DNA Origami as a Tool for Assembling Functional Biohybrid Nanomaterials

Recent advances in nanotechnology have given us a versatile toolbox of nanoscale objects with different functionalities. However, approaches for constructing stimuli-responsive and highly ordered macroscopic materials from these nanometer-sized components are still needed. The DNA origami technique enables the fabrication of custom-designed, well-defined, and highly addressable DNA-based structures and could therefore aid in the development of more advanced nanomaterials. In this doctoral thesis, the use of DNA origami in bottom-up nanofabrication was explored with the aim to construct functional biohybrid nanomaterials with high structural order. In publications I and II, the co-assembly of (negatively charged) DNA origami and cationic lipids was studied. The results demonstrated that DNA origami may serve as templates and nucleation sites for the formation of ordered lipid assemblies. The formed lipid matrix encapsulated the DNA origami, which also enhanced the DNA origami stability against endonuclease digestion. Moreover, the encapsulated DNA origami could be released from the lipid assemblies on demand by addition of competitive polyanions (publication I) or by illumination with long-wavelength UV light (publication II). In publication III, for one, highly ordered gold nanoparticle (AuNP) superlattices were assembled by employing electrostatic interactions between the cationic AuNPs and DNA origami. The ionic strength of the solution was used to control the assembly, and well-defined three-dimensional tetragonal superlattices were formed by gradually decreasing the salt concentration. Finally, in publication IV, pH-responsive and dynamically reconfigurable DNA-origami based lattices were constructed. Two pH-sensitive latches relying on Hoogsteen-type triplex formation were incorporated into the arms of the lattice-forming DNA origami unit, and thus the unit and the whole lattice could switch between an open and a closed state depending on the pH of the surrounding solution. The work shows that the library of stimuli-responsive elements initially developed for small DNA-based devices could be used to induce dynamicity also in considerably larger, hierarchical DNA origami lattices. In conclusion, the results demonstrate that DNA origami could function as a versatile self-assembling building block for advanced nanomaterials. The thesis highlights the potential of using DNA origami to fabricate highly ordered nanomaterials by electrostatic self-assembly and contributes to a broader understanding of such assemblies in bottom-up nanofabrication. In addition, the developed methods could aid in the engineering of more sophisticated stimuli-responsive hierarchical nanomaterials.