Injectable Bioelectrode Hydrogel with Changeable Degradability

Efficient transmission of biological signals can be achieved by the use of implantable bioelectrodes. Metal-based bioelectrodes are associated with tissue inflammation, inefficient signal transduction, and uncontrolled stability in living biological systems.

Researchers from the Gwangju Institute of Science and Technology (GIST), Korea have developed a graphene-based conductive hydrogel as a bioelectrode material to address the challenges associated with traditional metal-based bioelectrodes. This conductive hydrogel is injectable, skin compatible, easy to use, and exhibits excellent signal transmission. In addition, their controllable degradability can enable the development of high-performance and convenient bioelectrodes with advanced applications. Image Credit: Prof. Jae Young Lee from GIST, Korea

Researchers from Korea have developed a new type of hydrogel to address this challenge. This graphene-based conductive hydrogel (ICH) was developed as an advanced implantable bioelectrode.

This ICH can be used as an advanced implantable bioelectrode because it is injectable, clearance life degradability control, and shows good signal transmission.

Electronic devices known as implantable bioelectrodes transmit signals to and from living biological systems to monitor or stimulate biological activity. Such devices can be constructed using a variety of materials and processes.

The right material for performance and biocompatibility is important because of its close contact with living tissue. Conductive hydrogels have attracted a lot of attention because of their superior flexibility, compatibility and interaction ability.

Convenience of use and performance in biological systems is hampered by the lack of injection and decomposition capabilities in conventional conductive hydrogels.

Against this backdrop, Korean researchers have now developed graphene-based conductive hydrogels with injectable and tunable degradation, advancing the design and development of state-of-the-art bioelectrodes.

This study was led by Professor Jae Young Lee from Gwangju Institute of Science and Technology (GIST) and published on 24 Februaryth2023, in the journal Small.

Traditional implanted electrodes often cause several problems, such as large incisions for implantation and uncontrollable body stability. In contrast, conductive hydrogel materials allow minimally invasive delivery and control over the functional in vivo lifespan of bioelectrodes and are thus highly desirable.

Jae Young Lee, Study Leader and Professor, Gwangju Institute of Science and Technology

To produce injectable conductive hydrogels (ICHs), scientists use thiol-modified reduced graphene oxide (F-rGO) as the conductive element due to its large surface area and outstanding electrical and mechanical characteristics.

To facilitate the preparation of stable and hydrolyzable ICH, they chose prepolymerized dimaleimide (PEG-2Mal)- and diaacrylate-functionalized polyethylene glycol (PEG-2Ac). This prepolymerizing agent then undergoes the reaction of thiolenes with poly(ethylene glycol)-tetrathiol (PEG-4SH) and F-rGO.

DICH produced using PEG-2Ac can decompose, whereas SICH prepared with PEG-2Mal is stable. Scientists observed that the innovative ICH is superior to many current ICHs by attaching efficiently to the network and recording the best readings.

Under laboratory conditions (in a controlled environment), SICH remained stable for one month, whereas DICH showed progressive deterioration from day three.

Upon introduction to mouse skin, DICH disappeared within three days of administration, while SICH persisted in its original form for seven days. Both ICHs were found to be skin compatible, and they exhibited regulated degradability.

The team assessed the efficacy of the ICH in catching life electromyographic signals in mouse muscle and skin. SICH and DICH exhibit excellent signal quality and outperform conventional metal electrodes.

SICH recordings can be monitored for three weeks, in contrast to DICH signals which are completely undetectable at five days. These results imply that the SICH electrode is suitable for extended signal monitoring, whereas the DICH electrode is suitable for temporary use that does not require surgical removal.

Prof. Lee concluded, “The new graphene-based ICH electrode we developed combines features such as high signal sensitivity, simplicity of use, minimal invasion and tunable degradability. Taken together, these properties could aid in the development of advanced bioelectronics and functional implantable bioelectrodes for various medical conditions, such as neuromuscular diseases and neurological disorders.

Journal Reference

Park, J., et al. (2023) Injection of Conductive Hydrogels with Modifiable Degradability as a New Implantable Bioelectrode. Small. doi:10.1002/small.202300250.


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