Smartphone-interfaced lab-on-a-chip devices for field-deployable enzyme-linked immunosorbent assay

The emerging technologies on mobile-based diagnosis and bioanalytical detection have enabled powerful laboratory assays such as enzyme-linked immunosorbent assay (ELISA) to be conducted in field-use lab-on-a-chip devices. In this paper, we present a low-cost universal serial bus (USB)-interfaced mobile platform to perform microfluidic ELISA operations in detecting the presence and concentrations of BDE-47 (2,2′,4,4′-tetrabromodiphenyl ether), an environmental contaminant found in our food supply with adverse health impact. Our point-of-care diagnostic device utilizes flexible interdigitated carbon black electrodes to convert electric current into a microfluidic pump via gas bubble expansion during electrolytic reaction. The micropump receives power from a mobile phone and transports BDE-47 analytes through the microfluidic device conducting competitive ELISA. Using variable domain of heavy chain antibodies (commonly referred to as single domain antibodies or Nanobodies), the proposed device is sensitive for a BDE-47 concentration range of 10⁻³–10⁴μg/l, with a comparable performance to that uses a standard competitive ELISA protocol. It is anticipated that the potential impact in mobile detection of health and environmental contaminants will prove beneficial to our community and low-resource environments.     

Supernatant decanting on a centrifugal platform

This study presents a novel approach to decant supernatant on a centrifugal platform. By manipulating the centrifugally induced pressure and the elastic deformation of the plastic lids in the decanting chamber, fixed amounts of the supernatant can be decanted into the detection chamber at lower rotational speeds. The experimental results showed that decanted volume is affected by the volume of deformation and the operating parameters. Factors that influence the decanting ratio are also discussed. This approach has the advantages of simple design and low manufacturing cost; further, it has no need of surface modification. It has been applied to on-disk separation of plasma from whole blood, and the results showed good stability and repeatability.     

A negative-pressure-driven microfluidic chip for the rapid detection of a bladder cancer biomarker in urine using bead-based enzyme-linked immunosorbent assay

This paper describes an integrated microfluidic chip that is capable of rapidly and quantitatively measuring the concentration of a bladder cancer biomarker, apolipoprotein A1, in urine samples. All of the microfluidic components, including the fluid transport system, the micro-valve, and the micro-mixer, were driven by negative pressure, which simplifies the use of the chip and facilitates commercialization. Magnetic beads were used as a solid support for the primary antibody, which captured apolipoprotein A1 in patients'' urine. Because of the three-dimensional structure of the magnetic beads, the concentration range of the target that could be detected was as high as 2000 ng ml⁻¹. Because this concentration is 100 times higher than that quantifiable using a 96-well plate with the same enzyme-linked immunosorbent assay (ELISA) kit, the dilution of the patient''s urine can be avoided or greatly reduced. The limit of detection was determined to be approximately 10 ng ml⁻¹, which is lower than the cutoff value for diagnosing bladder cancer (11.16 ng ml⁻¹). When the values measured using the microfluidic chip were compared with those measured using conventional ELISA using a 96-well plate for five patients, the deviations were 0.9%, 6.8%, 9.4%, 1.8%, and 5.8%. The entire measurement time is 6-fold faster than that of conventional ELISA. This microfluidic device shows significant potential for point-of-care applications.     

Adsorption and isolation of nucleic acids on cellulose magnetic beads using a three-dimensional printed microfluidic chip

While advances in genomics have enabled sensitive and highly parallel detection of nucleic acid targets, the isolation and extraction of the nucleic acids remain a critical bottleneck in the workflow. We present here a simple 3D printed microfluidic chip that allows for the vortex and centrifugation free extraction of nucleic acids. This novel microfluidic chip utilizes the presence of a water and oil interface to filter out the lysate contaminants. The pure nucleic acids, while bound on cellulose particles, are magnetically moved across the oil layer. We demonstrated efficient and rapid extraction of spiked Human Papillomavirus (HPV) 18 plasmids in specimen transport medium, in under 15 min. An overall extraction efficiency of 61% is observed across a range of HPV plasmid concentrations (5 × 10¹ to 5 × 10⁶ copies/100 μl). The magnetic, interfacial, and viscous drag forces inside the microgeometries of the chip are modeled. We have also developed a kinetics model for the adsorption of nucleic acids on cellulose functionalized superparamagnetic beads. We also clarify here the role of carrier nucleic acids in the adsorption and isolation of nucleic acids. Based on the various mechanistic insights detailed here, customized microfluidic devices can be designed to meet the range of current and emerging point of care diagnostics needs.     

Resistive pulse sensing of magnetic beads and supraparticle structures using tunable pores

Tunable pores (TPs) have been used for resistive pulse sensing of 1 μm superparamagnetic beads, both dispersed and within a magnetic field. Upon application of this field, magnetic supraparticle structures (SPSs) were observed. Onset of aggregation was most effectively indicated by an increase in the mean event magnitude, with data collected using an automated thresholding method. Simulations enabled discrimination between resistive pulses caused by dimers and individual particles. Distinct but time-correlated peaks were often observed, suggesting that SPSs became separated in pressure-driven flow focused at the pore constriction. The distinct properties of magnetophoretic and pressure-driven transport mechanisms can explain variations in the event rate when particles move through an asymmetric pore in either direction, with or without a magnetic field applied. Use of TPs for resistive pulse sensing holds potential for efficient, versatile analysis and measurement of nano- and microparticles, while magnetic beads and particle aggregation play important roles in many prospective biosensing applications.     

Experimental validation of numerical study on thermoelectric-based heating in an integrated centrifugal microfluidic platform for polymerase chain reaction amplification

A comprehensive study involving numerical analysis and experimental validation of temperature transients within a microchamber was performed for thermocycling operation in an integrated centrifugal microfluidic platform for polymerase chain reaction (PCR) amplification. Controlled heating and cooling of biological samples are essential processes in many sample preparation and detection steps for micro-total analysis systems. Specifically, the PCR process relies on highly controllable and uniform heating of nucleic acid samples for successful and efficient amplification. In these miniaturized systems, the heating process is often performed more rapidly, making the temperature control more difficult, and adding complexity to the integrated hardware system. To gain further insight into the complex temperature profiles within the PCR microchamber, numerical simulations using computational fluid dynamics and computational heat transfer were performed. The designed integrated centrifugal microfluidics platform utilizes thermoelectrics for ice-valving and thermocycling for PCR amplification. Embedded micro-thermocouples were used to record the static and dynamic thermal responses in the experiments. The data collected was subsequently used for computational validation of the numerical predictions for the system response during thermocycling, and these simulations were found to be in agreement with the experimental data to within ∼97%. When thermal contact resistance values were incorporated in the simulations, the numerical predictions were found to be in agreement with the experimental data to within ∼99.9%. This in-depth numerical modeling and experimental validation of a complex single-sided heating platform provide insights into hardware and system design for multi-layered polymer microfluidic systems. In addition, the biological capability along with the practical feasibility of the integrated system is demonstrated by successfully performing PCR amplification of a Group B Streptococcus gene.     

Specific binding and magnetic concentration of CD8+ T-lymphocytes on electrowetting-on-dielectric platform

In the quest to create a low-power portable lab-on-a-chip system, we demonstrate the specific binding and concentration of human CD8+ T-lymphocytes on an electrowetting-on-dielectric (EWOD)-based digital microfluidic platform using antibody-conjugated magnetic beads (MB-Abs). By using a small quantity of nonionic surfactant, we enable the human cell-based assays with selective magnetic binding on the EWOD device in an air environment. High binding efficiency (～92%)of specific cells on MB-Abs is achieved due to the intimate contact between the cells and the magnetic beads (MBs) produced by the circulating flow within the small droplet. MBs have been used and cells manipulated in the droplets actuated by EWOD before; reported here is a cell assay of a clinical protocol on the EWOD device in air environment. The present technique can be further extended to capture other types of cells by suitable surface modification on the MBs.     

A multiplexed immunoaggregation biomarker assay using a two-stage micro resistive pulse sensor

We present an immunoaggregation assay chip for multiplexed biomarkers detection. This chip is based on immunoaggregation of antibody functionalized microparticles (Ab-MPs) to quantify concentrations of multiple biomarkers simultaneously. A mixture of multiple types of Ab-MPs probes with different sizes and magnetic properties, which were functionalized by different antibodies, was used for the multiplexed assay. The interactions between biomarkers and their specific Ab-MPs probes caused the immunoaggregation of Ab-MPs. A two-stage micro resistive pulse sensor was used to differentiate and count the Ab-MP aggregates triggered by different biomarkers via size and magnetic property for multiplexed detection. The volume fraction of each type of Ab-MP aggregates indicates the concentration of the corresponding target biomarker. In our study, we demonstrated multiplexed detection of two model biomarkers (human ferritin and mouse anti-rabbit IgG) in 10% fetal bovine serum, using anti-ferritin Ab and anti-mouse IgG Ab functionalized MPs. We found that the volume fraction of Ab-MP aggregates increased with the increased biomarker concentrations. The detection ranges from 5.2 ng/ml to 208 ng/ml and 3.1 ng/ml to 5.12 × 10⁴ng/ml were achieved for human ferritin and mouse anti-rabbit IgG. This bioassay chip is able to quantitatively detect multiple biomarkers in a single test without fluorescence or enzymatic labeling process and hence is promising to serve as a useful tool for rapid detection of multiple biomarkers in biomedical research and clinical applications.     

An integrated microfluidic platform to fabricate single-micrometer asymmetric giant unilamellar vesicles (GUVs) using dielectrophoretic separation of microemulsions

We present a microfluidic technique that generates asymmetric giant unilamellar vesicles (GUVs) in the size range of 2–14 μm. In our method, we (i) create water-in-oil emulsions as the precursors to build synthetic vesicles, (ii) deflect the emulsions across two oil streams containing different phospholipids at high throughput to establish an asymmetric architecture in the lipid bilayer membranes, and (iii) direct the water-in-oil emulsions across the oil–water interface of an oscillating oil jet in a co-flowing confined geometry to encapsulate the inner aqueous phase inside a lipid bilayer and complete the fabrication of GUVs. In the first step, we utilize a flow-focusing geometry with precisely controlled pneumatic pressures to form monodisperse water-in-oil emulsions. We observed different regimes in forming water-in-oil multiphase flows by changing the applied pressures and discovered a hysteretic behavior in jet breakup and droplet generation. In the second step of GUV fabrication, an oil stream containing phospholipids carries the emulsions into a separation region where we steer the emulsions across two parallel oil streams using active dielectrophoretic and pinched-flow fractionation separations. We explore the effect of applied DC voltage magnitude and carrier oil stream flow rate on the separation efficiency. We develop an image processing code that measures the degree of mixing between the two oil streams as the water-in-oil emulsions travel across them under dielectrophoretic steering to find the ideal operational conditions. Finally, we utilize an oscillating co-flowing jet to complete the formation of asymmetric giant unilamellar vesicles and transfer them to an aqueous phase. We investigate the effect of flow rates on properties of the co-flowing jet oscillating in the whipping mode (i.e., wavelength and amplitude) and define the phase diagram for the oil-in-water jet. Assays used to probe the lipid bilayer membrane of fabricated GUVs showed that membranes were unilamellar, minimal residual oil remained trapped between the two lipid leaflets, and 83% asymmetry was achieved across the lipid bilayers of GUVs.     

Estimation of the levels of atrial natriuretic peptide (ANP) in cardiac blood samples by a simple and indigenous enzyme linked immunosorbent assay

Levels of Atrial Natriuretic Peptide (ANP) were estimated in twenty four blood samples collected from the right and the left ventricles of the patients undergoing cardiac catheterization by an Enzyme Linked Immunosorbent Assay (ELISA) developed to the sensitivity of 5 pp/well and within 10% of interassay coeficient of variance. Simultaneously, levels of ANP in plasma samples from the systemic venous blood of seventy five normal subjects were also estimated which ranged between 25–60 pg/ml.     

Serum arylsulfatase A assay in metachromatic leukodystrophy: An experience in a neuropsychiatric set-up

Metachromatic leukodystrophy is a lysosomal disease caused mainly by a deficiency of the enzyme arylsulfatase A. The assay of arylsulfatase A in the serum provides a fast and easy method for the confirmatory diagnosis of this disorder. Serum arylsulfatase A was estimated in 52 normal healthy control subjects and 269 patients with symptoms of cerebral white matter disease in order to diagnose and confirm metachromatic leukodystrophy. A total of eight cases of metachromatic leukodystrophy with a low serum arylsulfatase A was detected, of which three cases were of the late-infantile type, four cases the juvenile type and only one case the adult type.     

政府干预、平台认知和采纳意向关系的实证研究

本文以国家交通运输物流公共信息平台(以下简称"LOGINK平台")为研究对象,采用统计分析和案例研究方法,以信息干预、技术干预、财政干预和行政干预为自变量,平台运作价值感知、战略价值感知和实施成本感知为中介变量,系统研究了不同政府干预方式对物流公共信息平台用户采纳意向的影响机理。研究结果表明,不同类型的政府干预方式对物流企业的物流公共信息平台采纳意向影响存在显著差异性,信息干预的总体影响最小,技术干预的总体影响最大。其中,对平台运作价值感知的影响中,技术干预的影响最大,信息干预的影响次之,财政干预和行政干预的影响不显著;对平台战略价值感知的影响中,从大到小依次是行政干预、技术干预和信息干预,财政干预的影响不显著;不同政府干预对平台实施成本感知的影响中,从大到小依次是技术干预、财政干预、行政干预,信息干预对平台实施成本感知的影响不显著。     

Dual-mode on-demand droplet routing in multiple microchannels using a magnetic fluid as carrier phase

We present dual-mode, on-demand droplet routing in a multiple-outlet microfluidic device using an oil-based magnetic fluid. Magnetite (Fe₃O₄) nanoparticle-contained oleic acid (MNOA) was used as a carrier phase for droplet generation and manipulation. The water-in-MNOA droplets were selectively distributed in a curved microchannel with three branches by utilizing both a hydrodynamic laminar flow pattern and an external magnetic field. Without the applied magnetic field, the droplets travelled along a hydrodynamic centerline that was displaced at each bifurcating junction. However, in the presence of a permanent magnet, they were repelled from the centerline and diverted into the desired channel when the repelled distance exceeded the minimum offset allocated to the channel. The repelled distance, which is proportional to the magnetic field gradient, was manipulated by controlling the magnet''s distance from the device. To evaluate routing performance, three different sizes of droplets with diameters of 63, 88, and 102 μm were directed into designated outlets with the magnet positioned at varying distances. The result demonstrated that the 102-μm droplets were sorted with an accuracy of ∼93%. Our technique enables on-demand droplet routing in multiple outlet channels by simply manipulating magnet positions (active mode) as well as size-based droplet separation with a fixed magnet position (passive mode).     

基于全球比较的中国汽车产业科技协同创新平台改革建议研究

汽车产业是典型的复杂产业,其发展需要多学科、多领域协同创新平台的支撑。本研究聚焦汽车产业科技协同创新平台,首先从组织架构、科技计划、项目管理三方面剖析了中国原有科技创新体系存在的主要问题;然后对美国、德国、日本等发达国家汽车产业科技创新体系进行了对比研究;最后针对中国汽车产业的发展现状,借鉴发达国家成功经验,从优化组织架构、设计创新链条、建立协同机制等方面提出中国汽车产业科技协同创新平台顶层设计和机制改革建议。     

The role of pre-innovation platform activity for diffusion success: Evidence from consumer innovations on a 3D printing platform

Digital platforms are becoming increasingly important for household sector innovators that seek support for the innovation process and that want to make innovations available to large audiences. Innovation development and diffusion is especially challenging for first-time innovators as they cannot build on experiences from prior innovations. We argue that first-time innovators can increase the diffusion success of their innovations by engaging in pre-innovation platform activities. We use the context of the 3D printing platform Thingiverse to show that a consumer's pre-innovation platform activity increases innovation diffusion success and that frequency, quality and relatedness of a consumer's pre-innovation platform activity promotes this effect. We find support that innovation quality, the use of recombinant innovations, and innovation documentation are three mechanisms through which pre-innovation platform activities translate into higher diffusion success of consumers’ first innovation.     

Isolation of cells for selective treatment and analysis using a magnetic microfluidic chip

This study describes the development and testing of a magnetic microfluidic chip (MMC) for trapping and isolating cells tagged with superparamagnetic beads (SPBs) in a microfluidic environment for selective treatment and analysis. The trapping and isolation are done in two separate steps; first, the trapping of the tagged cells in a main channel is achieved by soft ferromagnetic disks and second, the transportation of the cells into side chambers for isolation is executed by tapered conductive paths made of Gold (Au). Numerical simulations were performed to analyze the magnetic flux and force distributions of the disks and conducting paths, for trapping and transporting SPBs. The MMC was fabricated using standard microfabrication processes. Experiments were performed with E. coli (K12 strand) tagged with 2.8 μm SPBs. The results showed that E. coli can be separated from a sample solution by trapping them at the disk sites, and then isolated into chambers by transporting them along the tapered conducting paths. Once the E. coli was trapped inside the side chambers, two selective treatments were performed. In one chamber, a solution with minimal nutrition content was added and, in another chamber, a solution with essential nutrition was added. The results showed that the growth of bacteria cultured in the second chamber containing nutrient was significantly higher, demonstrating that the E. coli was not affected by the magnetically driven transportation and the feasibility of performing different treatments on selectively isolated cells on a single microfluidic platform.     

Building a cross-border e-commerce talent training platform based on logistic regression model

Student success is crucial to the process of building a Cross-border e-commerce (CBEC) talent development platform. Analysis of the important aspects impacting performance and performance prediction are carried out with the goal of enhancing students' academic outcomes. To better forecast student outcomes, a logistic regression model is used for factor analysis, and a penalty function is implemented. Parameters are reconciled using K-fold cross-validation, and then estimated using the coordinate descent technique. Model performance validation findings indicated that the Area Under the curve (AUC) for the minimax concave penalty (MCP) and smoothlyclippedabsolutedeviation(SCAD) penalized logistic regression models were 0.772 and 0.771, respectively. Both the MCP and SCAD penalized logistic regression models have overall accuracies of 0.738 and 0.739, respectively. Researchers found that for MCP, the correlation coefficient was 0.99949, and for SCAD, it was 0.99958, between the projected value and the anticipated value of students' performance. Due to their superior prediction accuracy, the MCP and SCAD penalized logistic regression models may be used as analytical tools in the development of the CBEC talent training platform.