7 research outputs found
Regularized lattice Boltzmann Multicomponent models for low Capillary and Reynolds microfluidics flows
We present a regularized version of the color gradient lattice Boltzmann (LB)
scheme for the simulation of droplet formation in microfluidic devices of
experimental relevance. The regularized version is shown to provide
computationally efficient access to Capillary number regimes relevant to
droplet generation via microfluidic devices, such as flow-focusers and the more
recent microfluidic step emulsifier devices.Comment: 9 pages, 5 figure
Probing of the microwave radiation effect on the green fluorescent protein luminescence in solution
Abstract Microwaves have a larger effect on the green fluorescent protein (GFP) fluorescence intensity than is observed by conventional thermal heating. Our measurements show that thermally heating a GFP solution from 7 to 40 • C results in a ∼1% decrease in fluorescence for every 1 • C. On the other hand, under 250 mW of localized microwave irradiation, the fluorescence can decrease by up to 3-10% with an accompanying temperature rise of only 1 • C
Regularized lattice Boltzmann multicomponent models for low capillary and Reynolds microfluidics flows
We present a regularized version of the color gradient lattice Boltzmann (LB) scheme for the simulation of droplet formation in microfluidic devices of experimental relevance. The regularized version is shown to provide computationally efficient access to capillary number regimes relevant to droplet generation via microfluidic devices, such as flow-focusers and the more recent microfluidic step emulsifier devices
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Label-free single-cell protein quantification using a drop-based mix-and-read system
Quantitative protein analysis of single cells is rarely achieved due to technical difficulties of detecting minute amounts of proteins present in one cell. We develop a mix-and-read assay for drop-based label-free protein analysis of single cells. This high-throughput method quantifies absolute, rather than relative, amounts of proteins and does not involve antibody labeling or mass spectrometry
Microfluidic Fabrication of Pluronic Vesicles with Controlled Permeability
Block copolymers with a low hydrophilic-to-lipophilic
balance form
membranes that are highly permeable to hydrophilic molecules. Polymersomes
with this type of membrane enable the controllable release of molecules
without membrane rupture. However, these polymersomes are difficult
to assemble because of their low hydrophobicity. Here, we report a
microfluidic approach to the production of these polymersomes using
double-emulsion drops with ultrathin shells as templates. The small
thickness of the middle oil phase enables the attraction of the hydrophobic
blocks of the polymers adsorbed at each of the oil/water interfaces
of the double emulsions; this results in the dewetting of the oil
from the surface of the innermost water drops of the double emulsions
and the ultimate formation of the polymersome. This approach to polymersome
fabrication enables control of the vesicle size and results in the
efficient encapsulation of hydrophilic ingredients that can be released
through the polymer membrane without membrane rupture. We apply our
approach to the fabrication of Pluronic L121 vesicles and characterize
the permeability of their membranes. Furthermore, we show that membrane
permeability can be tuned by blending different Pluronic polymers.
Our work thus describes a route to producing Pluronic vesicles that
are useful for the controlled release of hydrophilic ingredients
Infrared Surface Plasmon Resonance: A Novel Tool for Real Time Sensing of Variations in Living Cells
We developed a novel surface plasmon resonance (SPR) method, based on Fourier transform infrared (FTIR) spectroscopy, as a label-free technique for studying dynamic processes occurring within living cells in real time. With this method, the long (micrometer) infrared wavelength produced by the FTIR generates an evanescent wave that penetrates deep into the sample. In this way, it enables increased depth of sensing changes, covering significant portions of the cell-height volumes. HeLa cells cultivated on a gold-coated prism were subjected to acute cholesterol enrichment or depletion using cyclodextrins. Cholesterol insertion into the cell plasma membrane resulted in an exponential shift of the SPR signal toward longer wavelengths over time, whereas cholesterol depletion caused a shift in the opposite direction. Upon application of the inactive analog α-cyclodextrin (α-CD), the effects were minimal. A similar trend in the SPR signal shifts was observed on a model membrane system. Our data suggest that FTIR-SPR can be implemented as a sensitive technique for monitoring in real time dynamic changes taking place in living cells
Crystalline Domain Structure and Cholesterol Crystal Nucleation in Single Hydrated DPPC:Cholesterol:POPC Bilayers
Grazing incidence X-ray diffraction measurements were performed on single hydrated bilayers and monolayers of DPPC:Cholesterol:POPC at varying concentrations. There are substantial differences in the phase and structure behavior of the crystalline domains formed within the bilayers relative to the corresponding monolayers, due to interactions between the opposing leaflets. Depending on the lipid composition, these interactions led to phase separation, changes in molecular tilt angle, or formation of cholesterol crystals. In monolayers, DPPC and cholesterol form a single crystalline phase at all compositions studied. In bilayers, a second crystalline phase appears when cholesterol levels are increased: domains of cholesterol and DPPC form monolayer thick crystals where each of the lipid leaflets diffracts independently, whereas excess cholesterol forms cholesterol bilayer thick crystals at a DPPC:Chol ratio < 46:54 +/- 2 mol %. The nucleation of the cholesterol crystals occurs at concentrations relevant to the actual cell plasma membrane composition