Francesca Apollonio

Considerations for Developing an RF Exposure System: A Review for in vitro Biological Experiments

This paper provides a detailed review and classification of exposure systems used in RF in vitro research from 1999 up to 2009. Since different endpoints and protocols are used in bioelectromagnetics studies, exposure systems cannot be standardized. However, a standardized procedure to achieve the optimum design of the exposure system is suggested. Following this procedure will lead to a known dose distribution within the biological sample and allow a better comparison with other in vitro studies. In addition, the quality of the study will be such that it will be more likely to be included in assessment procedures such as health-risk assessments.

Integrated models for the analysis of biological effects of EM fields used for mobile communications

The understanding of the modalities of interaction of electromagnetic (EM) fields with biological material is a key point in the identification of possible induced effects. Since the beginnings of bioelectromagnetic research studies, most of the attention has been focused on the effects on nervous systems and neuronal cells. The importance of this target has recently increased due to the wide diffusion of mobile terminals, used close to the head. In this paper, an integrated interaction model is proposed. The model, validated in each part of its components with experimental data, allows to obtain a quantitative link from the external applied field to the effects on neurons (isolated or linked to similar others). The models is firstly based on the evaluation of the EM field at cellular membrane level, then on the evaluation of the effects induced on each component of the model growing from the low biophysical level (membrane channels) to the biological one (neuron time behavior). The use of well-assessed models for the simulations of each part allows both the evaluation of the effect at different levels of complexity and the employment of this effect acting as an input on the upper level. This approach allows, for the first time, a complete quantitative evaluation of the effects on neurons due to the fields from the existing mobile systems, and can be a useful instrument for the evaluation of the possible health impact of new technologies.

Feasibility for Microwaves Energy to Affect Biological Systems Via Nonthermal Mechanisms: A Systematic Approach

The understanding of possible nonthermal bio-effects has been an open question during the last five decades. In this paper, the authors present a critical literature review of the models of the interaction mechanisms, together with an overview of all the publications finding positive results for in vitro and in vivo studies. The systematic approach consisted of pooling together the positive studies on the basis of the endpoints and the biological systems, to identify specific plausible targets of the action of the electromagnetic fields and the related pathways. Such a classification opens the way to the discussion of some hypotheses of interaction mechanisms considered as first transduction step. The authors conclude that only through a multiscale methodology it is possible to perform a comprehensive study of the nonthermal effects, based on affordable and realistic in silico models.

Broadband Electrical Detection of Individual Biological Cells

To resolve the dilemma of cell clogging or solution parasitics encountered by Coulter counters and to evolve a general-purpose electrical detection technique, we used broadband microwave measurements to overcome electrode polarization, ac dielectrophoresis to precisely place cells between narrowly spaced electrodes, and relatively wide microfluidic channels to prevent cell clogging. This unique combination of approaches resulted in reproducible sensing of single Jurkat and HEK cells, both live and dead, of different cultures at different times.

Effect of high exogenous electric pulses on protein conformation: myoglobin as a case study.

Protein folding and unfolding under the effect of exogenous perturbations remains a topic of great interest, further enhanced by recent technological developments in the field of signal generation that allow the use of intense ultrashort electric pulses to directly interact at microscopic level with biological matter. In this paper, we show results from molecular dynamics (MD) simulations of a single myoglobin molecule in water exposed to pulsed and static electric fields, ranging from 10(8) to 10(9) V/m, compared to data with unexposed conditions. We have found that the highest intensity (10(9) V/m) produced a fast transition (occurring within a few hundreds of picoseconds) between folded and unfolded states, as inferred by secondary structures and geometrical analysis. Fields of 10(8) V/m, on the contrary, produced no significant denaturation, although a relevant effect on the protein dipolar behavior was detected.

Quantitative assessment of dielectric parameters for membrane lipid bi-layers from RF permittivity measurements

In this article, we propose and validate theoretical and experimental methods to quantitatively assess the Debye dielectric model of membrane lipid bi-layers. This consists of two steps: permittivity measurements of biological solutions (liposomes), and estimation of the model parameters by inverse application of the Effective Medium Theory. The measurements are conducted in the frequency domain between 100 MHz and 2 GHz using a modified coaxial connector, at the temperatures of 27 and 30 degrees C. Estimations have been performed using a three-layered model based on the Maxwell-Wagner formulation. Debye parameters (mean value +/- standard error) found from fitting experimental data are: epsilon(s) = 11.69 +/- 0.09, epsilon(infinity) = 4.00 +/- 0.07, f(relax) = 179.85 +/- 6.20 MHz and epsilon(s) = (1.1 +/- 0.1) x 10(-7) S/m. This model can be used in microdosimetric studies aiming to precisely determine the E-field distribution in a biological target down to the single cell level. In this context the use of an accurate membrane dielectric model, valid through a wide frequency range, is particularly appropriate.

Microdosimetry for Nanosecond Pulsed Electric Field Applications: A Parametric Study for a Single Cell

A microdosimetric study of nanosecond pulsed electric fields, including dielectric dispersivity of cell compartments, is proposed in our paper. A quasi-static solution based on the Laplace equation was adapted to wideband signals and used to address the problem of electric field estimation at cellular level. The electric solution was coupled with an asymptotic electroporation model able to predict membrane pore density. An initial result of our paper is the relevance of the dielectric dispersivity, providing evidence that both the transmembrane potential and the pore density are strongly influenced by the choice of modeling used. We note the crucial role played by the dielectric properties of the membrane that can greatly impact on the poration of the cell. This can partly explain the selective action reported on cancerous cells in mixed populations, if one considers that tumor cells may present different dielectric responses. Moreover, these kinds of studies can be useful to determine the appropriate setting of nsPEF generators as well as for the design and optimization of new-generation devices.

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Devices used for biological experiments on cell cultures can present a low impedance. In this paper, a numerical and experimental characterization of a high-voltage, nanosecond-pulse, 10-Ω generator is proposed. The generator makes use of a combination of microstrip-line technology and laser-triggered photoconductive semiconductor switches that operate in the linear regime. A standard electroporation cuvette is used to load the generator. SPICE and finite-difference time-domain (FDTD) models of the whole setup (i.e., the generator and the cuvette) are developed. Numerical characterization is performed comparing SPICE analysis and FDTD simulations. Experimental characterization on a built prototype is carried out by means of a wideband frequency voltage sensor. A good level of consistency is obtained between the numerical and the experimental voltage intensities measured across the cuvette electrodes.

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Noise has already been shown to play a constructive role in neuronal processing and reliability, according to stochastic resonance (SR). Here another issue is addressed, concerning noise role in the detectability of an exogenous signal, here representing an electromagnetic (EM) field. A Hodgkin–Huxley like neuronal model describing a myelinated nerve fiber is proposed and validated, excited with a suprathreshold stimulation. EM field is introduced as an additive voltage input and its detectability in neuronal response is evaluated in terms of the output signal-to-noise ratio. Noise intensities maximizing spiking activity coherence with the exogenous EM signal are clearly shown, indicating a stochastic resonant behavior, strictly connected to the model frequency sensitivity. In this study SR exhibits a window of occurrence in the values of field frequency and intensity, which is a kind of effect long reported in bioelectromagnetic experimental studies. The spatial distribution of the modeled structure also allows to investigate possible effects on action potentials saltatory propagation, which results to be reliable and robust over the presence of an exogenous EM field and biological noise. The proposed approach can be seen as assessing biophysical bases of medical applications funded on electric and magnetic stimulation where the role of noise as a cooperative factor has recently gained growing attention.

High-Voltage Nanosecond Pulse Generator

In this paper, different customized systems for microwave permittivity measurements on liquid samples, based on reflectometric measurements, are presented and analyzed. Their performance is compared against the one deriving from the most widely adopted commercial measurement setup. The systems are designed with the aim of providing less expensive solutions without compromising measurement accuracy. The purpose of the first proposed solution is to replace the commercial measurement software exploiting a reformulation of the classical theory. Based on this alternative formulation, a “homemade” probe is built by properly modifying an N-type coaxial connector, thus providing a system requiring a lower quantity of liquid under test. Moreover, a different experimental approach which uses time-domain reflectometry (TDR) instrumentation is presented. Such solution is by far the least expensive, as it allows avoiding the use of costly instrumentation (such as a vector network analyzer). In order to metrologically characterize the proposed solutions, a series of repeated measurements is performed on a set of well-referenced liquids. After extracting the Cole–Cole parameters through each of the considered measurement methods, the resulting type A uncertainty is evaluated. Finally, comparison with literature data allows the estimation of measurement bias. The analysis evidences that custom solutions generally exhibit an accuracy comparable to the one of the commercial solution, with a slight degradation of performance for the TDR-based setup, which, however, compensates for this drawback with its appealing low cost.