Evaluation of osmium(II) complexes as mediators accessible for biosensors

The evaluation of Os(II) complexes as mediators accessible for biosensors was examined according to the determinations of the redox potentials of Os(II) complexes and the second-order rate constants of the reactions as shown in Eqs. (1) and (2). The mixed ligand(1)GOxred+2Os(III)→ks(g)GOxox+2Os(II)+2H+(GOx: glucose oxidase)(2)HRPox+2Os(II)+2H+→ks(h)HRPred+2Os(III)(HRP: horseradish peroxidase) xes of Os(II) were synthesized and the redox potentials of Os(III/II) complexes could be lowered by the use of 4,4′-dimethyl-2,2′-bipyridine, imidazole and chloride ion as ligands. The second-order rate constants of the reactions as shown in Eqs. (1) and (2) were greater than that for ferrocenecarboxylic acid (FcCOOH) as a mediator. It is consequently concluded that the mixed ligand complexes of Os(II) can be more efficient mediators than FcCOOH for the fabrication of glucose and hydrogen peroxide sensors.