151
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Dewan A, Kim J, McLean RH, Vanapalli SA, Karim MN. Growth kinetics of microalgae in microfluidic static droplet arrays. Biotechnol Bioeng 2012; 109:2987-96. [PMID: 22711504 DOI: 10.1002/bit.24568] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 04/24/2012] [Accepted: 05/18/2012] [Indexed: 01/21/2023]
Abstract
We investigated growth kinetics of microalgae, Chlorella vulgaris, in immobilized arrays of nanoliter-scale microfluidic drops. These static drop arrays enabled simultaneous monitoring of growth of single as well as multiple cells encapsulated in individual droplets. To monitor the growth, individual drop volumes were kept nearly intact for more than a month by controlling the permeation of water in and out of the microfluidic device. The kinetic growth parameters were quantified by counting the increase in the number of cells in each drop over time. In addition to determining the kinetic parameters, the cell-size distribution of the microalgae was correlated with different stages of the growth. The single-cell growth kinetics of C. vulgaris showed significant heterogeneity. The specific growth rate ranged from 0.55 to 1.52 day(-1) for different single cells grown in the same microfluidic device. In comparison, the specific growth rate in bulk-scale experiment was 1.12 day(-1). It was found that the average cell size changes significantly at different stages of the cell growth. The mean cell-size increased from 5.99 ± 1.08 to 7.33 ± 1.3 µm from exponential to stationary growth phase. In particular, when multiple cells are grown in individual drops, we find that in the stationary growth phase, the cell size increases with the age of cell suggesting enhanced accumulation of fatty acids in older cells.
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Affiliation(s)
- Alim Dewan
- Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409, USA
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152
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Lagus TP, Edd JF. High throughput single-cell and multiple-cell micro-encapsulation. J Vis Exp 2012:e4096. [PMID: 22733254 DOI: 10.3791/4096] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
UNLABELLED Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement from a bulk fluid environment with applications in high throughput screening, cytometry, and mass spectrometry. We describe a method to not only encapsulate single cells, but to repeatedly capture a set number of cells (here we demonstrate one- and two-cell encapsulation) to study both isolation and the interactions between cells in groups of controlled sizes. By combining drop generation techniques with cell and particle ordering, we demonstrate controlled encapsulation of cell-sized particles for efficient, continuous encapsulation. Using an aqueous particle suspension and immiscible fluorocarbon oil, we generate aqueous drops in oil with a flow focusing nozzle. The aqueous flow rate is sufficiently high to create ordering of particles which reach the nozzle at integer multiple frequencies of the drop generation frequency, encapsulating a controlled number of cells in each drop. For representative results, 9.9 μm polystyrene particles are used as cell surrogates. This study shows a single-particle encapsulation efficiency P(k=1) of 83.7% and a double-particle encapsulation efficiency P(k=2) of 79.5% as compared to their respective Poisson efficiencies of 39.3% and 33.3%, respectively. The effect of consistent cell and particle concentration is demonstrated to be of major importance for efficient encapsulation, and dripping to jetting transitions are also addressed. INTRODUCTION Continuous media aqueous cell suspensions share a common fluid environment which allows cells to interact in parallel and also homogenizes the effects of specific cells in measurements from the media. High-throughput encapsulation of cells into picoliter-scale drops confines the samples to protect drops from cross-contamination, enable a measure of cellular diversity within samples, prevent dilution of reagents and expressed biomarkers, and amplify signals from bioreactor products. Drops also provide the ability to re-merge drops into larger aqueous samples or with other drops for intercellular signaling studies. The reduction in dilution implies stronger detection signals for higher accuracy measurements as well as the ability to reduce potentially costly sample and reagent volumes. Encapsulation of cells in drops has been utilized to improve detection of protein expression, antibodies, enzymes, and metabolic activity for high throughput screening, and could be used to improve high throughput cytometry. Additional studies present applications in bio-electrospraying of cell containing drops for mass spectrometry and targeted surface cell coatings. Some applications, however, have been limited by the lack of ability to control the number of cells encapsulated in drops. Here we present a method of ordered encapsulation which increases the demonstrated encapsulation efficiencies for one and two cells and may be extrapolated for encapsulation of a larger number of cells. To achieve monodisperse drop generation, microfluidic "flow focusing" enables the creation of controllable-size drops of one fluid (an aqueous cell mixture) within another (a continuous oil phase) by using a nozzle at which the streams converge. For a given nozzle geometry, the drop generation frequency f and drop size can be altered by adjusting oil and aqueous flow rates Q(oil) and Q(aq). As the flow rates increase, the flows may transition from drop generation to unstable jetting of aqueous fluid from the nozzle. When the aqueous solution contains suspended particles, particles become encapsulated and isolated from one another at the nozzle. For drop generation using a randomly distributed aqueous cell suspension, the average fraction of drops D(k) containing k cells is dictated by Poisson statistics, where D(k) = λ(k) exp(-λ)/(k!) and λ is the average number of cells per drop. The fraction of cells which end up in the "correctly" encapsulated drops is calculated using P(k) = (k x D(k))/Σ(k' x D(k)'). The subtle difference between the two metrics is that D(k) relates to the utilization of aqueous fluid and the amount of drop sorting that must be completed following encapsulation, and P(k) relates to the utilization of the cell sample. As an example, one could use a dilute cell suspension (low λ) to encapsulate drops where most drops containing cells would contain just one cell. While the efficiency metric P(k) would be high, the majority of drops would be empty (low D(k)), thus requiring a sorting mechanism to remove empty drops, also reducing throughput. Combining drop generation with inertial ordering provides the ability to encapsulate drops with more predictable numbers of cells per drop and higher throughputs than random encapsulation. Inertial focusing was first discovered by Segre and Silberberg and refers to the tendency of finite-sized particles to migrate to lateral equilibrium positions in channel flow. Inertial ordering refers to the tendency of the particles and cells to passively organize into equally spaced, staggered, constant velocity trains. Both focusing and ordering require sufficiently high flow rates (high Reynolds number) and particle sizes (high Particle Reynolds number). Here, the Reynolds number Re =uD(h)/ν and particle Reynolds number Rep =Re(a/D(h))², where u is a characteristic flow velocity, D(h) [=2wh/(w+h)] is the hydraulic diameter, ν is the kinematic viscosity, a is the particle diameter, w is the channel width, and h is the channel height. Empirically, the length required to achieve fully ordered trains decreases as Re and Re(p) increase. Note that the high Re and Re(p) requirements (for this study on the order of 5 and 0.5, respectively) may conflict with the need to keep aqueous flow rates low to avoid jetting at the drop generation nozzle. Additionally, high flow rates lead to higher shear stresses on cells, which are not addressed in this protocol. The previous ordered encapsulation study demonstrated that over 90% of singly encapsulated HL60 cells under similar flow conditions to those in this study maintained cell membrane integrity. However, the effect of the magnitude and time scales of shear stresses will need to be carefully considered when extrapolating to different cell types and flow parameters. The overlapping of the cell ordering, drop generation, and cell viability aqueous flow rate constraints provides an ideal operational regime for controlled encapsulation of single and multiple cells. Because very few studies address inter-particle train spacing, determining the spacing is most easily done empirically and will depend on channel geometry, flow rate, particle size, and particle concentration. Nonetheless, the equal lateral spacing between trains implies that cells arrive at predictable, consistent time intervals. When drop generation occurs at the same rate at which ordered cells arrive at the nozzle, the cells become encapsulated within the drop in a controlled manner. This technique has been utilized to encapsulate single cells with throughputs on the order of 15 kHz, a significant improvement over previous studies reporting encapsulation rates on the order of 60-160 Hz. In the controlled encapsulation work, over 80% of drops contained one and only one cell, a significant efficiency improvement over Poisson (random) statistics, which predicts less than 40% efficiency on average. In previous controlled encapsulation work, the average number of particles per drop λ was tuned to provide single-cell encapsulation. We hypothesize that through tuning of flow rates, we can efficiently encapsulate any number of cells per drop when λ is equal or close to the number of desired cells per drop. While single-cell encapsulation is valuable in determining individual cell responses from stimuli, multiple-cell encapsulation provides information relating to the interaction of controlled numbers and types of cells. Here we present a protocol, representative results using polystyrene microspheres, and discussion for controlled encapsulation of multiple cells using a passive inertial ordering channel and drop generation nozzle.
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Affiliation(s)
- Todd P Lagus
- Department of Mechanical Engineering, Vanderbilt University, USA
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153
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Velasco D, Tumarkin E, Kumacheva E. Microfluidic encapsulation of cells in polymer microgels. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:1633-42. [PMID: 22467645 DOI: 10.1002/smll.201102464] [Citation(s) in RCA: 178] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 01/03/2012] [Indexed: 05/07/2023]
Abstract
In this Concept article, recent advances in microfluidic platforms for the generation of cell-laden hydrogel particles (microgels) are reported. Advances in the continuous microfluidic encapsulation of cells in droplets and microgels are critically reviewed, and currently used methods for the encapsulation of cells in polymer microgels are discussed. An outlook on current applications and future directions in this field of research are also presented. This article will be of interest to chemists, materials scientists, cell biologists, bioengineers, and pharmacologists.
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Affiliation(s)
- Diego Velasco
- Department of Chemistry, University of Toronto, 80 Saint George Street, Toronto, Ontario, Canada
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154
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Lin R, Fisher JS, Simon MG, Lee AP. Novel on-demand droplet generation for selective fluid sample extraction. BIOMICROFLUIDICS 2012; 6:24103-2410310. [PMID: 22655015 PMCID: PMC3360719 DOI: 10.1063/1.3699972] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 03/05/2012] [Indexed: 05/11/2023]
Abstract
A novel microfluidic device enabling selective generation of droplets and encapsulation of targets is presented. Unlike conventional methods, the presented mechanism generates droplets with unique selectivity by utilizing a K-junction design. The K-junction is a modified version of the classic T-junction with an added leg that serves as the exit channel for waste. The dispersed phase fluid enters from one diagonal of the K and exits the other diagonal while the continuous phase travels in the straight leg of the K. The intersection forms an interface that allows the dispersed phase to be controllably injected through actuation of an elastomer membrane located above the inlet channel near the interface. We have characterized two critical components in controlling the droplet size-membrane actuation pressure and timing as well as identified the region of fluid in which the droplet will be formed. This scheme will have applications in fluid sampling processes and selective encapsulation of materials. Selective encapsulation of a single cell from the dispersed phase fluid is demonstrated as an example of functionality of this design.
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Affiliation(s)
- Robert Lin
- University of California-Irvine, Irvine, California 92697, USA
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155
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Um E, Rha E, Choi SL, Lee SG, Park JK. Mesh-integrated microdroplet array for simultaneous merging and storage of single-cell droplets. LAB ON A CHIP 2012; 12:1594-1597. [PMID: 22422143 DOI: 10.1039/c2lc21266h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We constructed a mesh-grid integrated microwell array which enables easy trapping and consistent addition of droplets. The grid acts as a microchannel structure to guide droplets into the microwells underneath, and also provides open access for additional manipulation in a high-throughput manner. Each droplet in the array forms a stable environment of pico-litre volume to implement a single-cell-based assay.
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Affiliation(s)
- Eujin Um
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, Republic of Korea
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156
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Baker CA, Roper MG. Online coupling of digital microfluidic devices with mass spectrometry detection using an eductor with electrospray ionization. Anal Chem 2012; 84:2955-60. [PMID: 22384846 DOI: 10.1021/ac300100b] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
MS detection coupled with digital microfluidic (DMF) devices has most commonly been demonstrated in an offline manner using matrix assisted laser desorption ionization. In this work, an eductor is demonstrated which facilitated online coupling of DMF with electrospray ionization MS detection. The eductor consisted of a transfer capillary, a standard ESI needle, and a tapered gas nozzle. As a pulse of N(2) was applied to the nozzle, a pressure differential was induced at the outlet of the ESI needle that pulled droplets from the DMF, past the ESI needle, and into the flow of gas exiting the nozzle, allowing detection by MS. Operating position, ionization potential, and N(2) pressure were optimized, with the optimum ionization potential and N(2) pressure found to be 3206 V and 80 psi, respectively. Online MS detection was demonstrated from both open and closed DMF devices using 2.5 μL and 630 nL aqueous droplets, respectively. Relative quantitation by DMF-MS was demonstrated by mixing droplets of caffeine with droplets of theophylline on an open DMF device and comparing the peak area ratio obtained to an on-chip generated calibration curve. This eductor-based method for transferring droplets has the potential for rapid, versatile, and high-throughput microfluidic analyses.
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Affiliation(s)
- Christopher A Baker
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
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157
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Tanweer F, Louise Green V, David Stafford N, Greenman J. Application of microfluidic systems in management of head and neck squamous cell carcinoma. Head Neck 2012; 35:756-63. [DOI: 10.1002/hed.22906] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 09/16/2011] [Accepted: 11/02/2011] [Indexed: 11/11/2022] Open
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158
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Najah M, Griffiths AD, Ryckelynck M. Teaching single-cell digital analysis using droplet-based microfluidics. Anal Chem 2012; 84:1202-9. [PMID: 22229495 DOI: 10.1021/ac202645m] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Microfluidics allows the manipulation of small quantities of reagents in a high-throughput manner and is therefore highly amenable to single cell characterization and more generally to digital analysis, with applications in fields as varied as genomics, diagnostics, directed evolution, and drug screening. The growing place of microfluidics in biology laboratories encouraged us to develop a teaching method where advanced undergraduate or first-year graduate-level students are taught to fabricate droplet-based microfluidic devices, characterize them, and finally use them to perform a digital analysis of bacterial samples based on a phenotypic marker.
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Affiliation(s)
- Majdi Najah
- Institut de Science et d'Ingénierie Supramoléculaires (ISIS), Université de Strasbourg, CNRS UMR 7006, 8 allée Gaspard Monge, 67083 Strasbourg Cedex, France
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159
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Abstract
This book chapter aims at providing an overview of all the aspects and procedures needed to develop a droplet-based workflow for single-cell analysis (see Fig. 10.1). The surfactant system used to stabilize droplets is a critical component of droplet microfluidics; its properties define the type of droplet-based assays and workflows that can be developed. The scope of this book chapter is limited to fluorinated surfactant systems that have proved to generate extremely stable droplets and allow to easily retrieve the encapsulated material. The formulation section discusses how the experimental parameters influence the choice of the surfactant system to use. The circuit design section presents recipes to design and integrate different droplet modules into a whole assay. The fabrication section describes the manufacturing of microfluidic chip including the surface treatment which is pivotal in droplet microfluidics. Finally, the last section reviews the experimental setup for fluorescence detection with an emphasis on cell injection and incubation.
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Affiliation(s)
- Eric Brouzes
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA.
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160
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Seemann R, Brinkmann M, Pfohl T, Herminghaus S. Droplet based microfluidics. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2012; 75:016601. [PMID: 22790308 DOI: 10.1088/0034-4885/75/1/016601] [Citation(s) in RCA: 488] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Droplet based microfluidics is a rapidly growing interdisciplinary field of research combining soft matter physics, biochemistry and microsystems engineering. Its applications range from fast analytical systems or the synthesis of advanced materials to protein crystallization and biological assays for living cells. Precise control of droplet volumes and reliable manipulation of individual droplets such as coalescence, mixing of their contents, and sorting in combination with fast analysis tools allow us to perform chemical reactions inside the droplets under defined conditions. In this paper, we will review available drop generation and manipulation techniques. The main focus of this review is not to be comprehensive and explain all techniques in great detail but to identify and shed light on similarities and underlying physical principles. Since geometry and wetting properties of the microfluidic channels are crucial factors for droplet generation, we also briefly describe typical device fabrication methods in droplet based microfluidics. Examples of applications and reaction schemes which rely on the discussed manipulation techniques are also presented, such as the fabrication of special materials and biophysical experiments.
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Affiliation(s)
- Ralf Seemann
- Experimental Physics, Saarland University, D-66123 Saarbrücken, Germany.
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161
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Cai LF, Zhu Y, Du GS, Fang Q. Droplet-based microfluidic flow injection system with large-scale concentration gradient by a single nanoliter-scale injection for enzyme inhibition assay. Anal Chem 2011; 84:446-52. [PMID: 22128774 DOI: 10.1021/ac2029198] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We described a microfluidic chip-based system capable of generating droplet array with a large scale concentration gradient by coupling flow injection gradient technique with droplet-based microfluidics. Multiple modules including sample injection, sample dispersion, gradient generation, droplet formation, mixing of sample and reagents, and online reaction within the droplets were integrated into the microchip. In the system, nanoliter-scale sample solution was automatically injected into the chip under valveless flow injection analysis mode. The sample zone was first dispersed in the microchannel to form a concentration gradient along the axial direction of the microchannel and then segmented into a linear array of droplets by immiscible oil phase. With the segmentation and protection of the oil phase, the concentration gradient profile of the sample was preserved in the droplet array with high fidelity. With a single injection of 16 nL of sample solution, an array of droplets with concentration gradient spanning 3-4 orders of magnitude could be generated. The present system was applied in the enzyme inhibition assay of β-galactosidase to preliminarily demonstrate its potential in high throughput drug screening. With a single injection of 16 nL of inhibitor solution, more than 240 in-droplet enzyme inhibition reactions with different inhibitor concentrations could be performed with an analysis time of 2.5 min. Compared with multiwell plate-based screening systems, the inhibitor consumption was reduced 1000-fold.
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Affiliation(s)
- Long-Fei Cai
- Institute of Microanalytical Systems, Department of Chemistry, Zhejiang University, Hangzhou, 310058, China
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162
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Casadevall i Solvas X, Niu X, Leeper K, Cho S, Chang SI, Edel JB, deMello AJ. Fluorescence detection methods for microfluidic droplet platforms. J Vis Exp 2011:3437. [PMID: 22215381 PMCID: PMC3346046 DOI: 10.3791/3437] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that accompany system miniaturisation. Advantages include the ability to efficiently process nano- to femoto- liter volumes of sample, facile integration of functional components, an intrinsic predisposition towards large-scale multiplexing, enhanced analytical throughput, improved control and reduced instrumental footprints. In recent years much interest has focussed on the development of droplet-based (or segmented flow) microfluidic systems and their potential as platforms in high-throughput experimentation. Here water-in-oil emulsions are made to spontaneously form in microfluidic channels as a result of capillary instabilities between the two immiscible phases. Importantly, microdroplets of precisely defined volumes and compositions can be generated at frequencies of several kHz. Furthermore, by encapsulating reagents of interest within isolated compartments separated by a continuous immiscible phase, both sample cross-talk and dispersion (diffusion- and Taylor-based) can be eliminated, which leads to minimal cross-contamination and the ability to time analytical processes with great accuracy. Additionally, since there is no contact between the contents of the droplets and the channel walls (which are wetted by the continuous phase) absorption and loss of reagents on the channel walls is prevented. Once droplets of this kind have been generated and processed, it is necessary to extract the required analytical information. In this respect the detection method of choice should be rapid, provide high-sensitivity and low limits of detection, be applicable to a range of molecular species, be non-destructive and be able to be integrated with microfluidic devices in a facile manner. To address this need we have developed a suite of experimental tools and protocols that enable the extraction of large amounts of photophysical information from small-volume environments, and are applicable to the analysis of a wide range of physical, chemical and biological parameters. Herein two examples of these methods are presented and applied to the detection of single cells and the mapping of mixing processes inside picoliter-volume droplets. We report the entire experimental process including microfluidic chip fabrication, the optical setup and the process of droplet generation and detection.
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163
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Xiang X, Chen L, Zhuang Q, Ji X, He Z. Real-time luminescence-based colorimetric determination of double-strand DNA in droplet on demand. Biosens Bioelectron 2011; 32:43-9. [PMID: 22196878 DOI: 10.1016/j.bios.2011.11.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2011] [Revised: 10/17/2011] [Accepted: 11/08/2011] [Indexed: 12/16/2022]
Abstract
We have developed a new luminescence-based colorimetric droplet platform for the determination of double-stranded DNAs (dsDNA). This colorimetric sensor was realized via choosing a fluorescent ensemble probe comprising water-soluble N-acetylcysteine-capped CdTe quantum dots (QDs) and Ru(bpy)(2)(dppx)(2+) (Ru). To provide a convenient and low cost droplet platform for colorimetry, the microvalve technique was adapted to adjust droplet size precisely, achieve the desired fusion of multiple droplets and trap droplets on demand, as well as implement concentration gradients of DNA on a single chip. In the colorimetric sensor, Ru served as both an effective quencher for QDs and a reporter for dsDNA. With increasing concentration of dsDNA, a gradually enhanced color response was observed because of the competition of dsDNA with QDs for Ru. Under the optimum conditions, this biosensing system exhibited not only good sensitivity and specificity for calf thymus DNA with the detection limit of 1.0 pg, but also coincident performances in diluted human serum with the detection limit of 0.9 pg. The droplet biosensor provides a highly efficient, rapid and visual method for dsDNA analysis. The colorimetric droplet platform could be useful as a simple research tool for the study of limited and precious regents such as protein and virus samples, etc.
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Affiliation(s)
- Xia Xiang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China
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164
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Deng NN, Meng ZJ, Xie R, Ju XJ, Mou CL, Wang W, Chu LY. Simple and cheap microfluidic devices for the preparation of monodisperse emulsions. LAB ON A CHIP 2011; 11:3963-3969. [PMID: 22025190 DOI: 10.1039/c1lc20629j] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Droplet microfluidics, which can generate monodisperse droplets or bubbles in unlimited numbers, at high speed and with complex structures, have been extensively investigated in chemical and biological fields. However, most current methods for fabricating microfluidic devices, such as glass etching, soft lithography in polydimethylsiloxane (PDMS) or assembly of glass capillaries, are usually either expensive or complicated. Here we report the fabrication of simple and cheap microfluidic devices based on patterned coverslips and microscope glass slides. The advantages of our approach for fabricating microfluidic devices lie in a simple process, inexpensive processing equipment and economical laboratory supplies. The fabricated microfluidic devices feature a flexible design of microchannels, easy spatial patterning of surface wettability, and good chemical compatibility and optical properties. We demonstrate their utilities for generation of monodisperse single and double emulsions with highly controllable flexibility.
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Affiliation(s)
- Nan-Nan Deng
- School of Chemical Engineering, Sichuan University, Chengdu, Sichuan, China
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165
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Yin H, Marshall D. Microfluidics for single cell analysis. Curr Opin Biotechnol 2011; 23:110-9. [PMID: 22133547 DOI: 10.1016/j.copbio.2011.11.002] [Citation(s) in RCA: 234] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 10/30/2011] [Accepted: 11/02/2011] [Indexed: 01/23/2023]
Abstract
Substantial evidence shows that the heterogeneity of individual cells within a genetically identical population can be critical to their chance of survival. Methods that use average responses from a population often mask the difference from individual cells. To fully understand cell-to-cell variability, a complete analysis of an individual cell, from its live state to cell lysates, is essential. Highly sensitive detection of multiple components and high throughput analysis of a large number of individual cells remain the key challenges to realise this aim. In this context, microfluidics and lab-on-a-chip technology have emerged as the most promising avenue to address these challenges. In this review, we will focus on the recent development in microfluidics that are aimed at total single cell analysis on chip, that is, from an individual live cell to its gene and proteins. We also discuss the opportunities that microfluidic based single cell analysis can bring into the drug discovery process.
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Affiliation(s)
- Huabing Yin
- Biomedical Engineering, School of Engineering, University of Glasgow, Glasgow G12 8LT, UK.
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166
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Vannoy CH, Tavares AJ, Noor MO, Uddayasankar U, Krull UJ. Biosensing with quantum dots: a microfluidic approach. SENSORS (BASEL, SWITZERLAND) 2011; 11:9732-63. [PMID: 22163723 PMCID: PMC3231262 DOI: 10.3390/s111009732] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 10/04/2011] [Accepted: 10/17/2011] [Indexed: 01/09/2023]
Abstract
Semiconductor quantum dots (QDs) have served as the basis for signal development in a variety of biosensing technologies and in applications using bioprobes. The use of QDs as physical platforms to develop biosensors and bioprobes has attracted considerable interest. This is largely due to the unique optical properties of QDs that make them excellent choices as donors in fluorescence resonance energy transfer (FRET) and well suited for optical multiplexing. The large majority of QD-based bioprobe and biosensing technologies that have been described operate in bulk solution environments, where selective binding events at the surface of QDs are often associated with relatively long periods to reach a steady-state signal. An alternative approach to the design of biosensor architectures may be provided by a microfluidic system (MFS). A MFS is able to integrate chemical and biological processes into a single platform and allows for manipulation of flow conditions to achieve, by sample transport and mixing, reaction rates that are not entirely diffusion controlled. Integrating assays in a MFS provides numerous additional advantages, which include the use of very small amounts of reagents and samples, possible sample processing before detection, ultra-high sensitivity, high throughput, short analysis time, and in situ monitoring. Herein, a comprehensive review is provided that addresses the key concepts and applications of QD-based microfluidic biosensors with an added emphasis on how this combination of technologies provides for innovations in bioassay designs. Examples from the literature are used to highlight the many advantages of biosensing in a MFS and illustrate the versatility that such a platform offers in the design strategy.
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Affiliation(s)
- Charles H. Vannoy
- Chemical Sensors Group, Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3359 Mississauga Rd. North, Mississauga, Ontario L5L 1C6, Canada; E-Mails: (C.H.V.); (A.J.T.); (M.O.N.); (U.U.)
| | | | | | | | - Ulrich J. Krull
- Chemical Sensors Group, Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3359 Mississauga Rd. North, Mississauga, Ontario L5L 1C6, Canada; E-Mails: (C.H.V.); (A.J.T.); (M.O.N.); (U.U.)
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167
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Gu SQ, Zhang YX, Zhu Y, Du WB, Yao B, Fang Q. Multifunctional Picoliter Droplet Manipulation Platform and Its Application in Single Cell Analysis. Anal Chem 2011; 83:7570-6. [DOI: 10.1021/ac201678g] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Shu-Qing Gu
- Department of Chemistry, Institute of Microanalytical Systems, Zhejiang University, Hangzhou 310058, China
| | - Yun-Xia Zhang
- Department of Chemistry, Institute of Microanalytical Systems, Zhejiang University, Hangzhou 310058, China
| | - Ying Zhu
- Department of Chemistry, Institute of Microanalytical Systems, Zhejiang University, Hangzhou 310058, China
| | - Wen-Bin Du
- Department of Chemistry, Institute of Microanalytical Systems, Zhejiang University, Hangzhou 310058, China
| | - Bo Yao
- Department of Chemistry, Institute of Microanalytical Systems, Zhejiang University, Hangzhou 310058, China
| | - Qun Fang
- Department of Chemistry, Institute of Microanalytical Systems, Zhejiang University, Hangzhou 310058, China
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168
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Pan J, Stephenson AL, Kazamia E, Huck WTS, Dennis JS, Smith AG, Abell C. Quantitative tracking of the growth of individual algal cells in microdroplet compartments. Integr Biol (Camb) 2011; 3:1043-51. [PMID: 21863189 DOI: 10.1039/c1ib00033k] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In this paper we introduce a simple droplet-based microfluidic system consisting of two separate devices to encapsulate and culture microalgae, in contrast to cultivation in bulk liquid medium. This microdroplet technology has been used to monitor the growth of individual microalgal cells in a constant environment for extended periods of time. Single cells from three species of green microalgae, (two freshwater species Chlamydomonas reinhardtii and Chlorella vulgaris, and one saline species Dunaliella tertiolecta), were encapsulated and incubated in microdroplet compartments of diameter of ∼80 μm, and their growth analysed over 10 days. In all cases, the doubling time of microalgae grown in microdroplets was similar to growth in bulk. The growth of C. reinhardtii in microdroplets of varying diameters and with different initial cell numbers per droplet was investigated, as well as the effect of varying medium conditions such as pH and nitrogen concentration. This methodology offers the opportunity to study characteristics over time of individual cells and colonies, as well as to screen large numbers of them.
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Affiliation(s)
- Jie Pan
- Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
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169
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Design of a model-based feedback controller for active sorting and synchronization of droplets in a microfluidic loop. AIChE J 2011. [DOI: 10.1002/aic.12740] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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170
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Liu K, Wang MW, Lin WY, Phung DL, Girgis MD, Wu AM, Tomlinson JS, Shen CKF. Molecular Imaging Probe Development using Microfluidics. Curr Org Synth 2011; 8:473-487. [PMID: 22977436 DOI: 10.2174/157017911796117205] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In this manuscript, we review the latest advancement of microfluidics in molecular imaging probe development. Due to increasing needs for medical imaging, high demand for many types of molecular imaging probes will have to be met by exploiting novel chemistry/radiochemistry and engineering technologies to improve the production and development of suitable probes. The microfluidic-based probe synthesis is currently attracting a great deal of interest because of their potential to deliver many advantages over conventional systems. Numerous chemical reactions have been successfully performed in micro-reactors and the results convincingly demonstrate with great benefits to aid synthetic procedures, such as purer products, higher yields, shorter reaction times compared to the corresponding batch/macroscale reactions, and more benign reaction conditions. Several 'proof-of-principle' examples of molecular imaging probe syntheses using microfluidics, along with basics of device architecture and operation, and their potential limitations are discussed here.
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Affiliation(s)
- Kan Liu
- College of Electronics and Information Engineering, Wuhan Textile University, Wuhan, 430073, China
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171
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Chen CH, Sarkar A, Song YA, Miller MA, Kim SJ, Griffith LG, Lauffenburger DA, Han J. Enhancing protease activity assay in droplet-based microfluidics using a biomolecule concentrator. J Am Chem Soc 2011; 133:10368-71. [PMID: 21671557 PMCID: PMC3165005 DOI: 10.1021/ja2036628] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We introduce an integrated microfluidic device consisting of a biomolecule concentrator and a microdroplet generator, which enhances the limited sensitivity of low-abundance enzyme assays by concentrating biomolecules before encapsulating them into droplet microreactors. We used this platform to detect ultralow levels of matrix metalloproteinases (MMPs) from diluted cellular supernatant and showed that it significantly (~10-fold) reduced the time required to complete the assay and the sample volume used.
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Affiliation(s)
- Chia-Hung Chen
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Aniruddh Sarkar
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Yong-Ak Song
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Miles A. Miller
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Sung Jae Kim
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Linda G. Griffith
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | | | - Jongyoon Han
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
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172
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Vinuselvi P, Park S, Kim M, Park JM, Kim T, Lee SK. Microfluidic technologies for synthetic biology. Int J Mol Sci 2011; 12:3576-93. [PMID: 21747695 PMCID: PMC3131579 DOI: 10.3390/ijms12063576] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 05/20/2011] [Accepted: 05/26/2011] [Indexed: 12/24/2022] Open
Abstract
Microfluidic technologies have shown powerful abilities for reducing cost, time, and labor, and at the same time, for increasing accuracy, throughput, and performance in the analysis of biological and biochemical samples compared with the conventional, macroscale instruments. Synthetic biology is an emerging field of biology and has drawn much attraction due to its potential to create novel, functional biological parts and systems for special purposes. Since it is believed that the development of synthetic biology can be accelerated through the use of microfluidic technology, in this review work we focus our discussion on the latest microfluidic technologies that can provide unprecedented means in synthetic biology for dynamic profiling of gene expression/regulation with high resolution, highly sensitive on-chip and off-chip detection of metabolites, and whole-cell analysis.
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Affiliation(s)
- Parisutham Vinuselvi
- School of Nano-Bioscience and Chemical Engineering, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Ulsan 689–798, Korea; E-Mails: (P.V.); (J.M.P.)
| | - Seongyong Park
- School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Ulsan 689–798, Korea; E-Mails: (S.P.); (M.K.)
| | - Minseok Kim
- School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Ulsan 689–798, Korea; E-Mails: (S.P.); (M.K.)
| | - Jung Min Park
- School of Nano-Bioscience and Chemical Engineering, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Ulsan 689–798, Korea; E-Mails: (P.V.); (J.M.P.)
| | - Taesung Kim
- School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Ulsan 689–798, Korea; E-Mails: (S.P.); (M.K.)
| | - Sung Kuk Lee
- School of Nano-Bioscience and Chemical Engineering, Ulsan National Institute of Science and Technology, 100 Banyeon-ri, Ulsan 689–798, Korea; E-Mails: (P.V.); (J.M.P.)
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173
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174
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Park SY, Wu TH, Chen Y, Teitell MA, Chiou PY. High-speed droplet generation on demand driven by pulse laser-induced cavitation. LAB ON A CHIP 2011; 11:1010-2. [PMID: 21290045 PMCID: PMC3967743 DOI: 10.1039/c0lc00555j] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We report on a pulse laser-driven droplet generation (PLDG) mechanism that enables on-demand droplet generation at rates up to 10,000 droplets per second in a single-layer PDMS-based microfluidic device. Injected droplet volumes can be continuously tuned between 1 pL and 150 pL with less than 1% volume variation.
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Affiliation(s)
- Sung-Yong Park
- Department of Mechanical and Aerospace Engineering, University of California at Los Angeles (UCLA), 43-147 Eng. IV, 420 Westwood Plaza, Los Angeles, CA 90095-1597, USA. Fax: +1-310-206-4830; Tel: +1-310-825-8620
| | | | - Yue Chen
- Department of Mechanical and Aerospace Engineering, University of California at Los Angeles (UCLA), 43-147 Eng. IV, 420 Westwood Plaza, Los Angeles, CA 90095-1597, USA. Fax: +1-310-206-4830; Tel: +1-310-825-8620
| | - Michael A. Teitell
- Departments of Pathology and Pediatrics, California NanoSystems Institute, Broad Stem Cell Research Center, Jonsson Cancer Center, and Molecular Biology Institute, UCLA, 4-762 MRL, 675 Young Drive South, Los Angeles, CA, 90095-1732, USA. Fax: +1-310-267-0382; Tel: +1-310-206-6754
| | - Pei-Yu Chiou
- Department of Mechanical and Aerospace Engineering, University of California at Los Angeles (UCLA), 43-147 Eng. IV, 420 Westwood Plaza, Los Angeles, CA 90095-1597, USA. Fax: +1-310-206-4830; Tel: +1-310-825-8620
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175
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Cecchini MP, Hong J, Lim C, Choo J, Albrecht T, deMello AJ, Edel JB. Ultrafast Surface Enhanced Resonance Raman Scattering Detection in Droplet-Based Microfluidic Systems. Anal Chem 2011; 83:3076-81. [DOI: 10.1021/ac103329b] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
| | - Jongin Hong
- Department of Chemistry, Chung-Ang University, Seoul 156-756, Korea
| | - Chaesung Lim
- Department of Bionano Engineering, Hanyang University, Sa-1-dong, Ansan 426-791, Korea
| | - Jaebum Choo
- Department of Bionano Engineering, Hanyang University, Sa-1-dong, Ansan 426-791, Korea
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176
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Marcoux PR, Dupoy M, Mathey R, Novelli-Rousseau A, Heran V, Morales S, Rivera F, Joly PL, Moy JP, Mallard F. Micro-confinement of bacteria into w/o emulsion droplets for rapid detection and enumeration. Colloids Surf A Physicochem Eng Asp 2011. [DOI: 10.1016/j.colsurfa.2010.12.013] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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177
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Rogers M, Leong C, Niu X, de Mello A, Parker KH, Boutelle MG. Optimisation of a microfluidic analysis chamber for the placement of microelectrodes. Phys Chem Chem Phys 2011; 13:5298-303. [PMID: 21344092 DOI: 10.1039/c0cp02810j] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The behaviour of droplets entering a microfluidic chamber designed to house microelectrode detectors for real time analysis of clinical microdialysate is described. We have designed an analysis chamber to collect the droplets produced by multiphase flows of oil and artificial cerebral spinal fluid. The coalescence chamber creates a constant aqueous environment ideal for the placement of microelectrodes avoiding the contamination of the microelectrode surface by oil. A stream of alternating light and dark coloured droplets were filmed as they passed through the chamber using a high speed camera. Image analysis of these videos shows the colour change evolution at each point along the chamber length. The flow in the chamber was simulated using the general solution for Poiseuille flow in a rectangular chamber. It is shown that on the centre line the velocity profile is very close to parabolic, and an expression is presented for the ratio between this centre line velocity and the mean flow velocity as a function of channel aspect ratio. If this aspect ratio of width/height is 2, the ratio of flow velocities closely matches that of Poiseuille flow in a circular tube, with implications for connections between microfluidic channels and connection tubing. The droplets are well mixed as the surface tension at the interface with the oil dominates the viscous forces. However once the droplet coalesces with the solution held in the chamber, the no-slip condition at the walls allows Poiseuille flow to take over. The meniscus at the back of the droplet continues to mix the droplet and acts as a piston until the meniscus stops moving. We have found that the no-slip conditions at the walls of the chamber, create a banding effect which records the history of previous drops. The optimal position for sensors is to be placed at the plane of droplet coalescence ideally at the centre of the channel, where there is an abrupt concentration change leading to a response time ≪16 ms, the compressed frame rate of the video. Further away from this point the response time and sensitivity decrease due to convective dispersion.
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Affiliation(s)
- Michelle Rogers
- Department of Bioengineering, Imperial College, London, UK SW7 2AZ
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178
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Vyawahare S, Griffiths AD, Merten CA. Miniaturization and parallelization of biological and chemical assays in microfluidic devices. ACTA ACUST UNITED AC 2011; 17:1052-65. [PMID: 21035727 DOI: 10.1016/j.chembiol.2010.09.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 08/31/2010] [Accepted: 09/07/2010] [Indexed: 12/29/2022]
Abstract
Microfluidic systems are an attractive solution for the miniaturization of biological and chemical assays. The typical sample volume can be reduced up to 1 million-fold, and a superb level of spatiotemporal control is possible, facilitating highly parallelized assays with drastically increased throughput and reduced cost. In this review, we focus on systems in which multiple reactions are spatially separated by immobilization of reagents on two-dimensional arrays, or by compartmentalization in microfabricated reaction chambers or droplets. These systems have manifold applications, and some, such as next-generation sequencing are already starting to transform biology. This is likely the first step in a biotechnological transformation comparable to that already brought about by the microprocessor in electronics. We discuss both current applications and likely future impacts in areas such as the study of single cells/single organisms and high-throughput screening.
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Affiliation(s)
- Saurabh Vyawahare
- Microfluidics Laboratory, Physical Sciences-Oncology Center, Physics Department, Princeton University, Princeton, NJ 08544, USA
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179
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Pompano RR, Liu W, Du W, Ismagilov RF. Microfluidics using spatially defined arrays of droplets in one, two, and three dimensions. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2011; 4:59-81. [PMID: 21370983 DOI: 10.1146/annurev.anchem.012809.102303] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Spatially defined arrays of droplets differ from bulk emulsions in that droplets in arrays can be indexed on the basis of one or more spatial variables to enable identification, monitoring, and addressability of individual droplets. Spatial indexing is critical in experiments with hundreds to millions of unique compartmentalized microscale processes--for example, in applications such as digital measurements of rare events in a large sample, high-throughput time-lapse studies of the contents of individual droplets, and controlled droplet-droplet interactions. This review describes approaches for spatially organizing and manipulating droplets in one-, two-, and three-dimensional structured arrays, including aspiration, laminar flow, droplet traps, the SlipChip, self-assembly, and optical or electrical fields. This review also presents techniques to analyze droplets in arrays and applications of spatially defined arrays, including time-lapse studies of chemical, enzymatic, and cellular processes, as well as further opportunities in chemical, biological, and engineering sciences, including perturbation/response experiments and personal and point-of-care diagnostics.
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Affiliation(s)
- Rebecca R Pompano
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
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180
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Jayasinghe SN. Bio-electrosprays: from bio-analytics to a generic tool for the health sciences. Analyst 2011; 136:878-90. [DOI: 10.1039/c0an00830c] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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181
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Casadevall i Solvas X, deMello A. Droplet microfluidics: recent developments and future applications. Chem Commun (Camb) 2011; 47:1936-42. [DOI: 10.1039/c0cc02474k] [Citation(s) in RCA: 254] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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182
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Zagnoni M, Cooper JM. Droplet microfluidics for high-throughput analysis of cells and particles. Methods Cell Biol 2011; 102:25-48. [PMID: 21704834 DOI: 10.1016/b978-0-12-374912-3.00002-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Droplet microfluidics (DM) is an area of research which combines lab-on-a-chip (LOC) techniques with emulsion compartmentalization to perform high-throughput, chemical and biological assays. The key issue of this approach lies in the generation, over tens of milliseconds, of thousands of liquid vessels which can be used either as a carrier, to transport encapsulated particles and cells, or as microreactors, to perform parallel analysis of a vast number of samples. Each compartment comprises a liquid droplet containing the sample, surrounded by an immiscible fluid. This microfluidic technique is capable of generating subnanoliter and highly monodispersed liquid droplets, which offer many opportunities for developing novel single-cell and single-molecule studies, as well as high-throughput methodologies for the detection and sorting of encapsulated species in droplets. The aim of this chapter is to give an overview of the features of DM in a broad microfluidic context, as well as to show the advantages and limitations of the technology in the field of LOC analytical research. Examples are reported and discussed to show how DM can provide novel systems with applications in high-throughput, quantitative cell and particle analysis.
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Affiliation(s)
- Michele Zagnoni
- Centre for Microsystems and Photonics, Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, G1 1XW, UK.
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183
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Srisa-Art M, deMello AJ, Edel JB. High-Efficiency Single-Molecule Detection within Trapped Aqueous Microdroplets. J Phys Chem B 2010; 114:15766-72. [DOI: 10.1021/jp105749t] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Monpichar Srisa-Art
- Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Pathumwan, Bangkok, 10330 Thailand, and Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom
| | - Andrew J. deMello
- Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Pathumwan, Bangkok, 10330 Thailand, and Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom
| | - Joshua B. Edel
- Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Pathumwan, Bangkok, 10330 Thailand, and Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom
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184
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Lee WC, Rigante S, Pisano AP, Kuypers FA. Large-scale arrays of picolitre chambers for single-cell analysis of large cell populations. LAB ON A CHIP 2010; 10:2952-8. [PMID: 20838671 DOI: 10.1039/c0lc00139b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We present a new method to analyze the cytoplasmic contents of single cells in large cell populations. This new method consists of an array of microchambers in which individual cells are collected, enclosed, and lysed to create a reaction mixture of the cytoplasm with extracellular detection agents. This approach was tested for the analysis of red blood cells in 10,000 microchambers in parallel. Single cells were routinely collected in more than 60% of microchambers, the collected cells were robustly (up to 99%) lysed by electric fields, and the cytoplasm enclosed in each microchamber was analyzed with fluorescence microscopy. Using a heterogeneous cell mixture, we verified that the new method could distinguish individual cells by cytoplasmic composition and the analysis compared well with conventional flow-cytometric evaluation of mixed cell populations. In contrast to flow-cytometry, the new method monitored single cells over time, thus characterizing the distributions of caspase activities of 5000 individual cells. This approach should be interesting for a variety of applications that would benefit from the ability to measure the distribution of cytoplasmic compounds in complex cell populations, including hematology, oncology, and immunology.
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Affiliation(s)
- Won Chul Lee
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr Way, Oakland, California 94609, USA
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185
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Hong J, Choi M, Edel JB, deMello AJ. Passive self-synchronized two-droplet generation. LAB ON A CHIP 2010; 10:2702-9. [PMID: 20717573 DOI: 10.1039/c005136e] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We describe the use of two passive components to achieve controllable and alternating droplet generation in a microfluidic device. The approach overcomes the problems associated with irregularities in channel dimensions and fluid flow rates, and allows precise pairing of alternating droplets in a high-throughput manner. We study droplet generation and self-synchronization in a quantitative fashion by using high-speed image analysis.
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Affiliation(s)
- Jongin Hong
- Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, UK
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186
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Abstract
Adding reagents to drops is one of the most important functions in droplet-based microfluidic systems; however, a robust technique to accomplish this does not exist. Here, we introduce the picoinjector, a robust device to add controlled volumes of reagent using electro-microfluidics at kilohertz rates. It can also perform multiple injections for serial and combinatorial additions.
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187
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Abbyad P, Tharaux PL, Martin JL, Baroud CN, Alexandrou A. Sickling of red blood cells through rapid oxygen exchange in microfluidic drops. LAB ON A CHIP 2010; 10:2505-12. [PMID: 20603684 DOI: 10.1039/c004390g] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We have developed a microfluidic approach to study the sickling of red blood cells associated with sickle cell anemia by rapidly varying the oxygen partial pressure within flowing microdroplets. By using the perfluorinated carrier oil as a sink or source of oxygen, the oxygen level within the water droplets quickly equilibrates through exchange with the surrounding oil. This provides control over the oxygen partial pressure within an aqueous drop ranging from 1 kPa to ambient partial pressure, i.e. 21 kPa. The dynamics of the oxygen exchange is characterized through fluorescence lifetime measurements of a ruthenium compound dissolved in the aqueous phase. The gas exchange is shown to occur primarily during and directly after droplet formation, in 0.1 to 0.5 s depending on the droplet diameter and speed. The controlled deoxygenation is used to trigger the polymerization of hemoglobin within sickle red blood cells, encapsulated in drops. This process is observed using polarization microscopy, which yields a robust criterion to detect polymerization based on transmitted light intensity through crossed polarizers.
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Affiliation(s)
- Paul Abbyad
- Laboratoire d'Optique et Biosciences (LOB), Ecole Polytechnique, INSERM U696, CNRS, 91128 Palaiseau, France
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188
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Affiliation(s)
- Dario Lombardi
- Department of Chemistry and Applied Biosciences, ETH Zurich, Wolfgang-Pauli-Str. 10, CH-8093 Zurich, Switzerland
| | - Petra S Dittrich
- Department of Chemistry and Applied Biosciences, ETH Zurich, Wolfgang-Pauli-Str. 10, CH-8093 Zurich, Switzerland
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189
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Kintses B, van Vliet LD, Devenish SRA, Hollfelder F. Microfluidic droplets: new integrated workflows for biological experiments. Curr Opin Chem Biol 2010; 14:548-55. [PMID: 20869904 DOI: 10.1016/j.cbpa.2010.08.013] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 08/08/2010] [Accepted: 08/09/2010] [Indexed: 11/30/2022]
Abstract
Miniaturization of the classical test tube to picoliter dimensions is possible in monodisperse water-in-oil droplets that are generated in microfluidic devices. The establishment of standard unit operations for droplet handling and the ability to carry out experiments with DNA, proteins, cells and organisms provides the basis for the design of more complex workflows to address biological challenges. The emerging experimental format makes possible a quantitative readout for large numbers of experiments with a precision comparable to the macroscopic scale. Directed evolution, diagnostics and compound screening are areas in which the first steps are being taken toward the long-term goal of transforming the way we design and carry out experiments.
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Affiliation(s)
- Balint Kintses
- Department of Biochemistry, University of Cambridge, United Kingdom
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190
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Sassa F, Laghzali H, Fukuda J, Suzuki H. Coulometric Detection of Components in Liquid Plugs by Microfabricated Flow Channel and Electrode Structures. Anal Chem 2010; 82:8725-32. [DOI: 10.1021/ac102289a] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Fumihiro Sassa
- Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan, and Department of Information Technologies for Health Care, Institute for Science and Technology, Joseph Fourier University, BP 53-38041 Grenoble Cedex 9, France
| | - Hind Laghzali
- Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan, and Department of Information Technologies for Health Care, Institute for Science and Technology, Joseph Fourier University, BP 53-38041 Grenoble Cedex 9, France
| | - Junji Fukuda
- Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan, and Department of Information Technologies for Health Care, Institute for Science and Technology, Joseph Fourier University, BP 53-38041 Grenoble Cedex 9, France
| | - Hiroaki Suzuki
- Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan, and Department of Information Technologies for Health Care, Institute for Science and Technology, Joseph Fourier University, BP 53-38041 Grenoble Cedex 9, France
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191
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Wlodkowic D, Cooper JM. Tumors on chips: oncology meets microfluidics. Curr Opin Chem Biol 2010; 14:556-67. [PMID: 20832352 DOI: 10.1016/j.cbpa.2010.08.016] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 08/11/2010] [Accepted: 08/12/2010] [Indexed: 01/22/2023]
Abstract
Despite over 2 million papers published on cancer so far, malignancy still remains a puzzlingly complex disease with overall low survival rates. Expanding our knowledge of the molecular mechanisms of malignancy and of resistance to therapy is crucial in guiding the successful design of anti-cancer drugs and new point-of-care diagnostics. The up-and-coming microfluidic Lab-on-a-Chip (LOC) technology and micro-total analysis systems (μTAS) are arguably the most promising platforms to address the inherent complexity of cellular systems with massive experimental parallelization and 4D analysis on a single cell level. This review discusses the emerging applications of microfluidic technologies and their advantages for cancer biology and experimental oncology. We also summarize the recent advances in miniaturized systems to study cancer cell microenvironment, cancer cytomics, and real-time (4D) pharmacological screening. Microfabricated systems, such as cell microarrays, together with on-chip label-less cytometry, and micro-sorting technologies, are all highlighted with the view of describing their potential applications in pharmacological screening, drug discovery, and clinical oncology. It is envisaged that microfluidic solutions may well represent the platform of choice for next generation in vitro cancer models.
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Affiliation(s)
- Donald Wlodkowic
- Auckland Microfabrication Facility, Department of Chemistry, University of Auckland, Auckland, New Zealand.
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192
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Abstract
A droplet-based microfluidic platform was used to perform on-chip droplet generation, merging and mixing for applications in multi-step reactions and assays. Submicroliter-sized droplets can be produced separately from three identical droplet-generation channels and merged together in a single chamber. Three different mixing strategies were used for mixing the merged droplet. For pure diffusion, the reagents were mixed in approximately 10 min. Using flow around the stationary droplet to induce circulatory flow within the droplet, the mixing time was decreased to approximately one minute. The shortest mixing time (10 s) was obtained with bidirectional droplet motion between the chamber and channel, and optimization could result in a total time of less than 1 s. We also tested this on-chip droplet generation and manipulation platform using a two-step thermal cycled bioreaction: nested TaqMan PCR. With the same concentration of template DNA, the two-step reaction in a well-mixed merged droplet shows a cycle threshold of approximately 6 cycles earlier than that in the diffusively mixed droplet, and approximately 40 cycles earlier than the droplet-based regular (single-step) TaqMan PCR.
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Affiliation(s)
- Fang Wang
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
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193
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Sgro AE, Chiu DT. Droplet freezing, docking, and the exchange of immiscible phase and surfactant around frozen droplets. LAB ON A CHIP 2010; 10:1873-7. [PMID: 20467690 PMCID: PMC5600195 DOI: 10.1039/c001108h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This paper describes a platform for cooling microfluidic chips so as to freeze aqueous droplets flowing in oil. Using a whole-chip cooling chamber, we can control the ambient temperature surrounding a microfluidic chip and induce cooling and freezing inside the channels. When combined with a droplet generation and droplet docking chip, this platform allows for the facile freezing of droplets immobilized in resistance-based docks. Depending on the design and shape of the docks, the frozen droplets can either be trapped stably in the docks or be released because deformed non-frozen aqueous droplets turn spherical when frozen, and thus can become dislodged from the docks. Additionally, using this chamber and chip combination we are able to exchange immiscible phases and surfactants surrounding the frozen droplets. The materials and methods are inexpensive and easily accessible to microfluidics researchers, making this a simple addition to an existing microfluidic platform.
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Affiliation(s)
- Allyson E Sgro
- Department of Chemistry, University of Washington, Seattle, WA 98195-1700, USA
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194
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Liu KK, Wu RG, Chuang YJ, Khoo HS, Huang SH, Tseng FG. Microfluidic systems for biosensing. SENSORS (BASEL, SWITZERLAND) 2010; 10:6623-61. [PMID: 22163570 PMCID: PMC3231127 DOI: 10.3390/s100706623] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 06/20/2010] [Accepted: 06/30/2010] [Indexed: 01/09/2023]
Abstract
In the past two decades, Micro Fluidic Systems (MFS) have emerged as a powerful tool for biosensing, particularly in enriching and purifying molecules and cells in biological samples. Compared with conventional sensing techniques, distinctive advantages of using MFS for biomedicine include ultra-high sensitivity, higher throughput, in-situ monitoring and lower cost. This review aims to summarize the recent advancements in two major types of micro fluidic systems, continuous and discrete MFS, as well as their biomedical applications. The state-of-the-art of active and passive mechanisms of fluid manipulation for mixing, separation, purification and concentration will also be elaborated. Future trends of using MFS in detection at molecular or cellular level, especially in stem cell therapy, tissue engineering and regenerative medicine, are also prospected.
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Affiliation(s)
- Kuo-Kang Liu
- School of Engineering, University of Warwick, Coventry CV4 7AL, UK
| | - Ren-Guei Wu
- Department of Engineering and System Science, National Tsing-Hua University, Hsinchu, Taiwan; E-Mails: (R.-G.W.), (H.S.K.)
| | - Yun-Ju Chuang
- Department of Biomedical Engineering, Ming Chuang University, Taoyuan County 333, Taiwan; E-Mail: (Y.-J.C.)
| | - Hwa Seng Khoo
- Department of Engineering and System Science, National Tsing-Hua University, Hsinchu, Taiwan; E-Mails: (R.-G.W.), (H.S.K.)
| | - Shih-Hao Huang
- Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean University, Keelung 202-24, Taiwan; E-Mail: (S.-H.H.)
| | - Fan-Gang Tseng
- Department of Engineering and System Science, National Tsing-Hua University, Hsinchu, Taiwan; E-Mails: (R.-G.W.), (H.S.K.)
- Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan; E-Mail: (F.-G.T.)
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195
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Zeng Y, Novak R, Shuga J, Smith MT, Mathies RA. High-performance single cell genetic analysis using microfluidic emulsion generator arrays. Anal Chem 2010; 82:3183-90. [PMID: 20192178 DOI: 10.1021/ac902683t] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
High-throughput genetic and phenotypic analysis at the single cell level is critical to advance our understanding of the molecular mechanisms underlying cellular function and dysfunction. Here we describe a high-performance single cell genetic analysis (SCGA) technique that combines high-throughput microfluidic emulsion generation with single cell multiplex polymerase chain reaction (PCR). Microfabricated emulsion generator array (MEGA) devices containing 4, 32, and 96 channels are developed to confer a flexible capability of generating up to 3.4 x 10(6) nanoliter-volume droplets per hour. Hybrid glass-polydimethylsiloxane diaphragm micropumps integrated into the MEGA chips afford uniform droplet formation, controlled generation frequency, and effective transportation and encapsulation of primer functionalized microbeads and cells. A multiplex single cell PCR method is developed to detect and quantify both wild type and mutant/pathogenic cells. In this method, microbeads functionalized with multiple forward primers targeting specific genes from different cell types are used for solid-phase PCR in droplets. Following PCR, the droplets are lysed and the beads are pooled and rapidly analyzed by multicolor flow cytometry. Using Escherichia coli bacterial cells as a model, we show that this technique enables digital detection of pathogenic E. coli O157 cells in a high background of normal K12 cells, with a detection limit on the order of 1/10(5). This result demonstrates that multiplex SCGA is a promising tool for high-throughput quantitative digital analysis of genetic variation in complex populations.
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Affiliation(s)
- Yong Zeng
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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196
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Theberge A, Courtois F, Schaerli Y, Fischlechner M, Abell C, Hollfelder F, Huck W. Microdroplets in Microfluidics: An Evolving Platform for Discoveries in Chemistry and Biology. Angew Chem Int Ed Engl 2010; 49:5846-68. [DOI: 10.1002/anie.200906653] [Citation(s) in RCA: 833] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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197
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Clausell-Tormos J, Griffiths AD, Merten CA. An automated two-phase microfluidic system for kinetic analyses and the screening of compound libraries. LAB ON A CHIP 2010; 10:1302-7. [PMID: 20445884 DOI: 10.1039/b921754a] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Droplet-based microfluidic systems allow biological and chemical reactions to be performed on a drastically decreased scale. However, interfacing the outside world with such systems and generating high numbers of microdroplets of distinct chemical composition remain challenging. We describe here an automated system in which arrays of chemically distinct plugs are generated from microtiter plates. Each array can be split into multiple small-volume copies, thus allowing several screens of the same library. The system is fully compatible with further on-chip manipulation(s) and allows monitoring of individual plugs over time (e.g. for recording reaction kinetics). Hence the technology eliminates several bottlenecks of current droplet-based microfluidic systems and should open the way for (bio-)chemical and cell-based screens.
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Affiliation(s)
- Jenifer Clausell-Tormos
- Institut de Science et d'Ingénierie Supramoléculaires (ISIS), Université de Strasbourg, CNRS UMR 7006, 8, allée Gaspard Monge, BP 70028, 67083, Strasbourg Cedex, France
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198
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Wang F, Burns MA. Multiphase bioreaction microsystem with automated on-chip droplet operation. LAB ON A CHIP 2010; 10:1308-15. [PMID: 20445885 PMCID: PMC2909751 DOI: 10.1039/b925705e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A droplet-based bioreaction microsystem has been developed with automated droplet generation and confinement. On-chip electronic sensing is employed to track the position of the droplets by sensing the oil/aqueous interface in real time. The sensing signal is also used to control the pneumatic supply for moving as well as automatically generating four different nanolitre-sized droplets. The actual size of droplets is very close to the designed droplet size with a standard deviation less than 3% of the droplet size. The automated droplet generation can be completed in less than 2 s, which is 5 times faster than using manual operation that takes at least 10 s. Droplets can also be automatically confined in the reaction region with feedback pneumatic control and digital or analog sensing. As an example bioreaction, PCR has been successfully performed in the automated generated droplets. Although the amplification yield was slightly reduced with the droplet confinement, especially while using the analog sensing method, adding additional reagents effectively alleviated this inhibition.
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Affiliation(s)
- Fang Wang
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Mark A. Burns
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
- ; Fax: 1-734-763-0459; Phone: 1-734-764-1516
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199
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Hashimoto M, Whitesides GM. Formation of bubbles in a multisection flow-focusing junction. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2010; 6:1051-1059. [PMID: 20411572 DOI: 10.1002/smll.200902164] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The formation of bubbles in a flow-focusing (FF) junction comprising multiple rectangular sections is described. The simplest junctions comprise two sections (throat and orifice). Systematic investigation of the influence on the formation of bubbles of the flow of liquid and the geometry of the junction identifies regimes that generate monodisperse, bidisperse, and tridisperse trains of bubbles. The mechanisms by which these junctions form monodisperse and bidisperse bubbles are inferred from the shapes of the gas thread during breakup: these mechanisms differ primarily by the process in which the gas thread collapses in the throat and/or orifice. The dynamic self-assembly of bidisperse bubbles leads to unexpected groupings of bubbles during their flow along the outlet channel.
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Affiliation(s)
- Michinao Hashimoto
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
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200
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Dixit SS, Kim H, Vasilyev A, Eid A, Faris GW. Light-driven formation and rupture of droplet bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:6193-200. [PMID: 20361732 PMCID: PMC2896059 DOI: 10.1021/la1010067] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We demonstrate the optical manipulation of nanoliter aqueous droplets containing surfactant or lipid molecules and immersed in an organic liquid using near-infrared light. The resulting emulsion droplets are manipulated using both the thermocapillary effect and convective fluid motion. Droplet-pair interactions induced in the emulsion upon optical initiation and control provide direct observations of the coalescence steps in intricate detail. Droplet-droplet adhesion (bilayer formation) is observed under several conditions. Selective bilayer rupture is also realized using the same infrared laser. The technique provides a novel approach to studying thin film drainage and interface stability in emulsion dynamics. The formation of stable lipid bilayers at the adhesion interface between interacting water droplets can provide an optical platform on which to build droplet-based lipid bilayer assays. The technique also has relevance to understanding and improving microfluidics applications by devising Petri dish-based droplet assays requiring no substrate fabrication.
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Affiliation(s)
- Sanhita S Dixit
- Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, California 94025, USA.
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