Diffusion Modeling in a Microchannel for Separation of Species

2004 ◽  
Author(s):  
P. K. Rajesh ◽  
P. Ponnambalam ◽  
N. Ramakrishnan ◽  
K. Prakasan
Keyword(s):  
Diffusion Process ◽  
Small Molecules ◽  
Microfluidic Device ◽  
Diffusion Rate ◽  
Microfluidic Channels ◽  
Diffusion Modeling ◽  
Large Molecules ◽  
Sample Stream ◽  
Large Particles ◽  
Optimization Of Geometry

Recently there is an increased interest in the design of microfluidic devices for research in biotechnological studies, applied to sample detection and analysis of species. When fluids are confined to small volumes, mixing results almost entirely by diffusion due to low velocities of flow in microchannels. As a result, it is possible to design microfluidic systems in which dissimilar fluids flow along side each other over long distances without significant mixing. The H-filter is a microfluidic device used for the extraction of molecular analytes from liquids containing interfering particles. The principle behind H filter is that small molecules will diffuse quickly from a sample stream to the buffer stream while very large molecules and particles will remain indefinitely in the sample stream because of their much larger size and much decreased diffusion rate. Because the Reynolds number in most microfluidic channels is generally kept well below 1, no turbulent mixing of fluids occurs. The only means by which solvents, solutes and suspended particles move in a direction transverse to the direction of flow is by diffusion. Differences in diffusion coefficients can be used to separate molecules of large particles over time. The time spent in flowing in a channel is proportional to the length of the channel. Before carrying out experiments, it is worthwhile to simulate the diffusion process in a microfluidic device for various properties of species and channel geometry. This paper attempts to model the diffusion process in an H-filter for typical species using CFD-ACE+, a software for solving problems in fluid dynamics with multi-physics capabilities. A module of CFD ACE+, called user-scalar that allows the user to define scalar quantities and boundary conditions for this scalar is used in the simulation. As seen from the studies, the diffusivities of species A and B in the buffer influence their diffusion. Optimization of geometry for a given species can be done with this method and separation can be achieved. The results from such a study will be useful for the design optimization and fabrication of such devices.

Why do phosphatidylinositol kinases have so many isoforms?

2009 ◽  
Vol 423 (1) ◽  
pp. e5-e8 ◽  
Author(s):  
Sang H. Min ◽  
Charles S. Abrams
Keyword(s):  
Small Molecules ◽  
Type I ◽  
Surface Receptors ◽  
Large Molecules ◽  
Phosphatidylinositol Kinases ◽  
Phosphatidylinositol Kinase ◽  
Biochemical Journal ◽  
Large Particles ◽  
Phosphoinositide 3 Kinase ◽  
Almost All

Macromolecules can be transported into the cells by endocytosis, either by phagocytosis or by pinocytosis. Typically, phagocytosis involves the uptake of solid large particles mediated by cell-surface receptors, whereas pinocytosis takes up fluid and solutes. The synthesis of PtdIns(4,5)P2 and PtdIns(3,4,5)P3 plays fundamental roles in all forms of endocytosis. Curiously, almost all eukaryotic cells have multiple isoforms of the kinases that synthesize these critical phosphatidylinositols. In this issue of the Biochemical Journal, Namiko Tamura, Osamu Hazeki and co-workers report that the subunit p110α of the type I PI3K (phosphoinositide 3-kinase) is implicated in the phagocytosis and the pinocytosis of large molecules, whereas the receptor-mediated pinocytosis and micropinocytosis of small molecules do not seem to be controlled by this mechanism. The present commentary discusses recent literature that has begun to unravel why cells need so many phosphatidylinositol kinase isoforms, which were previously believed to be redundant.

scholarly journals Building Nanoglands

2011 ◽  
Vol 133 (02) ◽  
pp. 23-26 ◽  
Author(s):  
Alessandro Grattoni ◽  
Scott Parazynski ◽  
Fazle Hussain
Keyword(s):  
Small Molecules ◽  
Continuous Flow ◽  
Low Dose ◽  
Metastatic Colon Cancer ◽  
Release Rates ◽  
Dose Administration ◽  
Large Molecules ◽  
Long Period ◽  
Molecular Concentration ◽  
Molecular Sizes

This article discusses the development of highly structured membranes for constant release of therapeutics over a broad range of molecular sizes, at release rates relevant for medical applications. In the experimental study, the constant release was achieved with small molecules such as leuprolide, a common treatment for prostate cancer, as well as with large molecules such as bevacizumab, widely used in the treatment of metastatic colon cancer. Such an approach could be applied to achieve the goal of metronomic delivery of chemotherapeutics, a constant low-dose administration of drugs over a long period of time. By exploiting nanochannels in passive systems, researchers were to achieve a controlled and constant delivery for extended periods of time, mimicking the basal and continuous flow of molecules from natural glands. This functionality cannot be attained at the macro- or microscale without the use of complex pumping devices and other moving components, because the diffusion of molecules is Fickian, meaning that the release rate is dictated by the gradient of molecular concentration.

Therapeutic delivery using cell-penetrating peptides

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Rupa R. Sawant ◽  
Niravkumar R. Patel ◽  
Vladimir P. Torchilin
Keyword(s):  
Small Molecules ◽  
Therapeutic Agent ◽  
Intracellular Delivery ◽  
Cell Penetrating Peptides ◽  
Current Status ◽  
Unique Challenge ◽  
Large Molecules ◽  
Therapeutic Delivery ◽  
Cell Penetrating ◽  
Stimuli Sensitive

AbstractIntracellular delivery of promising therapeutic agents as well as nanocarriers presents a unique challenge. However, with the discovery of the cell-penetrating peptides (CPPs), overcoming this obstacle seems more plausible. In many cases, CPPs conjugated with therapeutic agent or therapeutic agent loaded-nanoparticles have shown promising results via increased cellular uptake. In this review, the current status of CPPs for the intracellular delivery of not just potential therapeutic small molecules but also large molecules like peptides, nucleic acids and nanocarriers is discussed. In addition, the design of ‘smart stimuli-sensitive nanocarrier’ to overcome the non-target-specificity of CPPs is also described.

Electrochemiluminescence detection for development of immunoassays and DNA probe assays for clinical diagnostics

1991 ◽  
Vol 37 (9) ◽  
pp. 1534-1539 ◽  
Author(s):  
G F Blackburn ◽  
H P Shah ◽  
J H Kenten ◽  
J Leland ◽  
R A Kamin ◽  
...  
Keyword(s):  
Small Molecules ◽  
Dynamic Range ◽  
New Technology ◽  
Clinical Diagnostics ◽  
Reaction Products ◽  
Large Molecules ◽  
Detection Systems ◽  
Highly Sensitive ◽  
Polymerase Chain ◽  
Set Up

Abstract Electrochemiluminescence (ECL) has been developed as a highly sensitive process in which reactive species are generated from stable precursors (i.e., the ECL-active label) at the surface of an electrode. This new technology has many distinct advantages over other detection systems: no radioisotopes are used; detection limits for label are extremely low (200 fmol/L); the dynamic range for label quantification extends over six orders of magnitude; the labels are extremely stable compared with those of most other chemiluminescent systems; the labels, small molecules (approximately 1000 Da), can be used to label haptens or large molecules, and multiple labels can be coupled to proteins or oligonucleotides without affecting immunoreactivity, solubility, or ability to hybridize; because the chemiluminescence is initiated electrochemically, selectivity of bound and unbound fractions can be based on the ability of labeled species to access the electrode surface, so that both separation and nonseparation assays can be set up; and measurement is simple and rapid, requiring only a few seconds. We illustrate ECL in nonseparation immunoassays for digoxin and thyrotropin and in separation immunoassays for carcinoembryonic antigen and alpha-fetoprotein. The application of ECL for detection of polymerase chain reaction products is described and exemplified by quantifying the HIV1 gag gene.

scholarly journals Infrared and optical spectroscopy of astrophysical molecules

1997 ◽  
Vol 178 ◽  
pp. 281-286
Author(s):  
Peter F. Bernath
Keyword(s):  
Small Molecules ◽  
Aromatic Hydrocarbons ◽  
Emission Spectroscopy ◽  
Far Infrared ◽  
Infrared Emission ◽  
Close Coupling ◽  
Large Molecules ◽  
Polycyclic Aromatic ◽  
Astrophysical Molecules ◽  
Recent Laboratory

The recent laboratory spectroscopy of a number of astrophysically important molecules are discussed. Examples include small molecules such as CrH, HF, FeF, SiS, CH4, H20, SiO and TiO as well as large molecules such as COO and polycyclic aromatic hydrocarbons (PAHs). Many of these examples illustrate the utility of infrared and far infrared emission spectroscopy. The close coupling of laboratory spectroscopy and molecular astronomy has led to advances in both areas.

Storing and releasing rhodamine as a model hydrophobic compound in polydimethylsiloxane microfluidic devices

Lab on a Chip ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 574-579 ◽  
Author(s):  
M. Adiraj Iyer ◽  
D. T. Eddington
Keyword(s):  
Microfluidic Device ◽  
Microfluidic Devices ◽  
Microfluidic Channels ◽  
Hydrophobic Compound ◽  
Small Hydrophobic

Polydimethylsiloxane (PDMS) is known to absorb small hydrophobic molecules. We propose to leverage this material to store and release small hydrophobic molecules into and from the PDMS matrix. This method could be used to deliver small hydrophobic molecules to microfluidic channels from the walls of a microfluidic device.

Rapid additive-free bacteria lysis using traveling surface acoustic waves in microfluidic channels

Lab on a Chip ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 4064-4070 ◽  
Author(s):  
Haiwei Lu ◽  
Kirk Mutafopulos ◽  
John A. Heyman ◽  
Pascal Spink ◽  
Liang Shen ◽  
...  
Keyword(s):  
Microfluidic Device ◽  
Acoustic Waves ◽  
High Efficiency ◽  
Surface Acoustic Waves ◽  
Microfluidic Channels ◽  
Wide Range

We introduce a microfluidic device that uses traveling surface acoustic waves to lyse bacteria with high efficiency. This lysis method should be applicable to a wide range of bacteria species and can be modified to analyze individual bacteria cells.

An Integrated PDMS Microfluidic Device for Dielectrophoretic Separation of Malignant Cells

2005 ◽  
Author(s):  
Thirukumaran T. Kanagasabapathi ◽  
Colin Dalton ◽  
Karan V. I. S. Kaler
Keyword(s):  
Microfluidic Device ◽  
Low Cost ◽  
Polystyrene Latex ◽  
Yeast Cells ◽  
Microfluidic Channels ◽  
Non Invasive ◽  
Latex Beads ◽  
Planar Electrodes ◽  
And Performance ◽  
Cancerous Cells

Dielectrophoresis (DEP) has been successfully applied and demonstrated to provide novel and non-invasive means for characterizing, manipulating, trapping, separating and isolating microscopic sized particles, including biological cells. In this article, we report on the design, fabrication and performance of a novel, low cost, integrated Poly(dimethylsiloxane) (PDMS)/DEP microfluidic device capable of controlled manipulation of microscopic sized cells and particles that can be simultaneously utilized both for DEP spectral analysis and cell sorting. We have prototyped microfluidic channels, with DEP microelectrodes incorporated within PDMS channels. Previously, we have evaluated the operation and performance of a prototype device using various dielectric and biological particles, including yeast cells and polystyrene latex beads. In this paper, we report initial experimental observations on malignant cancerous cells. Non-viable cells, due to positive DEP, were attracted to the planar electrodes at frequencies between 200–600 kHz and were clearly repelled from the electrodes, due to negative DEP, at frequencies above 10 MHz.

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