Titration curves showing the increase in the electrocatalytic guanine oxidation current when the pH is raised at redox polymer film-coated ITO electrodes. From left to right, 1), PVIPAA-Ru(bpy-COOMe)2Cl; 2), PVPPAA-Ru(bpy)2Cl; 3), PVPPAA-Ru(bpy-Me)2Cl; 4), PVIPAA-Ru(bpy)2Cl; 5), PVPPAA-Ru(bpy-OMe)2Cl; and 6), PVIPAA-Ru(bpy-OMe)2Cl.