Developing sensory layers as combination of S-layer proteins, aptamers and fluorescence dyes

In recent years detection of pharmaceuticals in drinking water and food becomes increasing relevance. Nevertheless, most recently used methods are complex and time consuming. Thus, new solutions are required allowing a fast and their reliable detection of pharmaceuticals.

Therefore we are developing sensory layers which are able to specifically detect small amounts of pharmaceuticals. This sensory device will consist of surface(S)-layer proteins, aptamers and fluorescence dyes.
S-layer proteins are structural proteins found in numerous bacteria and archaea. They have the ability to self assembly in aqueous solutions and on surfaces building highly ordered paracrystalline structures. On the surface of such a layer different functional groups are available which can be modified without the loss of its paracrystalline structure. Hence S-layer proteins are useful binding blocks for the defined arrangement of aptamers and fluorescence on an area of a few nanometers. Thereby aptamers serve as receptor for specific analytes and two fluorescence dyes allowing a FRET a signal transducer system.

In first experiments we coupled the model aptamer, Anti-thrombin-aptamer, on S-layer proteins and proved its functionality after being linked to the protein. Furthermore we modified S-layer proteins with a FRET pair containing a green and red fluorescence dye and succeed to detect a FRET between those S-layer linked fluorescence dyes.

In subsequent work we will assemble the components, aptamers and fluorescence dyes, on the S layer proteins. The aptamer will bind the specific analyte. It is supposed that the binding will affect the fluorescence dyes and disturb FRET due to their close proximity to each other. As a result a sensory layer is created which uses the high specifity of aptamers in combination with the sensitivity of fluorescence dyes, thus enabling the easy and reliable detection of analytes by an optical signal.