Small bioactive molecules as dual functional co-dopants for conducting polymers

Area of Science:

• Biomaterials Science
• Neuroscience
• Polymer Chemistry

Background:

• Biological responses to neural interfacing electrodes can be modulated by biofunctionalizing conducting polymer (CP) coatings.
• Small bioactive molecules with anti-inflammatory properties offer a potential strategy for modulating these responses.

Purpose of the Study:

• To investigate the use of small bioactive molecules, specifically dexamethasone phosphate (DP) and valproic acid (VA), as dopants for poly(ethylenedioxythiophene) (PEDOT) conducting polymers.
• To explore the impact of DP and VA, individually and as a codoped system, on the material properties and bioactivity of PEDOT coatings.
• To compare these novel doped systems with conventional p-toluenesulfonate (pTS) doped PEDOT.

Main Methods:

• Electropolymerization of PEDOT using anionic DP and VA as dopants, both individually and in combination (codoping).
• Characterization of electrical and mechanical properties of the doped PEDOT coatings.
• Evaluation of the anti-inflammatory bioactivity using a whole-blood model, measuring levels of the pro-inflammatory cytokine TNF-α.

Main Results:

• DP and VA doping reduced the electrical properties of PEDOT compared to PEDOT/pTS.
• Codoping with both DP and VA significantly improved PEDOT electroactivity and attenuated mechanical friability compared to individual doping.
• All DP and VA doped CP coatings demonstrated significant reduction in TNF-α levels in a whole-blood inflammation model, retaining bioactivity.

Conclusions:

• Small charged bioactive molecules can effectively act as dopants for conducting polymers.
• Codoping with ions of varied size and doping affinity offers a strategy to overcome limitations associated with large, bulky biomolecular dopants.
• This approach holds promise for developing improved neural interfacing electrodes with enhanced biocompatibility and reduced inflammatory responses.