1,721,051 research outputs found
A wide-band bio-chip for real-time optical detection of bioelectromagnetic interactions with cells
No full textThe analytical and numerical design, implementation, and experimental validation of a new grounded closed coplanar waveguide for wide-band electromagnetic exposures of cells and their optical detection in real-time is reported. The realized device fulfills high-quality requirements for novel bioelectromagnetic experiments, involving elevated temporal and spatial resolutions. Excellent performances in terms of matching bandwidth (less than -10 dB up to at least 3 GHz), emission (below 1 × 10-6 W/m2) and efficiency (around 1) have been obtained as revealed by both numerical simulations and experimental measurements. A low spatial electric field inhomogeneity (coefficient of variation of around 10 %) has been achieved within the cell solutions filling the polydimethylsiloxane reservoir of the conceived device. This original bio-chip based on the grounded closed coplanar waveguide concept opens new possibilities for the development of controlled experiments combining electromagnetic exposures and sophisticated imaging using optical spectroscopic techniques. © 2018 The Author(s)
Characterization of a portable and low cost system for practical dielectric spectroscopy
No full textA portable setup for measurements of complex permittivity based on ad-hoc arrangements is proposed and its performance compared to the ones of a bench system. The measurement setup consists of a portable spectrum analyzer (used as vector network analyzer, VNA) connected to an open-end coaxial cable for S11 acquisition. Scattering parameters were processed using custom Labview software specifically developed to obtain complex permittivity of liquids and soft materials in real-time. A suitable calibration procedure, based on a differential principle, enables accurate measurements. Raw results showed that the portable setup provides noisier traces if compared to the performance of a high precision laboratory VNA. However, accurate permittivity data have been achieved introducing filtering to eliminate signal oscillations and spurious noise without loss of information associated to liquid dielectric relaxations. This procedure, applied to standard liquids (ethanol, ethanediol, 2-propanol) showed good performance in terms of bias and precision. Water solutions, used for cell culturing purposes, both conductive and non-conductive, were also successfully measured. The obtained results are a proof of concept that the proposed procedure is a reliable technique to perform fast, low-cost and on site permittivity measurements, useful for diagnostic or therapeutic applications. © 2018 IEEE
Assessment of cytoplasm conductivity by nanosecond pulsed electric fields
No full textThe aim of this paper is to propose a new method for the better assessment of cytoplasm conductivity, which is critical to the development of electroporation protocols as well as insight into fundamental mechanisms underlying electroporation. For this goal, we propose to use nanosecond electrical pulses to bypass the complication of membrane polarization and a single cell to avoid the complication of the application of the 'mixing formulas.' Further, by suspending the cell in a low-conductivity medium, it is possible to force most of the sensing current through the cytoplasm for a more direct assessment of its conductivity. For proof of principle, the proposed technique was successfully demonstrated on a Jurkat cell by comparing the measured and modeled currents. The cytoplasm conductivity was best assessed at 0.32 S/m and it is in line with the literature. The cytoplasm conductivity plays a key role in the understanding of the basis mechanism of the electroporation phenomenon, and in particular, a large error in the cytoplasm conductivity determination could result in a correspondingly large error in predicting electroporation. Methods for a good estimation of such parameter become fundamental. © 1964-2012 IEEE
Proving lightning role in the evolution of life. Comment on "Lightning-triggered electroporation and electrofusion as possible contributors to natural horizontal gene transfer" by Tadej Kotnik.
No full textSingle cell microdosimetric studies comparing ideal and measured nanosecond pulsed electric fields
No full textRecently, the promising effects induced by pulsed electric fields with high intensity and short duration have been highlighted. At the nanosecond time scale, electric pulse targets become both the plasmatic membrane and the sub-cellular structures (possibility of intracellular manipulation). In this paper, a circuit cell model with nucleus is presented, validated and used in order to assess the different cellular and sub-cellular (i.e. nucleus) effects, comparing ideal nanosecond pulsed electric fields (nsPEFs) waveforms with the ones measured from a planar, broadband matched microchamber. © 2013 IEEE
Coplanar stripline microchamber for electrical detection of live and dead biological cells
No full textAn improved microchamber for electrical detection of biological cells was designed, fabricated and tested. The microchamber was formed between a gold coplanar stripline fabricated on a sapphire microscope slide and a single microfluidic channel fabricated in a polydimethylsiloxane cover. Compared with the previous design of a coplanar waveguide on a quartz slide with multiple microfluidic channels, the present microchamber was more sensitive, compact, rugged, and transparent. Tests on Jurkat cells in both time and frequency domains demonstrated single-cell sensing potential, as well as discrimination of live vs. dead cells. The test results could be explained by a simple equivalent-circuit model, which efficiently de-embedded the intrinsic cell properties from solution and electrode effects. © 2013 European Microwave Association
Cells and electropulsation microchambers modeling for linear and nonlinear optical microspectroscopy
No full textMechanisms underlining the cell membrane permeabilization and consequent cellular and intracellular effects are still debated. To shed light on the involvement of phospholipids and water molecules rearrangements in this phenomenon, linear and non-linear optical imaging and microspectroscopy seem particularly appropriate. To combine optical detection with electric pulses used for permeabilization of cells, three delivery setups (microchambers) are presented in this paper. Design and numerical characterization are described and systems performances compared in terms of electromagnetic emissions. The dosimetry of the less radiating microchamber was analyzed in time domain and compared with transmission measurements. Microdosimetry in time domain was also performed to study electric field distribution at cell level. These data give interesting information for interpreting cell microspectroscopic results. © 2018 IEEE
Shared knowledge, gaps and challenges of microdosimetry: Realistic models of cells and endoplasmic reticulum
No full textIn the study of the biophysical mechanisms at the basis of the EM field interaction leading to biomedical applications, one needs also to know the field strength at the microscopic scale to establish a quantitative relation between the field and the observed effect. Here authors will show the results on the TMP of the plasma membrane and the endoplasmic reticulum (ER) due a 2D realistic shaping of the ER itself, both analysed in the frequency domain and for an electric pulsed field of 10 ns. © 2018 IEEE
An in vivo exposure-system for wide-band electric pulses
No full textIn this paper, the dosimetry of small animals arranged on a monopolar patch antenna for bioelectromagnetic experiments is reported. Numerical simulations were carried out to verify the matching of the antenna in the presence of a dielectric box to accommodate the small animals. This strategy, reducing the dielectric differences between the various irradiated materials, improves largely the efficiency of the setup. The induced electric field in the biological samples reached tens of V/m for an input voltage of 1 V, which is one of the highest efficiency obtained so far for these types of exposure setup. A very short electric pulse (on-time duration of 1 ns) is transferred mostly undistorted to the biological sample guaranteeing controlled experimental exposure conditions. Optimization of the positioning of the small animals was also analyzed. Our setup can be used to study effects of short and intense electric pulses in vivo only poorly addressed so far. © 2018 Institution of Engineering and Technology.All Rights Reserved
Frequency spectrum of induced transmembrane potential and permeabilization efficacy of bipolar electric pulses
No full textIn this paper a simple prediction method for the bipolar pulse cancellation effect is proposed, based on the frequency analysis of the TMP spectra of a single cell and the computed relative global spectral content up to a defined frequency threshold. We present a spectral analysis of pulses applied in experiments, and we extract the induced TMP from a microdosimetric model of the cell. The induced TMP computation is carried out on a hemispherical multi-layered cell model in the time domain. The analysis is presented for a variety of unipolar and bipolar input signals in the nanosecond and the microsecond time scales. Our evaluations are in good agreement with experimental results for bipolar pulse cancellation of electropermeabilization-induced Ca2+ influx using 300 ns, 750 kV/m pulses and with other results reported in recent literature. © 2017 Elsevier B.V
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