Living Bioelectronics: Strategies for Developing an Effective Long‐Term Implant with Functional Neural Connections

Abstract

Existing bionic implants use metal electrodes, which have low charge transfer capacity and poor tissue integration. This limits their use in next‐generation, high resolution devices. Coating and other modification techniques have been explored to improve the performance of metal electrodes. While this has enabled increased charge transfer properties and integration of biologically responsive components, stable long term performance remains a significant challenge. This progress report provides a background on electrode modification techniques, exploring state‐of‐the art approaches to improving implantable electrodes. The new frontier of cell‐based electronics, is introduced detailing approaches that use tissue engineering principles applied to bionic devices. These living bioelectronic technologies aim to enable devices to grow into target tissues, creating direct neural connections. Ideally, this approach will create a paradigm shift in biomedical electrode design. Rather than relying on unwieldy metal electrodes and direct current injection, living bioelectronics will use cells embedded within devices to provide communication through synaptic connections. This report details the challenge of designing electrodes that can bridge the technology gap between conventional metal electrode interfaces and new living electrodes through considering electrical, chemical, physical and biological characteristics.

Stretchable Conductive Polymers and Composites Based on PEDOT and PEDOT:PSS

“…It is softer, thereby reducing the mechanical mismatch with biological tissues which can lead to scaring, nontoxic, conducting both electrons and ions, it has a lower impedance and a higher charge injection capacity than metals, and it can be chemically tuned to modulate the mechanical and electronic properties or to allow covalent attachment of biomolecules . PEDOT, PEDOT:PSS, and their stretchable derivatives have been extensively reported in bioelectronic applications (Figure ), for example, in electrophysiology, sensors and actuators for biomedical applications, ion pumps, organic electrochemical devices and transistors (OECTs) for biosensing, tissue engineering, mechanobiology, neural interfaces, and drug delivery …”

Electrodeposited PEDOT:Nafion Composite for Neural Recording and Stimulation

“…The functionalization of microelectrodes with conductive polymers (CPs) is a well‐known procedure to improve the electrical properties of metal surfaces and is typically achieved by means of electrochemical deposition . The highly porous morphology of CPs yields enhanced electroactive surface areas, thereby leading to a significant decrease in the electrochemical impedance.…”

Enzyme‐Free Detection of Glucose with a Hybrid Conductive Gel Electrode

“…We perform a single‐step electropolymerization procedure to assemble the three components, that is, the receptor (PBA), the reporting component (PEDOT:PSS), and the PAAm gel ( Figure a). Compared with other techniques for polymer deposition, electropolymerization gives the flexibility to form hybrid structures compatible with a variety of conducting substrates . This hybrid architecture ensures structural integrity as well as strong adherence to the substrate, promising for operational stability.…”