Nanorobotics is a key area of application. We have made robust 2-state and 3-state sequence-dependent devices that change states by varied hybridization topology. Bipedal walkers, both clocked and autonomous have been built. We have constructed a molecular assembly line by combining a DNA origami layer with three 2-state devices, so that there are eight different states represented by their arrangements. We have demonstrated that all eight products (including the null product) can be built from this system.
A central goal of DNA nanotechnology is the self-assembly of periodic matter. We have constructed 2-dimensional DNA arrays with designed patterns from many different motifs. We have used DNA scaffolding to organize active DNA components. Active DNA components include DNAzymes and DNA nanomechanical devices; both are active when incorporated in 2D DNA lattices. We have used pairs of 2-state devices to capture a variety of different DNA targets.
One of the key aims of DNA-based materials research is to construct complex material patterns that can be reproduced. We have recently built such a system from bent TX molecules, which can reach 2 generations of replication. This system represents a first step in self-reproducing materials.
Recently, we have self-assembled a 3D crystalline array and have solved its crystal structure to 4 Å resolution, using unbiased crystallographic methods, shown below. More than ten other crystals have been designed following the same principles of sticky-ended cohesion. We can use crystals with two molecules in the crystallographic repeat to control the color of the crystals. Thus, structural DNA nanotechnology has fulfilled its initial goal of controlling the structure of DNA in three dimensions.
However, this is a milestone, not an end point. We must now advance to controlling the structure of other components as guests in DNA structures. We have achieved this object in 1D with amyloid fibrils, and in 1D, 2D and in 3D with gold nanoparticles. However, this is still a highly problematic enterprise, both synthetically and analytically. When control of non-DNA species can be achieved routinely, a new era in nanoscale control will await us.
This research has been supported by the NIGMS, NSF, ARO, ONR and DOE.