An in vitro model for investigating impedance changes with cell growth and electrical stimulation: implications for...

Area of Science:

• Biomedical Engineering
• Neuroscience
• Materials Science

Background:

• Electrode impedance increases post-implantation in neural prostheses, attributed to fibrous tissue encapsulation.
• Elevated impedance necessitates higher power for neural stimulation, impacting device efficacy.

Purpose of the Study:

• To develop and validate an in vitro model of the electrode-tissue interface.
• To investigate the relationship between cell coverage, cell type, and electrode impedance.
• To analyze the effects of electrical stimulation on electrode impedance in a controlled cellular environment.

Main Methods:

• Cultured three cell types (MDCK, fibroblasts, macrophages) on electrode surfaces.
• Measured electrode impedance under varying cell coverage.
• Applied charge-balanced biphasic electrical stimulation to cell-covered electrodes.

Main Results:

• Electrode impedance increased proportionally with the extent of cell coverage.
• Different cell types exhibited varying degrees of impedance increase, with MDCK cells causing the highest.
• Electrical stimulation induced transient impedance fluctuations, mirroring in vivo observations.

Conclusions:

• The in vitro model accurately replicates in vivo electrode impedance changes related to tissue coverage.
• Cellular coverage is a primary determinant of electrode impedance.
• This model provides a valuable tool for understanding mechanisms underlying neural prosthesis impedance.