We unveil experimental evidence that put into question the widely held notion concerning the impact of nanoparticles on the bioelectrocatalytic parameters of enzymatic electrodes. Comparative studies of the bioelectrocatalytic properties of fungal bilirubin oxidase from Myrothecium verrucaria adsorbed on gold electrodes, modified with gold nanoparticles of different diameters, clearly indicate that neither the direct electron transfer rate (standard heterogeneous electron transfer rate constants were calculated to be 31±9 s(-1)) nor the biocatalytic activity of the adsorbed enzyme (bioelectrocatalytic constants were calculated to be 34±11 s(-1)) depends on the size of the nanoparticles, which had diameters close to or larger than those of the enzyme molecules.
Keywords: bilirubin oxidase; bioelectrocatalysis; direct electron transfer; gold nanoparticle.