Intracortical polyimide electrodes with a bioresorbable coating.

Area of Science:

• Biomaterials Engineering
• Neuroscience
• Medical Devices

Background:

• Polyimide electrodes are used for neural recording but can cause tissue damage.
• Mechanical mismatch between implants and brain tissue can lead to inflammation and signal loss.
• Bioresorbable coatings can modify implant properties and reduce tissue response.

Purpose of the Study:

• To develop and evaluate a bioresorbable saccharose coating for polyimide electrodes.
• To assess the impact of the coating on intracortical insertion forces.
• To monitor the long-term tissue response to coated electrodes using electrochemical impedance spectroscopy and histology.

Main Methods:

• Polyimide electrodes were coated with molten saccharose.
• Electrodes were implanted into the cortex of Wistar rats.
• Insertion forces were recorded during implantation.
• Electrochemical impedance spectroscopy was performed up to 13 weeks post-implantation.
• Equivalent circuit modeling was used to analyze impedance spectra.
• Histology was performed at 7, 45, and 201 days post-implantation.

Main Results:

• Saccharose coating successfully stiffened electrodes for easier insertion.
• Electrochemical impedance spectroscopy revealed an acute inflammatory response peaking at 2 weeks and resolving by 4 weeks.
• Histology confirmed the highest tissue reaction at 45 days, consistent with impedance data.
• Adequate signal-to-noise ratio was achieved for multiunit activity recording.

Conclusions:

• Saccharose coating is a viable strategy to improve polyimide electrode insertion and reduce initial mechanical mismatch.
• The coating effectively modulates the foreign body response, leading to reduced inflammation over time.
• Coated electrodes show promise for long-term stable neural recording with minimal tissue reaction.