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Methods and Technologies

Recognition of the Pathogen

Every organism can be identified through specific structures on its surface. These structures may be used by pathogens like viruses, bacteria or fungi to attach and to infect their host. But also pathogens have specific surface structures that can be recognised by antibodies which normally leads to the elimination of the pathogen. The mechanism of this specific pathogen-host interaction will be used in the IZIB for the development of new sensor-actor-molecules.

At first such minimal structures are identified that allow the binding of the pathogen. Therefore, short peptides but also specific glycan structures can be used. With the arrangement of the binding structures on a scaffold, a "superantibody" will be generated that binds a specific pathogen. As the surface and antibody structures are extremely complex, extensive work in screening and synthesis is necessary to filter the appropriate minimal structures and to generate new artificial binders. Therefore, the potential of array technologies is used as well as cDNA-banks of pathogen genomes or antibody technologies.

Assembly on a Scaffold

For the design of a "superantibody" the development of scaffold structures where peptides or glycans can be bound is necessary. These scaffold structures must be balanced between flexibility and stability. Flexibility is essential to allow a manifold combination of multiple recognition domains. But the anchorage of recognition and signalling elements is only possible on stable matrices.

The basis of the used polymer scaffold are functional nonbiodegradable hydrogels. The flexible design of the scaffold systems and connecting elements leads to a highly variable platform that can be adapted to the recognition of different pathogens. Independent from the signal generation by downstream cascades the development of hydrogels that change their physical properties after binding of the analytes could lead to polymer scaffolds with integrated signal generation.

Generation of the Signal

The binding of the pathogen should induce a signal that could be recognised without any sophisticated technical instruments. Because of the size of pathogens and the frequency of binding events a simple signal cascade will not suffice - signal amplification is necessary.

This signal amplification can be achieved by usage of redox reactions that are generated after the binding event. A close contact between recognition structures and redox partners is ensured by coupling all molecules to the same polymer scaffold. This close contact guarantees the efficient transfer of chemical and electric signals. At the end of the redox reaction cascade a coupled enzyme reaction occurs that induces a visible colour reaction.

But it is also possible to bypass redox reactions by using chromophore systems. With the binding of the pathogen, changes in the direct chromophore environment are induced that change their absorption or emission spectrum. These changes could be directly recognised.