Rational design and applications of conducting polymer hydrogels as electrochemical biosensors

Conducting polymer hydrogels (CPHs) are conducting polymer-based materials that contain high water content and have physical properties, resembling the extracellular environment. Synergizing the advantages of both the organic conductors and hydrogels, CPHs emerged to be candidates for high performance biosensors by providing advantageous interfaces for electrochemical bio-electrodes. Examples include the following: (1) the interface between a biomaterial and an artificial inorganic electrode material; (2) the hybrid electronic interface between an ionic carrier and an electron charge carrier; and (3) the extension of the planar electrode surface to a three-dimensional (3D) porous surface. CPHs with rationally designed 3D nanostructures and molecular structures are advantageous for enhancing the biocompatibility of the electrode, improving enzyme immobilization, creating protective layers to control diffusion, and wiring the electron transference. This review presents a brief overview of the current state-of-the-art research in electrochemical biosensors based on CPHs and describes future directions.