TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The enzyme comprises at least one oxidoreductase enzyme capable of oxidizing a substrate. The oxidoreductase enzyme is selected from oxidase, dehydrogenase and hydrogenase enzyme (preferably oxidase, especially glucose oxidase).    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The mediator comprises a compound containing osmium. The electrolyte comprises lithium perchlorate.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Ink: The ink further comprises at least one of a mediator, a cross-linking agent, a substrate, and a monomer of an electrically conductive polymer and an electrolyte. The ink exists in a water soluble first form and a water insoluble second form, where the first and second form comprises a nano-scale conducting material, a binding agent, an aqueous buffer and an enzyme. The conductive ink comprises: a single walled carboxylic acid functionalized carbon nanotube; 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride; N-hydroxy succinimide ester; polyethyleneimine; an aqueous buffer; and glucose oxidase. Preferred Components: The nano-scale conducting material comprises a carbon nanotube. The carbon nanotube is selected from a single-wall carbon nanotube and a multi-wall carbon nanotube. The carbon nanotube contains a functional group (preferably carboxylic acid group). The binding agent is polyethyleneimine. The mediator is selected from hydroquinone, ferrocene, ferricyanide, flavin adenine dinucleotide, nicotinamide adenine dinucleotide, tetrathiafulvalene and an azine compound. The cross linking agent is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxy succinimide ester and/or lysozyme.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The electrically conductive polymer is selected from polypyrrole (PPY), polyaniline (PANI), polyacetylene (PAC), poly(p-phenylene vinylene) (PPV) which is electrochemically, enzymatically, or chemically polymerized. EXAMPLE - No suitable example given.