The ability of self-assembly and forming defined nanostructures enables the use of S-layer proteins as building blocks in a biomolecular construction kit for the generation of a universal nanobiotechnological matrix. By using the matrix as a nano pinboard for further components or just the nanostructure itself, a great variety of applications in modular nanobiotechnology, biomimetics, bioanalytics and medical diagnostics are imaginable.

Focusing on the repetitive features of S-layer proteins to form a well defined nano lattice, the use as filtration units become reasonable. So-called isoporous S-layer ultrafiltration membranes (SUM) combine the advantages of a constant lattice with a well-defined pore size and the presence of functional groups in defined positions and orientations which are a common problem of current ultrafiltration membranes.

A current topic in S-layer research is the design of more sensitive and improved optical and electrochemical sensors. One example is the luminescence lifetime based oxygen sensor. The key benefits of using S-layer proteins for this type of sensor are the imparted anti-fouling properties and the good biocompatibility. This is especially valuable for sensing applications in complex biological fluids or implantable sensors.

The self-assembly and immobilization properties of S-layer fusion proteins also open new innovative perspectives in clinical applications like immune therapy, blood purification and drug targeting. The genetic fusion of an allergen to SbsC S-layer proteins from Geobacillus stearothermophilus combine reduced allergenicity with immunomodulatory capacity. These qualities make them to an ideal allergen carrier/adjuvant in specific immunotherapy, which is the only causative treatment for type I allergy.

In conclusion, S-layer proteins are one of the most innovative and promising discoveries for combining biology with engineering in the new field of nanobiotechnology.

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Impact on the Parts Registry

With our approach in the field of functional S-layer proteins we made it easy for future iGEM teams to create compact, well defined nanobiotechnological surfaces with chosen characteristics and to realize their own projects in a cell-free and biosafe way.

We provided two different fully BioBrick-compatible S-layer genes to the partsregistry (BBa_K525301 and BBa_K525401) which cover the lattice geometries oblique and square, so future iGEM-teams are able to choose the one they like to use for their application. Because of the Freiburg assembly standard it is easy to create fusion proteins with the S-layer self-assembly domain on the one side and a functional domain on the other side.

Take a look at our practical guide to do it yourself nanobiotechnology to plan and realize your project with our S-layer proteins.

NAD+ detection


The reviewed molecular beacon based NAD+ bioassay can be applied to biochemical and biomedical studies. Accordingly, it can be utilized to detect NAD+/NADH-dependent enzymatic processes. The low limit of detection, its reliability and manageability provides a practical alternative to present colorimetric, fluorometric, chemiluminescent, electrochemical or mass spectrometric methods detecting NAD+ or NADH. In context of clinical applications and therapeutics the NAD+ bioassay can be useful to monitor cellular NAD+ levels during treatments of tissues or cell cultures for identification of drug targets, for instance. It may also be applied in the field of diagnostics. Finally, the principle of the proposed NAD+ bioassay can be used for cell-free optical biosensors by taking molecular beacons either immobilized on the sensor surface or being present in the reaction medium.

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Impact on the Parts Registry

With our provided NAD+-dependent DNA ligase from E. coli (BBa_K525710) in the combination with a molecular beacon, we made it possible for future iGEM teams to detect and measure any NAD+ producing reaction. As shown in the results the detection is highly sensitive and selective.

By fusing your NAD+ producing enzymes to our provided S-layer proteins (BBa_K525301 and BBa_K525401), it is possible to combine these fusion protein with our provided S-layer fused DNA ligase (BBa_K525005 and BBa_K525006) to create a nanobiotechnological surface and to establish a biosensor with close proximity of the detecting and the indicating part.