In this paper, we employ two peroxidases (horseradish peroxidase, HRP and cytochrome c peroxidase, CcP) to demonstrate their ability to retain their redox and biological functions after their immobilisation on mesoporous TiO(2) and SnO(2) electrodes. We will also demonstrate the use of HRP immobilised on the metal oxide electrodes for the development of reagentless optical and electrochemical biosensors for the detection of hydrogen peroxide (H(2)O(2)) with low detection limit of 0.04 and 1 microM, respectively.