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Vesicle biomechanics in a time-varying magnetic field.

Ye H, Curcuru A - BMC Biophys (2015)

Bottom Line: The densities of these charges were trivial at low frequency ranges, but significant at high frequency ranges.This work provides an analytical framework and insight into factors affecting cellular biomechanics under a time-varying magnetic field.Biological effects of clinical TMS are not likely to occur via alteration of the biomechanics of brain cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Loyola University Chicago, 1032 W. Sheridan Rd, Chicago, IL 60660 USA.

ABSTRACT

Background: Cells exhibit distortion when exposed to a strong electric field, suggesting that the field imposes control over cellular biomechanics. Closed pure lipid bilayer membranes (vesicles) have been widely used for the experimental and theoretical studies of cellular biomechanics under this electrodeformation. An alternative method used to generate an electric field is by electromagnetic induction with a time-varying magnetic field. References reporting the magnetic control of cellular mechanics have recently emerged. However, theoretical analysis of the cellular mechanics under a time-varying magnetic field is inadequate. We developed an analytical theory to investigate the biomechanics of a modeled vesicle under a time-varying magnetic field. Following previous publications and to simplify the calculation, this model treated the inner and suspending media as lossy dielectrics, the membrane thickness set at zero, and the electric resistance of the membrane assumed to be negligible. This work provided the first analytical solutions for the surface charges, electric field, radial pressure, overall translational forces, and rotational torques introduced on a vesicle by the time-varying magnetic field. Frequency responses of these measures were analyzed, particularly the frequency used clinically by transcranial magnetic stimulation (TMS).

Results: The induced surface charges interacted with the electric field to produce a biomechanical impact upon the vesicle. The distribution of the induced surface charges depended on the orientation of the coil and field frequency. The densities of these charges were trivial at low frequency ranges, but significant at high frequency ranges. The direction of the radial force on the vesicle was dependent on the conductivity ratio between the vesicle and the medium. At relatively low frequencies (<200 KHz), including the frequency used in TMS, the computed radial pressure and translational forces on the vesicle were both negligible.

Conclusions: This work provides an analytical framework and insight into factors affecting cellular biomechanics under a time-varying magnetic field. Biological effects of clinical TMS are not likely to occur via alteration of the biomechanics of brain cells.

No MeSH data available.


Related in: MedlinePlus

Frequency dependence of translational force. Absolute value of the amplitude of the net translational force was plotted. Notation and parameter values were the same as in Figure 2A. A. Maximal amplitude of translational force as a function of the field frequency in a linear plot (A1) and in a log plot (A2). B. Phase of the translational as a function of the field frequency. Phase lag was defined between the phases of the magnetic field and the translational force.
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Fig6: Frequency dependence of translational force. Absolute value of the amplitude of the net translational force was plotted. Notation and parameter values were the same as in Figure 2A. A. Maximal amplitude of translational force as a function of the field frequency in a linear plot (A1) and in a log plot (A2). B. Phase of the translational as a function of the field frequency. Phase lag was defined between the phases of the magnetic field and the translational force.

Mentions: Therefore, the forces generated by the interaction between the induced surface charges and the field could theoretically contributed to the translational movement of the cell. The force was dependent of both the frequency and conductivity ratios. Figure 6 illustrated the frequency dependency of the translation force. Higher field frequency was associated with larger translational force. However, these forces were quantitatively trivial to introduce vesicle movement. For TMS frequency of 10 KHz, the translational force was 1.1 × 10−16N. At 200 KHz, the translational force was 4.2 × 10−14N. A force of 10−9N to 10−5N is needed for cell migration to occur in the electric field [37].Figure 6


Vesicle biomechanics in a time-varying magnetic field.

Ye H, Curcuru A - BMC Biophys (2015)

Frequency dependence of translational force. Absolute value of the amplitude of the net translational force was plotted. Notation and parameter values were the same as in Figure 2A. A. Maximal amplitude of translational force as a function of the field frequency in a linear plot (A1) and in a log plot (A2). B. Phase of the translational as a function of the field frequency. Phase lag was defined between the phases of the magnetic field and the translational force.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4306248&req=5

Fig6: Frequency dependence of translational force. Absolute value of the amplitude of the net translational force was plotted. Notation and parameter values were the same as in Figure 2A. A. Maximal amplitude of translational force as a function of the field frequency in a linear plot (A1) and in a log plot (A2). B. Phase of the translational as a function of the field frequency. Phase lag was defined between the phases of the magnetic field and the translational force.
Mentions: Therefore, the forces generated by the interaction between the induced surface charges and the field could theoretically contributed to the translational movement of the cell. The force was dependent of both the frequency and conductivity ratios. Figure 6 illustrated the frequency dependency of the translation force. Higher field frequency was associated with larger translational force. However, these forces were quantitatively trivial to introduce vesicle movement. For TMS frequency of 10 KHz, the translational force was 1.1 × 10−16N. At 200 KHz, the translational force was 4.2 × 10−14N. A force of 10−9N to 10−5N is needed for cell migration to occur in the electric field [37].Figure 6

Bottom Line: The densities of these charges were trivial at low frequency ranges, but significant at high frequency ranges.This work provides an analytical framework and insight into factors affecting cellular biomechanics under a time-varying magnetic field.Biological effects of clinical TMS are not likely to occur via alteration of the biomechanics of brain cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Loyola University Chicago, 1032 W. Sheridan Rd, Chicago, IL 60660 USA.

ABSTRACT

Background: Cells exhibit distortion when exposed to a strong electric field, suggesting that the field imposes control over cellular biomechanics. Closed pure lipid bilayer membranes (vesicles) have been widely used for the experimental and theoretical studies of cellular biomechanics under this electrodeformation. An alternative method used to generate an electric field is by electromagnetic induction with a time-varying magnetic field. References reporting the magnetic control of cellular mechanics have recently emerged. However, theoretical analysis of the cellular mechanics under a time-varying magnetic field is inadequate. We developed an analytical theory to investigate the biomechanics of a modeled vesicle under a time-varying magnetic field. Following previous publications and to simplify the calculation, this model treated the inner and suspending media as lossy dielectrics, the membrane thickness set at zero, and the electric resistance of the membrane assumed to be negligible. This work provided the first analytical solutions for the surface charges, electric field, radial pressure, overall translational forces, and rotational torques introduced on a vesicle by the time-varying magnetic field. Frequency responses of these measures were analyzed, particularly the frequency used clinically by transcranial magnetic stimulation (TMS).

Results: The induced surface charges interacted with the electric field to produce a biomechanical impact upon the vesicle. The distribution of the induced surface charges depended on the orientation of the coil and field frequency. The densities of these charges were trivial at low frequency ranges, but significant at high frequency ranges. The direction of the radial force on the vesicle was dependent on the conductivity ratio between the vesicle and the medium. At relatively low frequencies (<200 KHz), including the frequency used in TMS, the computed radial pressure and translational forces on the vesicle were both negligible.

Conclusions: This work provides an analytical framework and insight into factors affecting cellular biomechanics under a time-varying magnetic field. Biological effects of clinical TMS are not likely to occur via alteration of the biomechanics of brain cells.

No MeSH data available.


Related in: MedlinePlus