Biomedical applications for nucleic acid nanodevices

The highly specific interactions between DNA and RNA molecules have been utilized for the design and production of synthetic nanostructures, molecular switches and computational devices of increasing complexity. Autonomous diagnostic or therapeutic molecular devices are widely considered as the most promising applications for such assemblies. In this chapter, we discuss a variety of specific examples of synthetic DNA-based nanostructures with potential applications in the biomedical context. For instance, DNA molecules can be used to construct switchable molecular containers that may host therapeutic substances, and that can be opened upon recognition of specific molecular markers. In order to realize DNA-based drug delivery units, researchers have just started to study the interaction of such artificial DNA nanoconstructs with living cells. In a slightly different context, molecular switches made from nucleic acids have been demonstrated to function as sensitive biosensors in vivo. The informationprocessing capabilities of DNA-based reaction networks have been used to realize autonomous molecular computers that are able to evaluate "diagnostic rules," and there are even several examples for molecular computations implemented in vivo. In the future, the different aspects of DNA nanotechnology-construction, actuation, and computation-will be integrated into "nanomedical molecular robots” (or "nanotheranostic” devices) that are able to assess the disease state of a cell or tissue and trigger an appropriate therapeutic response.