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Cyclospora cayetanensis: Portrait of an Intriguing and Enigmatic Protistan Parasite
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Annunziata Giangaspero, Robin B. Gasser
Electrorotation is a non-invasive technique, capable of detecting changes in the morphology and physicochemical properties of microorganisms. During electrorotation, particles are subjected to a uniform rotating electric field that makes the particles rotate. The induced rotation of the particle is a sensitive function of the particle's dielectric properties, namely, the conductivity and permeability of the organism's constituent components, that is, the wall (if present), the plasma membrane, and the cytoplasm. Electrorotation studies, which have been also studied for Giardia duodenalis, have demonstrated that the membrane conductivity of nonviable oo/cysts is significantly greater than that of viable ones [197,198]. This decrease in the internal conductivity of the oo/cysts means that there is a physical degradation of the membrane with loss of its ability to act as a barrier to passive ion flow [197,198]. Although this technique compares favorably with oocyst sporulation detection, neither technique can be considered completely reliable. The ideal method would correlate sporulation with infectivity using animal models. However, as said, the lack of animal models and in vitro cultivation methods to determine the infectivity of Cyclospora, means, at this stage, that oocyst sporulation remains the only indicator of viability.
An impedance flow cytometry with integrated dual microneedle for electrical properties characterization of single cell
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2023
Muhammad Asraf Mansor, Mohd Ridzuan Ahmad, Michal Petrů, Seyed Saeid Rahimian Koloor
Label-free analysis in the microfluidic single-cell impedance technique is widely utilized for early cancer detection, disease development prediction and therapeutic intervention suggestions. The label-free analysis technique is a significant study due to how it reflects cell phenotype, such as biophysical electrical or mechanical properties. It is label-free means that the cells are not changed by chemical reagents or by extensive handling [1]. This label-free method protects cells from adverse effects associated with label production and is helpful in a wide range of applications. Microfluidic impedance spectroscopy is one commonly employed label-free method that is capable to measure the electrical characteristics of cells. Electrokinetic techniques based on alternating current (AC), particularly electrorotation and/or dielectrophoresis, have been utilized in the past [2–4]. The AC electrokinetic approach is a powerful tool capable of extracting the electrical properties of the cell; however, they lack high throughput, even though recent approaches have improved this [5–7].
Toxicity assessment of biological suspensions using the dielectric impedance spectroscopy technique
Published in International Journal of Radiation Biology, 2018
S. Muñoz, J. L. Sebastián, P. Antoranz, J. P. García-Cambero, A. Sanchis-Otero
To obtain the complex permittivity (ε̃=ε-jσ/ωε0) of the embryo suspension ε̃sus, we have used Maxwell–Wagner formalism. The effective Clausius–Mossotti factor of a suspension with spherical particles of volume Vcell is given by (Gimsa and Wachner 1999; Sekine et al. 2005). P is the volume fraction of the particles and K=ε0Re(ε̃egw)Vcell. Therefore, we referred back to the cell values of Table 1 to determine the cell volume Vcell and parameter K. For the calculation of the complex polarizability α̃eff, we have followed the analytical procedure outlined in a previously published work (Sebastián et al. 2008). This procedure essentially consists in considering a complex effective dipole as the point dipole which, when immersed in the same dielectric medium as the original cell, produces the same dipolar electric field in magnitude and phase. For the shelled embryo cell model, we calculated the interface complex charge densities at the interfaces between different lossy layers (interior, yolk membrane, perivitelline and chorion) so that, in terms of electric field, the polarized particle is equivalent to these interface charge distributions placed in the egg-water medium. The effective polarizability is then given by i and ε̃i are the volume and the complex permittivity of each layer, respectively, and |Ẽ|i is the electric field distribution within layer i = 1, 2, 3, 4 (interior, yolk membrane, perivitelline and chorion) that is numerically calculated using the FE technique. Figure 2 shows the calculated real and imaginary parts of the polarizability of the four-shelled embryo model as a function of the frequency spectra. It is important to note that the process described above avoided the need to consider a simplified spherical equivalent homogenous model for the real embryo structure, and it could also serve to complement electrorotation (ER) experiments.