Figure 13 Illustration of the method of layer-by-layer adsorption for constructing polyion-protein films.

Figure 14 shows an idealized structure of layer-by-layer films. In reality, nearest neighbor protein and polyion layers are probably more intimately mixed, as documented for films of linear polycations and polyanions [80], Most enzymes in these films retain high activity. Polyions used to make such films are shown in Figure 15. Metal oxide nanoparticles can also be used as the polyanion component.