Utility of lab-on-a-chip technology for high-throughput nucleic acid and protein analysis

On-chip electrophoresis can provide size separations of nucleic acids and proteins similar to more traditional slab gel electrophoresis. Lab-on-a-chip (LoaC) systems utilize on-chip electrophoresis in conjunction with sizing calibration, sensitive detection schemes, and sophisticated data analysis to achieve rapid analysis times (<120 s). This work describes the utility of LoaC systems to enable and augment systems biology investigations. RNA quality, as assessed by an RNA integrity number score, is compared to existing quality control (QC) measurements. High-throughput DNA analysis of multiplex PCR samples is used to stratify gene sets for disease discovery. Finally, the applicability of a high-throughput LoaC system for assessing protein purification is demonstrated. The improvements in workflow processes, speed of analysis, data accuracy and reproducibility, and automated data analysis are illustrated.     

Fit-to-Flow (F2F) interconnects: universal reversible adhesive-free microfluidic adaptors for lab-on-a-chip systems

World-to-chip (macro-to-micro) interface continues to be one of the most complicated, ineffective, and unreliable components in the development of emerging lab-on-a-chip systems involving integrated microfluidic operations. A number of irreversible (e.g., adhesive gluing) and reversible techniques (e.g., press fitting) have attempted to provide dedicated fluidic passage from standard tubing to miniature on-chip devices, none of which completely addresses the above concerns. In this paper, we present standardized adhesive-free microfluidic adaptors, referred to as Fit-to-Flow (F2F) Interconnects, to achieve reliable hermetic seal, high-density tube packing, self-aligned plug-in, reworkable connectivity, straightforward scalability and expandability, and applicability to broad lab-on-a-chip platforms; analogous to the modular plug-and-play USB architecture employed in modern electronics. Specifically, two distinct physical packaging mechanisms are applied, with one utilizing induced tensile stress in elastomeric socket to establish reversible seal and the other using negative pressure to provide on demand vacuum shield, both of which can be adapted to a variety of experimental configurations. The non-leaking performance (up to 336 kPa) along with high tube-packing density (of 1 tube/mm(2)) and accurate self-guided alignment (of 10 μm) have been characterized. In addition, a 3D microfluidic mixer and a 6-level chemical gradient generator paired with the corresponding F2F Interconnects have been devised to illustrate the applicability of the universal fluidic connections to classic lab-on-a-chip operations.     

Nanomaterials and lab-on-a-chip technologies

Lab-on-a-chip (LOC) platforms have become important tools for sample analysis and treatment with interest for DNA, protein and cells studies or diagnostics due to benefits such as the reduced sample volume, low cost, portability and the possibility to build new analytical devices or be integrated into conventional ones. These platforms have advantages of a wide set of nanomaterials (NM) (i.e. nanoparticles, quantum dots, nanowires, graphene etc.) and offer excellent improvement in properties for many applications (i.e. detectors sensitivity enhancement, biolabelling capability along with other in-chip applications related to the specificities of the variety of nanomaterials with optical, electrical and/or mechanical properties). This review covers the last trends in the use of nanomaterials in microfluidic systems and the related advantages in analytical and bioanalytical applications. In addition to the applications of nanomaterials in LOCs, we also discuss the employment of such devices for the production and characterization of nanomaterials. Both framed platforms, NMs based LOCs and LOCs for NMs production and characterization, represent promising alternatives to generate new nanotechnology tools for point-of-care diagnostics, drug delivery and nanotoxicology applications.     

Microfluidic platforms for lab-on-a-chip applications

We review microfluidic platforms that enable the miniaturization, integration and automation of biochemical assays. Nowadays nearly an unmanageable variety of alternative approaches exists that can do this in principle. Here we focus on those kinds of platforms only that allow performance of a set of microfluidic functions--defined as microfluidic unit operations-which can be easily combined within a well defined and consistent fabrication technology to implement application specific biochemical assays in an easy, flexible and ideally monolithically way. The microfluidic platforms discussed in the following are capillary test strips, also known as lateral flow assays, the "microfluidic large scale integration" approach, centrifugal microfluidics, the electrokinetic platform, pressure driven droplet based microfluidics, electrowetting based microfluidics, SAW driven microfluidics and, last but not least, "free scalable non-contact dispensing". The microfluidic unit operations discussed within those platforms are fluid transport, metering, mixing, switching, incubation, separation, droplet formation, droplet splitting, nL and pL dispensing, and detection.     

Electrochemical techniques for lab-on-a-chip applications

During the last few years there has been a rapid increase in the use of electrochemical reactions in lab-on-a-chip devices. This development, which has so far mainly focussed on electrochemical detection in chip-based capillary electrophoresis, can be explained by the fact that electrochemical techniques and devices are particularly well-suited for inclusion in lab-on-a-chip systems. The most important reason for this is that the required electrodes can readily be manufactured and miniaturised without loss of analytical performance using conventional microfabrication methods. In this Research Highlight article, the developments during the last three years concerning electrochemical techniques for lab on-a-chip applications are discussed, with particular focus on emerging electrochemical methods for sample clean-up and preconcentration, electrochemical derivatisation and electrochemical detection in chip-based capillary electrophoresis.     

Sustainable fabrication of micro-structured lab-on-a-chip

We have demonstrated a robust platform that can not only sustainably fabricate a lab-on-a-chip (LOC) device using microinjection molding but also elucidate the filling process of microstructures based on the multiscale analysis. In addition, a novel dimensionless number, i.e., the filling number μ(f) which can provide an insight into the underlying filling mechanism for micropillars, has been proposed based on the understanding of the characteristics of polymeric flow and cavity dimension. This study suggests a solid experimental and numerical tool for the production of microfluidic devices with the use of a micromolding technique, which is expected to help materialize the commercialization of the LOC devices in a more sustainable manner.     

Droplet-based microfluidic lab-on-a-chip for glucose detection

A microfluidic lab-on-a-chip (LoC) platform for in vitro measurement of glucose for clinical diagnostic applications is presented in this paper. The LoC uses a discrete droplet format in contrast to conventional continuous flow microfluidic systems. The droplets act as solution-phase reaction chambers and are manipulated using the electrowetting effect. Glucose is measured using a colorimetric enzyme-kinetic method based on Trinder’s reaction. The color change is detected using an absorbance measurement system consisting of a light emitting diode and a photodiode. The linear range of the assay is 9-100 mg/dl using a sample dilution factor of 2 and 15-300 mg/dl using a sample dilution factor of 3. The results obtained on the electrowetting system compare favorably with conventional measurements done on a spectrophotometer, indicating that there is no change in enzyme activity under electrowetting conditions.     

Principles of droplet electrohydrodynamics for lab-on-a-chip

Electrically controlled droplet-based labs-on-a-chip operate under the principles of electro-capillarity and dielectrophoresis. The microfluidic mechanics of manipulating electrified droplets are complex and not entirely understood. In this article, we analyse these operating principles, especially electrowetting on dielectric (a form of electro-capillarity) and dielectrophoresis, under a unified framework of droplet electrohydrodynamics. We differentiate them by their electric origins and their energy transduction mechanisms. Our study shows that both electrowetting on dielectric and dielectrophoresis are effective for droplet generation and manipulation. In addition, our study demonstrates: (1) the presence of a wetting contribution to dielectrophoresis; and (2) contact angle reduction is merely an observable consequence of, not a condition for, the occurrence of electrowetting on dielectric. Simulations are used extensively in this article to illustrate device operation, to expose underlying physics, and to validate our conclusions. Simulations of electrically driven droplet generation, droplet translocation, droplet fusion, and droplet fission are presented.     

Multiport flow-control system for lab-on-a-chip microfluidic devices

A multiport system suitable for pressure control on a lab-on-a-chip microfluidic device is described. An algorithm and a strategy for calculating pressures were developed to control the flow from multiple reservoirs for the microfluidic devices. Dye mixing and enzyme assay titration experiments were performed using pressure-driven flow only. Results show a good linear response over two orders of dynamic range.     

功能型微流控芯片实验室的研究及其应用

功能型微流控芯片实验室由芯片、芯片工作站、功能芯片试剂盒等3部分组成. 开展了不同类型的芯片设计,研制了有不同集成度和不同结构的玻璃芯片以及PMMA、PDMS和SU-8等塑料芯片,其中注塑型PMMA塑料芯片已具备规模生产的能力.     

Rapid liposome quality assessment using a lab-on-a-chip

Although liposomes have many outstanding features such as biocompatibility, biodegradability, low toxicity and structural diversity, and are successfully applied in many areas of chemistry and biotechnology, a lack of characterization standards and quality control tools are still inhibiting the translation of liposome technology into clinical routine. The greatest obstacle to clinical scale commercialization is the inability to ensure liposome formulation stability because small size variations or altered surface chemistries can significantly influence in vivo distribution and excretion kinetics that could in turn lead to unpredictable therapy outcomes. To enhance the product development process we have developed a microfluidic biochip containing embedded dielectric microsensors capable of providing quantitative results on formulation composition and stability based on the monitoring of the unique electric properties of liposomes. Computational fluid dynamic (CFD) simulations confirmed that microfluidics offer reproducible and well-defined measurement conditions where a moving liposome suspension within a microchannel behaves like a bulk material. Results of this study demonstrate the ability of microfluidics, in combination with dielectric spectroscopy and multivariate data analysis methods, to identify nine different liposomes. We also show that various liposome modifications such as membrane-bound surface proteins, lipid bilayer soluble drugs, as well as protein and dye encapsulations, can be detected in the absence of any labels or indicators. Since shelf-life stability of a liposome formulation is regarded of prime importance for regulatory approval and clinical application, we further provide a possible practical application of the developed liposome analysis platform as a high-throughput tool for industrial quality insurance purposes.     

Fuel cell-powered microfluidic platform for lab-on-a-chip applications

The achievement of a higher degree of integration of components--especially micropumps and power sources--is a challenge currently being pursued to obtain portable and totally autonomous microfluidic devices. This paper presents the integration of a micro direct methanol fuel cell (μDMFC) in a microfluidic platform as a smart solution to provide both electrical and pumping power to a Lab-on-a-Chip system. In this system the electric power produced by the fuel cell is available to enable most of the functionalites required by the microfluidic chip, while the generated CO(2) from the electrochemical reaction produces a pressure capable of pumping a liquid volume through a microchannel. The control of the fuel cell operating conditions allows regulation of the flow rate of a liquid sample through a microfluidic network. The relation between sample flow rate and the current generated by the fuel cell is practically linear, achieving values in the range of 4-18 μL min(-1) while having an available power between 1-4 mW. This permits adjusting the desired flow rate for a given application by controlling the fuel cell output conditions and foresees a fully autonomous analytical Lab-on-a-Chip in which the same device would provide the electrical power to a detection module and at the same time use the CO(2) pumping action to flow the required analytes through a particular microfluidic design.     

A disposable planar peristaltic pump for lab-on-a-chip

We demonstrate a simple planar peristaltic pump fabricated in poly(dimethylsiloxane) (PDMS) via soft lithography and suitable for microfluidic integration.     

Sheath-assisted focusing of microparticles on lab-on-a-chip platforms

Lab-on-a-chip (LOC) technologies can take advantage of sheath flows for particle/cell focusing before sensing or sorting. The integration of focusing with other microscale manipulation techniques (e.g., sorting) creates a trade-off between the throughput of the device and its performance. Therefore, exploring the effective parameters for cells/particles focusing enables us to improve the desired output of LOC devices. A common configuration for sheath-assisted focusing is Y junctions, which are parametrically studied in this paper. First, a computational model was developed and validated by comparing it with our experimental results. Using COMSOL Multiphysics modeling, the effects of multiple parameters were studied. These parameters include the sheath flow ratio (sheath flow over total flow), width ratio (width of the sheath inlet over the total width), junction angles, and particle size on the focusing width and the distribution of the particles within the focusing region. Then, the numerical data were used to develop two generalized linear models to predict the focusing width of the particles and the standard deviation of the position of the particles. The results showed that the focusing width is greatly impacted by the sheath flow rate ratio. Further, the standard deviation of the position of the particles, which represents the concentration of the particles, is mostly dependent on the flow rate ratio, width ratio, and particle size. Our results provide a better understanding of how the device geometrical and operational factors affect the position of the particles in the development of high-performance on-chip sensing and sorting of both cells and particles.     

Drop mixing in a microchannel for lab-on-a-chip platforms

We present theory, simulations, and experiments for discrete drop mixing in microchannels. The drops are placed sequentially in a channel and then moved at a set velocity to achieve mixing. The mixing occurs in three different regimes (diffusion-dominated, dispersion-dominated, and convection-dominated) depending on the Péclet number (Pe) and the drop dimensions. Introducing the modified Péclet number (Pe*), we show asymptotic curves that can be used to predict the mixing time and the required distance for mixing for any of the three regimes. Simulations of the mixing experiments using COMSOL agree with the theoretical limits. In our experimental work, we used a polydimethylsiloxane (PDMS) microchannel with a membrane air bypass valve to remove the air between drops. This approach enables precise control of the mixing and merging site. Experimental, simulation, and theoretical results all agree and show that mixing can occur in fractions of a second to hours, depending on the parameters used.     

Optical sensing in microfluidic lab-on-a-chip by femtosecond-laser-written waveguides

We use direct femtosecond laser writing to integrate optical waveguides into a commercial fused silica capillary electrophoresis chip. High-quality waveguides crossing the microfluidic channels are fabricated and used to optically address, with high spatial selectivity, their content. Fluorescence from the optically excited volume is efficiently collected at a 90° angle by a high numerical aperture fiber, resulting in a highly compact and portable device. To test the platform we performed electrophoresis and detection of a 23-mer oligonucleotide plug. Our approach is quite powerful because it allows the integration of photonic functionalities, by simple post-processing, into commercial LOCs fabricated with standard techniques. Figure Femtosecond laser written waveguides can selectively excite fluorescence in a microfluidic channel of a commercial lab-on-a-chip. A compact scheme for on-chip detection by laser induced fluorescence is applied to capillary electrophoresis of a 23-mer Cy3-labeled oligonucleotide     

聚合酶链式反应-限制性片段长度多态性和芯片生物分析技术用于渤海地区鱼种鉴定

以渤海湾具有重要商业价值的9种海鱼(小黄鱼、花鲈、蓝点马鲛、鲐、钝吻黄盖鲽、棘头梅童鱼、许氏平鲉、高眼鲽和长蛇鲻)为研究对象,利用聚合酶链式反应(PCR)-限制性片段长度多态性(RFLP)和芯片生物分析技术对其进行鱼种鉴定。首先提取其基因组脱氧核糖核酸(DNA),对其细胞色素b的特定片段(464 bp)进行扩增,然后选择DdeI、HaeIII和NlaIII3种限制性内切酶进行酶切,并利用芯片生物分析技术得到酶切产物的特异图谱和确切的片段大小,从而有效区分了9种海鱼。研究结果表明,PCR-RFLP和芯片生物分析技术在鱼种鉴定上具有精确、鉴别和快速三大优势,可为鱼类食品检测提供科学依据。