Controlling Nerve Growth with an Electric Field Induced Indirectly in Transparent Conductive Substrate Materials

Area of Science:

• Biomaterials Science
• Neuroscience
• Electrochemistry

Background:

• Innovative neurostimulation therapies need advanced electrode materials, including poly(3,4-ethylenedioxythiophene) (PEDOT) and iridium oxide (IrO_x).
• Understanding how electrode electrochemistry influences nerve growth is crucial for developing effective therapies.

Purpose of the Study:

• To investigate how different conductive materials affect amphibian neuron growth under wireless electrical stimulation.
• To determine if induced electric dipoles in materials control neurite extension speed and direction.

Main Methods:

• Amphibian neurons were cultured on transparent films of various electronic and electronic-ionic conductors (gold, platinum, PEDOT-PSS, IrO_x, (Ir-Ti)O_x).
• A wireless dipole was induced in the materials via electrodes in the culture medium.
• Neurite growth on stimulated and unstimulated materials was monitored and analyzed.

Main Results:

• Neuronal growth was not correlated with surface texture or hydrophilicity on unstimulated materials.
• Electrical stimulation induced a dipole in all conductive materials, altering neuron growth patterns.
• Stimulation slowed and steered neurite growth on gold, but not platinum; growth on PEDOT-PSS resembled glass; IrO_x and (Ir-Ti)O_x showed faster, random growth.

Conclusions:

• Electrochemical changes induced in conductive materials by electrical stimulation selectively control nerve growth speed and direction.
• The electric dipole induced in conductive materials plays a key role in controlling nerve growth.
• Findings will impact electrotherapies using wireless stimulation of implanted material arrays, especially those requiring transparency.