Electron-conducting redox hydrogels: Design, characteristics and synthesis.

Redox hydrogels constitute the only electron-conducting phase in which water-soluble chemicals and biochemicals dissolve and diffuse. The combination of solubility and diffusion makes the electron-conducting gels permeable to water-soluble biochemicals and chemicals. The electron-conducting redox hydrogels serve to electrically connect the redox centers of enzymes to electrodes, enabling their use whenever leaching of electron-shuttling diffusional redox mediators must be avoided, which is the case in subcutaneously implanted biosensors for diabetes management and in miniature, potentially implantable, glucose-O2 biofuel cells. Because the hydrogels envelope the redox enzymes, they electrically wire the reaction centers to electrodes irrespective of spatial orientation and connect to electrode redox centers of multiple enzyme layers. Hence, the attained current densities of enzyme substrate electrooxidation or electroreduction are much higher than with enzyme monolayers packed onto electrode surfaces.