Immuno-chromatic probe based lateral flow assay for point-of-care detection of Japanese encephalitis virus NS1 protein biomarker in clinical samples using a smartphone-based approach

Simultaneous multiple target detection platform based on vertical flow immunoassay

In general, vertical flow assay (VFA) has a disadvantage of requiring a complex analysis process that involves manually injecting various reagents (target analyte, washing buffer, detection conjugate, etc.) sequentially. However, in this study, we have developed an innovative paper-based VFA device that replaces the complex analysis process with one-step and enables the detection of multiple targets. The fabrication process of the multi-target detection VFA device is as follows: preparation and pre-treatment of the strip materials, design of strip cartridge, design of the multiple detection VFA device, optimization experiments for strip sample flow rates, determination of device analysis time, determination of device limit of detection (LOD), multiple target signal uniformity experiment, immunoglobulin G (IgG) and C-reactive protein (CRP) antigen-antibody multiple detection experiment, and data extraction and analysis method. The use of paper-based materials enables the device to be produced at cost-effective, and cartridge production allowed for uniform array formation. IgG and CRP are used to evaluate the performance of the device as common biomarkers. The device proposed in this study is currently under research. To validate multiple target detection capability of the VFA device proposed in this study, two types of antigens-antibodies (Human IgG and Human CRP) were employed. The detection limit is 0.15 μg/mL for IgG and 0.19 μg/mL for CRP in naked eye. Furthermore, it was confirmed that there is no cross-reactivity caused by the device structure through IgG and CRP antigens. In conclusion, the VFA device proposed in this study consists of a one-step analysis process, and it has been confirmed that it can detect multiple targets simultaneously.

Design and fabrication of a competitive lateral flow assay using gold nanoparticle as capture probe for the rapid and on-site detection of penicillin antibiotic in food samples

Lateral flow assays (LFAs) are among the utmost cost-efficient, paper-based point-of-care (POC) diagnostic devices. Herein, we have reported the fabrication of a competitive LFA for on-site detection of penicillin. Various parameters such as Ab concentration for conjugation, Pen-BSA conjugate concentration, pore size of membrane, and blocking buffer were standardised for the fabrication of LFA. Different concentrations of penicillin (1 pM-1 mM) were added to the sample pad to observe the color intensity. The visual detection limit (LOD) achieved from the LFA was 10 nM for Penicillin that correlated with the LOD calculated from the 'ColorGrab' colorimeter application. Additionally, LFA showed insignificant cross reactivity with other β-lactam antibiotics and were also validated with spiked food samples such as milk, meat and egg. Hence, the fabricated LFA can be successfully utilised for the POC detection of penicillin in food samples on large scale.

Recent Advances in Lateral Flow Assays for Viral Protein Detection with Nanomaterial-Based Optical Sensors

Controlling the progression of contagious diseases is crucial for public health management, emphasizing the importance of early viral infection diagnosis. In response, lateral flow assays (LFAs) have been successfully utilized in point-of-care (POC) testing, emerging as a viable alternative to more traditional diagnostic methods. Recent advancements in virus detection have primarily leveraged methods such as reverse transcription-polymerase chain reaction (RT-PCR), reverse transcription-loop-mediated isothermal amplification (RT-LAMP), and the enzyme-linked immunosorbent assay (ELISA). Despite their proven effectiveness, these conventional techniques are often expensive, require specialized expertise, and consume a significant amount of time. In contrast, LFAs utilize nanomaterial-based optical sensing technologies, including colorimetric, fluorescence, and surface-enhanced Raman scattering (SERS), offering quick, straightforward analyses with minimal training and infrastructure requirements for detecting viral proteins in biological samples. This review describes the composition and mechanism of and recent advancements in LFAs for viral protein detection, categorizing them into colorimetric, fluorescent, and SERS-based techniques. Despite significant progress, developing a simple, stable, highly sensitive, and selective LFA system remains a formidable challenge. Nevertheless, an advanced LFA system promises not only to enhance clinical diagnostics but also to extend its utility to environmental monitoring and beyond, demonstrating its potential to revolutionize both healthcare and environmental safety.

Specific separation and sensitive detection of foodborne pathogens by phage-derived bacterial-binding protein-nano magnetic beads coupled with smartphone-assisted paper sensor

Foodborne pathogen infection poses a significant threat to public health and is considered as one of the most serious hazards in global food safety. Herein, a sensitive and efficient method for on-site monitoring of foodborne pathogens was developed by using a smartphone-assisted paper-sensor combined with phage-derived bacterial-binding proteins-nano magnetic beads (PBPs-MBs). PBPs including tail fiber protein (TFP:gp13), cell-wall binding domain (CBD) of endolysin and tailspike protein (TSP) coated on the surface of MBs were applied for rapid separation and enrichment of targeted bacteria (Escherichia coli O157:H7, Staphylococcus aureus and Salmonella typhimurium, respectively) from food samples in 20 min before detection on paper-based sensors. The paper-based sensor was loaded with the lytic agent (polymyxin B) to induce bacterial lysis and release specific endogenous enzymes. Subsequently, three distinct chromogenic substrates were hydrolyzed by their corresponding enzymes, resulting in characteristic color changes on the paper, respectively. In addition, a smartphone APP for red-green-blue (RGB) color analysis of paper was able to directly detect three foodborne pathogens. As a result, the limit of detection (LOD) values for three foodborne pathogens were found to be 2.44 × 102, 2.68 × 104 and 4.62 × 103 CFU/mL, respectively, which were much lower than other studies (106-108 CFU/mL) based on enzymes. Moreover, the feasibility of this approach was further assessed through the successful detection of targeted bacteria in real samples with satisfactory recovery rates. In conclusion, this smartphone-assisted biosensor offers promising application potential for point-of-care testing (POCT) of foodborne pathogens in resource-scarce areas.

Diagnosing arthropod-borne flaviviruses: non-structural protein 1 (NS1) as a biomarker

In recent decades, the presence of flaviviruses of concern for human health in Europe has drastically increased,exacerbated by the effects of climate change - which has allowed the vectors of these viruses to expand into new territories. Co-circulation of West Nile virus (WNV), Usutu virus (USUV), and tick-borne encephalitis virus (TBEV) represents a threat to the European continent, and this is further complicated by the difficulty of obtaining an early and discriminating diagnosis of infection. Moreover, the possibility of introducing non-endemic pathogens, such as Japanese encephalitis virus (JEV), further complicates accurate diagnosis. Current flavivirus diagnosis is based mainly on RT-PCR and detection of virus-specific antibodies. Yet, both techniques suffer from limitations, and the development of new assays that can provide an early, rapid, low-cost, and discriminating diagnosis of viral infection is warranted. In the pursuit of ideal diagnostic assays, flavivirus non-structural protein 1 (NS1) serves as an excellent target for developing diagnostic assays based on both the antigen itself and the antibodies produced against it. This review describes the potential of such NS1-based diagnostic methods, focusing on the application of flaviviruses that co-circulate in Europe.

An Integrated Approach to Improve the Assay Performance of Quantum Dot-Based Lateral Flow Immunoassays by Using Silver Deposition

Traditional quantum dot-based lateral flow immunoassay (QD-LFIA) is limited to signal loss in part by the blinking, photobleaching and oxidative quenching of QD probes. Inspired by the good application of silver deposition on QD surfaces in tissue imaging, and in the context of improving the assay performance without compromising the simplicity and practicality, we report that introducing the QD-silver combination to the LFIA system, has the advantages of accuracy improvement, signal enhancement and user friendliness promotion, but maintains the cost-effective property and commercial accessibility of QD-LFIA. The effect was shown by using CdSe/ZnS QD-LFIA coupled with anti-sodium pentachlorophenate antibody, which provided a 4-fold improvement in the signal, a 2.5-fold improvement in the detection limit and a zero false-negative rate for sodium pentachlorophenate analysis in chicken samples. The proposed LFIA integrates the possibilities of colorimetric and fluorometric detection with different detection limits (fluorometric at 10 ng/mL and colorimetric at 4 ng/mL) and with acceptable detection times (fluorometric at 12 min and colorimetric at 27 min). The current results indicate that this QD-silver combined LFIA is complementary to conventional fluorescence LFIA and could be an inexpensive, versatile, and sensitive alternative.

Lateral Flow Assay for Hepatitis B Detection: A Review of Current and New Assays

From acute to chronic hepatitis, cirrhosis, and hepatocellular cancer, hepatitis B infection causes a broad spectrum of liver diseases. Molecular and serological tests have been used to diagnose hepatitis B-related illnesses. Due to technology limitations, it is challenging to identify hepatitis B infection cases at an early stage, particularly in a low- and middle-income country with constrained resources. Generally, the gold-standard methods to detect hepatitis B virus (HBV) infection requires dedicated personnel, bulky, expensive equipment and reagents, and long processing times which delay the diagnosis of HBV. Thus, lateral flow assay (LFA), which is inexpensive, straightforward, portable, and operates reliably, has dominated point-of-care diagnostics. LFA consists of four parts: a sample pad where samples are dropped; a conjugate pad where labeled tags and biomarker components are combined; a nitrocellulose membrane with test and control lines for target DNA-probe DNA hybridization or antigen-antibody interaction; and a wicking pad where waste is stored. By modifying the pre-treatment during the sample preparation process or enhancing the signal of the biomarker probes on the membrane pad, the accuracy of the LFA for qualitative and quantitative analysis can be improved. In this review, we assembled the most recent developments in LFA technologies for the progress of hepatitis B infection detection. Prospects for ongoing development in this area are also covered.

Point-of-care detection of Japanese encephalitis virus biomarker in clinical samples using a portable smartphone-enabled electrochemical "Sensit" device

Japanese encephalitis (JE), a neglected tropical zoonotic disease prevalent in south-east Asian and western pacific countries, caused by the flavivirus JE virus (JEV), has a dearth of electrochemical point-of-care (PoC) diagnostic tools available to manage endemic breakouts. To overcome this, we have developed a screen-printed carbon electrode (SPCE) immunosensor for rapid PoC detection of JEV nonstructural 1 (NS1) antigen (Ag), found circulating in serum of infected individuals using a smartphone based portable "Sensit" device. The modification of SPCE surface with JEV NS1 antibody (Ab) was confirmed via observation of globular protein structures via scanning electron microscopy (SEM), increase in electrode surface hydrophilicity via contact angle measurement and decrease in current via differential pulse voltammetry (DPV). The fabrication and testing parameters were optimized based on highest current output obtained using DPV. The SPCE was tested for detection limit of target JEV NS1 Ag ranging from 1 fM to 1 μM, which was determined as 0.45 fM in spiked serum. The disposable immunosensor was also found to be highly specific in detecting JEV NS1 Ag over other flaviviral NS1 Ag. Finally, the modified SPCE was clinically validated by testing 62 clinical JEV samples using both a portable miniaturized electrochemical "Sensit" device coupled with a smartphone and a laboratory-based potentiostat. The results were corroborated with gold-standard RT-PCR and showed 96.77% accuracy, 96.15% sensitivity, and 97.22% specificity. Hence, this technique may further be developed into a one-step rapid diagnostic tool for JEV, especially in rural areas.

Recent Advances in Molecular and Immunological Diagnostic Platform for Virus Detection: A Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused an ongoing coronavirus disease (COVID-19) outbreak and a rising demand for the development of accurate, timely, and cost-effective diagnostic tests for SARS-CoV-2 as well as other viral infections in general. Currently, traditional virus screening methods such as plate culturing and real-time PCR are considered the gold standard with accurate and sensitive results. However, these methods still require sophisticated equipment, trained personnel, and a long analysis time. Alternatively, with the integration of microfluidic and biosensor technologies, microfluidic-based biosensors offer the ability to perform sample preparation and simultaneous detection of many analyses in one platform. High sensitivity, accuracy, portability, low cost, high throughput, and real-time detection can be achieved using a single platform. This review presents recent advances in microfluidic-based biosensors from many works to demonstrate the advantages of merging the two technologies for sensing viruses. Different platforms for virus detection are classified into two main sections: immunoassays and molecular assays. Moreover, available commercial sensing tests are analyzed.

Immunochromatographic assay for the point-of-care diagnosis of food borne Salmonella strains using smartphone application

Salmonella strain is a prevalent pathogen, affecting poultry industry and hence human population around the world. Host-specific pathogen infections including fowl typhoid, pullorum disease and typhoid fever affects poultry birds, causing huge economic loss worldwide. This study explored the fabrication of immunochromatographic (ICG) strip by colorimetric method integrated with smartphone ColorGrab application for the detection of Salmonella using in-house generated antibodies (Abs) conjugated with gold nanoparticles. The developed point-of-care diagnostic platform was fabricated in-house and tested to detect the presence of Salmonella in a linear range of 10⁷-10⁰ CFU/mL with the limit of detection (LOD) of 10³, 10² and 10⁴ CFU/mL respectively, for Salmonella gallinarum (S.gal), Salmonella pullorum (S.pul) and Salmonella enteritidis (S.ent), which was further confirmed by smartphone-based ColorGrab application. The fabricated ICG strips were further validated using spiked fecal, meat, and milk samples which provided results in 10 mins with stability at 4 °C and 37 °C up to 28 days. Hence, the fabricated in-house ICG strip can be used as a portable, cost-effective diagnostic device for rapid detection of Salmonella strains in food samples.

Development of sensitive magnetic nanoparticle assisted rapid sandwich assay(s-MARSA) to monitor Parkinson's disease and Schizophrenia pharmacotherapy

Parkinson's disease and Schizophrenia fall under low dopamine neurodegenerative and high dopamine psychiatric disorders respectively. Pharmacological interventions to correct mid-brain dopamine concentrations sometimes overshoots the physiological dopamine levels leading to psychosis in Parkinson's disease patients and, extra-pyramidal symptoms in schizophrenia patients. Currently no validated method is available to monitor side effects in such patients, Apolipoprotein E is one of the CSF biomarkers identified in the recent past that shows an inverse relation to mid-brain dopamine concentration. In this study, we have developed s-MARSA for the detection of Apolipoprotein E from ultra-small volume (2 μL) of CSF. s-MARSA exhibits a broad detection range (5 fg mL^-1 to 4 μg mL^-1) with a better detection limit and could be performed within an hour utilizing only a small volume of CSF sample. The values measured by s-MARSA strongly correlates with the values measured by ELISA. Our method has advantages over ELISA in having a lower detection limit, a broader linear detection range, shorter analysis time, and requiring a low volume of CSF samples. The developed s-MARSA method holds promise for the detection of Apolipoprotein E with clinical utility for monitoring pharmacotherapy of Parkinson's and Schizophrenia patients.

A Systematic Review on the Advanced Techniques of Wearable Point-of-Care Devices and Their Futuristic Applications

Personalized point-of-care testing (POCT) devices, such as wearable sensors, enable quick access to health monitoring without the use of complex instruments. Wearable sensors are gaining popularity owing to their ability to offer regular and continuous monitoring of physiological data by dynamic, non-invasive assessments of biomarkers in biofluids such as tear, sweat, interstitial fluid and saliva. Current advancements have concentrated on the development of optical and electrochemical wearable sensors as well as advances in non-invasive measurements of biomarkers such as metabolites, hormones and microbes. For enhanced wearability and ease of operation, microfluidic sampling, multiple sensing, and portable systems have been incorporated with materials that are flexible. Although wearable sensors show promise and improved dependability, they still require more knowledge about interaction between the target sample concentrations in blood and non-invasive biofluids. In this review, we have described the importance of wearable sensors for POCT, their design and types of these devices. Following which, we emphasize on the current breakthroughs in the application of wearable sensors in the realm of wearable integrated POCT devices. Lastly, we discuss the present obstacles and forthcoming potentials including the use of Internet of Things (IoT) for offering self-healthcare using wearable POCT.

Gold nanoparticle conjugate-based lateral flow immunoassay (LFIA) for rapid detection of RBD antigen of SARS-CoV-2 in clinical samples using a smartphone-based application

The coronavirus disease 2019 (COVID-19) pandemic has emphasized the need for development of a rapid diagnostic device for the effective treatment and its mitigation. Lateral flow immunoassay (LFIA) belongs to a class of diagnostic devices, which has the benefit of providing quick results, easy to handle, low cost, and on-site applicable. So far, several LFIA has been developed for the detection of infectious severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), however, only a few of them are antigen (Ag)-based. Here, we describe an antibody (Ab)-labeled gold nanoparticles (AuNPs)-based LFIA (AuNPs-LFIA) for the detection of Receptor-Binding Domain (RBD) of SARS-CoV-2. For this, RBD Ab of SARS-CoV-2 was conjugated with the AuNPs, which served as a detecting probe. The fabricated LFIA strip was optimized for different parameters such as membrane pore size, blocking conditions, Ab coating concentration, and conjugate incubation. The optimized LFIA strips were validated in spiked buffer samples and the optimal limit of detection was found to be 1 ng/ml, which was confirmed by a smartphone-based application. Moreover, the developed AuNPs-LFIA strips effectively detected RBD Ag in 100 clinical samples with 94.3% sensitivity and 90.9% specificity in clinical samples when compared with the gold standard (RT-PCR). The fabricated LFIAs are reported to have storage stability of up to 21 days at 4°C and room temperature (RT). Hence, the developed LFIA can be used as a portable, cost-effective diagnostic device for rapid detection of SARS-CoV-2.

A brief review on novel biomarkers identified and advanced biosensing technologies developed for rapid diagnosis of Japanese Encephalitis Virus

Advanced biosensor technology research is imperative for the management of infectious disease outbreaks such as Japanese Encephalitis (JE), a zoonotic disease caused by the flavivirus JE virus (JEV) which is transmitted to humans (dead-end hosts) from the amplification host, pigs, via mosquitoes. To avoid future pandemic scenarios, proactive research rather than responsive research in the field of diagnostics is a requirement for development of rapid, sensitive and specific screening detection methods. In this mini-review, we have critically compared and evaluated the different types of biomarkers (antigen, antibody, nucleic acid) identified for JEV diagnostics and their specific roles in the manifestation of the infection which may be potentially used for therapeutics and drug development as no treatment is available for JE. Furthermore, different biosensors developed for the detection of JEV biomarkers have been discussed in detail to give an overview of the working principles (electrochemical, optical, etc.), fabrication components (signal amplifier, bioreceptor, etc.), detection limits and response times. This review provides a compact compiled base on available JEV diagnostic research work being currently carried out along with their limitations, future prospective, and major challenges faced. This will enable future development of rapid point-of-care diagnostic screening methods for JEV infection management, which may help reduce number of fatalities.