Multilayer assembly of calf thymus DNA and poly(4-vinylpyridine) derivative bearing [Os(bpy)2Cl]2+: redox behavior within DNA film

Polyelectrolyte multilayer (PEM) films containing polycationic osmium (Os) bipyridyl (bpy) complex-attached poly(4-vinylpyridine) (PVP) derivative [Os(bpy)2Cl]2+-PVP (Os-PVP) and polyanionic calf thymus DNA (CT-DNA) on the surface of gold (Au) electrodes were prepared using a layer-by-layer self-assembly method, and their redox properties were studied. Os complex shows different redox behavior with CT-DNA film in comparison with other PEM film which is composed of ordinary polymers. A cyclic voltammetric study suggested that the outermost polyanionic DNA layer does not hinder the redox reaction of Os complex within the Os-PVP/CT-DNA multilayer film, which may be helpful to understand the electron transfer mechanism with the DNA film. For all the Os-complex-containing PEM layers studied, a diffusion-free electron transfer from the Os complex moieties in these films to the electrode surface was observed. An electrocatalytic oxidation of ascorbic acid (AA) by this DNA-containing PEM film-covered electrode was also proposed.