A Serological Point-of-Care Test for the Detection of IgG Antibodies against Ebola Virus in Human Survivors

Detecting the therapeutic drugs in blood samples through PDMS-printed paper spray mass spectrometry

In this paper, paper microfluidic channel fabricated by directly screen-printing of polydimethylsiloxane (PDMS) is proposed for paper spray mass spectrometry analysis of therapeutic drugs in the blood samples. Compared with traditional paper spray, PDMS-printed paper spray (PP-PS) allows fluid to flow to the tip of paper with less sample loss which significantly improved the signal intensity of target compounds in blood samples. As paper can reduce the matrix effect, PP-PS also has a greater advantage than electro-spray Ionization (ESI) when directly analyzing complex biological sample in terms of the detection efficiency. Linearity and limits of detection (LOD) were evaluated for five psychotropic drugs: olanzapine, quetiapine, 9-hydroxyrisperidone, clozapine, risperidone. As a result, PP-PS improved the signal intensity of the psychotropic drugs at a concentration of 250 ng/ml in blood samples by a factor of 2-5 times and lowered the relative standard deviation (RSD) by a factor of 2-5.6 times compared with traditional paper spray. And PP-PS also improved signal intensity by a factor of 9-33 times compared with ESI. Quantitative experiments of PP-PS mass spectrometry indicated that the linear range was 5-500 ng/ml and the LOD were improved by a factor of 5-71 times for all these drugs compared with traditional paper spray. In addition, PP-PS was applied to the home-made miniaturized mass spectrometer and the precursor ions of all five psychotropic drugs (250 ng/ml) in the mass spectrometry results were obtained as well. These could prove that PP-PS has the potential to analyze complex biological samples in application on the miniaturized mass spectrometer which can be used outside the laboratory.

A handheld fluorescent lateral flow immunoassay platform for highly sensitive point-of-care detection of methamphetamine and tramadol

The escalating issue of drug abuse poses a significant threat to public health and societal stability worldwide. An on-site drug detection platform is vital for combating drug abuse and trafficking, as it eliminates the need for additional tools, extensive processes, or specialized training. Therefore, it is imperative to develop a fast, sensitive, non-invasive, and reliable multiplex drug testing platform. In this study, we have presented a silica core@dual quantum dot-shell nanocomposite (SI/DQD)-based fluorescent lateral flow immunoassay (LFIA) platform for the highly sensitive and simultaneous point-of-care (POC) detection of methamphetamine (MET) and tramadol (TR). A 3D-printed attachment was designed to integrate optical and electrical components, facilitating the miniaturization of the instrument and reducing both cost and complexity. The device's advanced hardware and effective fluorescence extraction algorithm with waveform reconstruction enable swift, automatic noise reduction and data analysis. SI/DQD nanocomposites were utilized as fluorescent nanotags in the LFIA strips due to their outstanding luminous efficiency and robustness. This LFIA platform achieves impressive detection limits (LODs) of 0.11 ng mL-1 for MET and 0.017 ng mL-1 for TR. The method has also successfully detected MET and TR in complex biological samples, demonstrating its practical application capabilities. The proposed fluorescent LFIA platform, based on SI/DQD technology, holds significant promise for the swift and accurate POC detection of these substances. Its affordability, compact size, and excellent analytical performance make it suitable for on-site drug testing, including at borders and roadside checks, and open up new possibilities for the design and implementation of drug testing methods.

Label-free direct detection of melamine using functionalized gold nanoparticles-based dual-fluorescence colorimetric nanoswitch sensing platform

Developing a simple, economical, sensitive, and selective method for label-free direct detection analytes is attractive, especially the strategies that could achieve signal amplification without complicated operations. Herein, a dual-fluorescence colorimetric nanoswitch sensing platform for label-free direct melamine (MEL) detection was established. We first explored the relationship between MEL-induced aggregation of gold nanoparticles (AuNPs) and size and determined the optimal size to be 37 nm. Using surfactant Triton X-100 to modify AuNPs and clarify possible interaction mechanisms to improve detection performance. The dynamic changes of surface plasmon resonance absorption peaks in the dispersed and aggregated states of AuNPs were skillfully utilized to match the emission of multicolor gold nanoclusters to trigger the multi-inner filter effect. Accompanied by the addition of MEL-induced AuNPs to change from dispersed to aggregated state, the fluorescence of green-emitting and red-emitting gradually turned on and turned off, respectively. The fluorescence turn-on mode detection limit was 10 times higher than the colorimetric method and as low as 5.5 ng/mL; the detection took only 10 min. The sensor detected MEL in spiked milk samples with a good recovery in the range of 81.2-111.0 % with a coefficient of variation less than 11.4 % and achieved a good correlation with commercial kits. The proposed sensor integrates numerous merits of label-free, multi-signal readout, self-calibration, simple operations, and economical, which provides a promising tool for convenient on-site detection of MEL.

Recent advancements of smartphone-based sensing technology for diagnosis, food safety analysis, and environmental monitoring

The emergence of computationally powerful smartphones, relatively affordable high-resolution camera, drones, and robotic sensors have ushered in a new age of advanced sensible monitoring tools. The present review article investigates the burgeoning smartphone-based sensing paradigms, including surface plasmon resonance (SPR) biosensors, electrochemical biosensors, colorimetric biosensors, and other innovations for modern healthcare. Despite the significant advancements, there are still scarcity of commercially available smart biosensors and hence need to accelerate the rates of technology transfer, application, and user acceptability. The application/necessity of smartphone-based biosensors for Point of Care (POC) testing, such as prognosis, self-diagnosis, monitoring, and treatment selection, have brought remarkable innovations which eventually eliminate sample transportation, sample processing time, and result in rapid findings. Additionally, it articulates recent advances in various smartphone-based multiplexed bio sensors as affordable and portable sensing platforms for point-of-care devices, together with statistics for point-of-care health monitoring and their prospective commercial viability.

Simultaneous detection of two subtypes of extracellular vesicles using ultrabright fluorescent nanosphere-based test strips

In recent years, the cargo profiles of extracellular vesicles (EVs), which were inherited from their parent cells, have emerged as a reliable biomarker for liquid biopsy (LB) in disease diagnosis, prognosis, and treatment monitoring. EVs secreted by different cells exhibit distinct characteristics, particularly in terms of disease diagnosis and prediction. However, currently available techniques for the quantitative analysis of EV cargoes, including enzyme-linked immunosorbent assay (ELISA), cannot specifically identify the cellular origin of EVs, thus seriously affecting the accuracy of EV-based liquid biopsy. In light of this, we here developed ultrabright fluorescent nanosphere (FNs)-based test strips which have the unique capability to specifically assess the levels of PD-L1-positive EVs (PD-L1+ EVs) derived from both tumor cells and immune cells in bodily fluids. The levels of PD-L1+ EV subpopulations in human saliva were quantified using the ultrabright fluorescent nanosphere-based test strips with more convenience and higher efficiency (detection time <30 min). Results demonstrated that the fluorescence intensity of the test line exhibited a good linear relationship respectively with the PD-L1 levels of tumor cell- (R2 = 0.993) and immune cell-derived EVs (R2 = 0.982) in human saliva. By assessing the levels of PD-L1+ EV subpopulations, our test strips hold immense potential for advancing the application of PD-L1+ EV subpopulation-based predictions in tumor diagnosis and prognosis evaluation. In summary, by integrating the benefits of FNs and lateral flow chromatography, we here provide a strategy to accurately measure the cargo levels of EVs originating from diverse cell sources in bodily fluids.

Portable all-in-one microfluidic system for CRISPR-Cas13a-based fully integrated multiplexed nucleic acid detection

Point-of-care testing of "sample in, answer out" is urgently needed for communicable diseases. Recently, rapid nucleic acid tests for infectious diseases have been developed for use in resource-limited areas, but they require types of equipment in central laboratories and are poorly integrated. In this work, a portable centrifugal microfluidic testing system is developed, integrated with magnetic bead-based nucleic acid extraction, recombinase-assisted amplification and CRISPR-Cas13a detection. The system, with the advantage of its power-supplied active rotating chip and highly programable flow control through integrated addressable active thermally-triggered wax valves, has a rapid turnaround time within 45 min, requiring only one user step. All reagents are preloaded into the chip and can be automatically released. By exploiting a multichannel chip, it is capable of simultaneously detecting 10 infectious viruses with limits of detection of 1 copy per reaction and 5 copies per reaction in plasmid samples and mock plasma samples, respectively. The system was used to analyse clinical plasma samples with good consistency compared to laboratory-based molecular testing. Moreover, the generalizability of our device is reported by successfully testing nasopharyngeal swabs and whole blood samples. The portable device does not require the operation of professional technicians, making it an excellent assay for on-site testing.

Revolutionary Point-of-Care Wearable Diagnostics for Early Disease Detection and Biomarker Discovery through Intelligent Technologies

Early-stage disease detection, particularly in Point-Of-Care (POC) wearable formats, assumes pivotal role in advancing healthcare services and precision-medicine. Public benefits of early detection extend beyond cost-effectively promoting healthcare outcomes, to also include reducing the risk of comorbid diseases. Technological advancements enabling POC biomarker recognition empower discovery of new markers for various health conditions. Integration of POC wearables for biomarker detection with intelligent frameworks represents ground-breaking innovations enabling automation of operations, conducting advanced large-scale data analysis, generating predictive models, and facilitating remote and guided clinical decision-making. These advancements substantially alleviate socioeconomic burdens, creating a paradigm shift in diagnostics, and revolutionizing medical assessments and technology development. This review explores critical topics and recent progress in development of 1) POC systems and wearable solutions for early disease detection and physiological monitoring, as well as 2) discussing current trends in adoption of smart technologies within clinical settings and in developing biological assays, and ultimately 3) exploring utilities of POC systems and smart platforms for biomarker discovery. Additionally, the review explores technology translation from research labs to broader applications. It also addresses associated risks, biases, and challenges of widespread Artificial Intelligence (AI) integration in diagnostics systems, while systematically outlining potential prospects, current challenges, and opportunities.

Recent Advances in DNA Nanotechnology-Based Sensing Platforms for Rapid Virus Detection

Several major viral pandemics in history have significantly impacted the public health of human beings. The COVID-19 pandemic has further underscored the critical need for early detection and screening of infected individuals. However, current detection techniques are confronted with deficiencies in sensitivity and accuracy, restricting the capability of detecting trace amounts of viruses in human bodies and in the environments. The advent of DNA nanotechnology has opened up a feasible solution for rapid and sensitive virus determination. By harnessing the designability and addressability of DNA nanostructures, a range of rapid virus sensing platforms have been proposed. This review overviewed the recent progress, application, and prospect of DNA nanotechnology-based rapid virus detection platforms. Furthermore, the challenges and developmental prospects in this field were discussed.

Nanoparticle-Based Bioaffinity Assays: From the Research Laboratory to the Market

Advances in the development of new biorecognition elements, nanoparticle-based labels as well as instrumentation have inspired the design of new bioaffinity assays. This review critically discusses the potential of nanoparticles to replace current enzymatic or molecular labels in immunoassays and other bioaffinity assays. Successful implementations of nanoparticles in commercial assays and the need for rapid tests incorporating nanoparticles in different roles such as capture support, signal generation elements, and signal amplification systems are highlighted. The limited number of nanoparticles applied in current commercial assays can be explained by challenges associated with the analysis of real samples (e.g., blood, urine, or nasal swabs) that are difficult to resolve, particularly if the same performance can be achieved more easily by conventional labels. Lateral flow assays that are based on the visual detection of the red-colored line formed by colloidal gold are a notable exception, exemplified by SARS-CoV-2 rapid antigen tests that have moved from initial laboratory testing to widespread market adaption in less than two years.

Affinity-Switchable Interaction of Biotin and Streptavidin for the Signal-ON Detection of Small Molecules

Lateral flow assay (LFA) based on gold nanoparticles (AuNPs) is a widely used analytical device for the rapid analysis of environmental hazards and biomarkers. Typically, a sandwich-type format is used for macromolecule detection, in which the appearance of a red test line indicates a positive result (Signal-ON). In contrast, small molecule detection usually relies on a competitive assay, where the absence of a test line indicates positive testing (Signal-OFF). However, such a "Signal-OFF" reading is usually detected within a narrower dynamic range and tends to generate false-negative signals at a low concentration. Moreover, inconsistent readings between macromolecule and small molecule testing might lead to misinterpretation when used by nonskilled individuals. Herein, we report a "Signal-ON" small molecule competitive assay based on the sterically modulated affinity-switchable interaction of biotin and streptavidin. In the absence of a small molecule target, a large steric hindrance can be imposed on the biotin to prevent interaction with streptavidin. However, in the presence of the small molecule target, this steric effect is removed, allowing the biotin to bind to streptavidin and generate the desired test line. In this article, we demonstrate the selective detection of two small molecule drugs, sulfonamides and trimethoprim, using this simple and modular affinity-switchable lateral flow assay (ASLFA). We believe that this affinity-switchable approach can also be adapted in drug discovery and clinical diagnosis, where the competitive assay format is always used for the rapid analysis of small molecules.

Decorated DNA-Based Scaffolds as Lateral Flow Biosensors

Here we develop Lateral Flow Assays (LFAs) that employ as functional elements DNA-based structures decorated with reporter tags and recognition elements. We have rationally re-engineered tile-based DNA tubular structures that can act as scaffolds and can be decorated with recognition elements of different nature (i.e. antigens, aptamers or proteins) and with orthogonal fluorescent dyes. As a proof-of-principle we have developed sandwich and competitive multiplex lateral flow platforms for the detection of several targets, ranging from small molecules (digoxigenin, Dig and dinitrophenol, DNP), to antibodies (Anti-Dig, Anti-DNP and Anti-MUC1/EGFR bispecific antibodies) and proteins (thrombin). Coupling the advantages of functional DNA-based scaffolds together with the simplicity of LFAs, our approach offers the opportunity to detect a wide range of targets with nanomolar sensitivity and high specificity.

Markers of terminally differentiated T-cells as predictors of vascular health in renal transplant recipients and healthy adults

Meta-analyses confirm a link between persistent human cytomegalovirus (HCMV) infections and cardiovascular disease, but the mechanisms are unclear. We assess whether proportions of T-cell populations are reliable predictors of subclinical atherosclerosis and/or reflect the burden of HCMV in healthy adults and renal transplant recipients (RTR). Samples were collected from healthy adults and RTR at baseline (T0) and after 32 (24-40) months (T1). Left carotid intima media thickness (cIMT) and proportions of T-cells expressing CD57, LIR-1 or the TEMRA phenotype increased in healthy adults and RTR. The T-cell populations correlated with levels of HCMV-reactive antibodies. Proportions of CD57+, LIR-1+ and TEMRA CD8+ T-cells correlated with left and right cIMT in healthy adults. Proportions of CD57+ and LIR-1+ CD8+ T-cells at T0 predicted left cIMT at T1 among healthy adults, but these associations disappeared after adjustment for covariates. We link LIR-1+ and CD57+CD8+ T-cells with the progression of cIMT in healthy adults.

New technologies and reagents in lateral flow assay (LFA) designs for enhancing accuracy and sensitivity

Lateral flow assays (LFAs) are a popular method for quick and affordable diagnostic testing because they are easy to use, portable, and user-friendly. However, LFA design has always faced challenges regarding sensitivity, accuracy, and complexity of the operation. By integrating new technologies and reagents, the sensitivity and accuracy of LFAs can be improved while minimizing the complexity and potential for false positives. Surface enhanced Raman spectroscopy (SERS), photoacoustic techniques, fluorescence resonance energy transfer (FRET), and the integration of smartphones and thermal readers can improve LFA accuracy and sensitivity. To ensure reliable and accurate results, careful assay design and validation, appropriate controls, and optimization of assay conditions are necessary. Continued innovation in LFA technology is crucial to improving the reliability and accuracy of rapid diagnostic testing and expanding its applications to various areas, such as food testing, water quality monitoring, and environmental testing.

Microparticle-Based Detection of Viruses

Surveillance of viral pathogens in both point-of-care and clinical settings is imperative to preventing the widespread propagation of disease-undetected viral outbreaks can pose dire health risks on a large scale. Thus, portable, accessible, and reliable biosensors are necessary for proactive measures. Polymeric microparticles have recently gained popularity for their size, surface area, and versatility, which make them ideal biosensing tools. This review cataloged recent investigations on polymeric microparticle-based detection platforms across eight virus families. These microparticles were used as labels for detection (often with fluorescent microparticles) and for capturing viruses for isolation or purification (often with magnetic microparticles). We also categorized all methods by the characteristics, materials, conjugated receptors, and size of microparticles. Current approaches were compared, addressing strengths and weaknesses in the context of virus detection. In-depth analyses were conducted for each virus family, categorizing whether the polymeric microparticles were used as labels, for capturing, or both. We also summarized the types of receptors conjugated to polymeric microparticles for each virus family.

Synthetic Antigen-Conjugated DNA Systems for Antibody Detection and Characterization

Antibodies are among the most relevant biomolecular targets for diagnostic and clinical applications. In this Perspective, we provide a critical overview of recent research efforts focused on the development and characterization of devices, switches, and reactions based on the use of synthetic antigen-conjugated DNA strands designed to be responsive to specific antibodies. These systems can find applications in sensing, drug-delivery, and antibody-antigen binding characterization. The examples described here demonstrate how the programmability and chemical versatility of synthetic nucleic acids can be used to create innovative analytical tools and target-responsive systems with promising potentials.

Low-Cost Microfluidic Systems for Detection of Neglected Tropical Diseases

Neglected tropical diseases (NTDs) affect tropical and subtropical countries and are caused by viruses, bacteria, protozoa, and helminths. These kinds of diseases spread quickly due to the tropical climate and limited access to clean water, sanitation, and health care, which make exposed people more vulnerable. NTDs are reported to be difficult and inefficient to diagnose. As mentioned, most NTDs occur in countries that are socially vulnerable, and the lack of resources and access to modern laboratories and equipment intensify the difficulty of diagnosis and treatment, leading to an increase in the mortality rate. Portable and low-cost microfluidic systems have been widely applied for clinical diagnosis, offering a promising alternative that can meet the needs for fast, affordable, and reliable diagnostic tests in developing countries. This review provides a critical overview of microfluidic devices that have been reported in the literature for the detection of the most common NTDs over the past 5 years.

Lateral flow immunoassay for rapid and sensitive detection of dsRNA contaminants in in vitro-transcribed mRNA products

High purity is essential in mRNA-based therapeutic applications. A major contaminant of in vitro-transcribed (IVT) mRNA manufacturing is double-stranded RNA (dsRNA), which can induce severe anti-viral immune responses. Detection methods, such as agarose gel electrophoresis, ELISA, and dot-blot assay, are used to detect the existence of dsRNA in IVT mRNA products. However, these methods are either not sensitive enough or time-consuming. To overcome these challenges, we develop a rapid, sensitive, and easy-to-implement colloidal gold nanoparticle-based lateral flow strip assay (LFSA) with sandwich format for the detection of dsRNA from IVT process. dsRNA contaminant can be determined visually on the test strip or quantitatively with a portable optical detector. This method allows for a 15 min detection of N1-methyl-pseudouridine (m1Ψ)-containing dsRNA with a detection limit of 69.32 ng/mL. Furthermore, we establish the correlation between the LFSA test results and the immune response caused by dsRNA in mice. The LFSA platform allows the rapid, sensitive, and quantitative monitoring of purity in massive IVT mRNA products and aids for the prevention of immunogenicity by dsRNA impurities.

Research progress in methods for detecting neutralizing antibodies against SARS-CoV-2

The emergence of SARS-CoV-2 has seriously affected the lives of people worldwide. Clarifying the attenuation rule of SARS-CoV-2 neutralizing antibody (NAb) in vivo is the key to prevent reinfection and recurrence of virus. Currently, the commonly used methods for detecting NAb include virus neutralization tests, pseudovirus neutralization assays, lateral flow immunochromatography and enzyme-linked immunosorbent assays. The detection of NAb not only can be used to evaluate the level of immunity after vaccination or infection but also can provide important theoretical support for virus reinfection, recurrence and vaccine iteration. In this research, the related technologies of SARS-CoV-2 NAb detection were reviewed, aiming to provide better research ideas for SARS-CoV-2 epidemic prevention and control.

The application of nanoparticles in point-of-care testing (POCT) immunoassays

The Covid-19 pandemic has led to greater recognition of the importance of the fast and timely detection of pathogens. Recent advances in point-of-care testing (POCT) technology have shown promising results for rapid diagnosis. Immunoassays are among the most extensive POCT assays, in which specific labels are used to indicate and amplify the immune signal. Nanoparticles (NPs) are above the rest because of their versatile properties. Much work has been devoted to NPs to find more efficient immunoassays. Herein, we comprehensively describe NP-based immunoassays with a focus on particle species and their specific applications. This review describes immunoassays along with key concepts surrounding their preparation and bioconjugation to show their defining role in immunosensors. The specific mechanisms, microfluidic immunoassays, electrochemical immunoassays (ELCAs), immunochromatographic assays (ICAs), enzyme-linked immunosorbent assays (ELISA), and microarrays are covered herein. For each mechanism, a working explanation of the appropriate background theory and formalism is articulated before examining the biosensing and related point-of-care (POC) utility. Given their maturity, some specific applications using different nanomaterials are discussed in more detail. Finally, we outline future challenges and perspectives to give a brief guideline for the development of appropriate platforms.

Smartphone-based diagnostics for biosensing infectious human pathogens

The widespread usage of smartphones has made accessing vast troves of data easier for everyone. Smartphones are powerful, handy, and easy to operate, making them a valuable tool for improving public health through diagnostics. When combined with other devices and sensors, smartphones have shown potential for detecting, visualizing, collecting, and transferring data, enabling rapid disease diagnosis. In resource-limited settings, the user-friendly operating system of smartphones allows them to function as a point-of-care platform for healthcare and disease diagnosis. Herein, we critically reviewed the smartphone-based biosensors for the diagnosis and detection of diseases caused by infectious human pathogens, such as deadly viruses, bacteria, and fungi. These biosensors use several analytical sensing methods, including microscopic imaging, instrumental interface, colorimetric, fluorescence, and electrochemical biosensors. We have discussed the diverse diagnosis strategies and analytical performances of smartphone-based detection systems in identifying infectious human pathogens, along with future perspectives.

Wearable nucleic acid testing platform - A perspective on rapid self-diagnosis and surveillance of infectious diseases

Wearable biosensors (WB) are currently attracting considerable interest for rapid detection and monitoring of biomarkers including metabolites, protein, and pathogen in bodily fluids (e.g., sweat, saliva, tears, and interstitial fluid). Another branch of WB termed wearable nucleic acid testing (NAT) is blossoming thanks to the development of microfluidic technology and isothermal nucleic acid amplification technique (iNAAT); however, there are only few reports on this. The wearable NAT is an emerging field of point-of-care (POC) diagnostics, and holds the promise for time-saving self-diagnosis, and evidence-based surveillance of infectious diseases in remote or low-resource settings. The use of wearable NAT can also be advanced to include molecular diagnosis, the identification of cancer biomarkers, genetic abnormalities, and other aspects. The wearable NAT provides the potential for evidence-based surveillance of infectious diseases when combined with internet connectivity and App software. To make the wearable NAT accessible to the end users, however, improvements must be made to the fabrication, cost, speed, sensitivity, specificity, sampling, iNAAT, analyzer, and a few other features. So, in this paper, we looked at the wearable NAT's most recent development, identified its difficulties, and defined its potential for managing infectious diseases quickly in the future. This is the wearable NAT review's first effort. We expect that this article will provide the concise resources needed to develop and deploy an efficient wearable NAT system.

Impact of nanotechnology on conventional and artificial intelligence-based biosensing strategies for the detection of viruses

Recent years have witnessed the emergence of several viruses and other pathogens. Some of these infectious diseases have spread globally, resulting in pandemics. Although biosensors of various types have been utilized for virus detection, their limited sensitivity remains an issue. Therefore, the development of better diagnostic tools that facilitate the more efficient detection of viruses and other pathogens has become important. Nanotechnology has been recognized as a powerful tool for the detection of viruses, and it is expected to change the landscape of virus detection and analysis. Recently, nanomaterials have gained enormous attention for their value in improving biosensor performance owing to their high surface-to-volume ratio and quantum size effects. This article reviews the impact of nanotechnology on the design, development, and performance of sensors for the detection of viruses. Special attention has been paid to nanoscale materials, various types of nanobiosensors, the internet of medical things, and artificial intelligence-based viral diagnostic techniques.

On-Site Remote Monitoring System with NIR Signal-Based Detection of Infectious Disease Virus in Opaque Salivary Samples

Infectious disease viruses, such as foot-and-mouth disease virus (FMDV), are highly contagious viruses that cause significant socioeconomic damage upon spreading. Developing an on-site diagnostic tool for early clinical detection and real-time surveillance of FMDV outbreaks is essential to prevent the further spread of the disease. However, early diagnosis of FMDV is still challenging due to the limited sensitivity and time-consuming manual result entry of commercial on-site tests for salivary samples. Here, we report a near-infrared (NIR) signal nanoprobe-based highly accurate detection and remote monitoring system toward FMDVs, which automates the analysis and reporting of diagnosis data. The NIR signal lateral flow immunoassay (LFA) was assembled with a nanoprobe with a stable emission intensity at 800 nm, minimizing the interference signal of opaque salivary samples. We investigated the clinical applicability of the NIR signal LFA at biosafety level 3 (BSL-3) laboratories using 147 opaque salivary samples. The NIR signal LFA achieved a 32-fold lower limit of detection (LOD) than a commercial LFA in detecting live FMDVs, including all isolates occurring in the Republic of Korea during 2010-2017. Our results showed that the NIR signal LFA successfully discriminated the FMDV-positive clinical salivary samples from healthy controls with a sensitivity of 96.9%, specificity of 100.0%, and AUC (area under the receiver operator characteristic curve) value of 0.999. Finally, we substantiated the real-time collection of diagnostic results using a customized portable NIR reader at nine different laboratories of government-certified quarantine institutions for foot-and-mouth disease (FMD).

Moving toward smart biomedical sensing

The development of novel biomedical sensors as highly promising devices/tools in early diagnosis and therapy monitoring of many diseases and disorders has recently witnessed unprecedented growth; more and faster than ever. Nonetheless, on the eve of Industry 5.0 and by learning from defects of current sensors in smart diagnostics of pandemics, there is still a long way to go to achieve the ideal biomedical sensors capable of meeting the growing needs and expectations for smart biomedical/diagnostic sensing through eHealth systems. Herein, an overview is provided to highlight the importance and necessity of an inevitable transition in the era of digital health/Healthcare 4.0 towards smart biomedical/diagnostic sensing and how to approach it via new digital technologies including Internet of Things (IoT), artificial intelligence, IoT gateways (smartphones, readers), etc. This review will bring together the different types of smartphone/reader-based biomedical sensors, which have been employing for a wide variety of optical/electrical/electrochemical biosensing applications and paving the way for future eHealth diagnostic devices by moving towards smart biomedical sensing. Here, alongside highlighting the characteristics/criteria that should be met by the developed sensors towards smart biomedical sensing, the challenging issues ahead are delineated along with a comprehensive outlook on this extremely necessary field.

Biosensors for healthcare: current and future perspectives

Biosensors are utilized in several different fields, including medicine, food, and the environment; in this review, we examine recent developments in biosensors for healthcare. These involve three distinct types of biosensor: biosensors for in vitro diagnosis with blood, saliva, or urine samples; continuous monitoring biosensors (CMBs); and wearable biosensors. Biosensors for in vitro diagnosis have seen a significant expansion recently, with newly reported clustered regularly interspaced short palindromic repeats (CRISPR)/Cas methodologies and improvements to many established integrated biosensor devices, including lateral flow assays (LFAs) and microfluidic/electrochemical paper-based analytical devices (μPADs/ePADs). We conclude with a discussion of two novel groups of biosensors that have drawn great attention recently, continuous monitoring and wearable biosensors, as well as with perspectives on the commercialization and future of biosensors.

Patterned Biolayers of Protein Antigens for Label-Free Biosensing in Cow Milk Allergy

This paper focuses on creating one-dimensional diffractive grooved structures of antigen proteins on glass substrates for the label-free detection of antibodies to dairy allergens. In particular, the fabrication of protein structures is carried out by combining microcontact printing with physisorption, imines coupling, and thiol-ene click chemistry. The work first sets up these patterning methods and discusses and compares the main aspects involved in them (structure, biolayer thickness, functionality, stability). Homogeneous periodic submicron structures of proteins are created and characterized by diffractive measurements, AFM, FESEM, and fluorescence scanning. Then, this patterning method is applied to proteins involved in cow milk allergy, and the resulting structures are implemented as optical transducers to sense specific immunoglobulins G. In particular, gratings of bovine serum albumin, casein, and β-lactoglobulin are created and assessed, reaching limits of detection in the range of 30-45 ng·mL^-1 of unlabeled antibodies by diffractive biosensing.

Nanotechnology-Enabled Biosensors: A Review of Fundamentals, Design Principles, Materials, and Applications

Biosensors are modern engineering tools that can be widely used for various technological applications. In the recent past, biosensors have been widely used in a broad application spectrum including industrial process control, the military, environmental monitoring, health care, microbiology, and food quality control. Biosensors are also used specifically for monitoring environmental pollution, detecting toxic elements' presence, the presence of bio-hazardous viruses or bacteria in organic matter, and biomolecule detection in clinical diagnostics. Moreover, deep medical applications such as well-being monitoring, chronic disease treatment, and in vitro medical examination studies such as the screening of infectious diseases for early detection. The scope for expanding the use of biosensors is very high owing to their inherent advantages such as ease of use, scalability, and simple manufacturing process. Biosensor technology is more prevalent as a large-scale, low cost, and enhanced technology in the modern medical field. Integration of nanotechnology with biosensors has shown the development path for the novel sensing mechanisms and biosensors as they enhance the performance and sensing ability of the currently used biosensors. Nanoscale dimensional integration promotes the formulation of biosensors with simple and rapid detection of molecules along with the detection of single biomolecules where they can also be evaluated and analyzed critically. Nanomaterials are used for the manufacturing of nano-biosensors and the nanomaterials commonly used include nanoparticles, nanowires, carbon nanotubes (CNTs), nanorods, and quantum dots (QDs). Nanomaterials possess various advantages such as color tunability, high detection sensitivity, a large surface area, high carrier capacity, high stability, and high thermal and electrical conductivity. The current review focuses on nanotechnology-enabled biosensors, their fundamentals, and architectural design. The review also expands the view on the materials used for fabricating biosensors and the probable applications of nanotechnology-enabled biosensors.

Portable general microfluidic device with complex electric field regulation functions for electrokinetic experiments

Electrokinetic sample manipulation is a key step for many kinds of microfluidic chips to achieve various functions, such as particle focusing and separation, fluid pumping and material synthesis. But these microfluidic experiments usually rely on large-scale signal generators for power supply, microscopes for imaging and other instruments for analysis, which hampers the portable process of microfluidic technology. Inspired by this situation, we herein designed a portable general microfluidic device (PGMD) with complex electric field regulation functions, which can accurately regulate static or continuous fluid samples. Through the graphical user interface (GUI) and modular design, the PGMD can generate multiple different electrical signals, and the micro-flow of fluid can be pumped through the built-in micropump, which can meet the requirements of most microfluidic experiments. Photos or videos of the microfluidic chip captured by the built-in microscope are received and displayed by a smartphone. We carried out a variety of microfluidic experiments such as induced-charge electroosmosis (ICEO), particle beam exit switching, thermal buoyancy flow and dielectrophoresis (DEP) on the PGMD. In addition, the PGMD can perform rapid microalgae concentration estimation in an outdoor environment, which can be used to guide microalgae cultivation, further demonstrating the development potential of this device in the field of microbial applications. Numerous results show that the PGMD has a high degree of integration and strong reliability, which expands the application of microfluidic electrokinetic experiments and provides technical support for the integration and portability of microfluidic experimental devices.

Flash Characterization of Smartphones Used in Point-of-Care Diagnostics

Rapidly growing interest in smartphone cameras as the basis of point-of-need diagnostic and bioanalytical technologies increases the importance of quantitative characterization of phone optical performance under real-world operating conditions. In the context of our development of lateral-flow immunoassays based on phosphorescent nanoparticles, we have developed a suite of tools for characterizing the temporal and spectral profiles of smartphone torch and flash emissions, and their dependence on phone power state. In this work, these tools are described and documented to make them easily available to others, and demonstrated by application to characterization of Apple iPhone 5s, iPhone 6s, iPhone 8, iPhone XR, and Samsung Note8 flash performance as a function of time and wavelength, at a variety of power settings. Flash and torch intensity and duration vary with phone state and among phone models. Flash has high variability when the battery charge is below 10%, thus, smartphone-based Point-of-Care (POC) tests should only be performed at a battery level of at least 15%. Some output variations could substantially affect the results of assays that rely on the smartphone flash.

Nanomaterial and interface advances in immunoassay biosensors

Biosensors have been used for a remarkable array of applications, including infectious diseases, environmental monitoring, cancer diagnosis, food safety, and numerous others. In particular, the global COVID-19 pandemic has exposed a need for rapid tests, so the type of biosensor that has gained considerable interest recently are immunoassays, which are used for rapid diagnostics. The performance of paper-based lateral flow and dipstick immunoassays is influenced by the physical properties of the nanoparticles (NPs), NP-antibody conjugates, and paper substrate. Many materials innovations have enhanced diagnostics by increasing sensitivity or enabling unique readouts. However, negative side effects can arise at the interface between the biological sample and biomolecules and the NP or paper substrate, such as non-specific adsorption and protein denaturation. In this Perspective, we discuss the immunoassay components and highlight chemistry and materials innovations that can improve sensitivity. We also explore the range of bio-interface issues that can present challenges for immunoassays.

Toward Next Generation Lateral Flow Assays: Integration of Nanomaterials

Lateral flow assays (LFAs) are currently the most used point-of-care sensors for both diagnostic (e.g., pregnancy test, COVID-19 monitoring) and environmental (e.g., pesticides and bacterial monitoring) applications. Although the core of LFA technology was developed several decades ago, in recent years the integration of novel nanomaterials as signal transducers or receptor immobilization platforms has brought improved analytical capabilities. In this Review, we present how nanomaterial-based LFAs can address the inherent challenges of point-of-care (PoC) diagnostics such as sensitivity enhancement, lowering of detection limits, multiplexing, and quantification of analytes in complex samples. Specifically, we highlight the strategies that can synergistically solve the limitations of current LFAs and that have proven commercial feasibility. Finally, we discuss the barriers toward commercialization and the next generation of LFAs.

Diagnostic Approaches For COVID-19: Lessons Learned and the Path Forward

Coronavirus disease 2019 (COVID-19) is a transmitted respiratory disease caused by the infection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although humankind has experienced several outbreaks of infectious diseases, the COVID-19 pandemic has the highest rate of infection and has had high levels of social and economic repercussions. The current COVID-19 pandemic has highlighted the limitations of existing virological tests, which have failed to be adopted at a rate to properly slow the rapid spread of SARS-CoV-2. Pandemic preparedness has developed as a focus of many governments around the world in the event of a future outbreak. Despite the largely widespread availability of vaccines, the importance of testing has not diminished to monitor the evolution of the virus and the resulting stages of the pandemic. Therefore, developing diagnostic technology that serves as a line of defense has become imperative. In particular, that test should satisfy three criteria to be widely adopted: simplicity, economic feasibility, and accessibility. At the heart of it all, it must enable early diagnosis in the course of infection to reduce spread. However, diagnostic manufacturers need guidance on the optimal characteristics of a virological test to ensure pandemic preparedness and to aid in the effective treatment of viral infections. Nanomaterials are a decisive element in developing COVID-19 diagnostic kits as well as a key contributor to enhance the performance of existing tests. Our objective is to develop a profile of the criteria that should be available in a platform as the target product. In this work, virus detection tests were evaluated from the perspective of the COVID-19 pandemic, and then we generalized the requirements to develop a target product profile for a platform for virus detection.

Ebola-Detect: A differential serodiagnostic assay for Ebola virus infections and surveillance in the presence of vaccine-induced antibodies

Background

Ebola virus (EBOV) vaccines containing glycoprotein (GP) provide protection against severe Ebola virus disease (EVD). EBO vaccinations elicit antibodies that are detectable in Ebola serodiagnostic tests, as EBOV GP is a major target antigen. This vaccine-induced seropositivity presents issues with early detection of natural EBOV infections, following vaccination and during surveillance, leading to ‘uninfected’ vaccine trial participants being falsely diagnosed as ‘EBOV infected’ potentially resulting in long-term social and economic distress. Since mass vaccinations are being employed to curtail the recurrent EBOV epidemics in multiple African countries, it is, therefore, essential to differentiate vaccine-induced from natural infection–induced antibodies by a differential serodiagnosis assay for accurate detection of Ebola virus infections.

Methods

To develop a serodiagnostic test that can differentiate between individuals with EBOV infection-induced antibodies and individuals with EBOV vaccine-induced antibodies, we analysed peptides of EBOV viral protein 40 (VP40), viral protein 35 (VP35) and nucleocapsid protein (NP) using an ELISA with a panel of 181 human sera collected from healthy controls, EBO vaccinees, and EBOV-infected survivors. Receiver Operating Characteristic (ROC) curve analysis was used to calculate sensitivity and specificity of the assay. A simple peptide-based serodiagnostic assay was used to evaluate detection of breakthrough EBOV infections in vaccinated non-human primates (NHP) in EBOV challenge studies.

Findings

We identified conserved peptide sequences in EBOV VP40, VP35 and NP, produced soon after EBOV infection that are not part of the current EBO vaccine target antigens. The new ELISA-based differential serodetection assay termed ‘EBOV-Detect’ demonstrated >94% specificity and 96% sensitivity for diagnosis of EBOV infection. Importantly, the uninfected vaccine-trial participants scored negative in ‘EBOV-Detect’ assay. The results from the NHPs EBOV challenge study established that post-EBO vaccination serum scored negative in ‘EBOV-Detect’ and all NHPs with Ebola breakthrough infections, following EBOV challenge, were serodiagnosed positively with EBOV-Detect.

Interpretation

The new ‘EBOV-Detect’ is a simple and sensitive serodiagnostic assay that can specifically differentiate between natural Ebola virus infected and those with vaccine-induced immunity. This could potentially be implemented as a robust diagnostic tool for epidemiology and surveillance of EBOV infections during and after outbreaks, especially in countries with mass Ebola vaccinations.

Funding

The antibody characterization work described in this manuscript was supported by FDA Office of Counterterrorism and Emerging Threats (OCET) - Medical Countermeasures initiative (MCMi) grant- OCET 2019-1018 and Defense Threat Reduction Agency (HDTRA1930447) funds to S.K.

A Review on Potential Electrochemical Point-of-Care Tests Targeting Pandemic Infectious Disease Detection: COVID-19 as a Reference

Fast and accurate point-of-care testing (POCT) of infectious diseases is crucial for diminishing the pandemic miseries. To fight the pandemic coronavirus disease 2019 (COVID-19), numerous interesting electrochemical point-of-care (POC) tests have been evolved to rapidly identify the causal organism SARS-CoV-2 virus, its nucleic acid and antigens, and antibodies of the patients. Many of those electrochemical biosensors are impressive in terms of miniaturization, mass production, ease of use, and speed of test, and they could be recommended for future applications in pandemic-like circumstances. On the other hand, self-diagnosis, sensitivity, specificity, surface chemistry, electrochemical components, device configuration, portability, small analyzers, and other features of the tests can yet be improved. Therefore, this report reviews the developmental trend of electrochemical POC tests (i.e., test platforms and features) reported for the rapid diagnosis of COVID-19 and correlates any significant advancements with relevant references. POCTs incorporating microfluidic/plastic chips, paper devices, nanomaterial-aided platforms, smartphone integration, self-diagnosis, and epidemiological reporting attributes are also surfed to help with future pandemic preparedness. This review especially screens the low-cost and easily affordable setups so that management of pandemic disease becomes faster and easier. Overall, the review is a wide-ranging package for finding appropriate strategies of electrochemical POCT targeting pandemic infectious disease detection.

Lateral flow assays for viruses diagnosis: Up-to-date technology and future prospects

Bacteria, viruses, and parasites are harmful microorganisms that cause infectious diseases. Early detection of diseases is critical to prevent disease transmission and provide epidemic preparedness, as these can cause widespread deaths and public health crises, particularly in resource-limited countries. Lateral flow assay (LFA) systems are simple-to-use, disposable, inexpensive diagnostic devices to test biomarkers in blood and urine samples. Thus, LFA has recently received significant attention, especially during the pandemic. Here, first of all, the design principles and working mechanisms of existing LFA methods are examined. Then, current LFA implementation strategies are presented for communicable disease diagnoses, including COVID-19, zika and dengue, HIV, hepatitis, influenza, malaria, and other pathogens. Furthermore, this review focuses on an overview of current problems and accessible solutions in detecting infectious agents and diseases by LFA, focusing on increasing sensitivity with various detection methods. In addition, future trends in LFA-based diagnostics are envisioned.

Nanomaterials for virus sensing and tracking

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

A novel lateral flow immunoassay strip based on a label-free magnetic Fe3O4@UiO-66-NH2 nanocomposite for rapid detection of Listeria monocytogenes

Listeria monocytogenes (L. monocytogenes) is one of the most lethal pathogenic bacteria. Although the traditional microbial culture method has high sensitivity and selectivity for the diagnosis of L. monocytogenes, it is time-consuming and not suitable for on-site detection. A rapid, convenient and visualized on-site detection method is particularly needed. In this work, Fe₃O₄@UiO-66-NH₂ was prepared for both magnetic separation and lateral flow immunoassay (LFIA) for the detection of L. monocytogenes by taking advantage of the easy separation of the magnetic core Fe₃O₄ and the high surface area of the outer layer UiO-66-NH₂. Fe₃O₄@UiO-66-NH₂ with a high surface area and good water-dispersibility and optical properties was synthesized by a simple hydrothermal process. It could directly adsorb on the surface of target bacteria and form Fe₃O₄@UiO-66-NH₂-bacteria conjugates, without the labeling of an antibody. After magnetic separation and concentration, the Fe₃O₄@UiO-66-NH₂-bacteria conjugates were detected by the antibody on the test line of the LFIA strip, resulting in a visible orange band. The capture efficiency and LFIA detection of Fe₃O₄@UiO-66-NH₂ were optimized in this study. Under the optimal conditions, a good linear correlation between the test line intensity and the concentration of L. monocytogenes was obtained in the range of 10⁵-10⁸ CFU mL^-1, and the limit of detection was 2.2 × 10⁶ CFU mL^-1 by the naked eye. The Fe₃O₄@UiO-66-NH₂-based LFIA strip showed strong specificity for L. monocytogenes, and the detection took 45 min without culture enrichment. Therefore, the proposed Fe₃O₄@UiO-66-NH₂-based strip showed the advantages of simple synthesis, being label-free, low cost, good selectivity and convenience.

Immunoprofiling of Severity and Stage of Bacterial Infectious Diseases by Ultrabright Fluorescent Nanosphere-Based Dyad Test Strips

Bacterial infectious diseases are common clinical diseases that seriously threaten human health, especially in countries and regions with poor environmental hygiene. Due to the lack of characteristic clinical symptoms and signs, it is a challenge to distinguish a bacterial infection from other infections, leading to misdiagnosis and antibiotic overuse. Therefore, there is an urgent need to develop a specific method for detection of bacterial infections. Herein, utilizing ultrabright fluorescent nanospheres (FNs) as reporters, immunochromatographic dyad test strips are developed for the early detection of bacterial infections and distinction of different stages of bacterial infectious diseases in clinical samples. C-reactive protein (CRP) and heparin-binding protein (HBP) are quantified and assayed because their levels in plasma are varied dynamically and asynchronously during the progression of the disease. The detection limits of CRP and HBP can reach as low as 0.51 and 0.65 ng/mL, respectively, due to the superior fluorescence intensity of each FN, which is 570 times stronger than that of a single quantum dot. The assay procedure can be achieved in 22 min, fully meeting the needs of rapid and ultrasensitive detection in the field. This constructed strip has been successfully used to profile the stage and severity of bacterial infections by monitoring the levels of CRP and HBP in human plasma samples, showing great potential as a point-of-care biosensor for clinical diagnosis. In addition to bacterial infections, the developed ultrabright FN-based point-of-care testing can be readily expanded for rapid, quantitative, and ultrasensitive detection of other trace substances in complex systems.

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

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

A free customizable tool for easy integration of microfluidics and smartphones

The integration of smartphones and microfluidics is nowadays the best possible route to achieve effective point-of-need testing (PONT), a concept increasingly demanded in the fields of human health, agriculture, food safety, and environmental monitoring. Nevertheless, efforts are still required to integrally seize all the advantages of smartphones, as well as to share the developments in easily adoptable formats. For this purpose, here we present the free platform appuente that was designed for the easy integration of microfluidic chips, smartphones, and the cloud. It includes a mobile app for end users, which provides chip identification and tracking, guidance and control, processing, smart-imaging, result reporting and cloud and Internet of Things (IoT) integration. The platform also includes a web app for PONT developers, to easily customize their mobile apps and manage the data of administered tests. Three application examples were used to validate appuente: a dummy grayscale detector that mimics quantitative colorimetric tests, a root elongation assay for pesticide toxicity assessment, and a lateral flow immunoassay for leptospirosis detection. The platform openly offers fast prototyping of smartphone apps to the wide community of lab-on-a-chip developers, and also serves as a friendly framework for new techniques, IoT integration and further capabilities. Exploiting these advantages will certainly help to enlarge the use of PONT with real-time connectivity in the near future.

High-Sensitive Detection and Quantitative Analysis of Thyroid-Stimulating Hormone Using Gold-Nanoshell-Based Lateral Flow Immunoassay Device

Au nanoparticles (AuNPs) have been used as signal reporters in colorimetric lateral flow immunoassays (LFAs) for decades. However, it remains a major challenge to significantly improve the detection sensitivity of traditional LFAs due to the low brightness of AuNPs. As an alternative approach, we overcome this problem by utilizing 150 nm gold nanoshells (AuNSs) that were engineered by coating low-density silica nanoparticles with a thin layer of gold. AuNSs are dark green, have 14 times larger surface area, and are approximately 35 times brighter compared to AuNPs. In this study, we used detection of thyroid-stimulating hormone (TSH) in a proof-of-concept assay. The limit of detection (LOD) with AuNS-based LFA was 0.16 µIU/mL, which is 26 times more sensitive than the conventional colorimetric LFA that utilizes AuNP as a label. The dynamic range of the calibration curve was 0.16−9.5 µIU/mL, making it possible to diagnose both hyperthyroidism (<0.5 µIU/mL) and hypothyroidism (>5 µIU/mL) using AuNS-based LFA. Thus, the developed device has a strong potential for early screening and diagnosis of diseases related to the thyroid hormone.

Noble Metal Nanoparticle Biosensors: From Fundamental Studies toward Point-of-Care Diagnostics

Noble metal nanoparticles (NMNPs) have become firmly established as effective agents to detect various biomolecules with extremely high sensitivity. This ability stems from the collective oscillation of free electrons and extremely large electric field enhancement under exposure to light, leading to various light-matter interactions such as localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering. A remarkable feature of NMNPs is their customizability by mechanisms such as particle etching, growth, and aggregation/dispersion, yielding distinct color changes and excellent opportunities for colorimetric biosensing in user-friendly assays and devices. They are readily functionalized with a large variety of capping agents and biomolecules, with resultant bioconjugates often possessing excellent biocompatibility, which can be used to quantitatively detect analytes from physiological fluids. Furthermore, they can possess excellent catalytic properties that can achieve significant signal amplification through mechanisms such as the catalytic transformation of colorless substrates to colored reporters. The various excellent attributes of NMNP biosensors have put them in the spotlight for developing high-performance in vitro diagnostic (IVD) devices that are particularly well-suited to mitigate the societal threat that infectious diseases pose. This threat continues to dominate the global health care landscape, claiming millions of lives annually. NMNP IVDs possess the potential to sensitively detect infections even at very early stages with affordable and field-deployable devices, which will be key to strengthening infectious disease management. This has been the major focal point of current research, with a view to new avenues for early multiplexed detection of infectious diseases with portable devices such as smartphones, especially in resource-limited settings.In this Account, we provide an overview of our original inspiration and efforts in NMNP-based assay development, together with some more sophisticated IVD assays by ourselves and many others. Our work in the area has led to our recent efforts in developing IVDs for high-profile infectious diseases, including Ebola and HIV. We emphasize that integration with digital platforms represents an opportunity to establish and efficiently manage widespread testing, tracking, epidemiological intelligence, and data sharing backed by community participation. We highlight how digital technologies can address the limitations of conventional diagnostic technologies at the point of care (POC) and how they may be used to abate and contain the spread of infectious diseases. Finally, we focus on more recent integrations of noble metal nanoparticles with Raman spectroscopy for accurate, noninvasive POC diagnostics with improved sensitivity and specificity.

Thermally Responsive Alkane Partitions for Assay Automation

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

"Three-in-One" Multifunctional Nanohybrids with Colorimetric Magnetic Catalytic Activities to Enhance Immunochromatographic Diagnosis

Colorimetric lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as signal reporters has been widely used in point-of-care testing. Nonetheless, the potential of traditional AuNP-based LFIA for the early diagnosis of disease is often compromised by limited sensitivity due to the insufficient colorimetric signal brightness of AuNPs. Herein, we develop a "three-in-one" multifunctional catalytic colorimetric nanohybrid (Fe₃O₄@MOF@Pt) composed of Fe₃O₄ nanoparticles, MIL-100(Fe), and platinum (Pt) nanoparticles. Fe₃O₄@MOF@Pt displays enhanced colorimetric signal brightness, fast magnetic response, and ultrahigh peroxidase-mimicking activity, which are beneficial to the enhancement of the sensitivity of LFIA by coupling with magnetic separation and catalytic amplification. When integrated with the dual-antibody sandwich LFIA platform, the developed Fe₃O₄@MOF@Pt can achieve an ultrasensitive immunochromatographic assay of procalcitonin with a sensitivity of 0.5 pg mL^-1, which is approximately 2280-fold higher than that of conventional AuNP-based LFIA and superior to previously published immunoassays. Therefore, this work suggests that the proposed catalytic colorimetric nanohybrid can act as promising signal reporters to enable ultrasensitive immunochromatographic disease diagnostics.

Generating Uniformly Cross-Reactive Ebolavirus spp. Anti-nucleoprotein Nanobodies to Facilitate Forward Capable Detection Strategies

It is often challenging for a single monoclonal antibody to cross-react equally with all species of a particular viral genus that are separated by time and geographies to ensure broad long-term global immunodiagnostic use. Here, we set out to isolate nanobodies or single-domain antibodies (sdAbs) with uniform cross-reactivity to the genus Ebolavirus by immunizing a llama with recombinant nucleoprotein (NP) representing the 5 cultivated species to assemble a phage display repertoire for mining. Screening sdAbs for reactivity against the C-terminal domain of NP guided the isolation of clones that could perform as both captor and tracer for polyvalent antigen in sandwich assays. Two promising sdAbs had equivalent reactivities across all 5 species and greatly enhanced the equilibrium concentration at 50% (EC₅₀) for recombinant NP when compared with a differentially cross-reactive nonimmune sdAb isolated previously. Uniform reactivity and enhanced sensitivity were relayed to live virus titrations, resulting in lower limits of detection of 2-5 pfu for the best sdAbs, representing 10-, 20-, and 100-fold improvements for Zaire, Sudan/Reston, and Taï Forest viruses, respectively. Fusions of the sdAbs with ascorbate peroxidase (APEX2) and mNeonGreen generated one-step immunoreagents useful for colorimetric and fluorescent visualization of cellular NP. Both sdAbs were also able to recognize recombinant NPs from the recently discovered Bombali virus, a putative sixth Ebolavirus species unknown at the start of these experiments, validating the forward capabilities of the sdAbs. The simplicity and modularity of these sdAbs should enable advances in antigen-based diagnostic technologies to be retuned toward filoviral detection relatively easily, thereby proactively safeguarding human health.