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Published on: February 24, 2012
Electrical stimulation causes rapid changes in electrode impedance of cell-covered electrodes
Carrie Newbold1, Rachael Richardson, Rodney Millard
1The HEARing CRC, Carlton, Australia. cnewbold@hearingcrc.org
Journal of Neural Engineering
|May 17, 2011
Summary
Electrical stimulation temporarily reduces electrode impedance by altering cell adhesion and cover. This in vitro model shows impedance changes are linked to current amplitude and cell layer porosity, aiding understanding of electrode-tissue interfaces.
Area of Science:
- Biomedical Engineering
- Electrophysiology
- Cellular Biology
Background:
- Electrode impedance changes after electrical stimulation were observed in animal and clinical studies.
- An in vitro model of the electrode-tissue interface was previously developed to study impedance changes due to cell and protein accumulation.
Purpose of the Study:
- To investigate the effects of charge-balanced biphasic current pulse trains on electrode impedance and cell cover in vitro.
- To establish a relationship between current amplitude, cell cover, and impedance changes.
- To understand the transient nature of impedance changes and their underlying mechanisms.
Main Methods:
- Utilized an established in vitro model of the electrode-tissue interface.
- Applied charge-balanced biphasic current pulse trains to electrodes.
- Measured changes in total impedance (Z(t)) and access resistance (R(a)).
- Quantified cell cover over electrodes and assessed cell adhesion post-stimulation.
Main Results:
- A significant and rapid decrease in total impedance and access resistance was observed immediately after electrical stimulation.
- The magnitude of impedance reduction correlated linearly with cell cover, dependent on current amplitude.
- Impedance changes were transient, returning to baseline levels within hours.
- Electrical stimulation caused a temporary loss of cells from the electrode surface, indicating altered cell adhesion.
- In vitro findings on impedance changes were consistent with in vivo observations.
Conclusions:
- Electrical stimulation transiently reduces electrode impedance in vitro, primarily due to changes in cell adhesion and layer porosity.
- The in vitro model successfully mimics observed in vivo impedance changes, providing insights into electrode-tissue interface dynamics.
- Stimulation parameters, specifically current amplitude, directly influence the degree of impedance reduction and cell cover alteration.
