70 research outputs found
Modeling the influence of Twitter in reducing and increasing the spread of influenza epidemics
In this paper we present compartmentalized neuron arraying (CNA) microfluidic circuits for the preparation of neuronal networks using minimal cellular inputs (10–100-fold less than existing systems). The approach combines the benefits of microfluidics for precision single cell handling with biomaterial patterning for the long term maintenance of neuronal arrangements. A differential flow principle was used for cell metering and loading along linear arrays. An innovative water masking technique was developed for the inclusion of aligned biomaterial patterns within the microfluidic environment. For patterning primary neurons the technique involved the use of meniscus-pinning micropillars to align a water mask for plasma stencilling a poly-amine coating. The approach was extended for patterning the human SH-SY5Y neuroblastoma cell line using a poly(ethylene glycol) (PEG) back-fill and for dopaminergic LUHMES neuronal precursors by the further addition of a fibronectin coating. The patterning efficiency Epatt was >75% during lengthy in chip culture, with ~85% of the outgrowth channels occupied by neurites. Neurons were also cultured in next generation circuits which enable neurite guidance into all outgrowth channels for the formation of extensive inter-compartment networks. Fluidic isolation protocols were developed for the rapid and sustained treatment of the different cellular and sub-cellular compartments. In summary, this research demonstrates widely applicable microfluidic methods for the construction of compartmentalized brain models with single cell precision. These minimalistic ex vivo tissue constructs pave the way for high throughput experimentation to gain deeper insights into pathological processes such as Alzheimer and Parkinson Diseases, as well as neuronal development and function in health
Free-Flow Zone Electrophoresis of Peptides and Proteins in PDMS Microchip for Narrow pI Range Sample Prefractionation Coupled with Mass Spectrometry
In this paper, we are evaluating the strategy of sorting peptides/proteins based on the charge to mass without resorting to ampholytes and/or isoelectric focusing, using a single- and two-step free-flow zone electrophoresis. We developed a simple fabrication method to create a salt bridge for free-flow zone electrophoresis in PDMS chips by surface printing a hydrophobic layer on a glass substrate. Since the surface-printed hydrophobic layer prevents plasma bonding between the PDMS chip and the substrate, an electrical junction gap can be created for free-flow zone electrophoresis. With this device, we demonstrated a separation of positive and negative peptides and proteins at a given pH in standard buffer systems and validated the sorting result with LC/MS. Furthermore, we coupled two sorting steps via off-chip titration and isolated peptides within specific pI ranges from sample mixtures, where the pI range was simply set by the pH values of the buffer solutions. This free-flow zone electrophoresis sorting device, with its simplicity of fabrication, and a sorting resolution of 0.5 pH unit, can potentially be a high-throughput sample fractionation tool for targeted proteomics using LC/MS.Korea Institute of Science and Technology. Intelligent Microsystems CenterMassachusetts Institute of Technology. Center for Environmental Health SciencesNational Institute of Environmental Health Sciences (Grant No. P30-ES002109)United States. National Institutes of Health (grant R21 EB008177
Liquid-infiltrated photonic crystals - enhanced light-matter interactions for lab-on-a-chip applications
Optical techniques are finding widespread use in analytical chemistry for
chemical and bio-chemical analysis. During the past decade, there has been an
increasing emphasis on miniaturization of chemical analysis systems and
naturally this has stimulated a large effort in integrating microfluidics and
optics in lab-on-a-chip microsystems. This development is partly defining the
emerging field of optofluidics. Scaling analysis and experiments have
demonstrated the advantage of micro-scale devices over their macroscopic
counterparts for a number of chemical applications. However, from an optical
point of view, miniaturized devices suffer dramatically from the reduced
optical path compared to macroscale experiments, e.g. in a cuvette. Obviously,
the reduced optical path complicates the application of optical techniques in
lab-on-a-chip systems. In this paper we theoretically discuss how a strongly
dispersive photonic crystal environment may be used to enhance the light-matter
interactions, thus potentially compensating for the reduced optical path in
lab-on-a-chip systems. Combining electromagnetic perturbation theory with
full-wave electromagnetic simulations we address the prospects for achieving
slow-light enhancement of Beer-Lambert-Bouguer absorption, photonic band-gap
based refractometry, and high-Q cavity sensing.Comment: Invited paper accepted for the "Optofluidics" special issue to appear
in Microfluidics and Nanofluidics (ed. Prof. David Erickson). 11 pages
including 8 figure
Synergism between particle-based multiplexing and microfluidics technologies may bring diagnostics closer to the patient
In the field of medical diagnostics there is a growing need for inexpensive, accurate, and quick high-throughput assays. On the one hand, recent progress in microfluidics technologies is expected to strongly support the development of miniaturized analytical devices, which will speed up (bio)analytical assays. On the other hand, a higher throughput can be obtained by the simultaneous screening of one sample for multiple targets (multiplexing) by means of encoded particle-based assays. Multiplexing at the macro level is now common in research labs and is expected to become part of clinical diagnostics. This review aims to debate on the “added value” we can expect from (bio)analysis with particles in microfluidic devices. Technologies to (a) decode, (b) analyze, and (c) manipulate the particles are described. Special emphasis is placed on the challenges of integrating currently existing detection platforms for encoded microparticles into microdevices and on promising microtechnologies that could be used to down-scale the detection units in order to obtain compact miniaturized particle-based multiplexing platforms
Computer simulation and theory of the diffusion- and flow-induced concentration dispersion in microfluidic devices and HPLC systems based on rectangular microchannels
Channel-free shear driven circular liquid chromatography
Shear stress has been exploited within a channel-free rotating plate system for the circular chromatographic separation of model analytes
Tunable Membranes for Free-Flow Zone Electrophoresis in PDMS Microchip Using Guided Self-Assembly of Silica Microbeads
Whole Cell Quenched Flow Analysis
This paper describes a microfluidic
quenched flow platform for
the investigation of ligand-mediated cell surface processes with unprecedented
temporal resolution. A roll–slip behavior caused by cell–wall–fluid
coupling was documented and acts to minimize the compression and shear
stresses experienced by the cell. This feature enables high-velocity
(100–400 mm/s) operation without impacting the integrity of
the cell membrane. In addition, rotation generates localized convection
paths. This cell-driven micromixing effect causes the cell to become
rapidly enveloped with ligands to saturate the surface receptors.
High-speed imaging of the transport of a Janus particle and fictitious
domain numerical simulations were used to predict millisecond-scale
biochemical switching times. Dispersion in the incubation channel
was characterized by microparticle image velocimetry and minimized
by using a horizontal Hele–Shaw velocity profile in combination
with vertical hydrodynamic focusing to achieve highly reproducible
incubation times (CV = 3.6%). Microfluidic quenched flow was used
to investigate the pY1131 autophosphorylation transition in the type
I insulin-like growth factor receptor (IGF-1R). This predimerized
receptor undergoes autophosphorylation within 100 ms of stimulation.
Beyond this demonstration, the extreme temporal resolution can be
used to gain new insights into the mechanisms underpinning a tremendous
variety of important cell surface events
Whole Cell Quenched Flow Analysis
This paper describes a microfluidic
quenched flow platform for
the investigation of ligand-mediated cell surface processes with unprecedented
temporal resolution. A roll–slip behavior caused by cell–wall–fluid
coupling was documented and acts to minimize the compression and shear
stresses experienced by the cell. This feature enables high-velocity
(100–400 mm/s) operation without impacting the integrity of
the cell membrane. In addition, rotation generates localized convection
paths. This cell-driven micromixing effect causes the cell to become
rapidly enveloped with ligands to saturate the surface receptors.
High-speed imaging of the transport of a Janus particle and fictitious
domain numerical simulations were used to predict millisecond-scale
biochemical switching times. Dispersion in the incubation channel
was characterized by microparticle image velocimetry and minimized
by using a horizontal Hele–Shaw velocity profile in combination
with vertical hydrodynamic focusing to achieve highly reproducible
incubation times (CV = 3.6%). Microfluidic quenched flow was used
to investigate the pY1131 autophosphorylation transition in the type
I insulin-like growth factor receptor (IGF-1R). This predimerized
receptor undergoes autophosphorylation within 100 ms of stimulation.
Beyond this demonstration, the extreme temporal resolution can be
used to gain new insights into the mechanisms underpinning a tremendous
variety of important cell surface events
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