Biosensor electrode mediators for regeneration of cofactors

A single use disposable electrode strip for attachment to the signal readout circuitry of a sensor system which measures ketone(s) in an aqueous sample, the strip comprising:

• a) an elongated support having a substantially flat, planar surface, adapted for releasable attachment to the readout circuitry;
• b) at least two conductors extending along the surface and comprising a first conductive element and a second conductive element for connection to the readout circuitry;
• c) a plurality of electrodes, at least one active electrode on the surface in contact with the first conductive element and a counter/reference electrode in contact with the second conductive element, wherein the active electrode comprises a conductive ink, the conductive ink comprising a conductive compound, ketone specific enzymes and a mediator compound, wherein the mediator compound consists of one of the two following formulae:
• where X and Y can independently be oxygen, sulphur, CR3R4, NR3, or NR3R4+ or the functional group CZ1Z2, where Z1 and Z2 are electron withdrawing groups;
• R1 and R2 can independently be a substituted or unsubstituted aromatic or heteroaromatic group;
• and R3 and R4 can independently be a hydrogen atom, a hydroxyl group or a substituted or unsubstituted alkyl, aryl, heteroaryl, amino, alkoxyl, or aryloxyl group ;
• and
• d) said active electrode and the reference/counter electrode being configured so that a small drop of the aqueous sample provides an electrical conduction path between the electrodes.