Electric Field-Assisted Positioning of Neurons on Pt Microelectrode Arrays

2003 ◽  
Vol 773 ◽  
Author(s):  
Shalini Prasad ◽  
Mo Yang ◽  
Xuan Zhang ◽  
Yingchun Ni ◽  
Vladimir Parpura ◽  
...  
Keyword(s):  
Electric Field ◽  
Electrical Activity ◽  
Electric Fields ◽  
Microelectrode Array ◽  
Electrode Array ◽  
Sprague Dawley ◽  
A Cell ◽  
Neuron Patterning

AbstractCharacterization of electrical activity of individual neurons is the fundamental step in understanding the functioning of the nervous system. Single cell electrical activity at various stages of cell development is essential to accurately determine in in-vivo conditions the position of a cell based on the procured electrical activity. Understanding memory formation and development translates to changes in the electrical activity of individual neurons. Hence, there is an enormous need to develop novel ways for isolating and positioning individual neurons over single recording sites. To this end, we used a 3x3 multiple microelectrode array system to spatially arrange neurons by applying a gradient AC field. We characterized the electric field distribution inside our test platform by using two dimensiona l finite element modeling (FEM) and determined the location of neurons over the electrode array. Dielectrophoretic AC fields were utilized to separate the neurons from the glial cells and to position the neurons over the electrodes. The neurons were obtained from 0-2-day-old rat (Sprague-Dawley) pups. The technique of using electric fields to achieve single neuron patterning has implications in neural engineering, elucidating a new and simpler method to develop and study neuronal activity as compared to conventional microelectrode array techniques.

Resonance electroconformational coupling: A proposed mechanism for energy and signal transductions by membrane proteins

1989 ◽  
Vol 9 (1) ◽  
pp. 13-26 ◽  
Author(s):  
Tian Yow Tsong ◽  
Dao-Sheng Liu ◽  
Francoise Chauvin ◽  
R. Dean Astumian
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Chemical Potential ◽  
Energy Coupling ◽  
Concentration Gradients ◽  
Coulombic Interaction ◽  
Oscillating Electric Field ◽  
A Cell ◽  
Signal Transductions

Recent experiments show that membrane ATPases are capable of absorbing free energy from an applied oscillating electric field and converting it to chemical bond energy of ATP or chemical potential energy of concentration gradients. Presumably these enzymes would also respond to endogenous transmembrane electric fields of similar intensity and waveform. A mechanism is proposed in which energy coupling is achieved via Coulombic interaction of an electric field and the conformational equilibria of an ATPase. Analysis indicates that only an oscillating or fluctuating electric field can be used by an enzyme to drive a chemical reaction away from equilibrium. In vivo, the stationary transmembrane potential of a cell must be modulated to become “locally” oscillatory if it is to derive energy and signal transduction processes.

Modelling and Fabrication of 3-D Carbon-MEMS for Dielectrophoretic Manipulation of Micro/Nanoparticles in Fluids

2009 ◽  
Vol 628-629 ◽  
pp. 435-440 ◽  
Author(s):  
Zi Rong Tang ◽  
M.Rizwan Malik ◽  
Tie Lin Shi ◽  
J. Gong ◽  
L. Nie ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Cross Sections ◽  
Microelectrode Array ◽  
Three Dimensional ◽  
Electrode Array ◽  
Nano Particles ◽  
Nano Technology ◽  
Aspect Ratios ◽  
Carbon Mems

Carbon-MEMS (C-MEMS) have emerged as a new category of devices for micro/nano technology with many potential applications. Dielectrophoretic manipulation of micro/nanoparticles with C-MEMS is studied in this paper. Through electric field distribution modeling in carbon electrode array, we analyze the strongest simulation effect results of electric field in three dimensional (3-D) surface plots depicting the magnitude of electric field in various cross sections at different heights above the channel floor for 2, 10, 30 and 50 μm high carbon electrodes. It is represented here that maximum intensity of electric field generates with the equality between the height above the channel floor and the height of the electrodes. Simulation parameters involved are for dielectrophoretic manipulation of micro/nano particles based on 3-D C-MEMS. The advantages of using 3-D C-MEMS electrodes over other techniques of creating high-throughput systems for dielectrophoretic manipulation environment surrounded by micro/nano horizons are: (i) complex microscale 3-D electrodes with high-aspect ratios can easily be shaped and patterned using conventional lithography (ii) carbon has a high window of stability thus allowing application of higher voltages (iii) there is no need for bulk micromachining or patterning electrodes on multiple planes (iv) the distance between electrodes can precisely be controlled through the lithography process. FEMLAB 3.4 Multiphysics Modeling software (COMSOL, Stockholm, Sweden) is used for the modeling of electric fields and one-layer C-MEMS microelectrode array was fabricated with SU-8 photoresist.

Factors Controlling Electropermeabilisation of Cell Membranes

2002 ◽  
Vol 1 (5) ◽  
pp. 319-327 ◽  
Author(s):  
M. P. Rols ◽  
M. Golzio ◽  
B. Gabriel ◽  
J. Teissié
Keyword(s):  
Cell Surface ◽  
Electric Field ◽  
Pulse Duration ◽  
Cell Membranes ◽  
Physical Parameters ◽  
Local Exchange ◽  
Physical Mechanisms ◽  
A Cell

Electric field pulses are a new approach for drug and gene delivery for cancer therapy. They induce a localized structural alteration of cell membranes. The associated physical mechanisms are well explained and can be safely controlled. A position dependent modulation of the membrane potential difference is induced when an electric field is applied to a cell. Electric field pulses with an overcritical intensity evoke a local membrane alteration. A free exchange of hydrophilic low molecular weight molecules takes place across the membrane. A leakage of cytosolic metabolites and a loading of polar drugs into the cytoplasm are obtained. The fraction of the cell surface which is competent for exchange is a function of the field intensity. The level of local exchange is strongly controlled by the pulse duration and the number of successive pulses. The permeabilised state is long lived. Its lifetime is under the control of the cumulated pulse duration. Cell viability can be preserved. Gene transfer is obtained but its mechanism is not a free diffusion. Plasmids are electrophoretically accumulated against the permeabilised cell surface and form aggregates due to the field effect. After the pulses, several steps follow: translocation to the cytoplasm, traffic to the nucleus and expression. Molecular structural and metabolic changes in cells remain mostly poorly understood. Nevertheless, while most studies were established on cells in culture ( in vitro), recent experiments show that similar effects are obtained on tissue ( in vivo). Transfer remains controlled by the physical parameters of the electrical treatment.

scholarly journals Transcranial Alternating Current Stimulation (tACS) Entrains Alpha Oscillations by Preferential Phase Synchronization of Fast-Spiking Cortical Neurons to Stimulation Waveform

2019 ◽  
Author(s):  
Ehsan Negahbani ◽  
Iain M. Stitt ◽  
Marshall Davey ◽  
Thien T. Doan ◽  
Moritz Dannhauer ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Cortical Neurons ◽  
Posterior Parietal Cortex ◽  
Phase Synchronization ◽  
Alternating Current ◽  
Arnold Tongue ◽  
Transcranial Alternating Current Stimulation ◽  
Neuronal Oscillators

SummaryModeling studies predict that transcranial alternating current stimulation (tACS) entrains brain oscillations, yet direct examination has been lacking or potentially contaminated by stimulation artefact. Here we first demonstrate how the posterior parietal cortex drives primary visual cortex and thalamic LP in the alpha-band in head-fixed awake ferrets. The spike-field synchrony is maximum within alpha frequency, and more prominent for narrow-spiking neurons than broad-spiking ones. Guided by a validated model of electric field distribution, we produced electric fields comparable to those in humans and primates (< 0.5 mV/mm). We found evidence to support the model-driven predictions of how tACS entrains neural oscillations as explained by the triangular Arnold tongue pattern. In agreement with the stronger spike-field coupling of narrow-spiking cells, tACS more strongly entrained this cell population. Our findings provide the firstin vivoevidence of how tACS with electric field amplitudes used in human studies entrains neuronal oscillators.

Controlled Separation and Trapping of Particles Using Two-frequency DEP

2005 ◽  
Author(s):  
Sophie Loire ◽  
Yanting Zhang ◽  
Frederic Bottausci ◽  
Noel C. MacDonald ◽  
Igor Mezic
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Traveling Wave ◽  
Electrode Array ◽  
Theoretical Work ◽  
Single Frequency ◽  
Ac Electroosmosis ◽  
Biomedical Analysis ◽  
Precise Control ◽  
Flow Effects

We present numerical simulations and experiments on dielectrophoretic (DEP) separation and trapping performed in a titanium-based microchannel linear electrode array. The use of electric fields and in particular dielectrophoresis (DEP) have a great potential to help miniaturize and increase the speed of biomedical analysis. Precise control and manipulation of micro/nano/bio particles inside those miniaturized devices depend greatly on our understanding of the phenomena induced by AC electric fields inside microchannels and how we take advantage of them. The studied DEP devices are composed of two parts: the inter-digitated titanium electrodes and the channel. The electrode substrate is constituted of two layers to form 4-phase traveling wave. Each electrode is 20 μm wide and separated from the other by a gap of 20 μm. The channel is 200 μm wide, 50 μm deep and 6 mm long. The device is designed to generate inhomogeneities in electric-field magnitude. This allows positive and negative DEP (p-DEP and n-DEP). Moreover, it can also produce inhomogeneities in electric-field phase, hence authorizing traveling wave DEP (twDEP). It is also capable of inducing two-frequency DEP, in contrast with most of the previous, single-frequency, designs. The advantages of two-frequency DEP were shown by theoretical work (Chang et al. 2003) and permit precise and optimal control of particles movements. We show that fluid flow effects are substantial and can affect the particle motion in a positive (enhanced trapping) and negative (trapping when separation is desired) way. We discuss the effects of AC-electroosmosis, electrothermal and dielectrophoresis combined. We discuss the advantages of two-frequency dielectrophoretic handling of bioparticles. We investigate the limits of particle size that can be accurately controlled.

scholarly journals Genetic Localization and Molecular Characterization of the nonS Gene Required for Macrotetrolide Biosynthesis inStreptomyces griseus DSM40695

2000 ◽  
Vol 44 (7) ◽  
pp. 1809-1817 ◽  
Author(s):  
Wyatt C. Smith ◽  
Longkuan Xiang ◽  
Ben Shen
Keyword(s):  
Polyketide Synthase ◽  
Isotope Labeling ◽  
Streptomyces Griseus ◽  
Open Reading Frames ◽  
A Cell ◽  
Cyclic Polyethers ◽  
The Difference ◽  
Reading Frames

ABSTRACT The macrotetrolides are a family of cyclic polyethers derived from tetramerization, in a stereospecific fashion, of the enantiomeric nonactic acid (NA) and its homologs. Isotope labeling experiments established that NA is of polyketide origin, and biochemical investigations demonstrated that 2-methyl-6,8-dihydroxynon-2E-enoic acid can be converted into NA by a cell-free preparation from Streptomyces lividans that expresses nonS. These results lead to the hypothesis that macrotetrolide biosynthesis involves a pair of enantiospecific polyketide pathways. In this work, a 55-kb contiguous DNA region was cloned from Streptomyces griseus DSM40695, a 6.3-kb fragment of which was sequenced to reveal five open reading frames, including the previously reported nonR andnonS genes. Inactivation of nonS in vivo completely abolished macrotetrolide production. Complementation of thenonS mutant by the expression of nonS intrans fully restored its macrotetrolide production ability, with a distribution of individual macrotetrolides similar to that for the wild-type producer. In contrast, fermentation of thenonS mutant in the presence of exogenous (±)-NA resulted in the production of nonactin, monactin, and dinactin but not in the production of trinactin and tetranactin. These results prove the direct involvement of nonS in macrotetrolide biosynthesis. The difference in macrotetrolide production between in vivo complementation of the nonS mutant by the plasmid-borne nonSgene and fermentation of the nonS mutant in the presence of exogenously added (±)-NA suggests that NonS catalyzes the formation of (−)-NA and its homologs, supporting the existence of a pair of enantiospecific polyketide pathways for macrotetrolide biosynthesis inS. griseus. The latter should provide a model that can be used to study the mechanism by which polyketide synthase controls stereochemistry during polyketide biosynthesis.

A Capacitance-Based Technique for Characterization of Dielectric Interfaces Using a Grid of Electrode Junctions

2013 ◽  
Author(s):  
Stephen H. Taylor ◽  
Suresh V. Garimella
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Generalized Solution ◽  
Design Criteria ◽  
Thermal Interface ◽  
Model Predictions ◽  
Dielectric Interfaces ◽  
Field Localization ◽  
Crossing Point

A sensor for detecting imperfections in the distribution of a dielectric thermal interface is proposed. The sensor can detect imperfections such as voids, cracks, and interface gap changes on the millimeter scale. A rake of long, parallel electrodes is imbedded flush into each opposing substrate face of a narrow gap interface, and exposed to the gap formed between the two surfaces. Electrodes are oriented such that their lengthwise dimension in one substrate runs perpendicular to the other. Capacitance measurements taken at each crossing point (junction) allow for characterization of the region, and subsequently, detection of voids present or changes in gap size. The electric field associated with each electrode junction is numerically simulated and analyzed. Design criteria for the electrode junctions that localize the electric fields are presented. The electrode configuration employed gives rise to a non-trivial network of interacting capacitances. Due to these interactions, the actual capacitance at any given junction cannot be measured directly; instead, the measurement represents an equivalent capacitance resulting from this network. A generalized solution for analyzing the circuit network is presented. An experimental test unit is described, and experimental data are presented for measurements from a typical electrode junction. The results agree with predictions from the network model for cases that meet the design criteria for electric field localization; when the localization criteria are not met, the measurements deviate from the model predictions as expected.

scholarly journals Electrode Cooling Effect on Out-of-Phase Electrothermal Streaming in Rotating Electric Fields

2017 ◽  
Author(s):  
Weiyu Liu ◽  
Yukun Ren ◽  
Ye Tao ◽  
Xiaoming Chen ◽  
Qisheng Wu
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Heat Dissipation ◽  
Electrode Array ◽  
Substrate Material ◽  
Microfluidic Chips ◽  
Metal Electrodes ◽  
Bulk Fluid ◽  
Dependent Flow ◽  
Electrothermal Flow

In this work, we focus on investigating electrothermal flow in a rotating electric field (ROT-ETF), with primary attention paid to the horizontal traveling-wave electrothermal (TWET) vortex induced at the center of the electric field. The frequency-dependent flow profiles in the microdevice are analyzed using different heat transfer models. Accordingly, we address in particular the importance of electrode cooling in ROT-ETF as metal electrodes of high thermal conductivity while substrate material of low heat dissipation capability are employed to develop such microfluidic chips. Under this circumstance, cooling of electrode array due to external natural convection on millimeter-scale electrode pads for external wire connection occurs and makes the internal temperature maxima shift from the electrode plane to a bit of distance right above the cross-shaped interelectrode gaps, giving rise to reversal of flow rotation from a typical repulsion-type to attraction-type induction vortex, which is in good accordance with our experimental observations of co-field TWET streaming at frequencies on the order of reciprocal charge relaxation time of the bulk fluid. These results point out a way to make a correct interpretation of out-of-phase electrothermal streaming behavior, which holds great potential for handing high-conductivity analytes in modern microfluidic systems.

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