Ultrafast rotary PCR system for multiple influenza viral RNA detection

Customizable Nichrome Wire Heaters for Molecular Diagnostic Applications

Accurate sample heating is vital for nucleic acid extraction and amplification, requiring a sophisticated thermal cycling process in nucleic acid detection. Traditional molecular detection systems with heating capability are bulky, expensive, and primarily designed for lab settings. Consequently, their use is limited where lab systems are unavailable. This study introduces a technique for performing the heating process required in molecular diagnostics applicable for point-of-care testing (POCT), by presenting a method for crafting customized heaters using freely patterned nichrome (NiCr) wire. This technique, fabricating heaters by arranging protrusions on a carbon black-polydimethylsiloxane (PDMS) cast and patterning NiCr wire, utilizes cost-effective materials and is not constrained by shape, thereby enabling customized fabrication in both two-dimensional (2D) and three-dimensional (3D). To illustrate its versatility and practicality, a 2D heater with three temperature zones was developed for a portable device capable of automatic thermocycling for polymerase chain reaction (PCR) to detect Escherichia coli (E. coli) O157:H7 pathogen DNA. Furthermore, the detection of the same pathogen was demonstrated using a customized 3D heater surrounding a microtube for loop-mediated isothermal amplification (LAMP). Successful DNA amplification using the proposed heater suggests that the heating technique introduced in this study can be effectively applied to POCT.

A roadmap to high-speed polymerase chain reaction (PCR): COVID-19 as a technology accelerator

The limit of detection (LOD), speed, and cost of crucial COVID-19 diagnostic tools, including lateral flow assays (LFA), enzyme-linked immunosorbent assays (ELISA), and polymerase chain reactions (PCR), have all improved because of the financial and governmental support for the epidemic. The most notable improvement in overall efficiency among them has been seen with PCR. Its significance for human health increased during the COVID-19 pandemic, when it emerged as the commonly used approach for identifying the virus. However, because of problems with speed, complexity, and expense, PCR deployment in point-of-care settings continues to be difficult. Microfluidic platforms offer a promising solution by enabling the development of smaller, more affordable, and faster PCR systems. In this review, we delve into the engineering challenges associated with the advancement of high-speed microfluidic PCR equipment. We introduce criteria that facilitate the evaluation and comparison of factors such as speed, LOD, cycling efficiency, and multiplexing capacity, considering sample volume, fluidics, PCR reactor geometry and materials, as well as heating/cooling methods. We also provide a comprehensive list of commercially available PCR devices and conclude with projections and a discussion regarding the current obstacles that need to be addressed in order to progress further in this field.

Portable rotary PCR system for real-time detection of Pseudomonas aeruginosa in milk

The rapid quantitative detection of Pseudomonas aeruginosa in milk is of great significance to food safety. Quantitative real-time polymerase chain reaction (qPCR) technology is a good choice to meet this requirement. A good qPCR system should show the advantages of being low cost, having low-power consumption, having potential for miniaturization and be portable. However, most of the time-domain-based qPCR systems reported to date do not meet these requirements. In this study, we propose a novel real-time rotary PCR reaction system (RRP) that meets all the abovementioned specifications, and contains four modules: a heating control module, a disposable PCR capillary tube, a mechanical control module, and a photoelectric detection module. The volume of our homemade-PCR capillary tube is only 3 μL. The total manufacturing cost is cheaper than $200, and the capillary tube is about 1.4 cents. The size parameter of the RRP is less than 300 mm × 150 mm × 150 mm, using low mobile power sources to operate. All the features mean that the RRP meets the advantages of low sample volumes, enhanced thermal conductivity and being portable. Through conducting the experimental quantitative detection of Pseudomonas aeruginosa in milk and theoretical simulations by COMSOL, we prove the feasibility of this rotary PCR real-time detection system, which has broad application prospects in the rapid detection of bacteria and food safety.

Advances in Simple, Rapid, and Contamination-Free Instantaneous Nucleic Acid Devices for Pathogen Detection

Pathogenic pathogens invade the human body through various pathways, causing damage to host cells, tissues, and their functions, ultimately leading to the development of diseases and posing a threat to human health. The rapid and accurate detection of pathogenic pathogens in humans is crucial and pressing. Nucleic acid detection offers advantages such as higher sensitivity, accuracy, and specificity compared to antibody and antigen detection methods. However, conventional nucleic acid testing is time-consuming, labor-intensive, and requires sophisticated equipment and specialized medical personnel. Therefore, this review focuses on advanced nucleic acid testing systems that aim to address the issues of testing time, portability, degree of automation, and cross-contamination. These systems include extraction-free rapid nucleic acid testing, fully automated extraction, amplification, and detection, as well as fully enclosed testing and commercial nucleic acid testing equipment. Additionally, the biochemical methods used for extraction, amplification, and detection in nucleic acid testing are briefly described. We hope that this review will inspire further research and the development of more suitable extraction-free reagents and fully automated testing devices for rapid, point-of-care diagnostics.

Sophisticated and precise: design and implementation of a real-time optical detection system for ultra-fast PCR

Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) has become indispensable in the realm of disease nucleic acid screening and diagnostics, owing to its remarkable precision and sensitivity, in which the real-time fluorescence detection system plays an extremely critical role. To solve the problems of long time and slow speed of traditional nucleic acid detection, PCR systems are evolving towards ultra-rapid configurations. Nonetheless, most extant ultra-rapid PCR systems either depend on endpoint detection for qualitative assessments due to inherent structural or heating constraints or circumvent the challenge of adapting optical systems to expeditious amplification systems, resulting in potential shortcomings in assay efficacy, volume, or expense. Consequently, this study proposed a design of a real-time fluorescence detection system for ultra-fast PCR, capable of executing six channels of real-time fluorescence detection. Through the meticulous calculation of the optical pathway within the optical detection module, effective regulation of system dimensions and the cost was accomplished. By devising an optical adaptation module, the signal-to-noise ratio was enhanced by approximately 307% without compromising the PCR temperature alteration rate. Ultimately, by employing a fluorescence model that accounted for the spatial attenuation effect of excitation light, as proposed herein, fluorescent dyes were arranged to evaluate the repeatability, channel interference, gradient linearity, and limit of detection of the system, which proved that the system had good optical detection performance. Finally, the real-time fluorescence detection of human cytomegalovirus (CMV) under 9 min ultra-fast amplification was achieved by a complete ultra-fast amplification experiment, which further validated the potential of the system to be applied to rapid clinical nucleic acid detection.

Modular design of centrifugal microfluidic system and its application in nucleic acid screening

Modular integration of functional components on the chip and increasement in control accuracy through real-time alteration in the force direction of droplets is an effective way to optimize centrifugal microfluidic systems and realize passive components, compact modules, and high-throughput control. Conventional centrifugal microfluidic chips are mainly driven and controlled by centrifugal force and Euler force. The control valves are easily affected by machining precision, making the control unstable. In this study, a novel centrifugal microfluidic system is introduced to improve the freedom and accuracy of chip control while facilitating the design and addition of passive functional components. Furthermore, we modularize the centrifugal microfluidic chip to greatly shorten the period of design and optimization cycle and achieve chip reusability and multi-threaded control. Finally, to verify the feasibility of the modular centrifugal microfluidic chip applied to high-throughput nucleic acid screening, we test the nucleic acid purification and detection colorimetric reactions based on the modular centrifugal microfluidic chip. Among them, Chelex-100 is used to realize the purification of nucleic acid in cell lysate, and the purified solution can realize amplification in the PCR instrument, and the nucleic acid detection results are consistent with the off-chip kit by experimental testing. The system has great flexibility and stability under the acceptable purity of nucleic acid, which indicates that the platform has great potential for large-scale rapid screening applications.

Advancing pathogen detection for airborne diseases

Airborne diseases including SARS, bird flu, and the ongoing Coronavirus Disease 2019 (COVID-19) have stimulated the demand for developing novel bioassay methods competent for early-stage diagnosis and large-scale screening. Here, we briefly summarize the state-of-the-art methods for the detection of infectious pathogens and discuss key challenges. We highlight the trend for next-generation technologies benefiting from multidisciplinary advances in microfabrication, nanotechnology and synthetic biology, which allow sensitive, rapid yet inexpensive pathogen assays with portable intelligent device.

Micro-PCR chip-based multifunctional ultrafast SARS-CoV-2 detection platform

When dealing with infectious pathogens, the point-of-care screening and diagnosis strategy should be low-cost, simple, rapid and accurate. Here, we report a multifunctional rapid PCR platform allowing both simultaneous screening of suspected cases and accurate identification and quantification of the virus. Based on the platform, samples suspected of being infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are screened first, after which subsequent precise quantification of the virus (SARS-CoV-2) can be performed if necessary. This fast screening technique offers a detection limit of 10 nucleic acid copies per test during the entire running time of 15 minutes, with a throughput of 9 samples at a time. Besides, depending on a droplet microfluidic chip, this platform could also provide assays of nucleic acids across four orders of magnitude of concentration within less than 15 minutes. Additionally, we successfully use the platform to quickly distinguish between positive and negative cases in clinical samples and rapidly quantify the viral load in each sample, which is consistent with standard RT-qPCR tests. As such, we demonstrate a promising and versatile rapid PCR platform for point-of-care diagnosis of infectious diseases.

Microfluidics-based strategies for molecular diagnostics of infectious diseases

Traditional diagnostic strategies for infectious disease detection require benchtop instruments that are inappropriate for point-of-care testing (POCT). Emerging microfluidics, a highly miniaturized, automatic, and integrated technology, are a potential substitute for traditional methods in performing rapid, low-cost, accurate, and on-site diagnoses. Molecular diagnostics are widely used in microfluidic devices as the most effective approaches for pathogen detection. This review summarizes the latest advances in microfluidics-based molecular diagnostics for infectious diseases from academic perspectives and industrial outlooks. First, we introduce the typical on-chip nucleic acid processes, including sample preprocessing, amplification, and signal read-out. Then, four categories of microfluidic platforms are compared with respect to features, merits, and demerits. We further discuss application of the digital assay in absolute nucleic acid quantification. Both the classic and recent microfluidics-based commercial molecular diagnostic devices are summarized as proof of the current market status. Finally, we propose future directions for microfluidics-based infectious disease diagnosis.

Application of centrifugal microfluidics in immunoassay, biochemical analysis and molecular diagnosis

Rapid diagnosis plays a vital role in daily life and is effective in reducing treatment costs and increasing curability, especially in remote areas with limited availability of resources. Among the various common methods of rapid diagnosis, centrifugal microfluidics has many unique advantages, such as less sample consumption, more precise valve control for sequential loading of samples, and accurately separated module design in a microfluidic network to minimize cross-contamination. Therefore, in recent years, centrifugal microfluidics has been extensively researched, and it has been found to play important roles in biology, chemistry, and medicine. Here, we review the latest developments in centrifugal microfluidic platforms in immunoassays, biochemical analyses, and molecular diagnosis, in recent years. In immunoassays, we focus on the application of enzyme-linked immunosorbent assay (ELISA); in biochemical analysis, we introduce the application of plasma and blood cell separation; and in molecular diagnosis, we highlight the application of nucleic acid amplification tests. Additionally, we discuss the characteristics of the methods under each platform as well as the enhancement of the corresponding performance parameters, such as the limit of detection, separation efficiency, etc. Finally, we discuss the limitations associated with the existing applications and potential breakthroughs that can be achieved in this field in the future.

Rapid PCR powered by microfluidics: A quick review under the background of COVID-19 pandemic

PCR has been widely used in different fields including molecular biology, pathogen detection, medical diagnosis, food detection and etc. However, the difficulty of promoting PCR in on-site point-of-care testing reflects on challenges relative to its speed, convenience, complexity, and even cost. With the emerging state-of-art of microfluidics, rapid PCR can be achieved with more flexible ways in micro-reactors. PCR plays a critical role in the detection of SARS-CoV-2. Under this special background of COVID-19 pandemic, this review focuses on the latest rapid microfluidic PCR. Rapid PCR is concluded in two main features, including the reactor (type, size, material) and the implementation of thermal cycling. Especially, the compromise between speed and sensitivity with microfluidic PCR is explored based on the system ratio of (thermal cycling time)/(reactor size). Representative applications about the detection of pathogens and SARS-CoV-2 viruses based on rapid PCR or other isothermal amplification are discussed as well.

Battery-Powered Portable Rotary Real-Time Fluorescent qPCR with Low Energy Consumption, Low Cost, and High Throughput

The traditional qPCR instrument is bulky, expensive, and inconvenient to carry, so we report a portable rotary real-time fluorescent PCR (polymerase chain reaction) that completes the PCR amplification of DNA in the field, and the reaction can be observed in real-time. Through the analysis of a target gene, namely pGEM-3Zf (+), the gradient amplification and melting curves are compared to commercial devices. The results confirm the stability of our device. This is the first use of a mechanical rotary structure to achieve gradient amplification curves and melting curves comparable to commercial instruments. The average power consumption of our system is about 7.6 W, which is the lowest energy consumption for real-time fluorescence quantification in shunting PCR and enables the use of our device in the field thanks to its self-contained power supply based on a lithium battery. In addition, all of the equipment costs only about 710 dollars, which is far lower than the cost of a commercial PCR instrument because the control system through mechanical displacement replaces the traditional TEC (thermoelectric cooler) temperature control. Moreover, the equipment has a low technical barrier, which can suit the needs of non-professional settings, with strong repeatability.

Review on pneumatic operations in centrifugal microfluidics

Centrifugal microfluidics allows for miniaturization, automation and parallelization of laboratory workflows. The fact that centrifugal forces are always directed radially outwards has been considered a main drawback for the implementation of complex workflows leading to the requirement of additional actuation forces for pumping, valving and switching. In this work, we review and discuss the combination of centrifugal with pneumatic forces which enables transport of even complex liquids in any direction on centrifugal systems, provides actuation for valving and switching, offers alternatives for mixing and enables accurate and precise metering and aliquoting. In addition, pneumatics can be employed for timing to carry out any of the above listed unit operations in a sequential and cascaded manner. Firstly, different methods to generate pneumatic pressures are discussed. Then, unit operations and applications that employ pneumatics are reviewed. Finally, a tutorial section discusses two examples to provide insight into the design process. The first tutorial explains a comparatively simple implementation of a pneumatic siphon valve and provides a workflow to derive optimum design parameters. The second tutorial discusses cascaded pneumatic operations consisting of temperature change rate actuated valving and subsequent pneumatic pumping. In conclusion, combining pneumatic actuation with centrifugal microfluidics allows for the design of robust fluidic networks with simple fluidic structures that are implemented in a monolithic fashion. No coatings are required and the overall demands on manufacturing are comparatively low. We see the combination of centrifugal forces with pneumatic actuation as a key enabling technology to facilitate compact and robust automation of biochemical analysis.

Sample-to-Answer Hepatitis B Virus DNA Detection from Whole Blood on a Centrifugal Microfluidic Platform with Double Rotation Axes

A point-of-care apparatus for hepatitis virus detection requires simple and easy-to-use processing steps and should have the same diagnostic capability as that in the central laboratory. However, no automated and efficient methods for hepatitis B virus (HBV) sample-to-answer detection include serum separation, and complete prestorage of reagents has been developed. We developed an automated sample-to-answer disc for rapid HBV detection from whole blood based on a double rotation axes centrifugal microfluidic platform. The disc with complete prestorage of reagents features fully automated and integrated serum separation from whole blood, magnetic bead-based DNA extraction, aliquoting of the nucleic acid, and real-time polymerase chain reaction. A laser diode for sequential release of prestored liquid reagents was used. Processing merely requires manual loading of the sample into the disc. We demonstrate successful sample-to-answer detection of HBV in a 500 μL whole blood sample with sample concentrations down to 10² copies/mL. The total time of the whole detection from sample-to-result is about 48 min. The disc provides a user-friendly molecular diagnostic system for rapid analysis of HBV without demanding a complicated laboratory instrument and major manual operation time. Overall, the results indicated that the developed disc could be used for HBV molecular diagnosis.

Combination of a centrifugal microfluidic device with a solution-loading cartridge for fully automatic molecular diagnostics

We present a centrifugal microfluidic device which is combined with a solution-loading cartridge for fully automatic molecular diagnostics of foodborne pathogens.

Effect of buffer composition on PNA–RNA hybridization studied in the microfluidic microarray chip

Herein, we report that peptide nucleic acid sequences (PNAs) have been used as the probe species for detection of RNA and that a microfluidic microarray (MMA) chip is used as the platform for detection of hybridizations between immobilized PNA probes and RNA targets. The RNA targets used are derived from influenza A sequences. This paper discusses the optimization of two probe technologies used for RNA detection and investigates how the composition of the probe buffer and the content of the hybridization solution can influence the overall results. Our data show that the PNA probe is a better choice than the DNA probe when there is low salt in the probe buffer composition. Furthermore, we show that the absence of salt (NaCl) in the hybridization buffer does not hinder the detection of RNA sequences. The results provide evidence that PNA probes are superior to DNA probes in term of sensitivity and adaptability, as PNA immobilization and PNA–RNA hybridization are less affected by salt content in the reaction buffers unlike DNA probes.

An integrated rotary microfluidic system with DNA extraction, loop-mediated isothermal amplification, and lateral flow strip based detection for point-of-care pathogen diagnostics

Point-of-care (POC) molecular diagnostics plays a pivotal role for the prevention and treatment of infectious diseases. In spite of recent advancement in microfluidic based POC devices, there are still rooms for development to realize rapid, automatic and cost-effective sample-to-result genetic analysis. In this study, we propose an integrated rotary microfluidic system that is capable of performing glass microbead based DNA extraction, loop mediated isothermal amplification (LAMP), and colorimetric lateral flow strip based detection in a sequential manner with an optimized microfluidic design and a rotational speed control. Rotation direction-dependent coriolis force and siphon valving structures enable us to perform the fluidic control and metering, and the use of the lateral flow strip as a detection method renders all the analytical processes for nucleic acid test simplified and integrated without the need of expensive instruments or human intervention. As a proof of concept for point-of-care DNA diagnostics, we identified the food-borne bacterial pathogen which was contaminated in water or milk. Not only monoplex Salmonella Typhimurium but also multiplex Salmonella Typhimurium and Vibrio parahaemolyticus were analysed on the integrated rotary genetic analysis microsystem with a limit of detection of 50 CFU in 80min. In addition, three multiple samples were simultaneously analysed on a single device. The sample-to-result capability of the proposed microdevice provides great usefulness in the fields of clinical diagnostics, food safety and environment monitoring.

Advances in digital polymerase chain reaction (dPCR) and its emerging biomedical applications

Since the invention of polymerase chain reaction (PCR) in 1985, PCR has played a significant role in molecular diagnostics for genetic diseases, pathogens, oncogenes and forensic identification. In the past three decades, PCR has evolved from end-point PCR, through real-time PCR, to its current version, which is the absolute quantitive digital PCR (dPCR). In this review, we first discuss the principles of all key steps of dPCR, i.e., sample dispersion, amplification, and quantification, covering commercialized apparatuses and other devices still under lab development. We highlight the advantages and disadvantages of different technologies based on these steps, and discuss the emerging biomedical applications of dPCR. Finally, we provide a glimpse of the existing challenges and future perspectives for dPCR.

Fully automated and colorimetric foodborne pathogen detection on an integrated centrifugal microfluidic device

This work describes fully automated and colorimetric foodborne pathogen detection on an integrated centrifugal microfluidic device, which is called a lab-on-a-disc. All the processes for molecular diagnostics including DNA extraction and purification, DNA amplification and amplicon detection were integrated on a single disc. Silica microbeads incorporated in the disc enabled extraction and purification of bacterial genomic DNA from bacteria-contaminated milk samples. We targeted four kinds of foodborne pathogens (Escherichia coli O157:H7, Salmonella typhimurium, Vibrio parahaemolyticus and Listeria monocytogenes) and performed loop-mediated isothermal amplification (LAMP) to amplify the specific genes of the targets. Colorimetric detection mediated by a metal indicator confirmed the results of the LAMP reactions with the colour change of the LAMP mixtures from purple to sky blue. The whole process was conducted in an automated manner using the lab-on-a-disc and a miniaturized rotary instrument equipped with three heating blocks. We demonstrated that a milk sample contaminated with foodborne pathogens can be automatically analysed on the centrifugal disc even at the 10 bacterial cell level in 65 min. The simplicity and portability of the proposed microdevice would provide an advanced platform for point-of-care diagnostics of foodborne pathogens, where prompt confirmation of food quality is needed.

A Review of Biomedical Centrifugal Microfluidic Platforms

Centrifugal microfluidic or lab-on-a-disc platforms have many advantages over other microfluidic systems. These advantages include a minimal amount of instrumentation, the efficient removal of any disturbing bubbles or residual volumes, and inherently available density-based sample transportation and separation. Centrifugal microfluidic devices applied to biomedical analysis and point-of-care diagnostics have been extensively promoted recently. This paper presents an up-to-date overview of these devices. The development of biomedical centrifugal microfluidic platforms essentially covers two categories: (i) unit operations that perform specific functionalities, and (ii) systems that aim to address certain biomedical applications. With the aim to provide a comprehensive representation of current development in this field, this review summarizes progress in both categories. The advanced unit operations implemented for biological processing include mixing, valving, switching, metering and sequential loading. Depending on the type of sample to be used in the system, biomedical applications are classified into four groups: nucleic acid analysis, blood analysis, immunoassays, and other biomedical applications. Our overview of advanced unit operations also includes the basic concepts and mechanisms involved in centrifugal microfluidics, while on the other hand an outline on reported applications clarifies how an assembly of unit operations enables efficient implementation of various types of complex assays. Lastly, challenges and potential for future development of biomedical centrifugal microfluidic devices are discussed.

LabDisk with complete reagent prestorage for sample-to-answer nucleic acid based detection of respiratory pathogens verified with influenza A H3N2 virus

Portable point-of-care devices for pathogen detection require easy, minimal and user-friendly handling steps and need to have the same diagnostic performance compared to centralized laboratories. In this work we present a fully automated sample-to-answer detection of influenza A H3N2 virus in a centrifugal LabDisk with complete prestorage of reagents. Thus, the initial supply of the sample remains the only manual handling step. The self-contained LabDisk automates by centrifugal microfluidics all necessary process chains for PCR-based pathogen detection: pathogen lysis, magnetic bead based nucleic acid extraction, aliquoting of the eluate into 8 reaction cavities, and real-time reverse transcription polymerase chain reaction (RT-PCR). Prestored reagents comprise air dried specific primers and fluorescence probes, lyophilized RT-PCR mastermix and stick-packaged liquid reagents for nucleic acid extraction. Employing two different release frequencies for the stick-packaged liquid reagents enables on-demand release of highly wetting extraction buffers, such as sequential release of lysis and binding buffer. Microfluidic process-flow was successful in 54 out of 55 tested LabDisks. We demonstrate successful detection of the respiratory pathogen influenza A H3N2 virus in a total of 18 LabDisks with sample concentrations down to 2.39 × 10(4) viral RNA copies per ml, which is in the range of clinical relevance. Furthermore, we detected RNA bacteriophage MS2 acting as internal control in 3 LabDisks with a sample concentration down to 75 plaque forming units (pfu) per ml. All experiments were applied in a 2 kg portable, laptop controlled point-of-care device. The turnaround time of the complete analysis from sample-to-answer was less than 3.5 hours.

The rotary zone thermal cycler: a low-power system enabling automated rapid PCR

Advances in molecular biology, microfluidics, and laboratory automation continue to expand the accessibility and applicability of these methods beyond the confines of conventional, centralized laboratory facilities and into point of use roles in clinical, military, forensic, and field-deployed applications. As a result, there is a growing need to adapt the unit operations of molecular biology (e.g., aliquoting, centrifuging, mixing, and thermal cycling) to compact, portable, low-power, and automation-ready formats. Here we present one such adaptation, the rotary zone thermal cycler (RZTC), a novel wheel-based device capable of cycling up to four different fixed-temperature blocks into contact with a stationary 4-microliter capillary-bound sample to realize 1-3 second transitions with steady state heater power of less than 10 W. We demonstrate the utility of the RZTC for DNA amplification as part of a highly integrated rotary zone PCR (rzPCR) system that uses low-volume valves and syringe-based fluid handling to automate sample loading and unloading, thermal cycling, and between-run cleaning functionalities in a compact, modular form factor. In addition to characterizing the performance of the RZTC and the efficacy of different online cleaning protocols, we present preliminary results for rapid single-plex PCR, multiplex short tandem repeat (STR) amplification, and second strand cDNA synthesis.

Integration of reverse transcriptase loop-mediated isothermal amplification with an immunochromatographic strip on a centrifugal microdevice for influenza A virus identification

A novel centrifugal microdevice which could perform reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) and immunochromatographic strip (ICS) based amplicon detection was demonstrated for simple and cost-effective influenza A virus identification. The proposed centrifugal microdevice consists of the sample and running buffer loading reservoirs, the RT-LAMP chamber, and the ICS for detecting gene expression. The entire process could be completed sequentially and automatically by simply controlling the rotation speed and by optimizing the microfluidic design. Monoplex and multiplex RT-LAMP reactions targeting H1 and/or M gene were executed at 66 °C for 40 min, and the resultant amplicons were successfully analysed on the ICS within 15 min. Influenza A H1N1 virus was subtyped by detecting H1 and M gene on the ICS even with 10 copies of viral RNAs. Highly specific and multiplex viral typing of the integrated RT-LAMP-ICS microdevice was also demonstrated. The combination of the rapid isothermal amplification with the simple colorimetric detection on a strip in a single centrifugal microdevice will provide an advanced genetic analysis platform in the field of on-site pathogen diagnostics.

Automated nucleic acid extraction from whole blood, B. subtilis, E. coli, and Rift Valley fever virus on a centrifugal microfluidic LabDisk

We present total nucleic acid extraction from whole blood, Gram-positiveBacillus subtilis, Gram-negativeEscherichia coli, andRift Valley feverRNA virus on a low-cost, centrifugal microfluidic cartridge processed in a portable processing device.

Centrifugal microfluidic platforms: advanced unit operations and applications

Review on miniaturization, integration, and automation of laboratory processes within centrifugal microfluidic platforms. For efficient implementation of applications, building blocks are categorized into unit operations and process chains.

Magnetic chemiluminescent immunoassay for human C-reactive protein on the centrifugal microfluidics platform

Schematic of the LabDisk-based hCRP MCIA. The antibody-coated dynabeads are sequentially transported through the immunoassay buffers by magnetic actuation. Finally the chemiluminescence signal is acquired from a detection cavity.

Integrated centrifugal reverse transcriptase loop-mediated isothermal amplification microdevice for influenza A virus detection

An integrated reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) microdevice which consists of microbead-assisted RNA purification and RT-LAMP with real-time monitoring by a miniaturized optical detector was demonstrated. The integrated RT-LAMP microdevice includes four reservoirs for a viral RNA sample (purified influenza A viral RNA or lysates), a washing solution (70% ethanol), an elution solution (RNase-free water), and an RT-LAMP cocktail, and two chambers (a waste chamber and an RT-LAMP reaction chamber). The separate reservoirs for a washing solution, an elution solution, and an RT-LAMP cocktail were designed with capillary valves for stable storage. Three influenza A virus strains (A/H1N1, A/H3N2, and A/H5N1) were used for RNA templates, and RT-LAMP primer sets were designed to detect hemagglutinin (HA) and conserved M gene. Sequential sample flow to the microbeads for RNA purification was achieved by centrifugal force with optimization of capillary valves and a siphon channel. Furthermore, the purified RNA solution was successfully isolated from the waste solution by changing the rotational direction, and combined with the RT-LAMP cocktail in the RT-LAMP reaction chamber for target gene amplification. Total process from the sample injection to the result was completed in 47 min. Influenza A H1N1 virus was confirmed on the integrated RT-LAMP microdevice even with 10 copies of viral RNAs, which revealed 10-fold higher sensitivity than that of a conventional RT-PCR. Subtyping and specificity test of influenza A H1N1 viral lysates were also performed and clinical samples were successfully genotyped to confirm influenza A virus on our proposed integrated microdevice.

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An integrated microdevice cosistng of RNA purification and RT-LAMP with real-time monitoring was demonstrated.

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Sequential sample transportation and purified RNA separation were automatically controlled by centrifugal force and optimized microchannels.

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Influenza viruses were isothermally amplified and the products were identified by using a miniaturized fluorescence detector.

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Limit of detection for influenza A H1N1 was 10 copies.

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Clinical samples were successfully analyzed on the microdevice.

A packaged paper fluidic-based microdevice for detecting gene expression of influenza A virus

Pathotyping and subtyping of influenza A virus were performed with a packaged paper fluidic-based analytical microdevice (PFAM) after one-step reverse transcription-polymerase chain reaction (RT-PCR). The PFAM contains two test lines: one for detecting M gene to identify the influenza A virus and another for haemagglutinin subtyping to determine the viral strain among H1N1, H3N2, and H5N1. The M gene and the haemagglutinin gene (H1, H3, and H5 genes) were amplified by using the Digoxigenin and the Texas Red modified primers, respectively, in the multiplex RT-PCR. The amplicon products were loaded in the conjugate pad of the PFAM in which the streptavidin coated gold nanoparticles were linked with the biotin moieties that were incorporated in the middle of the DNA strands, and then captured by the anti-Digoxigenin and anti-Texas Red immobilized on the test lines. Influenza A H1N1, H3N2, and H5N1 could be identified with a limit of detection of 10(2) copies of RNA templates in 10 min. Pathotyping and subtyping of the clinical nasopharyngeal swab samples were also analyzed whose results were confirmed by real-time RT-PCR.

A microbead-incorporated centrifugal sample pretreatment microdevice

In this study, we present a novel bead-incorporated centrifugal sample pretreatment microdevice to purify influenza A H3N2 viral RNA. Simple revolution per minute (RPM) control can lead to RNA capture on a bead-bed, and the sequential loading of a washing solution and an elution solution. Tetraethoxy orthosilicate (TEOS)-treated glass microbeads were utilized as a capture matrix. The sample pretreatment microdevice consists of four reservoirs for storing an RNA sample, a washing solution, an elution solution, and a collected sample, and they were merged at the microbead-bed microchannel. The washing solution reservoir and the elution solution reservoir were connected to the bead-bed microchannel through a capillary valve and a siphon channel, respectively. An RNA sample (a lysed influenza A H3N2 virus), a washing solution (70% ethanol) and an elution solution (water or a reverse transcription-polymerase chain reaction (RT-PCR) cocktail) were loaded into the designated reservoirs, and they were successively transported to the bead-bed by RPM control owing to the optimized channel design. Purified RNAs could be obtained in 440 s. Then, a target H3 gene was amplified by an off-chip based real-time RT-PCR to evaluate the capture efficiency of RNA on our proposed microdevice. 81% of RNAs were successfully captured and purified. Interestingly, the use of the RT-PCR cocktail itself as an elution solution resulted in a 76% capture yield. Furthermore, we successfully performed RNA purification from the clinical nasopharyngeal swabs to identify the subtype of the influenza A virus. This platform provides high potential for the direct integration of the sample pretreatment microdevice into the downstream micro-PCR unit to create a total genetic analysis microsystem.

Polymerase chain reaction-free variable-number tandem repeat typing using gold nanoparticle-DNA monoconjugates

In this work, we report a novel polymerase chain reaction (PCR)-free variable-number tandem repeat (VNTR) typing method using a T-shaped gold nanoparticle-DNA monoconjugate, called the "watching-gene assay". The T-shaped DNA probe was synthesized by "click" chemistry and linked with the gold nanoparticle to form the gold nanoparticle-DNA monoconjugate (a VNTR probe). Through a simple annealing and ligation reaction of the VNTR probe on a synthetic DNA template mimicking the human D1S80 VNTR locus, the number of tandem repeat units could be deciphered by counting the self-assembled gold nanoparticles. The number of tandem repeat units could be identified with more than 50% yield if the repeat number was less than four. In the case of the real human genomic DNA, the 18 repeat unit number could be successfully revealed by observing the 18-gold-nanoparticle cluster, which exactly corresponded to the number of tandem repeats of the real sample. Our "watching-gene assay" is rapid, simple, and direct for data interpretation, thereby providing an advanced PCR-free genetic polymorphism analysis platform.

A rotary microsystem for simple, rapid and automatic RNA purification

In this work, we demonstrate a novel rotary microsystem for simple, rapid and automatic influenza viral RNA purification. The microdevice consists of a silica sol-gel matrix for RNA capture, and three reservoirs for a RNA sample (R(S)), a washing solution (R(W)) and an elution buffer (R(E)) that were connected with different dimensional microfluidic channels (120 μm for R(S), 40 μm for R(W), and 20 μm for R(E)). The hydrophobic property of PDMS and the narrow microchannel served as a passive capillary microvalve, and the loading of the solutions were controlled by centrifugal force. 5 μL of a lysate sample of influenza A H1N1 virus, a washing solution and an elution buffer were injected in each designated reservoir, and the virus sample, the washing solution, and the elution buffer were sequentially loaded into the sol-gel chamber at 1600, 2000, and 2500 RPM, enabling the viral RNA to be captured in the sol-gel solid phase, purified, and eluted in 5 min. The RNA capture yield was measured as ~80%, and the H1 and M gene were successfully amplified from the recovered purified H1N1 viral RNA by reverse-transcriptase PCR. Such a novel rotary sample preparation system eliminates any complicated hardware and human intervention, and performs the RNA extraction with high speed and high fidelity.