Electrically insulating proteins can be made redox conducting through incorporation of a high density of electron relaying redox centers. Electrons diffuse in the resulting redox conductors by self-exchange between identical and electron transfer between different relaying centers. When the self-exchange rate of the relays and their density are high, the flux of electrons through a 1-mu-m-thick film of a three-dimensional macromolecular network can match or exceed the rate of supply of electrons to or from the ensemble of enzyme molecules covalently bound to it. The network now molecularly "wires" the enzyme molecules to the electrode, and the current measures the turnover of the "wired" enzyme molecules. When the enzyme turnover is substrate flux, i.e., concentration limited, the current increases with the concentration of the substrate. The resulting amperometric biosensors have current densities as high as 10(-3) A cm-2 and sensitivities reaching 1 A cm-2 M-1. Because currents as small as 10(-13) A are measurable with standard electrochemical instruments, the biosensors can be miniaturized to < 10-mu-m dimensions. A practical example of enzyme "wiring" involves (a) forming a macromolecular complex between glucose oxidase and a water-soluble 10(2)-kDa [Os(bpy)2Cl]+/2+-containing redox polyamine and (b) cross-linking the complex with a water-soluble diepoxide to form a hydrophilic, substrate and product permeable approximately 1-mu-m-thick redox epoxy film. In redox epoxy film based glucose sensors interference by electrooxidizable ascorbate, urate, and acetaminophen is avoided through their peroxidase-catalyzed preoxidation in an H2O2 generating surface layer. The novel microelectrodes have no leachable components.