Electrical properties of tissues from a microscopic model of confined electrolytes.
Phys Med Biol 2023;
68. [PMID:
37084738 DOI:
10.1088/1361-6560/accf5b]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Accepted: 04/21/2023] [Indexed: 04/23/2023]
Abstract
OBJECTIVE
In the presence of oscillatory electric fields, the motion of electrolyte ions in biological tissues is often limited by the confinement created by cell and organelle walls. This confinement induces the organization of the ions into dynamic double layers. This work determines the contribution of these double layers to the bulk conductivity and permittivity of tissues.
APPROACH
Tissues are modeled as repeated units of electrolyte regions separated by dielectric walls. Within the electrolyte regions, a coarse-grained model is used to describe the associated ionic charge distribution. The model emphasizes the role of the displacement current in
addition to the ionic current and enables the evaluation of macroscopic conductivities and permittivities.
MAIN RESULTS
We obtain analytical expressions for the bulk conductivity and permittivity as a function of the frequency of the oscillatory electric
field. These expressions explicitly include the geometric information of the repeated structure and the contribution of the dynamic double layers. The low-frequency limit of the conductivity expression yields a result predicted by the Debye permittivity
form. The model also provides a microscopic interpretation of the Maxwell-Wagner effect.
SIGNIFICANCE
The results obtained contribute to the interpretation of the macroscopic measurements of electrical properties of tissues in terms of their
microscopic structure. The model enables a critical assessment of the justification for the use of macroscopic models to analyze the transmission of electrical signals through tissues.
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