Two different flexible osmium functionalised polymers were investigated for their ability to efficiently "wire" pyranose oxidase when immobilised on graphite electrodes. The two Os-polymers differ in redox potential and the length of the side chains, where the Os2+/3+-functionalities are located. The performance of the redox polymers as mediators for the enzyme was tested with glucose. As well as analytical characteristics, the optimum operational conditions for the biosensor were investigated for both types of redox polymers: poly(I-vinylimidazole)12[osmium (4,4'-dimethyl-2,2'-bipyridyl)(2)Cl-2](2+/+) (osmium redox polymer I) and poly(vinylpyridine)-[osmium-(N,N'-methylated-2,2'-biimidalzole)(3)](2+/3+) complex (osmium redox polymer II). All results are given as a comparison of the two systems. (c) 2005 Elsevier B.V. All rights reserved.