An all-in-one point-of-care testing device for multiplexed detection of respiratory infections

Peptide nucleic acid probe-assisted paper-based electrochemical biosensor for multiplexed detection of respiratory viruses

The similar transmission patterns and early symptoms of respiratory viral infections, particularly severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza (H1N1), and respiratory syncytial virus (RSV), pose substantial challenges in the diagnosis, therapeutic management, and handling of these infectious diseases. Multiplexed point-of-care testing for detection is urgently needed for prompt and efficient disease management. Here, we introduce an electrochemical paper-based analytical device (ePAD) platform for multiplexed and label-free detection of SARS-CoV-2, H1N1, and RSV infection using immobilized pyrrolidinyl peptide nucleic acid probes. Hybridization between the probes and viral nucleic acid targets causes changes in the electrochemical response. The resulting sensor offers high sensitivity and low detection limits of 0.12, 0.35, and 0.36 pM for SARS-CoV-2 (N gene), H1N1, and RSV, respectively, without showing any cross-reactivities. The amplification-free detection of extracted RNA from 42 nasopharyngeal swab samples was successfully demonstrated and validated against reverse-transcription polymerase chain reaction (range of cycle threshold values: 17.43-25.89). The proposed platform showed excellent clinical sensitivity (100 %) and specificity (≥97 %) to achieve excellent agreement (κ ≥ 0.914) with the standard assay, thereby demonstrating its applicability for the screening and diagnosis of these respiratory diseases.

One-step time-resolved cascade logic gate microfluidic chip for home testing of SARS-CoV-2 and flu B

Home testing technology strategy is critical for early screening of disease. However, current home testing technologies often require complex processes, which limits their application. In this study, a time-resolved cascade logic gate microfluidic chip (TCLMC) was revealed to enable capillary force-based one-step operation without manual intervention or professional equipment. By analogy with logic gates in the circuit, TCLMC could automatically control the fluid flow and regulate the incubation time to optimize the immunoassay. The limit of detection of TCLMC for SARS-CoV-2 and influenza B virus (Flu B) was 134.94 and 79.17 pg mL-1 within 10 min. Additionally, this study tested saliva samples from 12 Flu B patients and 24 healthy controls to verify its clinical application. The results showed that TCLMC had high sensitivity (100%), specificity (100%), and accuracy (100%). This study provides a new one-step strategy for home testing and demonstrates its great potential in the diagnosis field.

Integrating machine learning and biosensors in microfluidic devices: A review

Microfluidic devices are increasingly widespread in the literature, being applied to numerous exciting applications, from chemical research to Point-of-Care devices, passing through drug development and clinical scenarios. Setting up these microenvironments, however, introduces the necessity of locally controlling the variables involved in the phenomena under investigation. For this reason, the literature has deeply explored the possibility of introducing sensing elements to investigate the physical quantities and the biochemical concentration inside microfluidic devices. Biosensors, particularly, are well known for their high accuracy, selectivity, and responsiveness. However, their signals could be challenging to interpret and must be carefully analysed to carry out the correct information. In addition, proper data analysis has been demonstrated even to increase biosensors' mentioned qualities. To this regard, machine learning algorithms are undoubtedly among the most suitable approaches to undertake this job, automatically learning from data and highlighting biosensor signals' characteristics at best. Interestingly, it was also demonstrated to benefit microfluidic devices themselves, in a new paradigm that the literature is starting to name "intelligent microfluidics", ideally closing this benefic interaction among these disciplines. This review aims to demonstrate the advantages of the triad paradigm microfluidics-biosensors-machine learning, which is still little used but has a great perspective. After briefly describing the single entities, the different sections will demonstrate the benefits of the dual interactions, highlighting the applications where the reviewed triad paradigm was employed.

Smartphone-driven centrifugal microfluidics for diagnostics in resource limited settings

The broad availability of smartphones has provided new opportunities to develop less expensive, portable, and integrated point-of-care (POC) platforms. Here, a platform that consists of three main components is introduced: a portable housing, a centrifugal microfluidic disc, and a mobile phone. The mobile phone supplies the electrical power and serves as an analysing system. The low-cost housing made from cardboard serves as a platform to conduct tests. The electrical energy stored in mobile phones was demonstrated to be adequate for spinning a centrifugal disc up to 3000 revolutions per minute (RPM), a rotation speed suitable for majority of centrifugal microfluidics-based assays. For controlling the rotational speed, a combination of magnetic and acoustic tachometry using embedded sensors of the mobile phone was used. Experimentally, the smartphone-based tachometry was proven to be comparable with a standard laser-based tachometer. As a proof of concept, two applications were demonstrated using the portable platform: a colorimetric sandwich immunoassay to detect interleukin-2 (IL-2) having a limit of detection (LOD) of 65.17 ng/mL and a fully automated measurement of hematocrit level integrating blood-plasma separation, imaging, and image analysis that takes less than 5 mins to complete. The low-cost platform weighing less than 150 g and operated by a mobile phone has the potential to meet the REASSURED criteria for advanced diagnostics in resource limited settings.

Evaluation of a Commercial Rapid Molecular Point-of-Care Assay for Differential Diagnosis Between SARS-CoV-2 and Flu A/B Infections in a Pediatric Setting

Given the ongoing COVID-19 pandemic, there is a need to identify SARS-CoV-2 and to differentiate it from other respiratory viral infections, especially influenza A and B, in various critical settings. Since their introduction, the use of rapid antigen tests has spread worldwide, but there is variability in their diagnostic accuracy. In the present study, we evaluated the clinical performance of the ID NOW™ COVID-19 2.0, a molecular point-of-care test (POCT) based on enzymatic isothermal amplification for the differential diagnosis of SARS-CoV-2 and influenza A/B in a pediatric emergency setting. A cohort of pediatric patients admitted between December 2022 and February 2023 were simultaneously tested with the POCT and standard laboratory molecular assay. Our findings showed high negative agreement of the POCT assay across the different age groups for SARS-CoV-2, influenza A, and influenza B (more than 98.0%), while its positive agreement varied significantly for the abovementioned viral species from 50.0% to 100%. These results highlight the potential of the ID NOW™ COVID-19 2.0 POCT assay as a reliable and rapid tool for excluding SARS-CoV-2 and influenza A/B infections in symptomatic pediatric patients, although its variable positive agreement suggests a need for confirmatory RT-qPCR testing in certain clinical and epidemiological settings in order to ensure accurate diagnosis and appropriate patient management.

Development and validation study of compact biophotonic platform for detection of serum biomarkers

The application of advances in personalized medicine requires the support of in vitro diagnostic techniques aimed at the accurate, fast, sensitive, and precise determination of selected biomarkers. Herein, a novel optical centrifugal microfluidic device is developed for clinical analysis and point-of-care diagnostics. Based on compact disc technology, the integrated biophotonic system enables multiple immunoassays in miniaturized mode. The disposable microfluidic discs are made in cyclic olefin copolymer (COP), containing arrays of immobilized probes. In the developed approach, up to six patient samples can each be tested simultaneously. A portable instrument (<2 kg) controls the assay and the high-sensitive reproducible optical detection in transmission mode. Also, the instrument incorporates specific functionalities for personalized telemedicine. The device (analytical method, disc platform, reader, and software) has been validated to diagnose IgE-mediated drug allergies, such as amoxicillin and penicillin G. The total and specific IgE to β-lactam antibiotics were determined in human serum from patients (25 μL). The excellent analytical performances (detection limit 0.24 ng/mL, standard deviation 7-20 %) demonstrated that the developed system could have the potential for a broader impact beyond the allergy field, as it applies to other IVD tests.

Influenza viruses and SARS-CoV-2 diagnosis via sensitive testing methods in clinical application

The identification of influenza viruses and SARS-CoV-2 has garnered increasing attention due of their longstanding global menace to human life and health. The point-of-care test is a potential approach for identifying influenza viruses and SARS-CoV-2 in clinical settings, leading to timely discovery, documentation, and treatment. The primary difficulties encountered with conventional detection techniques for influenza viruses and SARS-CoV-2 are the limited or inadequate ability to identify the presence of the viruses, the lack of speed, precision, accuracy, sensitivity, and specificity, often resulting in a failure to promptly notify disease control authorities. Recently, point-of-care test methods, along with nucleic acid amplification, optics, electrochemistry, lateral/vertical flow, and minimization, have been demonstrated the characteristics of reliability, sensitivity, specificity, stability, and portability. A point-of-care test offers promising findings in the early detection of influenza viruses and SARS-CoV-2 in both scientific research and practical use. In this review, we will go over the principles, advantages, limitations, and real-world applications of point-of-care diagnostics. The significance of constraints of detection, throughput, sensitivity, and specificity in the analysis of clinical samples in settings with restricted resources is underscored. This discussion concludes with their prospects and challenges.

Supramolecular Hydrogels for 3D Biosensors and Bioassays

Supramolecular hydrogels play a pivotal role in many fields of biomedical research, including emerging applications in designing advanced tools for point-of-care testing, clinical diagnostics, and lab-on-chip analysis. This review outlines the growing relevance of supramolecular hydrogels in biosensing and bioassay devices, highlighting recent advancements that deliver increased sensitivity, real-time monitoring, and multiplexing capabilities through the distinctive properties of these nanomaterials. Furthermore, the exploration extends to additional applications, such as using hydrogels as three-dimensional matrices for cell-based assays.

Advancing Microfluidic Immunity Testing Systems: New Trends for Microbial Pathogen Detection

Pathogenic microorganisms play a crucial role in the global disease burden due to their ability to cause various diseases and spread through multiple transmission routes. Immunity tests identify antigens related to these pathogens, thereby confirming past infections and monitoring the host's immune response. Traditional pathogen detection methods, including enzyme-linked immunosorbent assays (ELISAs) and chemiluminescent immunoassays (CLIAs), are often labor-intensive, slow, and reliant on sophisticated equipment and skilled personnel, which can be limiting in resource-poor settings. In contrast, the development of microfluidic technologies presents a promising alternative, offering automation, miniaturization, and cost efficiency. These advanced methods are poised to replace traditional assays by streamlining processes and enabling rapid, high-throughput immunity testing for pathogens. This review highlights the latest advancements in microfluidic systems designed for rapid and high-throughput immunity testing, incorporating immunosensors, single molecule arrays (Simoas), a lateral flow assay (LFA), and smartphone integration. It focuses on key pathogenic microorganisms such as SARS-CoV-2, influenza, and the ZIKA virus (ZIKV). Additionally, the review discusses the challenges, commercialization prospects, and future directions to advance microfluidic systems for infectious disease detection.

Multiplexed Detection Strategies for Biosensors Based on the CRISPR-Cas System

A growing number of applications require simultaneous detection of multiplexed nucleic acid targets in a single reaction, which enables higher information density in combination with reduced assay time and cost. Clustered regularly interspaced short palindromic repeats (CRISPR) and the CRISPR-Cas system have broad applications for the detection of nucleic acids due to their strong specificity, high sensitivity, and excellent programmability. However, realizing multiplexed detection is still challenging for the CRISPR-Cas system due to the nonspecific collateral cleavage activity, limited signal reporting strategies, and possible cross-reactions. In this review, we summarize the principles, strategies, and features of multiplexed detection based on the CRISPR-Cas system and further discuss the challenges and perspective.

Exploring affinity chromatography in proteomics: A comprehensive review

Over the past decades, the proteomics field has undergone rapid growth. Progress in mass spectrometry and bioinformatics, together with separation methods, has brought many innovative approaches to the study of the molecular biology of the cell. The potential of affinity chromatography was recognized immediately after its first application in proteomics, and since that time, it has become one of the cornerstones of many proteomic protocols. Indeed, this chromatographic technique exploiting the specific binding between two molecules has been employed for numerous purposes, from selective removal of interfering (over)abundant proteins or enrichment of scarce biomarkers in complex biological samples to mapping the post-translational modifications and protein interactions with other proteins, nucleic acids or biologically active small molecules. This review presents a comprehensive survey of this versatile analytical tool in current proteomics. To navigate the reader, the haphazard space of affinity separations is classified according to the experiment's aims and the separated molecule's nature. Different types of available ligands and experimental strategies are discussed in further detail for each of the mentioned procedures.

A Highly Sensitive Dual-Drive Microfluidic Device for Multiplexed Detection of Respiratory Virus Antigens

Conventional microfluidic systems that rely on capillary force have a fixed structure and limited sensitivity, which cannot meet the demands of clinical applications. Herein, we propose a dual-drive microfluidic device for sensitive and flexible detection of multiple pathogenic microorganisms antigens/antibodies. The device comprises a portable microfluidic analyzer and a dual-drive microfluidic chip. Along with capillary force, a second active driving force is provided by a removable self-driving valve in the waste chamber. The interval between these two driving forces can be adjusted to control the reaction time in the microchannel, optimizing the formation of antigen-antibody complexes and enhancing sensitivity. Moreover, the material used in the self-driving valve can be changed to adjust the active force strength needed for different tests. The device offers quantitative analysis for respiratory syncytial virus antigen and SARS-CoV-2 antigen using a 35 μL sample, delivering results within 5 min. The detection limits of the system were 1.121 ng/mL and 0.447 ng/mL for respiratory syncytial virus recombinant fusion protein and SARS-CoV-2 recombinant nucleoprotein, respectively. Although the dual-drive microfluidic device has been used for immunoassay for respiratory syncytial virus and SARS-CoV-2 in this study, it can be easily adapted to other immunoassay applications by changing the critical reagents.

Microbial biofilms for self-powered noncontact sensing

Noncontact sensing technology plays a vital role in the intelligent human-machine interface, as the essential medium for exchanging information between human and electronic devices. To date, several inorganic materials-based noncontact sensing techniques have been used to accurately detect touch, electrical property, and physical motion. However, limited available materials, dependence on additional power supplies, and poor power production performance, have seriously obstructed the practical applications of noncontact sensing technology. Here, we developed simple self-powered noncontact sensors (SNSs) assembled using a typical G. sulfurreducens biofilm as the core component. In noncontact mode, the sensor demonstrated excellent self-powered sensing performance with maximum voltage output of 10 V and a current of 60 nA, a maximum sensing range of 40 cm which is the farthest reported to date. Depending on its excellent sensing characteristic, the SNSs was used to monitor human breathing in this work. Furthermore, an array of united SNSs was able to localize external electric fields and effectively extend the sensing area by increasing the number of devices. Compared to traditional inorganic materials, microbial biofilms have the advantages of wide existence, self-proliferation, low cost, environmental friendliness, and ultra-fast self-healing property (seconds level). The proposed biofilm SNSs in our work provides new insights for noncontact power generation of biomaterials and self-driven sensing.

Microfluidic systems for infectious disease diagnostics

Microorganisms, encompassing both uni- and multicellular entities, exhibit remarkable diversity as omnipresent life forms in nature. They play a pivotal role by supplying essential components for sustaining biological processes across diverse ecosystems, including higher host organisms. The complex interactions within the human gut microbiota are crucial for metabolic functions, immune responses, and biochemical signalling, particularly through the gut-brain axis. Viruses also play important roles in biological processes, for example by increasing genetic diversity through horizontal gene transfer when replicating inside living cells. On the other hand, infection of the human body by microbiological agents may lead to severe physiological disorders and diseases. Infectious diseases pose a significant burden on global healthcare systems, characterized by substantial variations in the epidemiological landscape. Fast spreading antibiotic resistance or uncontrolled outbreaks of communicable diseases are major challenges at present. Furthermore, delivering field-proven point-of-care diagnostic tools to the most severely affected populations in low-resource settings is particularly important and challenging. New paradigms and technological approaches enabling rapid and informed disease management need to be implemented. In this respect, infectious disease diagnostics taking advantage of microfluidic systems combined with integrated biosensor-based pathogen detection offers a host of innovative and promising solutions. In this review, we aim to outline recent activities and progress in the development of microfluidic diagnostic tools. Our literature research mainly covers the last 5 years. We will follow a classification scheme based on the human body systems primarily involved at the clinical level or on specific pathogen transmission modes. Important diseases, such as tuberculosis and malaria, will be addressed more extensively.

A Magnetic-Optical Triple-Mode Lateral Flow Immunoassay for Sensitive and Rapid Detection of Respiratory Adenovirus

Human respiratory adenovirus (ADV) is a highly infectious respiratory virus with potential for pandemics. There are currently no specific drugs to treat ADV worldwide, so early rapid detection of ADV infection is essential. In this study, we developed an innovative magnetic-optical triple-mode lateral flow immunoassay (LFIA) using magnetic quantum dots as immunomarkers. This novel approach addresses the need for rapid and accurate ADV detection, allowing for multimodal quantitative/semiquantitative analysis of magnetic, fluorescent, and visible signals within a mere 15 min. The lower limit of detection (LOD) for magnetic, fluorescent, and visual signals was determined to be 5.6 × 103, 1.2 × 103, and 1.95 × 104 copies/mL, respectively. The detection range for ADV using this approach was 1.2 × 103-5 × 107 copies/mL. Additionally, semiquantitative analysis, which is user-friendly and does not necessitate specialized equipment, was successfully implemented. Notably, seven respiratory viruses showed no cross-reactivity with the generated LFIA test strips. The intrabatch repeatability exhibited a coefficient of variation (CV) of less than 5%, while the interbatch repeatability had a CV of less than 15%. Furthermore, recovery values ranged from 95% to 106.8% for samples analyzed concurrently with dual signals at the same spiking concentration. The assay developed in this study boasts a wide detection range and exceptional sensitivity and specificity. This technique is exceptionally well-suited for on-site rapid detection, with the potential for personal self-testing and early ADV infection diagnosis. Its versatility extends to a broad array of application scenarios.

A magnetic control enrichment technique combined with terahertz metamaterial biosensor for detecting SARS-CoV-2 spike protein

The highly contagious SARS-CoV-2 virus, responsible for the COVID-19 pandemic continues to pose significant challenges to public health. Developing new methods for early detection and diagnosis is crucial in combatting the disease, mitigating its impact and be prepared for future challenges in pandemic diseases. In this study, we propose a terahertz (THz) biosensing technology that capitalizes on the properties of THz metamaterial in conjunction with magnetic nanoparticles. This approach can accurately identify the SARS-CoV-2 spike protein by pinpointing its location on the THz resonance sources grooved surface. The magnetic nanoparticles are employed to selectively bind with target molecules, and migrate towards the THz metamaterial unit cell when exposed to an applied magnetic field. The presence of target molecules in to the metamaterial variation in the frequency, amplitude, and phase of the resonance response, thus enabling swift, accurate and sensitive detection. To assess the effectiveness of the proposed technique, we have conducted a comparative analysis between real samples on platforms controlled by magnetic manipulation and those without the control. It was confirmed that the proposed THz sensing method demonstrated a linear detection range spanning from 0.005 ng mL-1 to 1000 ng mL-1 with a detection limit of 0.002 ng mL-1. Furthermore, it exhibited a frequency shift of 24 GHz and a stability index of 95%. The THz biosensing technique may pave a new avenue in identifying and preempting the spread of potential pandemic diseases.

AIE Nanozyme-Based Long Persistent Chemiluminescence and Fluorescence for POCT of Pathogenic Bacteria

Pathogenic bacteria are widely distributed in diverse environments and significantly threaten human health. Point-of-care testing (POCT) is a valuable way for early warnings of bacteria threat. Herein, a chemiluminescence (CL)-based ratiometric sensing platform was constructed for sensitive POCT of bacteria according to a newly designed aggregation-induced emission (AIE) molecule. The new AIE molecule presents oxidase-like properties (named as AIEzyme) and can trigger long persistent CL of luminol (LUM) with strong intensity in the absence of H2O2. The CL emission can be monitored with the naked eye for over 2 h. The emission mechanism is explored and may be attributed to the persistent reactive oxygen species generation of the AIEzyme according to the cyclic energy transfer between the AIEzyme and luminol, which catalyzes CL of luminol. Based on the CL resonance energy transfer mechanism, an afterglow luminescence system is further developed, which is used to construct a ratiometric biosensor for detection of pathogenic bacteria. With a homemade holder as a detection room and a smartphone as an analyzer, the portable biosensing platform is used for quantitative POCT of bacteria in real samples with good recovery. The detection is free of H2O2 and an external excitation source, which not only simplifies the operation but reduces interference. Specifically, the long persistent luminescence and the ratiometric strategy can significantly improve accuracy, providing an instructive way for point-of-need analysis, for example, SARS-CoV-2 detection and bioimaging analysis.

Trends of respiratory virus detection in point-of-care testing: A review

In resource-limited conditions such as the COVID-19 pandemic, on-site detection of diseases using the Point-of-care testing (POCT) technique is becoming a key factor in overcoming crises and saving lives. For practical POCT in the field, affordable, sensitive, and rapid medical testing should be performed on simple and portable platforms, instead of laboratory facilities. In this review, we introduce recent approaches to the detection of respiratory virus targets, analysis trends, and prospects. Respiratory viruses occur everywhere and are one of the most common and widely spreading infectious diseases in the human global society. Seasonal influenza, avian influenza, coronavirus, and COVID-19 are examples of such diseases. On-site detection and POCT for respiratory viruses are state-of-the-art technologies in this field and are commercially valuable global healthcare topics. Cutting-edge POCT techniques have focused on the detection of respiratory viruses for early diagnosis, prevention, and monitoring to protect against the spread of COVID-19. In particular, we highlight the application of sensing techniques to each platform to reveal the challenges of the development stage. Recent POCT approaches have been summarized in terms of principle, sensitivity, analysis time, and convenience for field applications. Based on the analysis of current states, we also suggest the remaining challenges and prospects for the use of the POCT technique for respiratory virus detection to improve our protection ability and prevent the next pandemic.

Newly Developed Electrochemiluminescence Based on Bipolar Electrochemistry for Multiplex Biosensing Applications: A Consolidated Review

Recently, there has been an upsurge in the extent to which electrochemiluminescence (ECL) working in synergy with bipolar electrochemistry (BPE) is being applied in simple biosensing devices, especially in a clinical setup. The key objective of this particular write-up is to present a consolidated review of ECL-BPE, providing a three-dimensional perspective incorporating its strengths, weaknesses, limitations, and potential applications as a biosensing technique. The review encapsulates critical insights into the latest and novel developments in the field of ECL-BPE, including innovative electrode designs and newly developed, novel luminophores and co-reactants employed in ECL-BPE systems, along with challenges, such as optimization of the interelectrode distance, electrode miniaturization and electrode surface modification for enhancing sensitivity and selectivity. Moreover, this consolidated review will provide an overview of the latest, novel applications and advances made in this field with a bias toward multiplex biosensing based on the past five years of research. The studies reviewed herein, indicate that the technology is rapidly advancing at an outstanding purse and has an immense potential to revolutionize the general field of biosensing. This perspective aims to stimulate innovative ideas and inspire researchers alike to incorporate some elements of ECL-BPE into their studies, thereby steering this field into previously unexplored domains that may lead to unexpected, interesting discoveries. For instance, the application of ECL-BPE in other challenging and complex sample matrices such as hair for bioanalytical purposes is currently an unexplored area. Of great significance, a substantial fraction of the content in this review article is based on content from research articles published between the years 2018 and 2023.

Multiplex Detection of Infectious Diseases on Microfluidic Platforms

Infectious diseases contribute significantly to the global disease burden. Sensitive and accurate screening methods are some of the most effective means of identifying sources of infection and controlling infectivity. Conventional detecting strategies such as quantitative polymerase chain reaction (qPCR), DNA sequencing, and mass spectrometry typically require bulky equipment and well-trained personnel. Therefore, mass screening of a large population using conventional strategies during pandemic periods often requires additional manpower, resources, and time, which cannot be guaranteed in resource-limited settings. Recently, emerging microfluidic technologies have shown the potential to replace conventional methods in performing point-of-care detection because they are automated, miniaturized, and integrated. By exploiting the spatial separation of detection sites, microfluidic platforms can enable the multiplex detection of infectious diseases to reduce the possibility of misdiagnosis and incomplete diagnosis of infectious diseases with similar symptoms. This review presents the recent advances in microfluidic platforms used for multiplex detection of infectious diseases, including microfluidic immunosensors and microfluidic nucleic acid sensors. As representative microfluidic platforms, lateral flow immunoassay (LFIA) platforms, polymer-based chips, paper-based devices, and droplet-based devices will be discussed in detail. In addition, the current challenges, commercialization, and prospects are proposed to promote the application of microfluidic platforms in infectious disease detection.

Partitioning-Induced Isolation of Analyte and Analysis via Multiscaled Aqueous Two-Phase System

Most fluorescence-based bioanalytical applications need labeling of analytes. Conventional labeling requires washing to remove the excess fluorescent labels and reduce the noise signals. These pretreatments are labor intensive and need specialized equipment, hindering portable applications in resource-limited areas. Herein, we use the aqueous two-phase system (ATPS) to realize the partitioning-induced isolation of labeled analytes from background signals without extra processing steps. ATPS is formed by mixing two polymers at sufficiently high concentrations. ATPS-based isolation is driven by intrinsic affinity differences between analytes and excess labels. To demonstrate the partitioning-induced isolation and analysis, fluorescein isothiocyanate (FITC) is selected as the interfering fluorophore, and a monoclonal antibody (IgG) is used as the analyte. To optimize ATPS compositions, different molecular weights and mass fractions of polyethylene glycol (PEG) and dextran and different phosphate-buffered saline (PBS) concentrations are investigated. Various operational scales of our approach are demonstrated, suggesting its compatibility with various bioanalytical applications. In centimeter-scale ATPS, the optimized distribution ratios of IgG and FITC are 91.682 and 0.998 using PEG 6000 Da and dextran 10,000 Da in 10 mM PBS. In millimeter-scale ATPS, the analyte is enriched to 6.067 fold using 15 wt % PEG 35,000 Da and 5 wt % dextran 500,000 Da in 10 mM PBS. In microscale ATPS, analyte dilutions are isolated into picoliter droplets, and the measured fluorescence intensities linearly correlated with the analyte concentrations (R² = 0.982).

Comparison of Pairwise Venous and Fingertip Plasma Using Quantitative Proteomics Based on Data-Independent Acquisition

Blood contains a great deal of health-related information and can be used to monitor human health status. Clinically, venous or fingertip blood is usually used for blood tests. However, the clinical application settings of the two sources of blood are unclear. In this study, the proteomes of pairwise venous plasma (VP) and fingertip plasma (FP) were analyzed, and the levels of 3797 proteins were compared between VP and FP. The Spearman's correlation coefficient for the relationship between protein levels of VP and FP ranges from 0.64 to 0.78 (p < 0.0001). The common pathways of VP and FP are related to cell-cell adhesion, protein stabilization, innate immune response, and complement activation, the classical pathway. The VP-overrepresented pathway is related to actin filament organization, while the FP-overrepresented pathway is related to the hydrogen peroxide catabolic process. ADAMTSL4, ADIPOQ, HIBADH, and XPO5 both in VP and FP are potential gender-related proteins. Notably, the VP proteome has a higher interpretation on age than the FP proteome, and CD14 is a potential age-related protein in VP but not in FP. Our study mapped the different proteomes between VP and FP, which can provide value for the standardization of clinical blood tests.

Challenges and perspectives of multi-virus biosensing techniques: A review

In the context of globalization, individuals have an increased chance of being infected by multiple viruses simultaneously, thereby highlighting the importance of developing multiplexed devices. In addition to sufficient sensitivity and rapid response, multi-virus sensing techniques are expected to offer additional advantages including high throughput, one-time sampling for parallel analysis, and full automation with data visualization. In this paper, we review the optical, electrochemical, and mechanical platforms that enable multi-virus biosensing. The working mechanisms of each platform, including the detection principle, transducer configuration, bio-interface design, and detected signals, are reviewed. The advantages and limitations, as well as the challenges in implementing various detection strategies in real-life scenarios, were evaluated. Future perspectives on multiplexed biosensing techniques are critically discussed. Earlier access to multi-virus biosensors will efficiently serve for immediate pandemic control, such as in emerging SARS-CoV-2 and monkeypox cases.

Visualized RNA detection of SARS-CoV-2 in a closed tube by coupling RT-PCR with nested invasive reaction

A simple, cost-effective and reliable diagnosis of pathogen nucleic acids assay is much required for controlling a pandemic of a virus disease, such as COVID-19. Our previously developed visualized detection of pathogen DNA in a single closed tube is very suitable for POCT. However, virus RNA could not be detected directly and should be reverse-transcribed into cDNA in advance. To enable this visualized assay to detect virus RNA directly, various types of reverse transcriptase were investigated, and finally we found that HiScript II reverse transcriptase could keep active and be well adapted to the one-pot visualized assay in optimized conditions. Reverse transcription, template amplification and amplicon identification by PCR coupled with invasive reaction, as well as visualization by self-assembling of AuNP probes could be automatically and sequentially performed in a closed tube under different temperature conditions, achieving "sample (RNA)-in-result (red color)-out" only by a simple PCR engine plus the naked eye. The visualized RT-PCR is sensitive to unambiguous detection of 5 copies of the N and ORFlab genes of SARS-CoV-2 RNA comparing favourably with qPCR methods (commercialized kit), is specific to genotype 3 variants (Alpha, Beta and Omicron) of SARS-CoV-2, and is very accurate for picking up 0.01% Omicron variant from a large amount of sequence-similar backgrounds. The method is employed in detecting 50 clinical samples, and 10 of them were detected as SARS-CoV-2 positive samples, identical to those by conventional RT-PCR, indicating that the method is cost-effective and labor-saving for pathogen RNA screening in resource-limited regions.

Application of microfluidic technologies on COVID-19 diagnosis and drug discovery

The ongoing coronavirus disease 2019 (COVID-19) pandemic has boosted the development of antiviral research. Microfluidic technologies offer powerful platforms for diagnosis and drug discovery for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnosis and drug discovery. In this review, we introduce the structure of SARS-CoV-2 and the basic knowledge of microfluidic design. We discuss the application of microfluidic devices in SARS-CoV-2 diagnosis based on detecting viral nucleic acid, antibodies, and antigens. We highlight the contribution of lab-on-a-chip to manufacturing point-of-care equipment of accurate, sensitive, low-cost, and user-friendly virus-detection devices. We then investigate the efforts in organ-on-a-chip and lipid nanoparticles (LNPs) synthesizing chips in antiviral drug screening and mRNA vaccine preparation. Microfluidic technologies contribute to the ongoing SARS-CoV-2 research efforts and provide tools for future viral outbreaks.

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.