Biofunctional conducting polymers: synthetic advances, challenges, and perspectives towards their use in implantable bioelectronic devices

Abstract

Conducting polymers (CPs) are organic semiconductors that have gained popularity in more recent years as components of bioelectronic devices designed to electrically communicate with biological environments. Synergy between the material and biological tissue, both on a structural and functional level, is paramount for the proper performance of an implantable biomedical device. As such, significant progress has been made on understanding the fundamental impact of the molecular and macro structure of CPs on their functional properties such as conductivity and charge mobility. At the same time, the development of a variety of synthetic approaches has yielded a library of CPs with improved mechanical and electronic properties. Specifically, chemical biofunctionalization of CP films has significantly decreased the foreign body response, the main contributor to device failure. Therefore, this review covers the advances and challenges made in the chemical biofunctionalization of CP films for potential implantable devices. This is achieved by covalently attaching the biocompatible or biofunctional group to the CP backbone via a reactive functional group to create a material with physical and electronic properties that better matches biological tissue. A perspective is presented that this synthetic chemistry approach to biofunctionalization is valuable for the integration of CPs into commercial implantable bioelectronic devices.

Guide to Leveraging Conducting Polymers and Hydrogels for Direct Current Stimulation

“…All these CPs have been extensively used in biomedical applications for bioelectrical measurements, electrical stimulation, drug delivery, and as bioactuators and biosensors. [ 23–27 ] Particularly, the use of PEDOT as a coating for stimulation electrodes has been at the center stage of research in the last decade due to the high electrochemical stability and three‐dimensional structure of this polymer, which allows the charge in the form of ions to be stored within the polymeric matrix to be released later through electrostatic interaction with the electrolyte and the charged polymer chains in a pseudo‐capacitive manner. [ 19,28–30 ]…”

“…All these CPs have been extensively used in biomedical applications for bioelectrical measurements, electrical stimulation, drug delivery, and as bioactuators and biosensors. [23][24][25][26][27] Particularly, the use of PEDOT as a coating for stimulation electrodes has been at the center stage of research in the last decade due to the high electrochemical stability and three-dimensional structure of this polymer, The tunable electrical properties of conducting polymers (CPs), their biocompatibility, fabrication versatility, and cost-efficiency make them an ideal coating material for stimulation electrodes in biomedical applications. Several biological processes like wound healing, neuronal regrowth, and cancer metastasis, which rely on constant electric fields, demand electrodes capable of delivering direct current stimulation (DCs) for long times without developing toxic electrochemical reactions.…”

A biocompatible and fully erodible conducting polymer enables implanted rechargeable Zn batteries

“… 18 Compared with the hydrolytically cleavable linkages at the polymer mainchain, side-chain engineering of ionizable and/or hydrolyzable carboxylic acid pendants concurrently allows for charge storage and modulation of dissolution kinetics without compromising electronic properties. 19 The electropolymerized film, eliminating the need for conductive additives, delivers a high capacity, outstanding rate, and cycling performance when coupled with a Zn anode. This battery demonstrates complete disappearance in vivo through a series of metabolic and hydrolytic reactions, and its biocompatibility is evidenced by live–dead cell imaging and histological analysis.…”

Phenylalanine-Assisted Conductivity Enhancement in PEDOT:PSS Films

“…To address the issue of biocompatibility, various work has been done by introducing biological materials into PEDOT:PSS or the PEDOT matrix itself. ,− Conducting polymers can either be functionalized with biological materials or these biological materials can be introduced as dopants into the conducting polymer matrix. Various bioderived materials such as dextran sulfate and xanthan gum have been used as PEDOT dopants, replacing PSS, which results in the formation of conductive biocompatible films.…”