Trajectories and Forces in Four-Electrode Chambers Operated in Object-Shift, Dielectrophoresis and Field-Cage Modes-Considerations from the System's Point of View.

In two previous papers, we calculated the dielectrophoresis (DEP) force and corresponding trajectories of high- and low-conductance 200-µm 2D spheres in a square 1 × 1-mm chamber with plane-versus-pointed, plane-versus-plane and pointed-versus-pointed electrode configurations by applying the law of maximum entropy production (LMEP) to the system. Here, we complete these considerations for configurations with four-pointed electrodes centered on the chamber edges. The four electrodes were operated in either object-shift mode (two adjacent electrodes opposite the other two adjacent electrodes), DEP mode (one electrode versus the other three electrodes), or field-cage mode (two electrodes on opposite edges versus the two electrodes on the other two opposite edges).

The System's Point of View Applied to Dielectrophoresis in Plate Capacitor and Pointed-versus-Pointed Electrode Chambers.

The DEP force is usually calculated from the object's point of view using the interaction of the object's induced dipole moment with the inducing field. Recently, we described the DEP behavior of high- and low-conductive 200-µm 2D spheres in a square 1 × 1-mm chamber with a plane-versus-pointed electrode configuration from the system's point of view. Here we extend our previous considerations to the plane-versus-plane and pointed-versus-pointed electrode configurations.

Dielectrophoresis from the System's Point of View: A Tale of Inhomogeneous Object Polarization, Mirror Charges, High Repelling and Snap-to-Surface Forces and Complex Trajectories Featuring Bifurcation Points and Watersheds.

Microscopic objects change the apparent permittivity and conductivity of aqueous systems and thus their overall polarizability. In inhomogeneous fields, dielectrophoresis (DEP) increases the overall polarizability of the system by moving more highly polarizable objects or media to locations with a higher field. The DEP force is usually calculated from the object’s point of view using the interaction of the object’s induced dipole or multipole moments with the inducing field.

Contributions to a Discussion of as a Capable Swimmer and Deep-Water Predator.

The new findings on swim tail strongly suggest that was a specialized deep-water predator. However, the tail must be seen in the context of the propelled body. The comparison of the flow characteristics of with geometrically similar animals and their swimming abilities under water must take their Reynolds numbers into account and provide a common context for the properties of ' tail and dorsal sail.

Active, Reactive, and Apparent Power in Dielectrophoresis: Force Corrections from the Capacitive Charging Work on Suspensions Described by Maxwell-Wagner's Mixing Equation.

A new expression for the dielectrophoresis (DEP) force is derived from the electrical work in a charge-cycle model that allows the field-free transition of a single object between the centers of two adjacent cubic volumes in an inhomogeneous field. The charging work for the capacities of the volumes is calculated in the absence and in the presence of the object using the external permittivity and Maxwell-Wagner's mixing equation, respectively. The model provides additional terms for the Clausius-Mossotti factor, which vanish for the mathematical boundary transition toward zero volume fraction, but which can be interesting for narrow microfluidic systems.

Subthalamic nucleus deep brain stimulation induces sustained neurorestoration in the mesolimbic dopaminergic system in a Parkinson's disease model.

Background: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an established therapeutic principle in Parkinson's disease, but the underlying mechanisms, particularly mediating non-motor actions, remain largely enigmatic.

Objective/hypothesis: The delayed onset of neuropsychiatric actions in conjunction with first experimental evidence that STN-DBS causes disease-modifying effects prompted our investigation on how cellular plasticity in midbrain dopaminergic systems is affected by STN-DBS.

Methods: We applied unilateral or bilateral STN-DBS in two independent cohorts of 6-hydroxydopamine hemiparkinsonian rats four to eight weeks after dopaminergic lesioning to allow for the development of a stable dopaminergic dysfunction prior to DBS electrode implantation.

A comparative analysis of detachment forces and energies in initial and mature cell-material interaction.

Single cell force spectroscopy (SCFS) enables data on interaction forces to be acquired during the very early adhesion phase. However, SCFS detachment forces and energies have not been compared so far with the forces and energies after maturation of the cell-material contact on a single cell level and with comparable time resolution. We used FluidFM® to physically attach single cells to the cantilever by aspiration through a microfluidic channel, in order to achieve the higher forces required for detaching maturely adhering cells.

Surface Coatings Modulate the Differences in the Adhesion Forces of Eukaryotic and Prokaryotic Cells as Detected by Single Cell Force Microscopy.

Single cell force microscopy was used to investigate the maximum detachment force (MDF) of primary neuronal mouse cells (PNCs), osteoblastic cells (MC3T3), and prokaryotic cells ( subsp. ) from different surfaces after contact times of 1 to 5 seconds. Positively charged silicon nitride surfaces were coated with positively charged polyethyleneimine (PEI) or poly-D-lysine.

Combined detection of AC-electrokinetic effects: Experiments with three-axial chicken red blood cells.

Dielectrophoresis (DEP), electrorotation (ROT), and electro-orientation were used for the dielectric spectroscopy of nucleated three-axial chicken red blood cells (CRBCs). Because the different AC-electrokinetic effects are not mutually independent, their DEP and ROT spectra were combined in ranges separated by the reorientation of the CRBCs in the inhomogeneous linear DEP and circular ROT fields. This behavior can be qualitatively described by a single-shell ellipsoidal model.

Combined AC-electrokinetic effects: Theoretical considerations on a three-axial ellipsoidal model.

AC fields induce charges at the structural interfaces of particles or biological cells. The interaction of these charges with the field generates frequency-dependent forces that are the basis for AC-electrokinetic effects such as dielectrophoresis (DEP), electrorotation (ROT), electro-orientation, and electro-deformation. The effects can be used for the manipulation or dielectric single-particle spectroscopy.

Furthering the state of knowledge on the electric properties of hemi-ellipsoidal single cells and cell patches on electrodes.

The impedance of electrodes with adherent biological cells correlates with cell viability and proliferation. To model this correlation, we exploited the idea that the introduction of a highly conductive layer into the equatorial equipotential slice of a system with an oriented, freely suspended, single ellipsoidal cell may split the system into mirror-symmetrical halves without changing the field distribution. Each half possesses half of the system's impedance and contains a hemiellipsoidal cell attached to the conductive layer, which can be considered a bottom electrode.

Spermidine-Induced Attraction of Like-Charged Surfaces Is Correlated with the pH-Dependent Spermidine Charge: Force Spectroscopy Characterization.

The ubiquitous molecule spermidine is known for its pivotal roles in the contact mediation, fusion, and reorganization of biological membranes and DNA. In our model system, borosilicate beads were attached to atomic force microscopy cantilevers and used to probe mica surfaces to study the details of the spermidine-induced attractions. The negative surface charges of both materials were largely constant over the measured pH range of pH 7.

Increased osteoblast viability at alkaline pH provides a new perspective on bone regeneration.

We investigated the effects of alkaline pH on developing osteoblasts. Cells of the osteoblast-like cell line MC3T3-E1 were initially cultured for six days in HEPES-buffered media with pH ranging from 7.2 to 9.

Deep Brain Stimulation of Hemiparkinsonian Rats with Unipolar and Bipolar Electrodes for up to 6 Weeks: Behavioral Testing of Freely Moving Animals.

Although the clinical use of deep brain stimulation (DBS) is increasing, its basic mechanisms of action are still poorly understood. Platinum/iridium electrodes were inserted into the subthalamic nucleus of rats with unilateral 6-OHDA-induced lesions of the medial forebrain bundle. Six behavioral parameters were compared with respect to their potential to detect DBS effects.

MC3T3 osteoblast-like cells cultured at alkaline pH: Microarray data (Affymetrix GeneChip Mouse 2.0 ST).

It is well known that pH plays a pivotal role in the control of bone remodeling. However, no comprehensive gene expression data are available for the effects of alkaline pH on osteoblasts. We cultured differentiating MC3T3-E1 osteoblast-like cells at pH 7.

WST-assay data reveal a pH dependence of the mitochondrial succinate reductase in osteoblast-like cells.

The data presented in this article are related to the research article entitled "Increased osteoblast viability at alkaline pH in vitro provides a new perspective on bone regeneration" (doi: 10.1016/j.bbrep.

Automated and manual patch clamp data of human induced pluripotent stem cell-derived dopaminergic neurons.

Human induced pluripotent stem cells can be differentiated into dopaminergic neurons (Dopa.4U). Dopa.

Cell Monitoring and Manipulation Systems (CMMSs) based on Glass Cell-Culture Chips (GC³s).

We developed different types of glass cell-culture chips (GC³s) for culturing cells for microscopic observation in open media-containing troughs or in microfluidic structures. Platinum sensor and manipulation structures were used to monitor physiological parameters and to allocate and permeabilize cells. Electro-thermal micro pumps distributed chemical compounds in the microfluidic systems.

Neuronal in vitro activity is more sensitive to valproate than intracellular ATP: Considerations on conversion problems of IC50 in vitro data for animal replacement.

We investigated the effects of acute valproate (VPA) on mouse embryonic primary cortex cells (MEPCs). Intracellular ATP concentrations were compared with changes in the mean action potential (AP) frequencies of MEPC networks growing on microelectrode arrays. Our data implies biphasic reactions towards increasing VPA concentrations for both parameters.

Design and Characterization of a Sensorized Microfluidic Cell-Culture System with Electro-Thermal Micro-Pumps and Sensors for Cell Adhesion, Oxygen, and pH on a Glass Chip.

We combined a multi-sensor glass-chip with a microfluidic channel grid for the characterization of cellular behavior. The grid was imprinted in poly-dimethyl-siloxane. Mouse-embryonal/fetal calvaria fibroblasts (MC3T3-E1) were used as a model system.

Maxwell's mixing equation revisited: characteristic impedance equations for ellipsoidal cells.

We derived a series of, to our knowledge, new analytic expressions for the characteristic features of the impedance spectra of suspensions of homogeneous and single-shell spherical, spheroidal, and ellipsoidal objects, e.g., biological cells of the general ellipsoidal shape.

The effect of hyperbaric air on the electric activity of neuronal in vitro networks.

Breathing hyperbaric air or gas mixtures, for example during diving or when working underwater is known to alter the electrophysiological behavior of neuronal cells, which may lead to restricted cognition. During the last few decades, only very few studies into hyperbaric effects have been published, especially for the most relevant pressure range of up to 10 bar. We designed a pressurized measuring chamber to record pressure effects on the electrical activity of neuronal networks formed by primary cells of the frontal cortex of NMRI mice.

Experimental verification of an equivalent circuit for the characterization of electrothermal micropumps: high pumping velocities induced by the external inductance at driving voltages below 5 V.

Electrothermal micropumps (ETμPs) use local heating to create conductivity and permittivity gradients in the pump medium. In the presence of such gradients, an external AC electric field influences smeared spatial charges in the bulk of the medium. When there is also a symmetry break, the field-charge interaction results in an effective volumetric force resulting in medium pumping.

Low fibronectin concentration overcompensates for reduced initial fibroblasts adhesion to a nanoscale topography: single-cell force spectroscopy.

Using single-cell force spectroscopy, we compared the initial adhesion of L929 fibroblasts to planar and nanostructured silicon substrates as a function of fibronectin concentration. The nanostructures were periodically grooved with a symmetric groove-summit period of 180 nm and a groove depth of 120 nm. Cell adhesion strength to the bare nanostructure was lower (79%± 13%) than to the planar substrate, which we attribute to reduced contact area.

Optimizing a rodent model of Parkinson's disease for exploring the effects and mechanisms of deep brain stimulation.

Deep brain stimulation (DBS) has become a treatment for a growing number of neurological and psychiatric disorders, especially for therapy-refractory Parkinson's disease (PD). However, not all of the symptoms of PD are sufficiently improved in all patients, and side effects may occur. Further progress depends on a deeper insight into the mechanisms of action of DBS in the context of disturbed brain circuits.