Multiplex diagnosis of viral infectious diseases (AIDS, hepatitis C, and hepatitis A) based on point of care lateral flow assay using engineered proteinticles

Multiplexed electrical detection of whole viruses from plasma in a microfluidic platform

The advancement of point-of-care diagnostics is crucial to improving patient outcomes, especially in areas with low access to hospitals or specialized laboratories. In particular, rapid, sensitive, and multiplexed detection of disease biomarkers has great potential to achieve accurate diagnosis and inform high quality care for patients. Our Coulter counting and immunocapture based detection system has previously shown its broad applicability in the detection of cells, proteins, and nucleic acids. This paper expands the capability of the platform by demonstrating multiplexed detection of whole-virus particles using electrically distinguishable hydrogel beads by demonstrating the capability of our platform to achieve simultaneous detection at clinically relevant concentrations of hepatitis A virus (>2 × 103 IU mL-1) and human parvovirus B19 virus like particles (>106 IU mL-1) from plasma samples. The expanded versatility of the differential electrical counting platform allows for more robust and diverse testing capabilities.

Point-of-Care Testing for Hepatitis Viruses: A Growing Need

Viral hepatitis, caused by hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), or hepatitis E virus (HEV), is a major global public health problem. These viruses cause millions of infections each year, and chronic infections with HBV, HCV, or HDV can lead to severe liver complications; however, they are underdiagnosed. Achieving the World Health Organization's viral hepatitis elimination goals by 2030 will require access to simpler, faster, and less expensive diagnostics. The development and implementation of point-of-care (POC) testing methods that can be performed outside of a laboratory for the diagnosis of viral hepatitis infections is a promising approach to facilitate and expedite WHO's elimination targets. While a few markers of viral hepatitis are already available in POC formats, tests for additional markers or using novel technologies need to be developed and validated for clinical use. Potential methods and uses for the POC testing of antibodies, antigens, and nucleic acids that relate to the diagnosis, monitoring, or surveillance of viral hepatitis infections are discussed here. Unmet needs and areas where additional research is needed are also described.

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.

A review of rapid food safety testing: using lateral flow assay platform to detect foodborne pathogens

The detrimental impact of foodborne pathogens on human health makes food safety a major concern at all levels of production. Conventional methods to detect foodborne pathogens, such as live culture, high-performance liquid chromatography, and molecular techniques, are relatively tedious, time-consuming, laborious, and expensive, which hinders their use for on-site applications. Recurrent outbreaks of foodborne illness have heightened the demand for rapid and simple technologies for detection of foodborne pathogens. Recently, Lateral flow assays (LFA) have drawn attention because of their ability to detect pathogens rapidly, cheaply, and on-site. Here, we reviewed the latest developments in LFAs to detect various foodborne pathogens in food samples, giving special attention to how reporters and labels have improved LFA performance. We also discussed different approaches to improve LFA sensitivity and specificity. Most importantly, due to the lack of studies on LFAs for the detection of viral foodborne pathogens in food samples, we summarized our recent research on developing LFAs for the detection of viral foodborne pathogens. Finally, we highlighted the main challenges for further development of LFA platforms. In summary, with continuing improvements, LFAs may soon offer excellent performance at point-of-care that is competitive with laboratory techniques while retaining a rapid format.

DropLab: an automated magnetic digital microfluidic platform for sample-to-answer point-of-care testing-development and application to quantitative immunodiagnostics

In point-of-care testing (POCT), tests are performed near patients and results are given rapidly for timely clinical decisions. Immunodiagnostic assays are one of the most important analyses for detecting and quantifying protein-based biomarkers. However, existing POCT immunodiagnostics mainly rely on the lateral flow assay (LFA), which has limited sensitivity or quantification capability. Although other immunodiagnostic assays, such as enzyme-linked immunosorbent assays (ELISAs), offer more sensitive and quantitative results, they require complex liquid manipulations that are difficult to implement in POCT settings by conventional means. Here, we show the development of DropLab, an automated sample-in-answer-out POCT immunodiagnostic platform based on magnetic digital microfluidic (MDM) technology. DropLab performs microbead-based ELISA in droplets to offer more sensitive and quantitative testing results. The intricate liquid manipulations required for ELISA are accomplished by controlling droplets with magnetic microbeads using MDM technology, which enables us to achieve full automation and easy operations with DropLab. Four ELISAs (the sample in triplicates and a negative control) can be run in parallel on the thermoformed disposable chip, which greatly improves the throughput and accuracy compared to those of other POCT immunodiagnostic devices. DropLab was validated by measuring two protein targets and one antibody target. The testing results showed that the limit of detection (LOD) of DropLab matched that of the conventional ELISA in a microwell plate. DropLab brings MDM one step closer to being a viable medical technology that is ready for real-world POCT applications.

Changing spatiotemporal patterns for hepatitis of unspecified aetiology in China, 2004-2021: a population-based surveillance study

Objectives

As global efforts continue toward the target of eliminating viral hepatitis by 2030, the emergence of acute hepatitis of unspecified aetiology (HUA) remains a concern. This study assesses the overall trends and changes in spatiotemporal patterns in HUA in China from 2004 to 2021.

Methods

We extracted the incidence and mortality rates of HUA from the Public Health Data Center, the official website of the National Health Commission of the People's Republic of China, and the National Notifiable Infectious Disease Surveillance System from 2004 to 2021. We used R software, ArcGIS, Moran's statistical analysis, and joinpoint regression to examine the spatiotemporal patterns and annual percentage change in incidence and mortality of the HUA across China.

Results

From 2004 to 2021, a total of 707,559 cases of HUA have been diagnosed, including 636 deaths. The proportion of HUA in viral hepatitis gradually decreased from 7.55% in 2004 to 0.72% in 2021. The annual incidence of HUA decreased sharply from 6.6957 per 100,000 population in 2004 to 0.6302 per 100,000 population in 2021, with an average annual percentage change (APC) reduction of -13.1% (p < 0.001). The same result was seen in the mortality (APC, -22.14%, from 0.0089/100,000 in 2004 to 0.0002/100,000 in 2021, p < 0.001). All Chinese provinces saw a decline in incidence and mortality. Longitudinal analysis identified the age distribution in the incidence and mortality of HUA did not change and was highest in persons aged 15-59 years, accounting for 70% of all reported cases. During the COVID-19 pandemic, no significant increase was seen in pediatric HUA cases in China.

Conclusion

China is experiencing an unprecedented decline in HUA, with the lowest incidence and mortality for 18 years. However, it is still important to sensitively monitor the overall trends of HUA and further improve HUA public health policy and practice in China.

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.

Lateral Flow Immunoassays for Detecting Viral Infectious Antigens and Antibodies

Abundant immunological assays currently exist for detecting pathogens and identifying infected individuals, making detection of diseases at early stages integral to preventing their spread, together with the consequent emergence of global health crises. Lateral flow immunoassay (LFIA) is a test characterized by simplicity, low cost, and quick results. Furthermore, LFIA testing does not need well-trained individuals or laboratory settings. Therefore, it has been serving as an attractive tool that has been extensively used during the ongoing COVID-19 pandemic. Here, the LFIA strip's available formats, reporter systems, components, and preparation are discussed. Moreover, this review provides an overview of the current LFIAs in detecting infectious viral antigens and humoral responses to viral infections.

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.

Digital Pregnancy Test Powered by an Air-Breathing Paper-Based Microfluidic Fuel Cell Stack Using Human Urine as Fuel

The direct integration of paper-based microfluidic fuel cells (μFC's) toward creating autonomous lateral flow assays has attracted attention. Here, we show that an air-breathing paper-based μFC could be used as a power supply in pregnancy tests by oxidizing the human urine used for the diagnosis. We present an air-breathing paper-based μFC connected to a pregnancy test, and for the first time, as far as we know, it is powered by human urine without needing any external electrolyte. It uses TiO2-Ni as anode and Pt/C as cathode; the performance shows a maximum value of voltage and current and power densities of ∼0.96 V, 1.00 mA cm-2, and 0.23 mW cm-2, respectively. Furthermore, we present a simple design of a paper-based μFC's stack powered with urine that shows a maximum voltage and maximum current and power densities of ∼1.89 V, 2.77 mA cm-2 and 1.38 mW cm-2, respectively, which powers the display of a pregnancy test allowing to see the analysis results.

Glycosylated gold nanoparticles in point of care diagnostics: from aggregation to lateral flow

Current point-of-care lateral flow immunoassays, such as the home pregnancy test, rely on proteins as detection units (e.g. antibodies) to sense for analytes. Glycans play a fundamental role in biological signalling and recognition events such as pathogen adhesion and hence they are promising future alternatives to antibody-based biosensing and diagnostics. Here we introduce the potential of glycans coupled to gold nanoparticles as recognition agents for lateral flow diagnostics. We first introduce the concept of lateral flow, including a case study of lateral flow use in the field compared to other diagnostic tools. We then introduce glycosylated materials, the affinity gains achieved by the cluster glycoside effect and the current use of these in aggregation based assays. Finally, the potential role of glycans in lateral flow are explained, and examples of their successful use given.

Antibody-based lateral flow (immune) assays are well established, but here the emerging concept and potential of using glycans as the detection agents is reviewed.

Detection of Single Nucleotide Polymorphism (SNP) Variation of a Gene Sequence on Membrane-Based Lateral-Flow Strips

This study used appropriate primers to distinguish the gene model, HLA-A31:01, on membrane-based lateral-flow (MBLF) strips from its allele, which is with an SNP. Using primers designed with a mismatch base on one or two sides next to the SNP spot was verified as a good approach. In the optimal condition, the detection limits of 1~0.1 ng/μL nucleotides were in agreement with reports in the literature, and the intra- and inter-assay tests ensured the detection reproducibility of this approach with CV% of 2.5%~15.9% and 1.7%~14.7%, respectively. The detection specificity was also validated by the tests on the selected negative-control genes. The tests on MBLF strips in this study showed an easy, robust, reproducible, and reliable detection methodology for untrained personnel at care points with limited instrument and particularly for avoiding medications from faulty prescriptions.

Lateral flow assays (LFA) as an alternative medical diagnosis method for detection of virus species: The intertwine of nanotechnology with sensing strategies

Viruses are responsible for multiple infections in humans that impose huge health burdens on individuals and populations worldwide. Therefore, numerous diagnostic methods and strategies have been developed for prevention, management, and decreasing the burden of viral diseases, each having its advantages and limitations. Viral infections are commonly detected using serological and nucleic acid-based methods. However, these conventional and clinical approaches have some limitations that can be resolved by implementing other detector devices. Therefore, the search for sensitive, selective, portable, and costless approaches as efficient alternative clinical methods for point of care testing (POCT) analysis has gained much attention in recent years. POCT is one of the ultimate goals in virus detection, and thus, the tests need to be rapid, specific, sensitive, accessible, and user-friendly. In this review, after a brief overview of viruses and their characteristics, the conventional viral detection methods, the clinical approaches, and their advantages and shortcomings are firstly explained. Then, LFA systems working principles, benefits, classification are discussed. Furthermore, the studies regarding designing and employing LFAs in diagnosing different types of viruses, especially SARS-CoV-2 as a main concern worldwide and innovations in the LFAs' approaches and designs, are comprehensively discussed here. Furthermore, several strategies addressed in some studies for overcoming LFA limitations like low sensitivity are reviewed. Numerous techniques are adopted to increase sensitivity and perform quantitative detection. Employing several visualization methods, using different labeling reporters, integrating LFAs with other detection methods to benefit from both LFA and the integrated detection device advantages, and designing unique membranes to increase reagent reactivity, are some of the approaches that are highlighted.

Paper-based analytical devices for virus detection: Recent strategies for current and future pandemics

The importance of user-friendly, inexpensive, sensitive, and selective detection of viruses has been highlighted again due to the recent Coronavirus disease 2019 (COVID-19) pandemic. Among the analytical tools, paper-based devices (PADs) have become a leading alternative for point-of-care (POC) testing. In this review, we discuss the recent development strategies and applications in nucleic acid-based, antibody/antigen-based and other affinity-based PADs using optical and electrochemical detection methods for sensing viruses. In addition, advantages and drawbacks of presented PADs are identified. Current state and insights towards future perspectives are presented regarding developing POC diagnosis platform for COVID-19. This review considers state-of-the-art technologies for further development and improvement in PADs performance for virus detection.

Ultrasensitive and Highly Specific Lateral Flow Assays for Point-of-Care Diagnosis

Lateral flow assays (LFAs) are paper-based point-of-care (POC) diagnostic tools that are widely used because of their low cost, ease of use, and rapid format. Unfortunately, traditional commercial LFAs have significantly poorer sensitivities (μM) and specificities than standard laboratory tests (enzyme-linked immunosorbent assay, ELISA: pM-fM; polymerase chain reaction, PCR: aM), thus limiting their impact in disease control. In this Perspective, we review the evolving efforts to increase the sensitivity and specificity of LFAs. Recent work to improve the sensitivity through assay improvement includes optimization of the assay kinetics and signal amplification by either reader systems or additional reagents. Together, these efforts have produced LFAs with ELISA-level sensitivities (pM-fM). In addition, sample preamplification can be applied to both nucleic acids (direct amplification) and other analytes (indirect amplification) prior to LFA testing, which can lead to PCR-level (aM) sensitivity. However, these amplification strategies also increase the detection time and assay complexity, which inhibits the large-scale POC use of LFAs. Perspectives to achieve future rapid (<30 min), ultrasensitive (PCR-level), and "sample-to-answer" POC diagnostics are also provided. In the case of LFA specificity, recent research efforts have focused on high-affinity molecules and assay optimization to reduce nonspecific binding. Furthermore, novel highly specific molecules, such as CRISPR/Cas systems, can be integrated into diagnosis with LFAs to produce not only ultrasensitive but also highly specific POC diagnostics. In summary, with continuing improvements, LFAs may soon offer performance at the POC that is competitive with laboratory techniques while retaining a rapid format.

Internet of medical things (IoMT)-integrated biosensors for point-of-care testing of infectious diseases

On global scale, the current situation of pandemic is symptomatic of increased incidences of contagious diseases caused by pathogens. The faster spread of these diseases, in a moderately short timeframe, is threatening the overall population wellbeing and conceivably the economy. The inadequacy of conventional diagnostic tools in terms of time consuming and complex laboratory-based diagnosis process is a major challenge to medical care. In present era, the development of point-of-care testing (POCT) is in demand for fast detection of infectious diseases along with “on-site” results that are helpful in timely and early action for better treatment. In addition, POCT devices also play a crucial role in preventing the transmission of infectious diseases by offering real-time testing and lab quality microbial diagnosis within minutes. Timely diagnosis and further treatment optimization facilitate the containment of outbreaks of infectious diseases. Presently, efforts are being made to support such POCT by the technological development in the field of internet of medical things (IoMT). The IoMT offers wireless-based operation and connectivity of POCT devices with health expert and medical centre. In this review, the recently developed POC diagnostics integrated or future possibilities of integration with IoMT are discussed with focus on emerging and re-emerging infectious diseases like malaria, dengue fever, influenza A (H1N1), human papilloma virus (HPV), Ebola virus disease (EVD), Zika virus (ZIKV), and coronavirus (COVID-19). The IoMT-assisted POCT systems are capable enough to fill the gap between bioinformatics generation, big rapid analytics, and clinical validation. An optimized IoMT-assisted POCT will be useful in understanding the diseases progression, treatment decision, and evaluation of efficacy of prescribed therapy.

Functionalized gold nanoparticles: promising and efficient diagnostic and therapeutic tools for HIV/AIDS

Functionalized gold nanoparticles are recognized as promising vehicles in the diagnosis and treatment of human immunodeficiency virus (HIV) owing to their excellent biocompatibility with biomolecules (like DNA or RNA), their potential for multivalency and their unique optical and structural properties. In this context, this review article focuses on the diverse detection abilities and delivery and uptake methodologies of HIV by targeting genes and proteins using gold nanoparticles on the basis of different shapes and sizes in order to promote its effective expression. In addition, recent trends in gold nanoparticle mediated HIV detection, delivery and uptake and treatment are highlighted considering their cytotoxic effects on healthy human cells.

Point-of-Use Rapid Detection of SARS-CoV-2: Nanotechnology-Enabled Solutions for the COVID-19 Pandemic

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the COVID-19 pandemic that has been spreading around the world since December 2019. More than 10 million affected cases and more than half a million deaths have been reported so far, while no vaccine is yet available as a treatment. Considering the global healthcare urgency, several techniques, including whole genome sequencing and computed tomography imaging have been employed for diagnosing infected people. Considerable efforts are also directed at detecting and preventing different modes of community transmission. Among them is the rapid detection of virus presence on different surfaces with which people may come in contact. Detection based on non-contact optical techniques is very helpful in managing the spread of the virus, and to aid in the disinfection of surfaces. Nanomaterial-based methods are proven suitable for rapid detection. Given the immense need for science led innovative solutions, this manuscript critically reviews recent literature to specifically illustrate nano-engineered effective and rapid solutions. In addition, all the different techniques are critically analyzed, compared, and contrasted to identify the most promising methods. Moreover, promising research ideas for high accuracy of detection in trace concentrations, via color change and light-sensitive nanostructures, to assist fingerprint techniques (to identify the virus at the contact surface of the gas and solid phase) are also presented.

Multiplex loop-mediated isothermal amplification-based lateral flow dipstick for simultaneous detection of 3 food-borne pathogens in powdered infant formula

In this study, we established a rapid, simple, and sensitive method for visual and point-of-care detection of Salmonella spp., Cronobacter spp., and Staphylococcus aureus in powdered infant formula (PIF) based on multiplex loop-mediated isothermal amplification (mLAMP) combined with lateral flow dipstick (LFD). Three different species-specific target genes, siiA of Salmonella spp., internal transcribed space (ITS) of Cronobacter spp., and nuc of Staph. aureus, were applied in the mLAMP with biotin-, digoxin-, and Texas Red-modified forward inner primers and fluorescein isothiocyanate (FITC)-modified backward inner primers. After mLAMP, a large number of modified amplicons were detected with LFD; one end of the amplicon was conjugated to the anti-FITC antibody on gold nanoparticles and the other end to streptavidin (anti-digoxin or anti-Texas Red antibody) on test lines. Visual inspection of the device relies on the presence of a red band formed by accumulation of sandwich composites. The detection limits of this mLAMP-LFD assay for Salmonella spp., Cronobacter spp., and Staph. aureus in PIF without enrichment were 4.2, 2.6, and 3.4 cfu/g, respectively. The whole method can be completed in less than 1 h. Thus, mLAMP-LFD is a rapid and efficient method for simultaneously detecting Salmonella spp., Cronobacter spp., and Staph. aureus in PIF.

Immunochromatographic System for Serodiagnostics of Cattle Brucellosis Using Gold Nanoparticles and Signal Amplification with Quantum Dots

In this article, we describe an immunochromatographic test system developed for rapid serodiagnostics of cattle brucellosis using two markers: Gold nanoparticles (GNPs) and quantum dots (QDs). The test system was compared with immunochromatographic serodiagnostics systems that use only one marker. The approbation of the test system was conducted on samples of cattle sera with low, but diagnostically significant titers of specific antibodies. We show that when two conjugates are used, the intensity of the detectable signal increases by 2–3 times compared with the test system using the QD conjugate and by more than nine times compared with the system using the GNP conjugate.

Viral antigen nanoparticles for discriminated and quantitative detection of different subtypes of anti-virus immunoglobulins

The aim of this study is to develop a novel method for the accurate diagnosis of the infection status of viral diseases, which requires discriminated and quantitative detection of different anti-virus immunoglubulin subtypes. Considering hepatitis A as a representative model disease, viral antigen nanoparticles (vAgNPs) were designed and synthesized by genetically presenting hepatitis A virus (HAV) antigens on the surface of human heavy chain ferritin (hFTH) nanoparticles to detect anti-HAV antibodies with discriminating immunoglobulin subtypes M and G (IgM and IgG, respectively). The vAgNPs also display multi-copies of hexa-histidine peptide (H6) on their surface to chemisorb gold ions (Au3+), which is vital for the autonomous generation of quantitatively meaningful detection signals. The quantitative level of anti-HAV IgM or IgG in 30 patient sera was successfully analyzed using the vAgNPs of HAV, which was performed through label-free one-step-immunoassay based on the self-enhancement of optical signals from gold nanoparticles clustered on the viral antigen nanoparticles. The diagnostic performance was compared with that of enzyme-linked immunosorbent assay (ELISA), which did not enable accurate quantitative assay due to the poor linearity between the antibody concentration and detection signal. Furthermore, these vAgNP-based immunoassays did not produce any false negative/positive signals, indicating 100% sensitivity and 100% specificity.

A new point-of-care test for the diagnosis of infectious diseases based on multiplex lateral flow immunoassays

Infectious diseases are transmissible or communicable illnesses and can spread quickly in some areas and become epidemics. It is critical to quickly diagnose initial infections and prevent further spread through in vitro diagnosis. However, current detection strategies have exhibited a lack of balance with regard to accuracy, time consumption, and portability until recently (e.g. serology, culturing, molecular tests, etc.). Alternatively, many studies have focused on point-of-care testing (POCT), which combines simple, rapid, and exact on-site diagnostic platforms. Moreover, multiplex detectability is necessary for emergency treatment depending on the stage of the disease or interactional infections. The lateral flow assay (LFA) is the most popular diagnostic tool that meets the required standards for colorimetric assays. Here, we review lateral flow assays based on the immune reactions for the simultaneous diagnosis of infectious diseases as the POC test. The assays employed various forms and approaches in terms of the multiplexing level system for improving the sensitivity and specificity. We briefly describe the state-of-the-art infection diagnostic methods and published performances that have been classified into three categories based on the application forms of the lateral flow immunoassay. Also, we discuss further uses of LFA and other technologies for more effective infectious disease POCT.

Microfluidic-controlled optical router for lab on a chip

In multiplexed analysis, lab on a chip (LoC) devices are advantageous due to the low sample and reagent volumes required. Although optical detection is preferred for providing high sensitivity in a contactless configuration, multiplexed optical LoCs are limited by the technological complexity for integrating multiple light sources and detectors in a single device. To address this issue, we present a microfluidic-controlled optical router that enables measurement in four individual optical channels using a single light source and detector, and without movable parts. The optofluidic device is entirely fabricated in polydimethylsiloxane (PDMS) by soft-lithography, compatible with standard microfabrication technologies, enabling monolithic integration in LoCs. In the device, in-coupled light from an optical fiber is collimated by a polymeric micro-lens and guided through a set of four sequentially connected micro-chambers. When a micro-chamber is filled with water, light is transmitted to the next one. If it is empty of liquid, however, total internal reflection (TIR) occurs at the PDMS-air interface, re-directing the light to the output optical fiber. The router presents high performance, with low cross-talk (<2%) and high switching frequencies (up to 0.343 ± 0.006 Hz), and provides a stable signal for up to 91% of the switching time. With this miniaturized, low-cost, simple and robust design, we expect the current technology to be integrated in the new generation of multiplexed photonic LoCs for biomarker analysis, even at the point of care.

Rapid Diagnostic Platform for Colorimetric Differential Detection of Dengue and Chikungunya Viral Infections

In this work, we demonstrate a rapid diagnostic platform with potential to transform clinical diagnosis of acute febrile illnesses in resource-limited settings. Acute febrile illnesses such as dengue and chikungunya, which pose high burdens of disease in tropical regions, share many nonspecific symptoms and are difficult to diagnose based on clinical history alone in the absence of accessible laboratory diagnostics. Through a unique color-mixing encoding and readout strategy, our platform enabled consistent and accurate multiplexed detection of dengue and chikungunya IgM/IgG antibodies in human clinical samples within 30 min. Our multiplex assay offers several advantages over conventional rapid diagnostic tests deployed in resource-limited settings, including a low sample volume requirement and the ability to concurrently detect four analytes. Our platform is a step toward multiplexed diagnostics that will be transformative for disease management in resource-limited settings by enabling informed treatment decisions through accessible evidence-based diagnosis.

Enhancing the Sensitivity of Lateral Flow Immunoassay by Centrifugation-Assisted Flow Control

Lateral flow immunoassay (LFIA) is widely used but is limited by its sensitivity. In this study, a novel centrifugation-assisted lateral flow immunoassay (CLFIA) was proposed that had enhanced sensitivity compared to traditional LFIA based on test strips. For CLFIA, a vaulted piece of nitrocellulose membrane was prepared and inserted into a centrifugal disc. Powered by the centrifugal force, the sample volume on the disc was not limited and the flow rate of the reaction fluid was steady and adjustable at different rotation speeds. It was found that lower rotation speeds and larger sample volumes resulted in greater signal intensity in the nitrocellulose membrane as well as higher sensitivity, indicating that the actively controlled flow on the disc allowed for sensitivity enhancement of CLFIA. To operate CLFIA on the centrifugal disc, a portable and cost-effective operating device was constructed to rotate the disc with a stepper motor and collect the results with a smartphone. The proposed method was successfully applied to detect prostate specific antigen (PSA) in human serum. Standard curves were established for CLFIA and LFIA, and both had correlation coefficients of up to 0.99. Under optimal conditions (1500 rpm rotation speed, 120 μL sample volume), the detection limit of CLFIA reached 0.067 ng/mL, showing a 6.2-fold improvement in sensitivity compared to that of LFIA. With clinical serum samples, a good correlation was observed between PSA concentrations measured by CLFIA and by a bulky commercial instrument in hospital. In summary, this portable, cost-effective, and easy-to-use system holds great promise for biomarker detection with enhanced sensitivity compared to traditional LFIA.

Performance of point-of-care diagnosis of AIDS: label-free one-step-immunoassay vs. lateral flow assay

The objective of this study is to develop an accurate, rapid, simple, and label-free assay technology that enables point-of-care diagnosis of AIDS. For this, 3-dimensional (3D) probes to sensitively detect anti-HIV antibodies were designed and synthesized by genetically presenting a HIV antigen (gp41) on the surface of engineered human ferritin nanoparticles. The 3D probes also present multi-copies of the hexa-histidine peptide (H₆) on their surface to chemisorb gold ions (Au³⁺), which is essential for the generation and self-enhancement of assay signals. The developed new assay technology (named "one-step-immunoassay") quickly produced clear optical signals through a simple and convenient one-step procedure. The diagnostic performance of the one-step-immunoassay was compared with that of the conventional lateral flow assay (LFA) using 30 AIDS patient and 20 healthy sera. The sensitivity of LFA was only 63% when a single antigen (gp41) was used but enhanced to 90% when three different antigens (gp41, p24, and gp120) were used together as the assay probes. In contrast, the one-step-immunoassay using only gp41 produced strong optical signals within 15 min without causing any false negative/positive signals, showing 100% sensitivity and 100% specificity and holding promising potential for clinical point-of-care diagnosis of AIDS.

Innovative technologies for point-of-care testing of viral hepatitis in low-resource and decentralized settings

According to the Global Burden of Diseases, chronic viral hepatitis B and C are one of the most challenging global health conditions that rank among the first causes of morbidity and mortality worldwide. Low- and middle-income countries are particularly affected by the health burden associated with HBV or HCV infection. One major gap in efficiently addressing the issue of viral hepatitis is universal screening. However, the costs and chronic lack of human resources for using traditional screening strategies based on serology and molecular biology preclude any scaling-up. Point-of-care tests have been deemed a powerful potential solution to fill the current diagnostics gap in low-resource and decentralized settings. Despite high interest resulting from their development in recent years, very few point-of-care devices have reached the market. Scaling down and automating all testing steps in 1 single device (eg, sample preparation, detection and readout) is indeed challenging. But innovations in multiple disciplines such as nanotechnologies, microfluidics, biosensors and synthetic biology have led to the creation of chip-sized laboratory systems called "lab-on-a-chip" devices. This review aims to explain how these innovations can overcome technological barriers that usually arise for each testing step while developing integrated point-of-care tests. Point-of-care test prototypes rarely meet the requirements for mass production, which also hinders their large-scale production. In addition to logistical hurdles, legal and economic constraints specific to the commercialization of in vitro diagnostics, which have also participated in the low transfer of innovative point-of-care tests to the field, are discussed.

Point-of-Care Testing and Personalized Medicine for Metabolic Disorders

This chapter describes innovations in biomarker testing that can facilitate earlier and better treatment of patients who suffer from metabolic disorders. The use of new microfluidic devices along with miniaturized biosensors and transducers enables analysis of a single drop of a blood within the time frame of a typical visit to a doctor's office. Steps are underway so that these approaches will incorporate both biochemical and clinical data, resulting in unique bioprofiles for each patient. This will allow earlier, personalized, and more effective therapeutic options. In addition, smartphone apps for self-monitoring will be used increasingly for the best possible patient outcomes.

Recent advances in nanoparticle-based lateral flow immunoassay as a point-of-care diagnostic tool for infectious agents and diseases

Recent advances in lateral flow immunoassay-based devices as a point-of-care analytical tool for the detection of infectious diseases are reviewed.

Signal self-enhancement by coordinated assembly of gold nanoparticles enables accurate one-step-immunoassays

Current immunoassays are in general performed through time-consuming multi-step procedures that depend on the use of premade signal-producing reporters and often cause assay inaccuracy. Here we report an advanced immunoassay technology that resolves the delayed, complex, and inaccurate assay problems of conventional immunoassays. We have developed an accurate, rapid, simple, and label-free one-step-immunoassay based on the self-enhancement of sensitive immunoassay signals in an assay solution. The nano-scale protein particles (hepatitis B virus capsid and human ferritin heavy chain particles) were genetically engineered to present many well-oriented antibody (or antigen) probes and multi-copies of poly-histidine peptides on their surface, resulting in the construction of 3-dimensional (3D) bioprobes that chemisorb gold ions via coordination bonding and sensitively detect both antigen and antibody analytes. Systematic numerical and experimental analyses show that the signal self-enhancement happens through two coupled reactions under reducing conditions: (1) 3D bioprobe-based sensitive immuno-detection of analytes and (2) coordinated assembly of free and chemisorbed gold nanoparticles around the 3D bioprobe-analyte-associated complexes, which is followed by the quick generation of apparent optical signals. This advanced one-step-immunoassay was successfully applied to diagnostic assays requiring high accuracy and/or speed, i.e. diagnosis of acute myocardial infarction and hepatitis C through detecting a cardiac protein (troponin I) and anti-hepatitis C virus antibodies in patient sera, indicating that it is applicable to the accurate and rapid detection of both antigen and antibody markers of a wide range of diseases.

Development of Multiplexed Infectious Disease Lateral Flow Assays: Challenges and Opportunities

Lateral flow assays (LFAs) are the mainstay of rapid point-of-care diagnostics, with the potential to enable early case management and transform the epidemiology of infectious disease. However, most LFAs only detect single biomarkers. Recognizing the complex nature of human disease, overlapping symptoms and states of co-infections, there is increasing demand for multiplexed systems that can detect multiple biomarkers simultaneously. Due to innate limitations in the design of traditional membrane-based LFAs, multiplexing is arguably limited to a small number of biomarkers. Here, we summarize the need for multiplexed LFA, key technical and operational challenges for multiplexing, inherent in the design and production of multiplexed LFAs, as well as emerging enabling technologies that may be able to address these challenges. We further identify important areas for research in efforts towards developing multiplexed LFAs for more impactful diagnosis of infectious diseases.

Quantitative differentiation of multiple virus in blood using nanoporous silicon oxide immunosensor and artificial neural network

In spite of the rapid developments in various nanosensor technologies, it still remains challenging to realize a reliable ultrasensitive electrical biosensing platform which will be able to detect multiple viruses in blood simultaneously with a fairly high reproducibility without using secondary labels. In this paper, we have reported quantitative differentiation of Hep-B and Hep-C viruses in blood using nanoporous silicon oxide immunosensor array and artificial neural network (ANN). The peak frequency output (f_p) from the steady state sensitivity characteristics and the first cut off frequency (f_c) from the transient characteristics have been considered as inputs to the multilayer ANN. Implementation of several classifier blocks in the ANN architecture and coupling them with both the sensor chips, functionalized with Hep-B and Hep-C antibodies have enabled the quantification of the viruses with an accuracy of around 95% in the range of 0.04fM-1pM and with an accuracy of around 90% beyond 1pM and within 25nM in blood serum. This is the most sensitive report on multiple virus quantification using label free method.

Culture-Independent Diagnostics for Health Security

The past decade has seen considerable development in the diagnostic application of nonculture methods, including nucleic acid amplification-based methods and mass spectrometry, for the diagnosis of infectious diseases. The implications of these new culture-independent diagnostic tests (CIDTs) include bypassing the need to culture organisms, thus potentially affecting public health surveillance systems, which continue to use isolates as the basis of their surveillance programs and to assess phenotypic resistance to antimicrobial agents. CIDTs may also affect the way public health practitioners detect and respond to a bioterrorism event. In response to a request from the Department of Homeland Security, Los Alamos National Laboratory and the Centers for Disease Control and Prevention cosponsored a workshop to review the impact of CIDTs on the rapid detection and identification of biothreat agents. Four panel discussions were held that covered nucleic acid amplification-based diagnostics, mass spectrometry, antibody-based diagnostics, and next-generation sequencing. Exploiting the extensive expertise available at this workshop, we identified the key features, benefits, and limitations of the various CIDT methods for providing rapid pathogen identification that are critical to the response and mitigation of a bioterrorism event. After the workshop we conducted a thorough review of the literature, investigating the current state of these 4 culture-independent diagnostic methods. This article combines information from the literature review and the insights obtained at the workshop.

Simultaneous Detection of Dual Nucleic Acids Using a SERS-Based Lateral Flow Assay Biosensor

A new class of surface-enhanced Raman scattering (SERS)-based lateral flow assay (LFA) biosensor has been developed for the simultaneous detection of dual DNA markers. The LFA strip in this sensor was composed of two test lines and one control line. SERS nano tags labeled with detection DNA probes were used for quantitative evaluation of dual DNA markers with high sensitivity. Target DNA, associated with Kaposi's sarcoma-associated herpesvirus (KSHV) and bacillary angiomatosis (BA), were tested to validate the detection capability of this SERS-based LFA strip. Characteristic peak intensities of SERS nano tags on two test lines were used for quantitative evaluations of KSHV and BA. The limits of detection for KSHV and BA, determined from our SERS-based LFA sensing platform, were estimated to be 0.043 and 0.074 pM, respectively. These values indicate approximately 10 000 times higher sensitivity than previously reported values using the aggregation-based colorimetric method. We believe that this is the first report of simultaneous detection of two different DNA mixtures using a SERS-based LFA platform. This novel detection technique is also a promising multiplex DNA sensing platform for early disease diagnosis.

Smart biosensors for multiplexed and fully integrated point-of-care diagnostics

Point-of-care diagnostics (PoC) and personalised medicine are highly valuable for the improvement of world health. Smartphone PoC platforms which precisely diagnose diseases and track their development through the detection of several bioanalytes represent one of the newest and most exciting advancements towards mass-screening applications. Here we focus on recent advances in both multiplexed and smartphone integrated PoC sensors.

Reversible and multi-cyclic protein-protein interaction in bacterial cellulosome-mimic system using rod-shaped viral nanostructure

The type II cohesin domain and type II dockerin of bacterial cellulosome were cloned from Clostridium thermocellum and expressed with the fusion of tobacco mosaic virus coat protein (TMVcp) and enhanced green fluorescent protein (EGFP), respectively, in Escherichia coli. The TMVcp-cohesin fusion protein was assembled to the stable and rod-shaped nanostructure (TMVcp-Coh rod) under a particular buffer condition, where many active cohesin proteins are biologically and densely displayed around the 3-dimensional surface of TMVcp-Coh rod. Using EGFP-dockerin as a fluorescent reporter, we confirmed that the Ca(2+)-dependent binding and dissociation between native cohesin and dockerin were reproduced with the two recombinant fusion proteins, TMVcp-cohesin and EGFP-dockerin. The multi-cyclic binding-dissociation operation of TMVcp-Coh rod and EGFP-dockerin was successfully performed with maintaining the reversible cohesin-dockerin interaction in every cycle. EGFP that was fused to dockerin as a proof-of-concept here can be switched to other functional proteins/peptides that need to be used in multi-cyclic operation.

Improved sensitivity of lateral flow assay using paper-based sample concentration technique

Lateral flow assays (LFAs) hold great promise for point-of-care testing, especially in resource-poor settings. However, the poor sensitivity of LFAs limits their widespread applications. To address this, we developed a novel device by integrating dialysis-based concentration method into LFAs. The device successfully achieved 10-fold signal enhancement in Human Immunodeficiency Virus (HIV) nucleic acid detection with a detection limit of 0.1 nM and 4-fold signal enhancement in myoglobin (MYO) detection with a detection limit of 1.56 ng/mL in less than 25 min. This simple, low-cost and portable integrated device holds great potential for highly sensitive detection of various target analytes for medical diagnostics, food safety analysis and environmental monitoring.

Addressing Barriers to the Development and Adoption of Rapid Diagnostic Tests in Global Health

Immunochromatographic rapid diagnostic tests (RDTs) have demonstrated significant potential for use as point-of-care diagnostic tests in resource-limited settings. Most notably, RDTs for malaria have reached an unparalleled level of technological maturity and market penetration, and are now considered an important complement to standard microscopic methods of malaria diagnosis. However, the technical development of RDTs for other infectious diseases, and their uptake within the global health community as a core diagnostic modality, has been hindered by a number of extant challenges. These range from technical and biological issues, such as the need for better affinity agents and biomarkers of disease, to social, infrastructural, regulatory and economic barriers, which have all served to slow their adoption and diminish their impact. In order for the immunochromatographic RDT format to be successfully adapted to other disease targets, to see widespread distribution, and to improve clinical outcomes for patients on a global scale, these challenges must be identified and addressed, and the global health community must be engaged in championing the broader use of RDTs.