Novel biosensors based on aptamer functionalized bacterial surface layers (S-layers)

Bacterial surface layers (S-layers) are the outermost protein-layer of many bacterial cells and archaea. The ability of the proteins to self-assemble on interfaces and surfaces to two-dimensional paracrystalline arrays, as well as the possibility to use these arrays as template for the deposition of nanoparticles makes them attractive for many technical applications such as filter materials, catalytic surfaces, electronic devices, or sensory surfaces.

Here we present a new concept of biosensors based on the application of S-layers. These biosensors are composed of three compounds:

1) Bacterial surface layer; these proteins are used for the nano-structuring of surfaces such as SiO2-wafers or glass; they provide a huge amount of orientated functional groups that can be used for coupling of molecules to the surface, thus introducing a high level of functionality in a small device
2) Aptamers, working as receptors; aptamers are oligonucleotides that specifically bind chemical compounds via their three-dimensional structure; the aptamers are coupled to S-layers
3) Fluorophores for detection, coupled to S-layers; two fluorophores are used as donor/acceptor pair; appropriate excitation/emission spectra and closest proximity permit FRET; FRET is interrupted when the analyte is binding to the aptamers

Our project that started in April 2009 aims the development of biosensors specific for pharmaceuticals such as antibiotics in waters. These chemicals are frequently found in surface waters and have been designated as a new class of pollutants. The novel sensor systems may facilitate the easy detection of these low-concentrated compounds.