Structural DNA nanotechnology has been advanced in an extraordinary pace in the past three decades and increasingly more complex structures have been demonstrated in the field based on the three major categories of structural units: DNA branched junction, DNA origami and SSTs. Overall, they have been developed as very handy tools in bioengineering applications.

One of the major challenges is to further scale up the self-assembly to build structures of expanded sizes and thus higher complexity. There are a number of ways to scale up DNA self-assembly, and the most direct one is to use a longer scaffold in origami approach; or in scaffold-free approach to increase the number of component species. However, it is not always convenient to obtain a long enough scaffold with satisfactory qual...[ Read more ]

Structural DNA nanotechnology has been advanced in an extraordinary pace in the past three decades and increasingly more complex structures have been demonstrated in the field based on the three major categories of structural units: DNA branched junction, DNA origami and SSTs. Overall, they have been developed as very handy tools in bioengineering applications.

One of the major challenges is to further scale up the self-assembly to build structures of expanded sizes and thus higher complexity. There are a number of ways to scale up DNA self-assembly, and the most direct one is to use a longer scaffold in origami approach; or in scaffold-free approach to increase the number of component species. However, it is not always convenient to obtain a long enough scaffold with satisfactory quality; and increasing number of component species can lead to an exponential drop in self-assembly yield. Hence, instead of one-pot self-assembly, higher-ordered structures can also be constructed in hierarchy from preformed structural units by either (i) sticky-end association, (ii) shape complementarity with blunt-end stacking, (iii) or the guidance from scaffold. Here, we demonstrated a new method, through the sticky-end association and toehold-mediated strand displacement, to form DNA nanostructures of higher order from the preformed SSTs.

For bioengineering applications, DNA nanostructures must meet several essential criteria: (i) programmability, each component tile can be independently included, removed or modified. (ii) simplicity, the assembly and disassembly must be rather simple and easy-to-implement. (iii) reversibility, the assembly and disassembly must be switchable and inducible. Therefore, SSTs can be a promising solution. Here, we demonstrated the ability to reconfigure the preformed DNA nanostructures, through the toehold-mediated strand displacement, into complex 2D and 3D conformations in a switchable and inducible manner. We also created complex DNA nanostructures for bioengineering applications: one 2D system to immobilize, target and image molecules of interest and one 3D system to detect, bind, protect and deliver specific molecules to their destinations.