Bacterial surface layers (S-layers) as building blocks for nanocomposites

Nanoscaled materials comprised of organic and inorganic components are becoming more and more important in nanotechnology due to the diversity of applications. The use of self-assembling organic systems as part of such a hybrid material, serving as template for the fabrication of arrays of inorganic nanoparticles, is an attractive approach for the development of new materials. Especially the proteinaceous bacterial surface layers (S-layers) that envelop bacterial cells are attractive for fabricating and patterning of nanostructures. These proteins are composed of protein monomers with the ability to self-assemble into two-dimensional arrays. The regular distributed pores of these paracrystalline arrays work as binding sites for various metals and offer ideal structures for the formation of regular distributed metallic nanoclusters of a defined size (15). Such arrays are very attractive for technical applications ranging from the development of novel catalysts to biomedical applications, development of innovative filter materials, the programmed assembly of nanometre scale electronic devices, and optical industry (7, 9). Another approach is the embedding of S-layer proteins into ceramics thus producing metal binding functionalized nanocomposites (12).
Our current work focuses on the synthesis and characterization of different S-layer templated inorganic nanoclusters. Due to quantum size effects nanosized grains often exhibit changed physical and chemical properties in comparison to bulk material. We demonstrate the fabrication of catalytic active nanoparticles such as ZnO. The photocatalytic properties of ZnO-particles are interesting for their application as nanoscaled catalytic material, i.e. for the degradation of pharmaceutical residues that are released in environment.