Vitamin C-reduced graphene oxide improves the performance and stability of multimodal neural microelectrodes

Brendan B Murphy; Nicholas V Apollo; Placid Unegbu; Tessa Posey; Nancy Rodriguez-Perez; Quincy Hendricks; Francesca Cimino; Andrew G Richardson; Flavia Vitale

doi:10.1016/j.isci.2022.104652

Vitamin C-reduced graphene oxide improves the performance and stability of multimodal neural microelectrodes

iScience. 2022 Jun 22;25(7):104652. doi: 10.1016/j.isci.2022.104652. eCollection 2022 Jul 15.

Authors

Brendan B Murphy^{1

2

3}, Nicholas V Apollo^{1

2

3}, Placid Unegbu^{1

2

3}, Tessa Posey⁴, Nancy Rodriguez-Perez⁵, Quincy Hendricks^{1

2}, Francesca Cimino^{1

2}, Andrew G Richardson^{2

6}, Flavia Vitale^{1

2

3

7}

Affiliations

¹ Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
² Center for Neuroengineering and Therapeutics, University of Pennsylvania, Philadelphia, PA 19104, USA.
³ Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA 19104, USA.
⁴ Department of Biomedical Engineering, University of South Carolina, Columbia, SC 29206, USA.
⁵ School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85281, USA.
⁶ Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA 19104, USA.
⁷ Department of Physical Medicine and Rehabilitation, University of Pennsylvania, Philadelphia, PA 19146, USA.

Abstract

Nanocarbons are often employed as coatings for neural electrodes to enhance surface area. However, processing and integrating them into microfabrication flows requires complex and harmful chemical and heating conditions. This article presents a safe, scalable, cost-effective method to produce reduced graphene oxide (rGO) coatings using vitamin C (VC) as the reducing agent. We spray coat GO + VC mixtures onto target substrates, and then heat samples for 15 min at 150°C. The resulting rGO films have conductivities of ∼44 S cm^-1, and are easily integrated into an ad hoc microfabrication flow. The rGO/Au microelectrodes show ∼8x lower impedance and ∼400x higher capacitance than bare Au, resulting in significantly enhanced charge storage and injection capacity. We subsequently use rGO/Au arrays to detect dopamine in vitro, and to map cortical activity intraoperatively over rat whisker barrel cortex, demonstrating that conductive VC-rGO coatings improve the performance and stability of multimodal microelectrodes for different applications.

Keywords: Biodevices; Bioelectronics; Nanomaterials.