Microfluidic Detection System Research Articles

Arsenic detection in water using microfluidic detection systems based on the leucomalachite green method

This work describes the first use of microfluidic detection technology for arsenic detection in water using leucomalachite green dye.

Numerical simulation of mixing and heat transfer in an integrated centrifugal microfluidic system for nested-PCR amplification and gene detection

Nucleic acid amplification via polymerase chain reaction (PCR) is one of the essential and powerful methods used in a myriad of bio-assays in clinical laboratories. Application of microfluidic devices in biologically-related processes like PCR can result in the usage of less volume of reactant samples and reduce the processing time. By implementing PCR systems on centrifugal microfluidic platforms, automation and portability can be easily achieved. Although several methods have been developed, most of them are still dealing with challenges of the required high processing time. This study presents the numerical simulation of a fully automated PCR system with the goal of enhancing the mixing quality of the agents comprising primers and samples and accelerating the thermocycling processes through applying a hybrid convective-radiative heat transfer mechanism resulting in an optimized time consumption. In this work, sample manipulation units such as siphon valves and capillary valves are precisely designed and optimized and the desired time of the operation is reduced considerably. In addition, the blending quality of sample and reactants – primers, polymerase enzyme and nucleotides in this case – is enhanced by employing two serpentine micromixers. The efficiency of these micromixers was improved considering rotational speed and geometrical parameters of the corresponding sections of the microfluidic device. Furthermore, instead of using a common convection-based thermocycling process, the novel presented system is designed based on a hybrid convective-radiative heat transfer mechanism and time consumption is significantly minimized and managed by conducting numerical optimizations.

Low-blinking SERS substrate for switchable detection of kanamycin

Metallic plasmonic nanoparticles generate surface-enhanced Raman Scattering (SERS) for wide sensing applications of biomolecules, gas and environmental contaminants. However, the metallic materials cause high thermal radiation during laser excitation in the opto-microfluidic systems and give rise to temporal intensity fluctuations, which is called blinking effects in SERS spectra. This work developed nanocomposite consisting of graphene oxide (GO) and gold nanoparticles (AuNPs) with high thermal stability and low thermal radiation, which provided plasmonic resonance while reduced blinking effect for SERS-based sensing in the microfluidic detection system. The system was applied to detect kanamycin in drinking water, orange juice, and milk by using Texas Red-dye conjugated Beacon aptamer, where the aptamer was designed to be specific and switchable in kanamycin recognition. The sensor was reusable, and its limit of detection was 0.75 nM in a linear range of 1 nM to 100 nM. The microfluidic SERS detection system can be potentially used for sensitive and reliable assays of small molecules.

Pseudo-Continuous Flow FTIR System for Glucose, Fructose and Sucrose Identification in Mid-IR Range.

In this paper, we present a new FTIR-based microfluidic system for Glucose, Fructose and Sucrose detection. The proposed microfluidic system is based on a pseudo-continuous flow coupled to a microscope-FTIR instrument. The detection and characterization of sugar samples were performed by recording their absorption spectrum in the wavelength range 700–1000 cm of the Mid-IR region. The proposed pseudo-continuous flow system is designed to improve the uniformity of the sample distribution in the analyzed area versus conventional systems. The obtained results for different sugars concentrations, show a very low measurement error of 4.35% in the absorption peak intensity, which is ten times lower than the error obtained using the conventional measurements.

Development of an Internet of Things Based Electrochemical Microfluidic System for Free Calcium Detection

This paper represents the design, fabrication, and implementation of an Internet of Things (IoT)-based electrochemical microfluidic system for free calcium concentration detection with a 3D printing technique. Free calcium solutions with desired concentrations between 0 and 40 µM can be obtained. The solutions were used to calibrate the system by using an impedance analyzer for monitoring the impedance change to determine the operating frequency. Continuously, an IoT enabled point of care device was used for real-time detection and to send signals to the cloud for sharing. The relationship between the concentration and reactance are y = − 1.3812 Lgx + 0.9809 at a wavelength of 450 Hz, with an R2 of 0.9719. We measured the calcium concentration changing from 39.8 µM to 1.35 µM (nearly real-time) by the PoC device and showed the concentration changes resulting with time on the cell phone app. The results depicted in this paper provide a strong platform for the precise and real-time monitoring of different biomedical samples.

Simple and label-free pathogen enrichment via homobifunctional imidoesters using a microfluidic (SLIM) system for ultrasensitive pathogen detection in various clinical specimens

Diseases caused by pathogenic microorganisms including bacteria and viruses can cause serious medical issues including death and result in huge economic losses. Despite the myriad of recent advances in the rapid and accurate detection of pathogens, large volume clinical samples with a low concentration of pathogens continue to present challenges for diagnosis and surveillance. We here report a simple and label-free approach via homobifunctional imidoesters (HIs) with a microfluidic platform (SLIM) to efficiently enrich and extract pathogens at low concentrations from clinical samples. The SLIM system consists of an assembled double microfluidic chip for streamlining large volume processing and HIs for capturing pathogens and isolating nucleic acids by both electrostatic and covalent interaction without a chaotropic detergent or bulky instruments. The SLIM system significantly increases the enrichment and extraction rate of pathogens (up to 80% at 10 CFU (colony forming unit) in a 1 mL volume within 50 min). We demonstrated its clinical utility in large sample volumes from 46 clinical specimens including environmental swabs, saliva, and blood plasma. The SLIM system showed higher sensitivity with these samples and could detect pathogens that were below the threshold of detection with other methods. Finally, by combining our SLIM approach with an isothermal optical sensor, pathogens could be detected at a very high sensitivity in blood plasma samples within 80 min via enrichment, extraction and detection steps. Our SLIM system thus provides a simple, reliable, cost-effective and ultrasensitive pathogen diagnosis platform for use with large volume clinical samples and would thus have significant utility for various infectious diseases.

Microfluidic System for Detection of Viral RNA in Blood Using a Barcode Fluorescence Reporter and a Photocleavable Capture Probe.

A microfluidic sample preparation multiplexer (SPM) and assay procedure is developed to improve amplification-free detection of Ebola virus RNA from blood. While a previous prototype successfully detected viral RNA following off-chip RNA extraction from infected cells, the new device and protocol can detect Ebola virus in raw blood with clinically relevant sensitivity. The Ebola RNA is hybridized with sequence specific capture and labeling DNA probes in solution and then the complex is pulled down onto capture beads for purification and concentration. After washing, the captured RNA target is released by irradiating the photocleavable DNA capture probe with ultraviolet (UV) light. The released, labeled, and purified RNA is detected by a sensitive and compact fluorometer. Exploiting these capabilities, a detection limit of 800 attomolar (aM) is achieved without target amplification. The new SPM can run up to 80 assays in parallel using a pneumatic multiplexing architecture. Importantly, our new protocol does not require time-consuming and problematic off-chip probe conjugation and washing. This improved SPM and labeling protocol is an important step toward a useful POC device and assay.

A digital microfluidic system for loop-mediated isothermal amplification and sequence specific pathogen detection

A digital microfluidic (DMF) system has been developed for loop-mediated isothermal amplification (LAMP)-based pathogen nucleic acid detection using specific low melting temperature (Tm) Molecular Beacon DNA probes. A positive-temperature-coefficient heater with a temperature sensor for real-time thermal regulation was integrated into the control unit, which generated actuation signals for droplet manipulation. To enhance the specificity of the LAMP reaction, low-Tm Molecular Beacon probes were designed within the single-stranded loop structures on the LAMP reaction products. In the experiments, only 1 μL of LAMP reaction samples containing purified Trypanosoma brucei DNA were required, which represented over a 10x reduction of reagent consumption when comparing with the conventional off-chip LAMP. On-chip LAMP for unknown sample detection could be accomplished in 40 min with a detection limit of 10 copies/reaction. Also, we accomplished an on-chip melting curve analysis of the Molecular Beacon probe from 30 to 75 °C within 5 min, which was 3x faster than using a commercial qPCR machine. Discrimination of non-specific amplification and lower risk of aerosol contamination for on-chip LAMP also highlight the potential utilization of this system in clinical applications. The entire platform is open for further integration with sample preparation and fluorescence detection towards a total-micro-analysis system.

A bead-based microfluidic system for joint detection in TORCH screening at point-of-care testing

A concise bead-based microfluidic system has been developed for joint detection in TORCH screening at point-of-care testing. Assisted by five functionalized polycarbonate single beads, totally five critical infections including TOX, RUB, CMV, HSV-1 and HSV-2 can be simultaneously detected with the microfluidic chip based on chemiluminescence. The microfluidic chip consists of multiple reaction chambers respectively for different reaction steps of the sandwiched chemiluminescence immunoassay, and each reaction chamber is divided into five interconnected independent cells to respectively hold five single beads in different position. With a guiding path, each single bead with a ferrous core can be easily transported between each two adjacent reaction chambers through magnetic control to consecutively react with the serum sample or other different reagents. Meanwhile, with magnetic control, each single bead within the reaction chamber can be moved back and forth to improve the detection sensitivity with enhanced mixing. In one time test, joint detection with five infections to one serum sample can be simultaneously implemented by introducing synchronous manipulation to five single beads. Chemiluminescence signal from five single beads is collected by a sensitive CCD camera in parallel. Qualitative detection is achieved by comparing the detection signal amplitude with the corresponding cutoff value for each infection. Experimental results show that accurate, simple, convenient and efficient TORCH screening can be achieved with the easy-to-operate and low-cost microfluidic system at resource-poor settings.

A microdevice for rapid, monoplex and colorimetric detection of foodborne pathogens using a centrifugal microfluidic platform

Outbreaks of foodborne diseases have become a global health concern; hence, many improvements and developments have been made to reduce the risk of food contamination. We developed a centrifugal microfluidic automatic wireless endpoint detection system integrated with loop mediated isothermal amplification (LAMP) for monoplex pathogen detection. Six identical sets were designed on the microfluidic compact disc (CD) to perform 30 genetic analyses of three different species of foodborne pathogens. The consecutive loading, mixing, and aliquoting of the LAMP primers/reagents and DNA sample solutions were accomplished using an optimized square-wave microchannel, metering chambers and revulsion per minute (RPM) control. We tested 24 strains of pathogenic bacteria (Escherichia coli, Salmonella spp and Vibrio cholerae), with 8 strains of each bacterium, and performed DNA amplification on the microfluidic CD for 60min. Then, the amplicons of the LAMP reaction were detected using the calcein colorimetric method and further analysed via the developed electronic system interfaced with Bluetooth wireless technology to transmit the results to a smartphone. The system showed a limit of detection (LOD) of 3 × 10−5ngμL−1 DNA by analysing the colour change when tested with chicken meat spiked with the three pathogenic bacteria. Since the entire process was performed in a fully automated way and was easy to use, our microdevice is suitable for point-of-care (POC) testing with high simplicity, providing affordability and accessibility even to poor, resource-limited settings.

A rapid, low-cost, and microfluidic chip-based system for parallel identification of multiple pathogens related to clinical pneumonia

An air-insulated microfluidic chip was designed for the automatic centrifugal distribution of samples to 24-test cells, enabling the parallel identification of multiple clinical pneumonia-related pathogens in 1.45-μL reactions without cross-contamination in 45 min. A portable nucleic acid analyzer that integrates mechanical, confocal optical, electronic, and software functions was also developed to collect fluorescence data in a Ø3 mm imaging field near the optical diffraction limit for highly sensitive fluorescence detection of nucleic acid amplification in real time. This microfluidic chip-based portable nucleic acid analyzer could detect low abundance nucleic acids present at as few as 10 copies. In a blinded experiment, specific identification of Mycoplasma pneumoniae, Staphylococcus aureus, and methicillin-resistant S. aureus was achieved with 229 clinical patient sputum samples. The total coincidence rate of our system and traditional RT-PCR with an ABI 7500 was 99.56%. Four samples accounting for the 0.44% inconformity were retested by gene sequencing, revealing that our system reported the correct results. This novel microfluidic chip-based detection system is cost-effective, rapid, sensitive, specific, and has a relatively high throughput for parallel identification, which is especially suitable for resource-limited facilities/areas and point-of-care testing.

An integrated microfluidic system for live bacteria detection from human joint fluid samples by using ethidium monoazide and loop-mediated isothermal amplification

Periprosthetic joint infection (PJI) is one of the severe complications of prosthetic joint replacement. Delayed PJI diagnosis may anchor bacteria in periprosthetic tissues, and removal of the prosthesis might be inevitable. The diagnosis of PJI depends on the identification of microorganisms by standard microbiological cultures or more advanced molecular diagnostic methods for detection of bacterial genes. However, these methods are relatively time-consuming, labor-intensive and not human error-free. Moreover, it is challenging to distinguish live from dead bacteria by using DNA-based molecular diagnostics since bacterial DNA will be remained in the tissue even after the death of the bacteria. In this work, an integrated microfluidic system has been developed to perform the entire molecular diagnostic process for the PJI diagnosis in a single chip. We combined the loop-mediated isothermal amplification (LAMP) with ethidium monoazide (EMA) in an integrated microfluidic system to identify live bacteria with reasonable sensitivity and high specificity. All the diagnostic processes including bacteria isolation, cell lysis, DNA amplification and optical detection can be automatically performed on the integrated microfluidic system by using a compact custom-made control system. The integrated system can accommodate four primers complementary to six regions of the target genes and improve the detection limit by using LAMP. The limit of detection in this multiple EMA-LAMP assay could be as low as 5 fg/reaction (~1 CFU/reaction) when choosing an optimized primer set as we demonstrated in mecA gene detection. Thus, the developed system for PJI diagnosis has great potential to become a point-of-care device.

ELISA‐type assays of trace biomarkers using microfluidic methods

Recently, great progress has been achieved for analytical technologies for biological substances. Traditionally, detection methods for analytes mainly rely on large instrumental analyses. These methods require costly equipment, skilled operators and long measurement time despite their generally low sensitivity. In contrast, immunoassays are becoming more and more popular for it is powerful, inexpensive, and convenient nature. Immunoassay has a range of applications, because it employs antibody, a protein produced by plasma cells in the acquired immune system to identify and neutralize diverse pathogens and other exogenous substances. However, the sensitivity of conventional immunoassays so far is limited by their reaction principles and detection methods. The microfluidics technology is the one that manipulates small volumes of fluid and flow, which has the potential to miniaturize many laboratory procedures. Immunoassays on microfluidic devices have been studied extensively and have gained significant attention owing to intrinsic advantages offered by the assay platforms. The techniques have allowed the miniaturization of conventional immunoassay and bring the advantages such as small volumes of samples and reagents as well as the decrease of contamination, which results in the decline of false-positive results. Ultimately, the combination of immunoassays with microfluidics affords a promising platform for multiple, sensitive, and automatic point-of-care diagnostics. Recent achievements on microfluidic devices and immunoassay detection systems including digital assay employing single molecule will be introduced in detail and the strategies for faster and more sensitive configurations in microfluidic immunosensors will be highlighted. WIREs Nanomed Nanobiotechnol 2017, 9:e1457. doi: 10.1002/wnan.1457 For further resources related to this article, please visit the WIREs website.

Rapid integrated microfluidic paper-based system for sulfur dioxide detection

An integrated platform consisting of a microfluidic paper-based/PMMA (Polymethyl-Methacrylate) chip and a small battery-operated detection system is proposed for the concentration detection of sulfur dioxide (SO2). In the proposed method, a small strip of filter paper is coated with acid-base indicator and then inserted into a PMMA microchip. The SO2 sample is then injected into the reservoir of the chip; prompting a reaction with the acid-base indicator. The chip is transferred to the detection system, where the reaction-induced color change is captured by a CMOS (Complementary Metal-Oxide Semiconductor) camera. Finally, the CMOS image is transferred to a cell phone via a USB (Universal Serial Bus) connector and the SO2 concentration is derived using self-written RGB color analysis software. The experimental results obtained for 10 control samples show that the correlation coefficient for the variation of the R(ed) signal intensity with the SO2 concentration is equal to R2=0.9971 in the low-concentration range (20∼600ppm) and R2=0.9920 in the high-concentration range (600∼5000ppm). The real-world applicability of the proposed platform is demonstrated by measuring the SO2 concentrations of fifteen commercial food samples. The concentration measurements deviate by no more than 4.29% from those obtained using a standard macroscale technique. Overall, the results presented in this study show that the proposed integrated microfluidic paper-based system provides a cheap, compact and reliable method for SO2 concentration measurement purposes.

A LAB-ON-A-PAPER FOR LOW-COST AND DISPOSABLE DETECTION OF URIC ACID AND BLOOD IN URINE SAMPLE SIMULTANEOUSLY

This work presents a low-cost and disposable paper based microfluidic system for detection of uric acid and blood in urine simultaneously. Detection is achieved by using a colorimetric or visual indicator. Immobilized specific reagents designed for the parameter under consideration act as capture molecules on the surface of the detection zone of a microfluidic system made of paper (cellulose). Fe-(III)tris-(1,10)-phenantroline and Tetramethylbenzidinecumene hydroperoxide and have been immobilized using absorption method for blood and uric acid detection respectively. For blood detection, the detection zone will be change from pale blue to dark blue, due to presence of hemoglobin, which in turn, resulted in oxidized reaction of tetramethylbenzidine by cumene hydroperoxide. While for uric acid detection zone, the color change from yellow to orange/red due to complexation of Fe(III)tris-(1,10)-phenantroline with uric acid in urine sample. The capability of lab on paper for detection of blood and uric acid in urine samples has been demonstrate successfully.

Automated Microfluidic Filtration and Immunocytochemistry Detection System for Capture and Enumeration of Circulating Tumor Cells and Other Rare Cell Populations in Blood.

Isolation by size using a filter membrane offers an antigen-independent method for capturing rare cells present in blood of cancer patients. Multiple cell types, including circulating tumor cells (CTCs), captured on the filter membrane can be simultaneously identified via immunocytochemistry (ICC) analysis of specific cellular biomarkers. Here, we describe an automated microfluidic filtration method combined with a liquid handling system for sequential ICC assays to detect and enumerate non-hematologic rare cells in blood.

A microfluidic detection system for quantitation of copper incorporating a wavelength-ratiometric fluorescent quantum dot pair

Described is a new approach to building a microfluidic quantum dot wavelength-ratiometric sensor system for quantifying copper in water and biological samples.

Design and Energy Analysis of Microfluidic Optical Detection System

Design and Energy Analysis of Microfluidic Optical Detection System

Electrochemical Microfluidic Immunoarray for Assessment of Aggressive Vs Indolent Forms of Prostate Cancer

Prostate cancer is the most common cause of cancer-related death in men in the US and throughout the world. Current practices for detection and staging of prostate cancer often fall short in terms of sensitivity, specificity and inability to distinguish between aggressive and indolent forms of prostate cancer. These limitations lead to unnecessary treatments that adversely affect the patients’ quality of life with minimal or no gain. Measurement of small panels of molecular signature biomarkers in serum holds tremendous potential for cancer diagnostics and personalized therapy. Here we describe a simple, low-cost, modular microfluidic system for on-line capture and detection of prostate cancer protein biomarkers. The protein panel includes PSA, CD-14, ERG, GOLM-1, PEDF-1, IGF-1, VEGF-D and IGFBP-3, many of which are thought to be specific for aggressive prostate cancer. The system features a small chamber for on-line protein capture from serum by magnetic beads labeled with many copies of analyte-specific antibodies and signal-transducing enzyme labels, positioned upstream of a detection chamber housing a nanostructured 8-electrode sensor array. Gold immunoarrays fabricated by ink-jet printing ($0.2) or commercial screen printed carbon arrays ($5) are fitted into the microfluidic detection chamber to achieve high sensitivity. Ultralow detection limit in the low fM range was achieved for multiplexed detection of the cancer biomarker proteins from as little as 5 uL. Measurements of this panel of selected biomarkers will be tested with prostate cancer patient samples in future to assess its diagnostic capability. Figure 1

Integrated microfluidic system for rapid detection of influenza H1N1 virus using a sandwich-based aptamer assay

The rapid spread of influenza-associated H1N1 viruses has caused serious concern in recent years. Therefore, there is an urgent need for the development of automatic, point-of-care devices for rapid diagnosis of the influenza virus. Conventional approaches suffer from several critical issues; notably, they are time-consuming, labor-intensive, and are characterized by relatively low sensitivity. In this work, we present a new approach for fluorescence-based detection of the influenza A H1N1 virus using a sandwich-based aptamer assay that is automatically performed on an integrated microfluidic system. The entire detection process was shortened to 30min using this chip-based system which is much faster than the conventional viral culture method. The limit of detection was significantly improved to 0.032 hemagglutination unit due to the high affinity and high specificity of the H1N1-specific aptamers. The results showed that the two-aptamer microfluidic system had about 103 times higher sensitivity than the conventional serological diagnosis. It was demonstrated that the developed microfluidic system may play as a powerful tool in the detection of the H1N1 virus.