded by approximately 1 million white blood cells and 1 billion red blood cells per millilitre of peripheral blood. Despite the various challenges in CTC detection, considerable progress in detection methods have been documented in recent times, particularly for methodologies incorporating nanomaterial-based platforms and/or integrated microfluidics. Herein, we summarize the importance of CTCs as biological markers for tumour detection, highlight their mechanism of cellular invasion and discuss the various challenges associated with CTC research, including vulnerability, heterogeneity, phenotypicity and size differences. In addition, we describe nanomaterial agents used for electrochemistry and surface plasmon resonance applications, which have recently been used to selectively capture cancer cells and amplify signals for CTC detection. The intrinsic properties of nanomaterials have also recently been exploited to achieve photothermal destruction of cancer cells. This review describes recent advancements and future perspectives in the CTC field.

Electrochemical detection of viruses and antibodies: A mini review

Near patient detection of viral infection represents a powerful approach for the control of emerging threats to global health. Moreover, the ability to identify individuals who have contracted the disease and developed antibodies that confer immunity is central to a return to normal daily activities. This review presents some of the recent advances in electrochemical sensors for the detection of viruses and their associated antibody profiles. Given the speed, portability, sensitivity and selectivity achieved using electrochemical detection, these sensor systems hold the promise of transformative change in clinical practice.

Blocking-free and self-contained immunoassay platform for one-step point-of-care testing

This paper reports a quantitative and sensitive one-step point-of-care testing (POCT) chip built on a perfluorinated substrate patterned with polydopamine microspots array. The capture antibody was covalently immobilized on the polydopamine microspots, while the fluorescently labelled detection antibody was physically adsorbed on the perfluorinated surface. The POCT chip allowed one-step sandwich immunoassay and was able to directly detect the analytes from the whole blood without sample preprocessing. By further taking advantages of the strong fluorescence quenching ability of the polydopamine, the blocking-free substrate was able to achieve similar performance in detecting and quantifying the protein biomarkers as the substrate with the blocking treatment. The blocking-free strategy not only made the fabrication of the chip simple and convenient, but also improved the chip's sensitivity for biomarker quantification. Finally, we demonstrated that the self-contained POCT platform maintained the performance for one-step immunoassay even after long-term storage. With the POCT platform, we are one step closer to a sample-in-answer-out diagnostic system.

Paper-based fluorogenic RNA aptamer sensors for label-free detection of small molecules

Sensors based on fluorogenic RNA aptamers have emerged in recent years. These sensors have been used for in vitro and intracellular detection of a broad range of biological and medical targets. However, the potential application of fluorogenic RNA-based sensors for point-of-care testing is still little studied. Here, we report a paper substrate-based portable fluorogenic RNA sensor system. Target detection can be simply performed by rehydration of RNA sensor-embedded filter papers. This affordable sensor system can be used for the selective, sensitive, and rapid detection of different target analytes, such as antibiotics and cellular signaling molecules. We believe that these paper-based fluorogenic RNA sensors show great potential for point-of-care testing of a wide range of targets from small molecules, nucleic acids, proteins, to various pathogens.

Development of Reverse Transcription Loop-Mediated Isothermal Amplification Assays Targeting Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)

The coronavirus disease 2019 (COVID-19) pandemic now has >2,000,000 confirmed cases worldwide. COVID-19 is currently diagnosed using quantitative RT-PCR methods, but the capacity of quantitative RT-PCR methods is limited by their requirement of high-level facilities and instruments. We developed and evaluated reverse transcription loop-mediated isothermal amplification (RT-LAMP) assays to detect genomic RNA of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus of COVID-19. RT-LAMP assays reported in this study can detect as low as 100 copies of SARS-CoV-2 RNA. Cross-reactivity of RT-LAMP assays to other human coronaviruses was not observed. A colorimetric detection method was adapted for this RT-LAMP assay to enable higher throughput.

Development of Reverse Transcription Loop-Mediated Isothermal Amplification Assays Targeting Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)

The coronavirus disease 2019 (COVID-19) pandemic now has >2,000,000 confirmed cases worldwide. COVID-19 is currently diagnosed using quantitative RT-PCR methods, but the capacity of quantitative RT-PCR methods is limited by their requirement of high-level facilities and instruments. We developed and evaluated reverse transcription loop-mediated isothermal amplification (RT-LAMP) assays to detect genomic RNA of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus of COVID-19. RT-LAMP assays reported in this study can detect as low as 100 copies of SARS-CoV-2 RNA. Cross-reactivity of RT-LAMP assays to other human coronaviruses was not observed. A colorimetric detection method was adapted for this RT-LAMP assay to enable higher throughput.

Development of Point-of-Care Biosensors for COVID-19

Coronavirus disease 2019 (COVID-19) outbreak has become a global pandemic. The deleterious effects of coronavirus have prompted the development of diagnostic tools to manage the spread of disease. While conventional technologies such as quantitative real time polymerase chain reaction (qRT-PCR) have been broadly used to detect COVID-19, they are time-consuming, labor-intensive and are unavailable in remote settings. Point-of-care (POC) biosensors, including chip-based and paper-based biosensors are typically low-cost and user-friendly, which offer tremendous potential for rapid medical diagnosis. This mini review article discusses the recent advances in POC biosensors for COVID-19. First, the development of POC biosensors which are made of polydimethylsiloxane (PDMS), papers, and other flexible materials such as textile, film, and carbon nanosheets are reviewed. The advantages of each biosensors along with the commercially available COVID-19 biosensors are highlighted. Lastly, the existing challenges and future perspectives of developing robust POC biosensors to rapidly identify and manage the spread of COVID-19 are briefly discussed.

Hybrid paper and 3D-printed microfluidic device for electrochemical detection of Ag nanoparticle labels

In the present article we report a new hybrid microfluidic device (hyFlow) comprising a disposable paper electrode and a three-dimensional (3D) printed plastic chip for the electrochemical detection of a magnetic bead-silver nanoparticle (MB-AgNP) bioconjugate. This hybrid device evolved due to the difficulty of incorporating micron-scale MBs into paper-only fluidic devices. Specifically, paper fluidic devices can entrap MB-containing conjugates within their cellulose or nitrocellulose fiber matrix. The hyFlow system was designed to minimize such issues and transport MB conjugates more efficiently to the electrochemical detection zone of the device. The hyFlow system retains the benefit of fluid transport by pressure-driven flow, however, no pump is required for its operation. The hyFlow device is capable of detecting either pre-formed MB-AgNP conjugates or conjugates formed in situ. The detection limit of AgNPs using this device is 12 pM, which represents just 22 AgNPs per MB.

Smartphone-based multiplex 30-minute nucleic acid test of live virus from nasal swab extract

Rapid, sensitive and specific detection and reporting of infectious pathogens is important for patient management and epidemic surveillance. We demonstrated a point-of-care system integrated with a smartphone for detecting live virus from nasal swab media, using a panel of equine respiratory infectious diseases as a model system for corresponding human diseases such as COVID-19. Specific nucleic acid sequences of five pathogens were amplified by loop-mediated isothermal amplification on a microfluidic chip and detected at the end of reactions by the smartphone. Pathogen-spiked horse nasal swab samples were correctly diagnosed using our system, with a limit of detection comparable to that of the traditional lab-based test, polymerase chain reaction, with results achieved in ∼30 minutes.

Diagnosing COVID-19: The Disease and Tools for Detection

COVID-19 has spread globally since its discovery in Hubei province, China in December 2019. A combination of computed tomography imaging, whole genome sequencing, and electron microscopy were initially used to screen and identify SARS-CoV-2, the viral etiology of COVID-19. The aim of this review article is to inform the audience of diagnostic and surveillance technologies for SARS-CoV-2 and their performance characteristics. We describe point-of-care diagnostics that are on the horizon and encourage academics to advance their technologies beyond conception. Developing plug-and-play diagnostics to manage the SARS-CoV-2 outbreak would be useful in preventing future epidemics.

Indirect Competitive Immunoassay on a Blu-ray Disc for Digitized Quantitation of Food Toxins

We report herein a Blu-ray disc technology enabled immunoassay (namely, assay-on-a-Blu-ray) protocol for the quantitation of food toxins. In particular, commercial Blu-ray discs (BDs) are activated as substrates to create indirect competitive immunoassays with the aid of microfluidic channel plates for the quantitation of aflatoxins; an unmodified Blu-ray drive is employed to read the digitized signal (error counts generated from gold/silver-particle-enhanced binding sites); and a free disc-quality control software is adapted to process the raw data. The performance of this BD-based digital detection platform has been tested for the quantitation of aflatoxin B1 (AFB1) in spiked corn samples and validated with standard high-performance liquid chromatography measurements. The detection limit attained is as low as 0.27 ppb with a dynamic response range up to 200 ppb, which meets the standards established by government agencies worldwide for food products. We truly believe that the application potential of such a BD-technology-based, portable device for multiplex on-site quantitative analysis of food products as well as environmental and biomedical samples in real time is unlimited.

Frugal Innovation for Point-of-Care Diagnostics Controlling Outbreaks and Epidemics

Today epidemics of infectious diseases occur more often and spread both faster and further due to globalization and changes in our lifestyle. One way to meet these biological threats are so-called "Frugal Innovations", which focus on the development of affordable, rapid, and easy-to-use diagnostics with widespread use. In this context, point-of-care-tests (POCTs), performed at the patient's bedside, reduce extensive waiting times and unnecessary treatments and enable effective containment measures. This Perspective covers advances in POCT diagnostics on the basis of frugal innovation characteristics that will enable a faster, less expensive, and more convenient reaction to upcoming epidemics. Established POCT systems on the health care market, as well as currently evolving technological advancements in that sector are discussed. Progress in POCT technology and insights on how to most effectively use them allows the handling of more patients in a shorter time frame and consequently improves clinical outcomes at lower cost.

Electrochemical attack and corrosion of platinum electrodes in dielectrophoretic diagnostic devices

Though the advances in microelectronic device fabrication have realized new capabilities in integrated analytical and diagnostic platforms, there are still notable limitations in point-of-care sample preparation. AC electrokinetic devices, especially those leveraging dielectrophoresis (DEP), have shown potential to solve these limitations and allow for sample-to-answer in a single point-of-care device. However, when working directly with whole blood or other high conductance (~ 1 S/m) biological fluids, the aggressive electrochemical conditions created by the electrode can fundamentally limit the device operation. In this study, platinum wire-based electrode devices spanning circular polytetrafluorethylene (PTFE) wells and a planar microarray device with sputtered platinum electrodes were tested in plasma and PBS buffers of differing concentration across a wide range of frequencies and electric field intensities (AC voltages) to determine their respective safe regions of operation and to gain an understanding about the failure mechanisms of this class of device. At frequencies of 10 kHz and below, the upper bound of operation is the degradation of electrodes due to electrochemical attack by chlorine overcoming the native platinum oxide passivation. At higher frequencies, 100 kHz and above, the dielectric loss and subsequent heating of the buffer will boil before the electrodes suffer observable damage, due to the slow irreversible reaction kinetics. Effective dielectrophoretic capture of small biological particles at these frequencies is limited, and heat/oxidative denaturation of target material are a major concern. A new class of smaller devices, ones capable of high throughput at voltages low enough to maintain the integrity of the platinum passivation layer, is needed to mitigate these fundamental limitations.

Development of Recombinant Immunoglobulin G-Binding Luciferase-Based Signal Amplifiers in Immunoassays

In general immunoassays, secondary antibodies are covalently linked with enzymes and bind to the Fc region of target-bound primary antibodies to amplify signals of low-abundant target molecules. The antibodies themselves are obtained from large mammals and are further modified with enzymes. In this study, we developed novel recombinant immunoglobulin G (IgG)-binding luciferase-based signal amplifiers (rILSAs) by genetically fusing luciferase (Nluc) with antimouse IgG1 nanobody (MG1Nb) and antibody-binding domain (ABD), individually or together, in a mix-and-match manner. We obtained three different highly pure rILSAs in large quantities using a bacterial overexpression system and one-step purification. Mouse-specific rILSA, MG1Nb-Nluc, and rabbit-specific rILSA, Nluc-ABD, selectively bound to target-molecule-bound mouse IgG1 and rabbit IgG primary antibodies, whereas the bispecific rILSA, MG1Nb-Nluc-ABD, mutually bound to both mouse IgG1 and rabbit IgG primary antibodies. All rILSAs exhibited an outstanding signal-amplifying capability comparable to those of conventional horseradish-peroxidase-conjugated secondary antibodies, regardless of the target molecules, in various immunoassay formats, such as enzyme-linked immunosorbent assay, Western blot, and lateral flow assays. Each rILSA was selected for its own individual purpose and applied to various types of target analytes, in combination with a variety of target-specific primary antibodies, effectively minimizing the use of animals as well as reducing the costs and time associated with the production and chemical conjugation of signal-amplifying enzymes.

Towards practical sample preparation in point-of-care testing: user-friendly microfluidic devices

Microfluidic technologies offer a number of advantages for sample preparation in point-of-care testing (POCT), but the requirement for complicated external pumping systems limits their wide use. To facilitate sample preparation in POCT, various methods have been developed to operate microfluidic devices without complicated external pumping systems. In this review, we introduce an overview of user-friendly microfluidic devices for practical sample preparation in POCT, including self- and hand-operated microfluidic devices. Self-operated microfluidic devices exploit capillary force, vacuum-driven pressure, or gas-generating chemical reactions to apply pressure into microchannels, and hand-operated microfluidic devices utilize human power sources using simple equipment, including a syringe, pipette, or simply by using finger actuation. Furthermore, this review provides future perspectives to realize user-friendly integrated microfluidic circuits for wider applications with the integration of simple microfluidic valves.

Blocking the Nanopores in a Layer of Nonconductive Nanoparticles: Dominant Effects Therein and Challenges for Electrochemical Impedimetric Biosensing

Blockage of a nanopore by an analyte molecule has emerged as a promising concept for electrochemical biosensing. Nanoporous structures can be formed on the electrode surface simply by packing spherical nanoparticles in a dense planar arrangement. Modification of the nanoparticles with human serum albumin (HSA) and its interaction with the corresponding antibody (anti-HSA) can induce nanopore-blockage which significantly hinders permeation of the redox probe ([Fe(CN₆)]^4-/3-). Interfaces of different parameters were studied using Electrochemical Impedance Spectroscopy (EIS), and counterintuitively, the influence of charge of the nanoparticles and other immobilized entities played a substantial role in the measurement. Our study reveals dominant effects including the presence of mixed output signal and resolves corresponding EIS biosensing-related challenges. Consequently, blocking the nanopores was introduced as an efficient technique which enables the application of EIS-based biosensing to real-world analytical issues.

Disease X: accelerating the development of medical countermeasures for the next pandemic

WHO has listed several priority diseases with epidemic potential for which there are no, or insufficient, medical countermeasures. In response, the Bill & Melinda Gates Foundation (with support from PricewaterhouseCoopers) coordinated subject matter experts to create a preparedness plan for Disease X. Disease X is caused by Pathogen X, an infectious agent that is not currently known to cause human disease, but an aetiologic agent of a future outbreak with epidemic or pandemic potential. We have identified crucial areas for acceleration in medical countermeasure product development and international coordination. We have also reviewed novel platforms and process improvements related to manufacturing, which could revolutionise the response to the next pandemic. Finally, we created several coordination and engagement guides. These guides range from the rational design of an intervention target product profile, to the key facets of vaccine and therapeutic development, to accelerated manufacturing and regulatory mechanisms. In this Personal View, we provide a high-level summary of the outcomes of the medical countermeasure development workstream, intended for a broad audience including academia, medical countermeasure developers, and multilateral coordinating bodies. We hope that they might find this piece useful in prioritising strategic investments and efforts to accelerate medical countermeasure development. We observed that in-depth analyses of clinical trial design, chemistry, manufacturing and control activities, and accelerated regulatory pathways are necessary for shortening the timelines for the product development of medical countermeasures. We intend to cover these topics in future publications.

Translating in vitro diagnostics from centralized laboratories to point-of-care locations using commercially-available handheld meters

There is a growing demand for high-performance point-of-care (POC) diagnostic technologies where in vitro diagnostics (IVD) is fundamental for prevention, identification, and treatment of many diseases. Over the past decade, a shift of IVDs from the centralized laboratories to POC settings is emerging. In this review, we summarize recent progress in translating IVDs from centralized labs to POC settings using commercially available handheld meters. After introducing typical workflows for IVDs and highlight innovative technologies in this area, we discuss advantages of using commercially available handheld meters for translating IVDs from centralized labs to POC settings. We then provide comprehensive coverage of different signal transduction strategies to repurpose the commercially-available handheld meters, including personal glucose meter, pH meter, thermometer and pressure meter, for detecting a wide range of targets by integrating biochemical assays with the meters for POC testing. Finally, we identify remaining challenges and offer future outlook in this area.

Biosensors for Personal Mobile Health: A System Architecture Perspective

Advances in mobile biosensors, integrating developments in materials science and instrumentation, are fueling an expansion in health data being collected and analyzed in decentralized settings. For example, semiconductor-based sensors are enabling measurement of vital signs, and microfluidic-based sensors are enabling measurement of biochemical markers. As biosensors for mobile health are becoming increasingly paired with smart devices, it will become critical for researchers to design biosensors - with appropriate functionalities and specifications - to work seamlessly with accompanying connected hardware and software. This article describes recent research in biosensors, as well as current mobile health devices in use, as classified into four distinct system architectures that take into account the biosensing and data processing functions required in personal mobile health devices. We also discuss the path forward for integrating biosensors into smartphone-based mobile health devices.

Present and Future of Surface-Enhanced Raman Scattering

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

Bead-Based Immunocomplex Entrapment Assays for Rapid, Sensitive, and Multiplexed Detection of Disease Biomarkers with Minimal User Intervention

Current interest in at-home diagnostic devices derives from their potential to disrupt expensive and time-consuming hospital-based diagnostic practices. Conventional immunoassays are often touted for use in at-home diagnostic devices, although in practice they are slow, labor-intensive and require expensive equipment. Here, we introduce bead-based sensors as alternative biomarker detection platforms for at-home diagnostic devices. The immunocomplex entrapment assay (ICEA), and the related enzyme-linked ICEA (ELICEA) offer enhancements over conventional immunoassays in terms of their speed, and minimal requirements for user intervention and instrumentation. In particular, we designed bead-based sensors to entrap large molecular weight complexes between target molecules and signal-generating immunoconjugates while allowing any unbound conjugates to escape from the bead. Confocal fluorescence microscopy was used to demonstrate the sensitivity, robustness, and reproducibility of the ICEA and ELICEA platforms. For example, we showed the intensity of signals generated by entrapped immunoconjugate complexes correlate linearly with the concentration of target molecule in the sample. We employed ICEA, and ELICEA platforms to detect human forms of immunoglobulins, albumin, and κ light chain (KLC). For example, we used ICEA to detect KLC at 5 μg·mL^-1 in urine, which would allow for earlier diagnosis of Bence-Jones disease compared to conventional assays. In addition, we showed bead-entrapped phosphatases (AP) in immunocomplexes generate insoluble, blue-colored dyes from AP-substrates that accumulate in beads and allow for visual and cellphone camera-based detection of IgG to 10 ng·mL^-1 within 20 min. Finally, we described ICEA and ELICEA platforms to analyze multiple target proteins within individual beads.

IoT PCR for pandemic disease detection and its spread monitoring

During infectious disease outbreaks, the centers for disease control need to monitor particular areas. Considerable effort has been invested in the development of portable, user-friendly, and cost-effective systems for point-of-care (POC) diagnostics, which could also create an Internet of Things (IoT) for healthcare via a global network. However, at present IoT based on a functional POC instrument is not available. Here we show a fast, user-friendly, and affordable IoT system based on a miniaturized polymerase chain reaction device. We demonstrated the system's capability by amplification of complementary deoxyribonucleic acid (cDNA) of the dengue fever virus. The resulting data were then automatically uploaded via a Bluetooth interface to an Android-based smartphone and then wirelessly sent to a global network, instantly making the test results available anywhere in the world. The IoT system presented here could become an essential tool for healthcare centers to tackle infectious disease outbreaks identified either by DNA or ribonucleic acid.

Percussion Entropy Analysis of Synchronized ECG and PPG Signals as a Prognostic Indicator for Future Peripheral Neuropathy in Type 2 Diabetic Subjects

Diabetic peripheral neuropathy (DPN) is one of the most common chronic complications of diabetes. It has become an essential public health crisis, especially for care in the home. Synchronized electrocardiogram (ECG) and photoplethysmography (PPG) signals were obtained from healthy non-diabetic (n = 37) and diabetic (n = 85) subjects without peripheral neuropathy, recruited from the diabetic outpatient clinic. The conventional parameters, including low-/high-frequency power ratio (LHR), small-scale multiscale entropy index (MEI_SS), large-scale multiscale entropy index (MEI_LS), electrocardiogram-based pulse wave velocity (PWV_mean), and percussion entropy index (PEI), were computed as baseline and were then followed for six years after the initial PEI measurement. Three new diabetic subgroups with different PEI values were identified for the goodness-of-fit test and Cox proportional Hazards model for relative risks analysis. Finally, Cox regression analysis showed that the PEI value was significantly and independently associated with the risk of developing DPN after adjustment for some traditional risk factors for diabetes (relative risks = 4.77, 95% confidence interval = 1.87 to 6.31, p = 0.015). These findings suggest that the PEI is an important risk parameter for new-onset DPN as a result of a chronic complication of diabetes and, thus, a smaller PEI value can provide valid information that may help identify type 2 diabetic patients at a greater risk of future DPN.

Radical polymerization reactions for amplified biodetection signals

This review summarizes various radical polymerization chemistries for amplifying biodetection signals and compares them from the practical point of view.

Smartphone-assisted Hepatitis C detection assay based on magnetic levitation

This work describes development of smartphone-assisted magnetic levitation assay for Point-of-Care (PoC) applications.

Development and optimization of thermal contrast amplification lateral flow immunoassays for ultrasensitive HIV p24 protein detection

Detection of human immunodeficiency virus (HIV) p24 protein at a single pg/ml concentration in point-of-care (POC) settings is important because it can facilitate acute HIV infection diagnosis with a detection sensitivity approaching that of laboratory-based assays. However, the limit of detection (LOD) of lateral flow immunoassays (LFAs), the most prominent POC diagnostic platform, falls short of that of laboratory protein detection methods such as enzyme-linked immunosorbent assay (ELISA). Here, we report the development and optimization of a thermal contrast amplification (TCA) LFA that will allow ultrasensitive detection of 8 pg/ml p24 protein spiked into human serum at POC, approaching the LOD of a laboratory test. To achieve this aim, we pursued several innovations as follows: (a) defining a new quantitative figure of merit for LFA design based on the specific to nonspecific binding ratio (BR); (b) using different sizes and shapes of gold nanoparticles (GNPs) in the systematic optimization of TCA LFA designs; and (c) exploring new laser wavelengths and power regimes for TCA LFA designs. First, we optimized the blocking buffer for the membrane and running buffer by quantitatively measuring the BR using a TCA reader. The TCA reader interprets the thermal signal (i.e., temperature) of GNPs within the membrane when irradiated by a laser at the plasmon resonance wavelength of the particle. This process results in higher detection and quantitation of GNPs than in traditional visual detection (i.e., color intensity). Further, we investigated the effect of laser power (30, 100, 200 mW), GNP size and shape (30 and 100 nm gold spheres, 150 nm gold-silica shells), and laser wavelength (532, 800 nm). Applying these innovations to a new TCA LFA design, we demonstrated that 100 nm spheres with a 100 mW 532 nm laser provided the best performance (i.e., LOD = 8 pg/ml). This LOD is significantly better than that of the current colorimetric LFA and is in the range of the laboratory-based p24 ELISA. In summary, this TCA LFA for p24 protein shows promise for detecting acute HIV infection in POC settings.

Detection of Potato ring rot Pathogen Clavibacter michiganensis subsp. sepedonicus by Loop-mediated isothermal amplification (LAMP) assay

Clavibacter michiganensis subsp. sepedonicus (CMS) is an important bacterial plant pathogen causing potato ring rot disease. Rapid diagnosis of CMS is crucial because of the economic losses caused by serious harvest losses. Although there are serological tests used in the rapid diagnosis of CMS, they are not widely used because of their low sensitivity. The DNA-based PCR methods, which are highly sensitive, do not have the possibility of on-site diagnosis, especially since they require serious laboratory infrastructure. In recent years, scientists have been working on alternative amplification methods to develop DNA-based point of care (POC) diagnostic methods. Accordingly, the loop-mediated isothermal amplification (LAMP) method, which was developed in the early 2000s, provides an important convenience for DNA-based tests to use in the field. Due to the unique design of primers, more amplification products could be create in a shorter time than conventional amplification methods without needing a temperature cycle, and it can be applied with the aid of a simple heater without requiring a laboratory environment. In this study, efficient LAMP method for the detection of CMS has optimized. For device-independent detection of LAMP products, colorimetric method and LFD has used.

A Fully Integrated In Vitro Diagnostic Microsystem for Pathogen Detection Developed Using a "3D Extensible" Microfluidic Design Paradigm

Microfluidics is facing critical challenges in the quest of miniaturizing, integrating, and automating in vitro diagnostics, including the increasing complexity of assays, the gap between the macroscale world and the microscale devices, and the diverse throughput demands in various clinical settings. Here, a "3D extensible" microfluidic design paradigm that consists of a set of basic structures and unit operations was developed for constructing any application-specific assay. Four basic structures-check valve (in), check valve (out), double-check valve (in and out), and on-off valve-were designed to mimic basic acts in biochemical assays. By combining these structures linearly, a series of unit operations can be readily formed. We then proposed a "3D extensible" architecture to fulfill the needs of the function integration, the adaptive "world-to-chip" interface, and the adjustable throughput in the X, Y, and Z directions, respectively. To verify this design paradigm, we developed a fully integrated loop-mediated isothermal amplification microsystem that can directly accept swab samples and detect Chlamydia trachomatis automatically with a sensitivity one order higher than that of the conventional kit. This demonstration validated the feasibility of using this paradigm to develop integrated and automated microsystems in a less risky and more consistent manner.

FRET-Created Traffic Light Immunoassay Based on Polymer Dots for PSA Detection

There have been enormous efforts for developing the next generations of fluorometric lateral flow immunochromatographic strip (ICTS) owing to the great advances in fluorescent materials in these years. Here we developed one type of fluorometric ICTS based on ultrabright semiconducting polymer dots (Pdots) in which the traffic light-like signals were created by energy transfer depending on the target concentration. This platform was successfully applied for qualitatively rapid screening and quantitatively precise analysis of prostate-specific antigen (PSA) in 10 min from merely one drop of the whole blood sample. This FRET-created traffic light ICTS possesses excellent specificity and an outstanding detection sensitivity of 0.32 ng/mL for PSA. Moreover, we conducted proof-of-concept experiments to demonstrate its potential for multiplexed detection of cancer biomarkers at the same time in an individual test strip by taking advantage of the traffic light signals. To the best of our knowledge, it is the first model of a traffic light-like immunoassay test strip based on Pdots with multiplexing ability. These results would pave an avenue for designing the next generation of point-of-care diagnostics.