Using nature´s genius for the functionalization of surfaces

Many useful physical and chemical methods have been developed to modify and functionalize surfaces of different materials. These techniques allow a broad variety of surface modifications ranging from nanostructuring, implanting ions over hydrophilization and hydrophobization to immobilization of functional molecules. Nevertheless, for some applications also biology offers interesting alternatives. Examples therefore are so called surface layer (S-layer) proteins. These self-assembling proteins form nanostructured lattices with different symmetries, provide regular arranged pores with defined size and possess different kinds of regular arranged functional groups. One of their intrinsic properties is to provide a physiological environment and to stabilize coupled biofunctional molecules. Additionally, S-layers from isolates recovered from heavy metal contaminated environments have outstanding metal binding properties and are highly stable. By combining S-layers with a layer-by-layer technique different materials can be furnished with such coatings.
The produced biohybrid materials can be directly used as selective metal filter material or can be further modified. The S-layer coatings are perfect templates for the production and immobilization of regular arranged precious metal nanoparticles (e.g. Pd, Pt, Au) with defined sizes and for the immobilization of commercially available nanoparticles. Thusly immobilized TiO2 nanoparticles (P25) show a higher catalytic activity compared to same amounts of suspended TiO2 nanoparticles. Incidentally, formed reactive oxygen species do not affect the S-layer support. As S-layers in nature act as immobilization matrix for exoenzymes, these biohybrid materials can also be modified with dyes and biofunctional molecules. Combining these last two, a new generation of biosensors can be developed.
These four examples demonstrate the S-layer technology platform possess a high potential for materials science and industrial application.