Hybrid Paper-Plastic Microchip for Flexible and High-Performance Point-of-Care Diagnostics

Rapid and sensitive point-of-care PTS-CRISPR assay for food safety monitoring of aflatoxin B1

Food safety is crucial for human health, but its effective on-site monitoring remains a challenge. Pregnancy test strip (PTS) is the successful point-of-care testing (POCT) product of the highest market share in the world, with the cost as low as $0.10 per test. Herein, combined with the CRISPR (clustered regularly interspaced short palindromic repeats) system, PTS-CRISPR was for the first time introduced into food safety monitoring, for rapid and sensitive POCT of aflatoxin B1. The low-cost, easy-to-operate PTS-CRISPR is expected to bring security to the grassroots food market.

Polyethylene Glycol-Mediated Directional Conjugation of Biological Molecules for Enhanced Immunoassays at the Point-of-Care

Rapid and reliable point-of-care (POC) diagnostic tests can have a significant impact on global health. One of the most common approaches for developing POC systems is the use of target-specific biomolecules. However, the conjugation of biomolecules can result in decreased activity, which may compromise the analytical performance and accuracy of the developed systems. To overcome this challenge, we present a polymer-based cross-linking protocol for controlled and directed conjugation of biological molecules. Our protocol utilizes a bifunctional thiol-polyethylene glycol (PEG)-hydrazide polymer to enable site-directed conjugation of IgG antibodies to the surface of screen-printed metal electrodes. The metal surface of the electrodes is first modified with thiolated PEG molecules, leaving the hydrazide groups available to react with the aldehyde group in the Fc fragments of the oxidized IgG antibodies. Using anti-Klebsiella pneumoniae carbapenemase-2 (KPC-2) antibody as a model antibody used for antimicrobial resistance (AMR) testing, our results demonstrate a ~10-fold increase in antibody coupling compared with the standard N-hydroxysuccinimide (NHS)-based conjugation chemistry and effective capture (>94%) of the target KPC-2 enzyme antigen on the surface of modified electrodes. This straightforward and easy-to-perform strategy of site-directed antibody conjugation can be engineered for coupling other protein- and non-protein-based biological molecules commonly used in POC testing and development, thus enhancing the potential for improved diagnostic accuracy and performance.

Challenges in Direct Detection of Flaviviruses: A Review

Arthropods transmit arboviruses via mosquito and tick bites to humans and other animals. The genus flavivirus, which causes diseases, sequelae, and thousands of deaths, mainly in developing and underdeveloped countries, is among the arboviruses of interest to public health. Given the importance of early and accurate diagnosis, this review analyzes the methods of direct detection of flaviviruses, such as reverse transcription loop-mediated isothermal amplification, microfluidics, localized surface plasmon resonance, and surface-enhanced Raman scattering, and presents the advantages, disadvantages, and detection limits identified in studies reported in the literature for each methodology. Among the different methods available, it is essential to balance four fundamental indicators to determine the ideal test: good sensitivity, high specificity, low false positive rate, and rapid results. Among the methods analyzed, reverse transcription loop-mediated isothermal amplification stands out, owing to result availability within a few minutes, with good sensitivity and specificity; in addition, it is the best-characterized methodology.

Biomarker Detection in Early Diagnosis of Cancer: Recent Achievements in Point-of-Care Devices Based on Paper Microfluidics

Microfluidics is very crucial in lab-on-a-chip systems for carrying out operations in a large-scale laboratory environment on a single chip. Microfluidic systems are miniaturized devices in which the fluid behavior and control can be manipulated on a small platform, with surface forces on the platform being greater than volumetric forces depending on the test method used. In recent years, paper-based microfluidic analytical devices (μPADs) have been developed to be used in point-of-care (POC) technologies. μPADs have numerous advantages, including ease of use, low cost, capillary action liquid transfer without the need for power, the ability to store reagents in active form in the fiber network, and the capability to perform multiple tests using various measurement techniques. These benefits are critical in the advancement of paper-based microfluidics in the fields of disease diagnosis, drug application, and environment and food safety. Cancer is one of the most critical diseases for early detection all around the world. Detecting cancer-specific biomarkers provides significant data for both early diagnosis and controlling the disease progression. μPADs for cancer biomarker detection hold great promise for improving cure rates, quality of life, and minimizing treatment costs. Although various types of bioanalytical platforms are available for the detection of cancer biomarkers, there are limited studies and critical reviews on paper-based microfluidic platforms in the literature. Hence, this article aims to draw attention to these gaps in the literature as well as the features that future platforms should have.

Micro and Nanoscale Technologies for Diagnosis of Viral Infections

Viral infection is one of the leading causes of mortality worldwide. The growth of globalization significantly increases the risk of virus spreading, making it a global threat to future public health. In particular, the ongoing coronavirus disease 2019 (COVID-19) pandemic outbreak emphasizes the importance of devices and methods for rapid, sensitive, and cost-effective diagnosis of viral infections in the early stages by which their quick and global spread can be controlled. Micro and nanoscale technologies have attracted tremendous attention in recent years for a variety of medical and biological applications, especially in developing diagnostic platforms for rapid and accurate detection of viral diseases. This review addresses advances of microneedles, microchip-based integrated platforms, and nano- and microparticles for sampling, sample processing, enrichment, amplification, and detection of viral particles and antigens related to the diagnosis of viral diseases. Additionally, methods for the fabrication of microchip-based devices and commercially used devices are described. Finally, challenges and prospects on the development of micro and nanotechnologies for the early diagnosis of viral diseases are highlighted.

Electronic and electrochemical viral detection for point-of-care use: A systematic review

Detecting viruses, which have significant impact on health and the economy, is essential for controlling and combating viral infections. In recent years there has been a focus towards simpler and faster detection methods, specifically through the use of electronic-based detection at the point-of-care. Point-of-care sensors play a particularly important role in the detection of viruses. Tests can be performed in the field or in resource limited regions in a simple manner and short time frame, allowing for rapid treatment. Electronic based detection allows for speed and quantitative detection not otherwise possible at the point-of-care. Such approaches are largely based upon voltammetry, electrochemical impedance spectroscopy, field effect transistors, and similar electrical techniques. Here, we systematically review electronic and electrochemical point-of-care sensors for the detection of human viral pathogens. Using the reported limits of detection and assay times we compare approaches both by detection method and by the target analyte of interest. Compared to recent scoping and narrative reviews, this systematic review which follows established best practice for evidence synthesis adds substantial new evidence on 1) performance and 2) limitations, needed for sensor uptake in the clinical arena. 104 relevant studies were identified by conducting a search of current literature using 7 databases, only including original research articles detecting human viruses and reporting a limit of detection. Detection units were converted to nanomolars where possible in order to compare performance across devices. This approach allows us to identify field effect transistors as having the fastest median response time, and as being the most sensitive, some achieving single-molecule detection. In general, we found that antigens are the quickest targets to detect. We also observe however, that reports are highly variable in their chosen metrics of interest. We suggest that this lack of systematisation across studies may be a major bottleneck in sensor development and translation. Where appropriate, we use the findings of the systematic review to give recommendations for best reporting practice.

Recent innovations in cost-effective polymer and paper hybrid microfluidic devices

Hybrid microfluidic systems that are composed of multiple different types of substrates have been recognized as a versatile and superior platform, which can draw benefits from different substrates while avoiding their limitations. This review article introduces the recent innovations of different types of low-cost hybrid microfluidic devices, particularly focusing on cost-effective polymer- and paper-based hybrid microfluidic devices. In this article, the fabrication of these hybrid microfluidic devices is briefly described and summarized. We then highlight various hybrid microfluidic systems, including polydimethylsiloxane (PDMS)-based, thermoplastic-based, paper/polymer hybrid systems, as well as other emerging hybrid systems (such as thread-based). The special benefits of using these hybrid systems have been summarized accordingly. A broad range of biological and biomedical applications using these hybrid microfluidic devices are discussed in detail, including nucleic acid analysis, protein analysis, cellular analysis, 3D cell culture, organ-on-a-chip, and tissue engineering. The perspective trends of hybrid microfluidic systems involving the improvement of fabrication techniques and broader applications are also discussed at the end of the review.

Multifunctional nanoscale lanthanide metal-organic framework based ratiometric fluorescence paper microchip for visual dopamine assay

Dopamine (DA) plays a significant role in the human body and cerebral nervous system, and the accurate and rapid assay of DA is essential for the diagnosis of related diseases. Herein, we proposed a turn-on ratiometric fluorescent DA assay strategy by integrating a specific DA-resorcinol chemical reaction with a multifunctional lanthanide metal-organic framework (Ln-MOF). First, Eu-BTC (1,3,5-benzenetricarboxylic acid) was synthesized and further modified to obtain Cu@Eu-BTC, which simultaneously plays multiple roles such as fluorescence internal standard, nanoreactor, cooperative catalysis effect and color shift enhancement. The Cu@Eu-BTC dispersion-based method exhibits ultra-sensitive (limit of detection, LOD is 0.01 μM) and wide-range linear response (0.04-30 μM) to DA in real serum. More importantly, it has excellent selectivity for DA, even in the presence of epinephrine and norepinephrine analogs. Thus, this method realizes the accurate and precise quantification of DA in serum (recoveries: 98.1%-110.1%, relative standard deviation RSD < 4.6%). Next, Cu@Eu-BTC was prepared into paper microchip, which has good storage stability (RSD < 3.5%, n = 3) in four weeks and achieves point-of-care visual DA assay coupled with smartphone-assisted portable detection device. The MOF paper microchip-based method shows low sample consumption (30 μL), high accuracy and precision for the quantification of DA in serum (recovery of 92.9%-106.2%, RSD < 5.3%), and gets the same assay results as the MOF dispersion-based method (relative error ≤ 6.83%). To our knowledge, this is the first time to propose the catalytic fluorescence turn-on detection strategy of DA based on a MOF paper microchip.

Cellulose-Based Flexible Functional Materials for Emerging Intelligent Electronics

There is currently enormous and growing demand for flexible electronics for personalized mobile equipment, human-machine interface units, wearable medical-healthcare systems, and bionic intelligent robots. Cellulose is a well-known natural biopolymer that has multiple advantages including low cost, renewability, easy processability, and biodegradability, as well as appealing mechanical performance, dielectricity, piezoelectricity, and convertibility. Because of its multiple merits, cellulose is frequently used as a substrate, binder, dielectric layer, gel electrolyte, and derived carbon material for flexible electronic devices. Leveraging the advantages of cellulose to design advanced functional materials will have a significant impact on portable intelligent electronics. Herein, the unique molecular structure and nanostructures (nanocrystals, nanofibers, nanosheets, etc.) of cellulose are briefly introduced, the structure-property-application relationships of cellulosic materials summarized, and the processing technologies for fabricating cellulose-based flexible electronics considered. The focus then turns to the recent advances of cellulose-based functional materials toward emerging intelligent electronic devices including flexible sensors, optoelectronic devices, field-effect transistors, nanogenerators, electrochemical energy storage devices, biomimetic electronic skins, and biological detection devices. Finally, an outlook of the potential challenges and future prospects for developing cellulose-based wearable devices and bioelectronic systems is presented.

Drug preconcentration and direct quantification in biofluids using 3D-Printed paper cartridge

Drug detection in biofluids has always been great importance for clinical diagnosis. Many detection technologies such as chromatography-mass spectrometry, have been applied to the detection of drugs. However, these technologies required multi-step operations, including complicated and time-consuming pretreatment processes and operations of bulky detection instruments, significantly limiting development of drug detection in clinical diagnosis. Herein, a portable 3D-printed paper cartridge was fabricated for fast sample preconcentration and direct drugs quantitative detection in biofluids by a portable Raman spectrometer. This cartridge contained both paper tip with silver nanowires to preconcentrate samples and achieve surface-enhanced Raman Scattering (SERS) measurement, and 3D-printed cartridge to build enclosed environment for the improvement of detection, which cost only one dollar. The preconcentration ability of the cartridge was up to 18.13-fold fluorescence enhancement and compared to the non-preconcentration method, it achieved 9.93-fold improvement of SERS performance. The anticancer drug of epirubicin hydrochloride, cyclophosphamide and their mixtures were quantitatively detected in the bovine serum or artificial urine. The integrated detection procedure required only 1 h, including sample pretreatment and preconcentration, drying, SERS measurements, and quantification analysis. This 3D-printed paper cartridge constituted a portable detection platform that would be potentially a practical and point-of-care detection tool for drug preconcentration and quantification on the clinical diagnosis.

Point-of-care diagnostics for infectious diseases: From methods to devices

The current widespread of COVID-19 all over the world, which is caused by SARS-CoV-2 virus, has again emphasized the importance of development of point-of-care (POC) diagnostics for timely prevention and control of the pandemic. Compared with labor- and time-consuming traditional diagnostic methods, POC diagnostics exhibit several advantages such as faster diagnostic speed, better sensitivity and specificity, lower cost, higher efficiency and ability of on-site detection. To achieve POC diagnostics, developing POC detection methods and correlated POC devices is the key and should be given top priority. The fast development of microfluidics, micro electro-mechanical systems (MEMS) technology, nanotechnology and materials science, have benefited the production of a series of portable, miniaturized, low cost and highly integrated POC devices for POC diagnostics of various infectious diseases. In this review, various POC detection methods for the diagnosis of infectious diseases, including electrochemical biosensors, fluorescence biosensors, surface-enhanced Raman scattering (SERS)-based biosensors, colorimetric biosensors, chemiluminiscence biosensors, surface plasmon resonance (SPR)-based biosensors, and magnetic biosensors, were first summarized. Then, recent progresses in the development of POC devices including lab-on-a-chip (LOC) devices, lab-on-a-disc (LOAD) devices, microfluidic paper-based analytical devices (μPADs), lateral flow devices, miniaturized PCR devices, and isothermal nucleic acid amplification (INAA) devices, were systematically discussed. Finally, the challenges and future perspectives for the design and development of POC detection methods and correlated devices were presented. The ultimate goal of this review is to provide new insights and directions for the future development of POC diagnostics for the management of infectious diseases and contribute to the prevention and control of infectious pandemics like COVID-19.

An Insight into Nanomedicinal Approaches to Combat Viral Zoonoses

BACKGROUND

Emerging viral zoonotic diseases are one of the major obstacles to secure the "One Health" concept under the current scenario. Current prophylactic, diagnostic and therapeutic approaches often associated with certain limitations and thus proved to be insufficient for customizing rapid and efficient combating strategy against the highly transmissible pathogenic infectious agents leading to the disastrous socio-economic outcome. Moreover, most of the viral zoonoses originate from the wildlife and poor knowledge about the global virome database renders it difficult to predict future outbreaks. Thus, alternative management strategy in terms of improved prophylactic vaccines and their delivery systems; rapid and efficient diagnostics and effective targeted therapeutics are the need of the hour.

METHODS

Structured literature search has been performed with specific keywords in bibliographic databases for the accumulation of information regarding current nanomedicine interventions along with standard books for basic virology inputs.

RESULTS

Multi-arrayed applications of nanomedicine have proved to be an effective alternative in all the aspects regarding the prevention, diagnosis, and control of zoonotic viral diseases. The current review is focused to outline the applications of nanomaterials as anti-viral vaccines or vaccine/drug delivery systems, diagnostics and directly acting therapeutic agents in combating the important zoonotic viral diseases in the recent scenario along with their potential benefits, challenges and prospects to design successful control strategies.

CONCLUSION

This review provides significant introspection towards the multi-arrayed applications of nanomedicine to combat several important zoonotic viral diseases.

Two-Dimensional Material-Based Biosensors for Virus Detection

Viral infections are one of the major causes of mortality and economic losses worldwide. Consequently, efficient virus detection methods are crucial to determine the infection prevalence. However, most detection methods face challenges related to false-negative or false-positive results, long response times, high costs, and/or the need for specialized equipment and staff. Such issues can be overcome by access to low-cost and fast response point-of-care detection systems, and two-dimensional materials (2DMs) can play a critical role in this regard. Indeed, the unique and tunable physicochemical properties of 2DMs provide many advantages for developing biosensors for viral infections with high sensitivity and selectivity. Fast, accurate, and reliable detection, even at early infection stages by the virus, can be potentially enabled by highly accessible surface interactions between the 2DMs and the analytes. High selectivity can be obtained by functionalization of the 2DMs with antibodies, nucleic acids, proteins, peptides, or aptamers, allowing for specific binding to a particular virus, viral fingerprints, or proteins released by the host organism. Multiplexed detection and discrimination between different virus strains are also feasible. In this Review, we present a comprehensive overview of the major advances of 2DM-based biosensors for the detection of viruses. We describe the main factors governing the efficient interactions between viruses and 2DMs, making them ideal candidates for the detection of viral infections. We also critically detail their advantages and drawbacks, providing insights for the development of future biosensors for virus detection. Lastly, we provide suggestions to stimulate research in the fast expanding field of 2DMs that could help in designing advanced systems for preventing virus-related pandemics.

Precipitation-based colorimetric multiplex immunoassay in hydrogel particles

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

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

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

Applications of paper as a support material in biomedical sciences: A decadal review

In human history, the paper has long been used as a platform to record and preserve information. However, over the decades, paper has found its application in Biomedical Sciences, too. Both paper-based microfluidic devices (μPADs) and paper-based cultures and scaffolds have shown immense potential to be used as a sensor as well as a supporting material for in vitro tissue engineering. μPADs can be used to perform low-cost and fast biomolecular assays at Point-Of-Care (POC). They are being used to detect various biomarkers like viral proteins, metabolites, oncogenes, and antigens; and conditions like Venous Thromboembolism (VTE). On the other hand, the paper has also been used to develop paper-based 3D cultures and scaffolds to test drugs, and monitor cytotoxic effects in vitro cell microenvironments and also as implantable tissues. In this review, we intend to enumerate the development in the field of μPADs, paper-based cell cultures, and paper-based scaffolds and their plethora of applications over the last decade.

Quantitative determination of H2O2 for detection of alanine aminotransferase using thin film electrodes

The abnormal concentrations or absence of biomolecules (e.g., proteins) in blood can further be used in diagnosis of a particular pathology at an early stage. Current studies are intensely focusing on the analysis of interaction and detection of biomolecules via point-of-care systems (POCs), allowing miniaturized and parallelized reactions, simultaneously. Recent developments have shown that the collaboration of electrochemical sensing techniques and POCs to overcome challenging problems in health-care settings provides new approaches in diagnosis and treatment of diseases. The aim of this study was to adapt the alanine aminotransferase (ALT) enzyme to the platinum (Pt) thin film electrode system and quantitatively determine the enzyme levels via enzymatically generated H₂O₂ with differential pulse voltammetry (DPV). A simple potentiostat architecture with expanded sweep range utilizing dual LMP91000 devices was developed and adapted to the needs of the biosensor. In order to calibrate the system, known concentrations of H₂O₂ were also tested. Moreover, signals associated with the other electroactive species coming from the ALT reaction were eliminated. Resulted potential range has been achieved between +500 mV and +900 mV and the linear range was found to be 0.05 M-0.5 M for H₂O₂, whereas 5 UL^-1 to 120 UL^-1 for ALT enzyme.

Development of a multiplex fully automated assay for rapid quantification of CD4+ T cells from whole blood

The development of cost-effective and rapid assays for the accurate counting of CD4 cells has remained prime focus for disease management. The lack of such assays has severely affected people living in resource-limited disease prevalent areas. CD4 count information plays a vital role in the effective management of HIV disease. There is an unmet need to develop rapid, cost-effective, portable and user-friendly point-of-care (POC) disease diagnostic platform technology for CD4+ T cell counting. Here, we have developed a flow-free magnetic actuation platform that uses antibody-coated magnetic beads to efficiently capture CD4+ T cells from a 30 μL drop of whole blood. On-chip cell lysate electrical impedance spectroscopy has been utilized to quantify the isolated CD4 cells. The developed assay has a limit of detection of 25 cells per μL and provides accurate CD4 counts in the range of 25-800 cells per μL. The whole immunoassay along with the enumeration process is very rapid and provides CD4 quantification results within 5 min time frame. The assay does not require off-chip sample preparation steps and minimizes human involvement to a greater extent. The developed impedance-based immunoassay has potential to significantly improve the CD4 enumeration process especially for POC settings.

Multilayered Microfluidic Paper-Based Devices: Characterization, Modeling, and Perspectives

Microfluidic paper-based analytical devices (μPADs) are simple but powerful analytical tools that are gaining significant recent attention due to their many advantages over more traditional monitoring tools. These include being inexpensive, portable, pump-free, and having the ability to store reagents. One major limitation of these devices is slow flow rates, which are controlled by capillary action in the hydrophilic pores of cellulosic paper. Recent investigations have advanced the flow rates in μPADs through the generation of a gap or channel between two closely spaced paper sheets. This multilayered format has opened up μPADs to new applications and detection schemes, where large gap sizes (>300 μm) provide at least 169× faster flow rates than single-layer μPADs, but do not conform to established mathematical models for fluid transport in porous materials, such as the classic Lucas-Washburn equation. In the present study, experimental investigations and analytical modeling are applied to elucidate the driving forces behind the rapid flow rates in these devices. We investigate a range of hypotheses for the systems fluid dynamics and establish a theoretical model to predict the flow rate in multilayered μPADs that takes into account viscous dissipation within the paper. Device orientation, sample addition method, and the gap height are found to be critical concerns when modeling the imbibition in multilayered devices.

Clickable cellulosic surfaces for peptide-based bioassays

The use of peptides in paper-based analytics is a highly appealing field, yet it suffers from severe limitations. This is mostly due to the loss of effective target recognition properties of this relatively small probes upon nonspecific adsorption onto cellulose substrates. Here we address this issue by introducing a simple polymer-based strategy to obtain clickable cellulose surfaces, that we exploited for the chemoselective bioconjugation of peptide bioprobes. Our method largely outperformed standard adsorption-based immobilization strategy in a challenging, real case immunoassay, namely the diagnostic discrimination of Zika + individuals from healthy controls. Of note, the clickable polymeric coating not only allows efficient peptides bioconjugation, but it provides favorable anti-fouling properties to the cellulosic support. We envisage our strategy to broaden the repertoire of cellulosic materials manipulation and promote a renewed interest in peptide-based paper bioassays.

Paper-based fluorometric immunodevice with quantum-dot labeled antibodies for simultaneous detection of carcinoembryonic antigen and prostate specific antigen

A method is described for simultaneous fluorometric determination of the biomarkers carcinoembryonic antigen (CEA) and prostate specific antigen (PSA) on the same zone of a paper-based immunodevice. Two kinds of CdTe quantum dots, with respective emission peaks at 525 nm and 605 nm under a single excitation wavelength of 272 nm, were used to label the antibodies against CEA and PSA. Then the capture antibodies of CEA and PSA were immobilized on the same zone of the paper-based device. With the difference of the colors of the quantum dot fluorescence (green and orange), CEA and PSA can be detected on the same zone of the paper-based device. By using of sandwich immunoassay format, CEA and PSA can be simultaneously detected in human serum samples with a linear response in the 1.0-40 ng·mL^-1 concentration range for both. The recovery rates of the serum sample were in the range of 95-105%. The method has the potential of being applied to the simultaneous determination of various other kinds of substances on a single multichannel paper-based chip. Graphical abstract Schematic presentation of the simultaneous fluorometric detection of two cancer biomarkers on the same zone of the paper-based immunodevice is provided. Two kinds of CdTe quantum dots with different emission peaks under the same excitation wavelength are labeled on different detection antibodies.

Advances in Diagnostic Methods for Zika Virus Infection

The Zika virus (ZIKV) is one of the most infamous mosquito-borne flavivirus on recent memory due to its potential association with high mortality rates in fetuses, microcephaly and neurological impairments in neonates, and autoimmune disorders. The severity of the disease, as well as its fast spread over several continents, has urged the World Health Organization (WHO) to declare ZIKV a global health concern. In consequence, over the past couple of years, there has been a significant effort for the development of ZIKV diagnostic methods, vaccine development, and prevention strategies. This review focuses on the most recent aspects of ZIKV research which includes the outbreaks, genome structure, multiplication and propagation of the virus, and more importantly, the development of serological and molecular detection tools such as Zika IgM antibody capture enzyme-linked immunosorbent assay (Zika MAC-ELISA), plaque reduction neutralization test (PRNT), reverse transcription quantitative real-time polymerase chain reaction (qRT-PCR), reverse transcription-loop mediated isothermal amplification (RT-LAMP), localized surface plasmon resonance (LSPR) biosensors, nucleic acid sequence-based amplification (NASBA), and recombinase polymerase amplification (RPA). Additionally, we discuss the limitations of currently available diagnostic methods, the potential of newly developed sensing technologies, and also provide insight into future areas of research.

Enhanced immunofluorescence detection of a protein marker using a PAA modified ZnO nanorod array-based microfluidic device

Zinc oxide (ZnO) often serves as protein microarray substrates owing to its outstanding fluorescence enhancement effect. However, the integration of functional substrates with microfluidic technology to detect cancer biomarkers still needs to be optimized and promoted, for example, the optimization of micro/nanostructure and hydrophilic modification strategies for fluorescence immunoassays. Here, ZnO nanorod arrays were constructed on the inner wall of glass capillaries through a microfluidic chemical method, and the electrostatic layer by layer self-assembly was applied to modify the nanorod array with hydrophilic polyelectrolyte-polyacrylic acid (PAA). The effects of the flow rate and the reagent concentration on the morphology of the ZnO nanorod array were investigated. The ZnO nanorod array-based glass capillary, prepared at 25 μL min-1 for 4 min with 50 mM Zn2+ in solution, showed a remarkable enhancement in fluorescence performance. In addition, the introduction of PAA suppressed the interference of nonspecific protein and improved the antibody loading capacity effectively. In the detection of carcinoembryonic antigen, the limit of detection reached 100 fg mL-1, which indicated that the ZnO@PAA nanorod array-based microfluidic device exhibits remarkable fluorescence detection performance towards protein markers and possesses potential to be applied to point-of-care diagnostics and high throughput cancer biomarker detection.