Recombinant spider silk proteins self-assemble into β-sheet-rich nanofibrils in a nucleation-based mechanism controlled by phosphate ions in aqueous buffers , Such conditions are highly suitable for incorporation of functional bio-macromolecules such as DNA or enzymes in the self-assembled nanostructures.
We established DNA-spider silk conjugates, in which self-assembly properties of a recombinant spider silk protein and functional properties of short DNA strands were combined in one chemical entity. The spider silk moiety maintained its ability to self-assemble into nanofibrils which expose nucleic acid strands suitable for specific fibril labeling, e.g., with correspondingly DNA-modified gold nanoparticles . Moreover, dynamic DNA interaction at elevated temperatures enabled the fibrils, made of two or three different complementary DNA-silk conjugates to hierarchically self-organize into nano-ribbons and microscopic rafts . Sequence specific DNA hybridization was used in DNA-directed immobilization of respective DNA-spider silk hybrids on complementary modified surfaces. Soft lithography enabled addressing of the conjugates onto predestined spots, whereas addition of the unmodified protein and phosphate buffer triggered the protein nucleation and fibrils self-assembly resulting in nanofibril-based patterns with a submicrometer resolution . In the latest approach, we conjugated the spider silk protein with 15- or 29-bp long anti-thrombin DNA-aptamers. The DNA sequences specifically bind to exosite I and II of thrombin, respectively. The spider silk moiety did not disturbe the binding and enabled immobilization of the functional DNAs via nanofibril self-assembly on surfaces. The capacity of the modified surfaces to bind thrombin, i.e., to inhibit fibrin clotting was studied in situ in human serum .
This work was financially supported by Deutsche Forschungsgemeindschaft (DFG grant SFB 840 TP A8) as well as the European Union grand ETZ-EFRE 2014−2020, Freistaat Bayern − Tschechien, Project Nr. 123.
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 M. Humenik, A. Molina & T. Scheibel, Biomacromolecules, submitted
 Unpublished data