Microchip System Research Articles

A microchip is for life — so choose wisely

Several factors need to be considered when choosing a microchip system for use in your practice, in order to provide a quality product for your clients that will last for the life of their animals, together with a trouble-free registration process. These factors include methods of implantation, scanners for microchip detection, databases for registration, method of data entry into the registration system, and types of microchip. While basic costs are one of the factors to be considered, this must be balanced with the various aspects that make the system more or less efficient, more or less likely to fail, and easier or harder to use.

A Transdermal Measurement Platform Based on Microfluidics

The Franz diffusion cell is one of the most widely used devices to evaluate transdermal drug delivery. However, this static and nonflowing system has some limitations, such as a relatively large solution volume and skin area and the development of gas bubbles during sampling. To overcome these disadvantages, this study provides a proof of concept for miniaturizing models of transdermal delivery by using a microfluidic chip combined with a diffusion cell. The proposed diffusion microchip system requires only 80 μL of sample solution and provides flow circulation. Two model compounds, Coomassie Brilliant Blue G-250 and potassium ferricyanide, were successfully tested for transdermal delivery experiments. The diffusion rate is high for a high sample concentration or a large membrane pore size. The developed diffusion microchip system, which is feasible, can be applied for transdermal measurement in the future.

A fully integrated microchip system for automated forensic short tandem repeat analysis.

We have successfully developed an integrated microsystem that combines two plastic microchips for DNA extraction and PCR amplification with a glass capillary array electrophoresis chip together in a compact control and detection instrument for automated forensic short tandem repeat (STR) analysis. DNA extraction followed by an "in situ PCR" was conducted in a single reaction chamber of the microchip based on a filter paper-based extraction methodology. PCR products were then mixed with sizing standards by an injection electrode and injected into the electrophoresis chip for four-color confocal fluorescence detection. The entire STR analysis can be completed in about two hours without any human intervention. Since the 15-plex STR system has a more stringent requirement for PCR efficiency, we optimized the structure of the plastic DNA extraction and amplification chip, in which the reaction chamber was formed by sandwiching a hollow structure layer with two blank cover layers, to reduce the adsorption of PCR reagents to the surfaces. In addition, PCR additives, bovine serum albumin, poly(ethylene glycol), and more magnesium chloride were included into the on-chip multiplex STR system. The limit-of-detection study demonstrated that our microsystem was able to produce full 15-plex STR profiles from 3.75 ng standard K562 DNA. Buccal swab and whole blood samples were also successfully typed by our system, validating the feasibility of performing rapid DNA typing in a "sample-in-answer-out" manner for on-site forensic human identification.

A novel CE microchip with micro pillars column & double-L injection design for Capacitance Coupled Contactless Conductivity detection technology

This novel capillary electrophoresis microchip, or also known as μTAS (micro total analysis system) was designed to separate complex aqueous based compounds, similar to commercial CE & microchip (capillary electrophoresis) systems, but more compact. This system can be potentially used for mobile/portable chemical analysis equipment. Un-doped silicon wafer & ultra-thin borofloat glass (Pyrex) wafers have been used to fabricate the device. Double-L injection feature, micro pillars column, bypass separation channel & hybrid- referenced C4D electrodes were designed to achieve a high SNR (signal to noise ratio), easy- separation, for a durable and reusable μTAS for CE use.

On-Chip Magnetic Bead Manipulation and Detection Using a Magnetoresistive Sensor-Based Micro-Chip: Design Considerations and Experimental Characterization.

The remarkable advantages micro-chip platforms offer over cumbersome, time-consuming equipment currently in use for bio-analysis are well documented. In this research, a micro-chip that includes a unique magnetic actuator (MA) for the manipulation of superparamagnetic beads (SPBs), and a magnetoresistive sensor for the detection of SPBs is presented. A design methodology, which takes into account the magnetic volume of SPBs, diffusion and heat transfer phenomena, is presented with the aid of numerical analysis to optimize the parameters of the MA. The MA was employed as a magnetic flux generator and experimental analysis with commercially available COMPEL™ and Dynabeads® demonstrated the ability of the MA to precisely transport a small number of SPBs over long distances and concentrate SPBs to a sensing site for detection. Moreover, the velocities of COMPEL™ and Dynabead® SPBs were correlated to their magnetic volumes and were in good agreement with numerical model predictions. We found that 2.8 μm Dynabeads® travel faster, and can be attracted to a magnetic source from a longer distance, than 6.2 μm COMPEL™ beads at magnetic flux magnitudes of less than 10 mT. The micro-chip system could easily be integrated with electronic circuitry and microfluidic functions, paving the way for an on-chip biomolecule quantification device.

Separation of motile sperm for in vitro fertilization from frozen-thawed bull semen using progesterone induction on a microchip

This study presents a novel method for the separation of motile sperm from non-progressive motile and immotile sperm and in vitro Fertilization (IVF). This separation of bull sperm was accomplished by inducing chemotaxis along a progesterone release agent in a 7.5-mm microchannel microchip composed of a biocompatible polydimethysiloxane layer and a glass gradient. The selected sperm was applied directly for IVF. In the first experiment, we tested the effect of different lengths of microchannnel (5mm, 7.5mm and 10mm) on quality parameter of separated sperm. The results showed that separated sperm using 7.5-mm microchannel chip were improved in sperm motility, swimming velocity, and beat frequency compared with other groups. In the second experiment, a medium containing sperm from swim-up method and outlet reservoir of our 7.5-mm microchannel chip was collected and mitochondrial activity of the sperm was determined by fluorescence microscopy. The sperm from the microchip had higher mitochondria activity (47.6%±6.0%) than the sperm from the swim-up method (23.6%±4.7%) (P<0.05). There were significant differences in rate of acrosome intactness between the swim-up method and the microchip (36.0%±4.1% vs. 66.8±2.1%, respectively, P<0.05). In the third experiment, we compared sperm penetration in the microchip-IVF system with a standard IVF method (droplet-IVF). The microchip-IVF group had the highest percentages of oocytes penetrated (82.2%±1.6% vs. 63.5%±2.4%) and monospermic oocytes (67.8%±3.4% vs. 42.4%±1.5%). In addition, early developmental competence of oocytes to the blastocyst stage was higher when the oocytes were inseminated in the microchip-IVF system compared with those inseminated in a standard droplet-IVF system. These results demonstrate that our microchip based on a sperm chemotaxis system is useful for motile sperm separation from frozen-thawed bull semen for IVF. Therefore, the optimized microchip system provides a good opportunity to sort motile bull sperm for IVF.

One-step preparation and application of mussel-inspired poly(norepinephrine)-coated polydimethylsiloxane microchip for separation of chiral compounds.

In this paper, using the self-polymerization of norepinephrine (NE) and its favorable film-forming property, a simple and green preparation approach was developed to modify a PDMS channel for enantioseparation of chiral compounds. After the PDMS microchip was filled with NE solution, poly(norepinephrine) (PNE) film was gradually formed and deposited on the inner wall of microchannel as permanent coating via the oxidation of NE by the oxygen dissolved in the solution. Due to possessing plentiful catechol and amine functional groups, the PNE-coated PDMS microchip exhibited much better wettability, more stable and suppressed EOF, and less nonspecific adsorption. The water contact angle and EOF of PNE-coated PDMS substrate were measured to be 13° and 1.68 × 10(-4) cm(2) V(-1) s(-1) , compared to those of 108° and 2.24 × 10(-4) cm(2) V(-1) s(-1) from the untreated one, respectively. Different kinds of chiral compounds, such as amino acid enantiomer, drug enantiomer, and peptide enantiomer were efficiently separated utilizing a separation length of 37 mm coupled with in-column amperometric detection on the PNE-coated PDMS microchips. This facile mussel-inspired PNE-based microchip system exhibited strong recognition ability, high-performance, admirable reproducibility, and stability, which may have potential use in the complex biological analysis.

Measurement of platelet aggregation functions using whole blood migration ratio in a microfluidic chip.

Platelets play a major role in maintaining endothelial integrity and hemostasis. Of the various soluble agonists, ADP is an important in vivo stimulus for inducing platelet aggregation. In this study, a simple, rapid, and affordable method was designed for testing bleeding time (BT) and platelet aggregation with a two-channel microfluidic chip. Whole blood migration ratio (MR) from a microchip system was evaluated in comparison to the closure time (CT) from PFA-100 assays (Siemens, Germany) and CD62P expression on platelets. To induce platelet aggregation, a combination of collagen (1.84 mg/ml) and ADP (37.5 mg/ml) were used as agonists. After adding the agonists to samples, whole blood MR from the microchip system was measured. The outcome of the assessment depended on reaction time and agonist concentration. MR of whole blood from the microchip system was significantly correlated with CT from PFA-100 (r = 0.61, p < 0.05, n = 60). In addition, MR was negatively correlated with CD62P expression (r =-0.95, p < 0.05, n = 60). These results suggest that the measurement of MR using agonists is an easy, simple and efficient method for monitoring platelet aggregation in normal and ADP-receptors defective samples, along with the BT test. Thus, usage of the current microfluidic method could expand to diverse applications, including efficacy assessments in platelet therapy.

A capillary flow immunoassay microchip utilizing inkjet printing-based antibody immobilization onto island surfaces—toward sensitive and reproducible determination of carboxyterminal propeptide of type I procollagen

A capillary-flow-driven microchip system requires no external power and has no moving off-chip components, in contrast with most microfluidic-based immunoassay systems which are complicated to operate and require external components. To accelerate the sensitive and reproducible determination of analytes required for practical point-of-care applications, we formed island microchannel surfaces on a microcapillary channel to allow stable antibody immobilization. The island surface was surrounded by a circular groove 10 μm deep and 150 μm wide and allowed uniform inkjet printing of antibody spots, complete bio-reagent replacement, and sensitive detection of luminescence intensity. Quantitative analysis of carboxyterminal propeptide of type I procollagen (PICP) concentrations using this microchannel was demonstrated between 0–600 ng·ml−1, which is adequate for the clinical estimation of PICP concentrations in the blood. This microchip system holds promise as a model diagnostic platform that is readily adaptable to hands-free operation.

High-resolution pluronic-filled microchip CE-SSCP analysis system via channel width control.

Although the resolution of CE-SSCP has been significantly improved by using a poly(ethyleneoxide)-poly(propyleneoxide)-poly(ethyleneoxide) (PEO-PPO-PEO; Pluronic(®)) triblock copolymer as a separation medium, CE-SSCP on a microchip format is not widely applicable because their resolution is limited by short channel length. Therefore, a strategy to improve the resolution in channels of limited lengths is highly required for enabling microchip-based CE-SSCP. In this study, we developed a high-resolution CE-SSCP microchip system by controlling the width of the pluronic-filled channel. We tested four different channel widths of 180, 240, 300, and 400 μm, and found that 300 μm showed the highest resolution in the separation of two pathogen specific markers. Potential applications of our method in various genetic analyses were also shown by using SNP markers for spinal muscular atrophy.

Nanostructured gold microelectrodes for SERS and EIS measurements by incorporating ZnO nanorod growth with electroplating.

In this paper, a fine gold nanostructure synthesized on selective planar microelectrodes in micro-chip is realized by using an advanced hybrid fabrication approach incorporating growth of nanorods (NRs) with gold electroplating. By this developed nanostructure, integration of in-situ surface-enhanced Raman spectroscopy (SERS) detection with electrochemical impedance spectroscopy (EIS) measurement for label-free, nondestructive, real-time and rapid monitoring on a single cell has been achieved. Moreover, parameters of Au nanostructures such as size of nanoholes/nanogaps can be controllably adjusted in the fabrication. We have demonstrated a SERS enhancement factor of up to ~2.24 × 106 and double-layer impedance decrease ratio of 90% ~ 95% at low frequency range below 200 kHz by using nanostructured microelectrodes. SERS detection and in-situ EIS measurement of a trapped single cell by using planar microelectrodes are realized to demonstrate the compatibility, multi-functions, high-sensitivity and simplicity of the micro-chip system. This dual function platform integrating SERS and EIS is of great significance in biological, biochemical and biomedical applications.

Pressure-actuated microfluidic devices for electrophoretic separation of pre-term birth biomarkers

We have developed microfluidic devices with pressure-driven injection for electrophoretic analysis of amino acids, peptides, and proteins. The novelty of our approach lies in the use of an externally actuated on-chip peristaltic pump and closely spaced pneumatic valves that allow well-defined, small-volume sample plugs to be injected and separated by microchip electrophoresis. We fabricated three-layer poly(dimethylsiloxane) (PDMS) microfluidic devices. The fluidic layer had injection and separation channels, and the control layer had an externally actuated on-chip peristaltic pump and four pneumatic valves around the T-intersection to carry out sample injection. An unpatterned PDMS membrane layer was sandwiched between the fluidic and control layers as the actuated component in pumps and valves. Devices with the same peristaltic pump design but different valve spacings (100, 200, 300, and 400 μm) from the injection intersection were fabricated using soft lithographic techniques. Devices were characterized through fluorescent imaging of captured plugs of a fluorescein-labeled amino acid mixture and through microchip electrophoresis separations. A suitable combination of peak height, separation efficiency, and analysis time was obtained with a peristaltic pump actuation rate of 50 ms, an injection time of 30 s, and a 200-μm valve spacing. We demonstrated the injection of samples in different solutions and were able to achieve a 2.4-fold improvement in peak height and a 2.8-fold increase in separation efficiency though sample stacking. A comparison of pressure-driven injection and electrokinetic injection with the same injection time and separation voltage showed a 3.9-fold increase in peak height in pressure-based injection with comparable separation efficiency. Finally, the microchip systems were used to separate biomarkers implicated in pre-term birth. Although these devices have initially been demonstrated as a stand-alone microfluidic separation tool, they have strong potential to be integrated within more complex systems.

Integration of a reconstituted cell-free protein-synthesis system on a glass microchip.

Recently, a cell-free protein synthesis system reconstituted solely from essential elements of the Escherichia coli translation system, termed protein synthesis using recombinant elements (PURE), has been widely used in synthetic biology to analyze fundamental life systems. Here, the system was integrated on a glass microchip system to construct a simple protein synthesis system. GFP template DNAs were immobilized on Sepharose microbeads by streptavidin-biotin binding. The beads were introduced into a Y-shaped microchannel in a glass microchip with a 10-μm height dam structure, and a PURE system reaction mixture was flowed through the microchannel. The recovered solutions had a higher fluorescent intensity than that of the reaction mixture before its introduction into the microchannel, thus verifying that GFP synthesis had been achieved. The microchip with DNA immobilized microbeads is reusable. This is advantageous over a conventional in vitro protein synthesis protocol requiring the preparation and addition of template DNA or mRNA into the reaction mixtures in aspect of simpleness and rapidness.

Considerações sobre o modelo experimental de hipertensão intracraniana e avaliação do sistema de microchip para monitoração de pressão epidural

Resumo Objetivo: Neste trabalho temos o objetivo de avaliar a acurácia do sistema de aferição da pressão intracraniana (PIC) epidural com microchip. Métodos: Foram estudados 27 suínos sob anestesia geraI, devidamente assistidos com monitoração ventilatória e hemodinâmica. Durante o experimento foi reproduzido um processo expansivo intracerebral programado no lobo frontal direito. O experimento constou de três grupos (A, B e C) com hipertensão intracraniana gerada com balão reproduzindo um hematoma intracerebral. Em todos os grupos foram calibrados os parâmetros normais: os dois sistemas de PIC foram comparados e estudados quanto à correlação dos valores aferidos. Resultados: O comportamento médio da PIC ao longo dos momentos de avaliação foi estatisticamente diferente entre os grupos (p &lt; 0,001). A reprodução de ressangramento resultou em elevação significativa da PIC (p &lt; 0,001). Avaliando-se a acurácia comparativa geral, verificou-se um coeficiente de correlação intraclasse de 0,8. Conclusão: O modelo de hipertensão intracraniana por balão em suínos é factível e confiável na geração de hipertensão intracraniana. O sistema de aferição de pressão intracraniana epidural apresenta elevado coeficiente de correlação com o sistema de aferição parenquimatoso na avaliação global.

High-Throughput Immunomagnetic Cell Detection Using a Microaperture Chip System

We report a microchip system based on a combination of immunomagnetic separation, microfluidics, and size-based filtration for high-throughput detection of rare cells. In this system, target cells bind to magnetic beads in vitro and flow parallel to a microchip with flow rates of milliliters/minute. A magnetic field draws the bead-bound cells toward the microchip, which contains apertures that allow passage of unbound beads while trapping the target cells. The cells captured on the chip can be investigated clearly under a microscope and released from the chip for further analysis. We first characterize the system by detecting cancer cell lines (MCF-7 and A549) in culture media. We then demonstrate detection of 100 MCF-7 cells spiked in 7.5 mL of human blood to simulate detection of circulating tumor cells present in cancer patient blood samples. On average, 85% of the spiked cells were detected. We expect this system to be highly useful in a wide variety of clinical as well as other applications that seek rare cells.

A glass/PDMS electrophoresis microchip embedded with molecular imprinting SPE monolith for contactless conductivity detection

A simple glass/PDMS microfluidic chip for on-line sample pretreatment and contactless conductivity detection, which consisted of a 0.17mm-thick glass cover and a PDMS substrate embedded with an SPE monolithic column, was presented in this paper. Using this integrated microchip system, sample extraction, injection, separation and detection were automatically performed in sequence. A sample of auramine O was concentrated by molecularly imprinted SPE (MISPE), eluted to sample reservoir, and injected by electromigration into separation channel for electrophoresis separation and contactless conductivity detection, with the calculated detection limit (S/N=3) being 2.5μgmL−1. The monolithic column was utilized to quantitatively extract auramine O, yielding an on-line enrichment factor of about 12. The microchip system is reliable and applicable to the analysis of auramine O in food sample.

21pm2-F1 化学反応を駆動源とする自励振動ゲルポンプの開発

We succeeded in development of a novel gel-pump-embedded microchip. The gel actuator directly converts the chemical energy of the Belousov-Zhabotinsky (BZ) reaction to the mechanical energy. The gel pump generates the adequate force as the micro-pump in the novel microchip system. The gel-pump-embedded microchip requires no electric cord and electric power source. That is because the microchip includes chemical energy source. The microchip does not need connection to the conventional syringe pumps. Therefore, the microchip avoids any contamination.

Distributed Microchip System Records Subsurface Temperature and Pressure

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 159583, ’A Distributed Microchip System for Subsurface Measurement,’ by Mengjiao Yu, Sufeng He, Yuanhang Chen, Nicholas Takach, SPE, and Peter LoPresti, The University of Tulsa; and Shaohua Zhou, SPE, and Nasser Al-Khanferi, SPE, Saudi Aramco, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 8-10 October. The paper has not been peer reviewed. A microchip system capable of measuring temperature and pressure over the entire wellbore was developed and tested in the field. When used in the field, tracers will be injected together with the drilling fluid. As the tracer travels through the wellbore, it will measure the temperature and pressure throughout the wellbore and store the data in the on-chip memory. Prototype The prototype of the instrument system is shown in Fig. 1. The instrument sys-tem developed in this work includes two major components: the surface devices (Fig. 1) and the tracers (Fig. 2). A tracer (approximately 7.5 mm in diameter) consists of a small system-on-chip integrated circuit (SOC IC), which includes sensors, microcontroller, memory, transmitter and receiver circuits, and density-control material (hollow spheres), all encapsulated in a protective-chemical-coating shell. The surface devices include an initiator to reset the circuit on the tracer be-fore the tracer is injected into the wellbore, and a data collector to retrieve data from the tracer’s on-chip memory when the tracer is carried back to the surface by the drilling fluid. The initiator and data collector will use wireless communication to reset the circuit and down-load data from the tracer, respectively. A magnetic tracer separator (see Fig. 1) will be installed after the data collector to recycle the tracers. A lithium cell (battery) used in the tracer contains stainless steel, which can enhance the separation of tracers from the drilling fluid in the magnetic tracer separator. When used in experiments or in the field, tracers will be injected together with the drilling fluid. Before a tracer is injected into the flowline, it passes through an initiator, which will reset the circuit for recording data. As the tracer travels through the wellbore, it will measure the temperature and pressure throughout the wellbore and store the data in the on-chip memory at a sampling rate set by the initiator. When the tracers are carried out of the borehole by the drilling fluid, they will pass through a data collector (controlled by a computer) through which the tracer will communicate with the surface devices to send the data stored in its on-chip memory.

Direct detection of cancer biomarkers in blood using a "place n play" modular polydimethylsiloxane pump.

Cancer biomarkers have significant potential as reliable tools for the early detection of the disease and for monitoring its recurrence. However, most current methods for biomarker detection have technical difficulties (such as sample preparation and specific detector requirements) which limit their application in point of care diagnostics. We developed an extremely simple, power-free microfluidic system for direct detection of cancer biomarkers in microliter volumes of whole blood. CEA and CYFRA21-1 were chosen as model cancer biomarkers. The system automatically extracted blood plasma from less than 3 μl of whole blood and performed a multiplex sample-to-answer assay (nano-ELISA (enzyme-linked immunosorbent assay) technique) without the use of external power or extra components. By taking advantage of the nano-ELISA technique, this microfluidic system detected CEA at a concentration of 50 pg/ml and CYFRA21-1 at a concentration of 60 pg/ml within 60 min. The combination of PnP polydimethylsiloxane (PDMS) pump and nano-ELISA technique in a single microchip system shows great promise for the detection of cancer biomarkers in a drop of blood.

Analysis of seven STR human loci for paternity testing by microchip electrophoresis

The aim of this work was to evaluate two paternity cases by microchip electrophoresis and the validation of the methodology by comparison of the results with those obtained in a commercial genetic analyzer. It was observed that when working with tetranucleotide regions, in which the minimal difference between the alleles was only four base pairs, the commercial microchip system did not present the resolution and repeatability needed. Nevertheless, the relative standard deviation was between 0 and 1.2% and the fragments detected were within the expected size ranges as described in the literature.