Nanostructured and biofunctionalized interfaces are of increasing importance in the development of DNA-and protein nanoarrays and as a research tool in biophysics and cell biology. A powerful and versatile top-down approach has been established which can open up new research avenues.

Carbon-containing nanofeatures are written at variable diameter by a focused electron beam on a poly(ethylene glycol) (PEG)-coated glass substrate. Proteins then physisorb to the nanofeatures rather than to the PEG surface.

Advantages of the strategy include unprecedented high contrast factors of patterned biomolecules, 1000-fold tuneable surface densities of biomolecules between different target sites, and the biological addressability of the immobilized proteins.

The alternative bottom-up strategy of nanofabrication can be pursued with self-assembling biomolecules of sophisticated structure.  One example are the planar protein lattices of bacterial S-layers that cover the cell wall of a myriad of bacteria. The atomic structure of an S-layer protein has been elucidated for the first time using X-ray crystallography and a model for the lattice is obtained in combination with cryo-EM and chemical cross-linking. The structure helps to understand the molecular determinants of self-assembly and paves the way for the rational engineering of functionalized bottom-up materials relevant in biomedicine.