Transcranial Electrical Stimulation and Recording of Brain Activity using Freestanding Plant‐Based Conducting Polymer Hydrogel Composites

Abstract

Transcranial electrical stimulation is a noninvasive neurostimulation technique with a wide range of therapeutic applications. However, current electrode materials are typically not optimized for this abiotic/biotic interface which requires high charge capacity, operational stability, and conformability. Here, a plant‐based composite electrode material based on the combination of aloe vera (AV) hydrogel and a conducting polymer (CP; poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate, PEDOT:PSS) is reported. This material system is fabricated into films and provides biocompatibility, conformability, and stability, while offering desirable electrical properties of the PEDOT:PSS. AVCP films are also molded onto the rough surface of the skull leading to a mechanically stable and robust interface. The in vivo efficacy of the AVCP films is verified to function as stimulating and recording electrodes by placing them on the skull of a rat and concomitantly inducing focal seizures and acquiring the evoked neural activity. AVCP films pave the way for high‐quality biological interfaces that are broadly applicable and can facilitate advances in closed‐loop responsive stimulation devices.

Responsive manipulation of neural circuit pathology by fully implantable, front-end multiplexed embedded neuroelectronics

“…In addition to these intracranial stimulation approaches, we tested the ability of the MTA device to modulate neural activity during transcranial electrical stimulation (TES). Because TES is applied to electrodes affixed to the surface of the rodent skull rather than implanted within the brain, higher voltages are required to combat attenuation by intervening tissue (8,11,27). MTA-delivered sinusoidal stimulation effectively and selectively entrained neural spiking, confirming the versatility of the MTA device for different neurostimulation applications (Fig.…”

“…For instance, closed-loop electrical stimulation significantly reduces seizures in rodents with epilepsy (7,8,11). Such experiments require tethering of rodents because the acquisition, processing, and stimulation of neural signals has to be performed by large external electronics, restricting the scalability, duration, and translation of such interventions.…”

Organic Bioelectronics: Using Highly Conjugated Polymers to Interface with Biomolecules, Cells, and Tissues in the Human Body

“…[ 328 ] PEDOT:PSS based electrodes have also been explored for transcranial electrical stimulation and monitoring, where the electrodes are placed onto the skull or scalp, rather than directly onto the brain. [ 234 ]…”

Soft Electronics Based on Stretchable and Conductive Nanocomposites for Biomedical Applications

“…(D,ii) Reproduced with permission. [ 133 ] Copyright 2019, Wiley‐VCH GmbH. (D,ii) Reproduced with permission.…”

“…[156] New enhancements immerged by generating conductive hydrogels. [25,133,[157][158][159] Overall there are three approaches (Figure 9Di) to implement conductivity in polymer biomaterials: implementing a conductive layer, incorporating conductive particles and growing conductive polymers within a polymeric scaffold. [132] Hydrogel composite materials allow a significant reduction in the Young's modulus at the neuron interface, which is currently not possible with any other conductive material.…”