Into the Mirror World:
Balancing Self-Assembly with Nuclease Resistance
It is now possible to create fully-addressable nanostructures from hundreds of unique synthetic DNA strands. Such structures have great potential in biomedical applications, e.g. serving as biocompatible vehicles for targeted drug delivery. However, being made of natural D-DNA, these structures are easily degraded by nucleases, making it difficult for them to survive under most biological and biomedical conditions. L-DNA, the mirror image of D-DNA, has the opposite chirality and cannot be so degraded due to the inability of nucleases to recognize and attack the mirrored substrate, and therefore serves as a good candidate for replacement in such applications. Unfortunately, commercial L-DNA is currently much more expensive than D-DNA. Here we demonstrate a method for inexpensively creating L-DNA structures with controlled shapes: a repetitive L-DNA structure is constructed on top of an inexpensive, all-unique D-DNA layer that serves as a template. The structure was synthesized in three steps. First, the D-DNA template was formed, exposing handles for L-DNA attachment at defined locations. Next, odd and even rows of L-DNA were sequentially introduced and hybridized to the template and assembled into desired structures. Finally, the L-DNA structure can be extracted by enzymatic degradation of the D-DNA template, giving an economical method for the self-assembly of nuclease-resistant nanostructures.