DNA constructions for nanomotors, cell delivery and crystallization

Yingmei Li, Purdue University


DNA nanotechnology is a rapidly developing researching area. Various stationary structures and nanomechanical devices have been created. The potential applications of DNA nanostructures include nanofabrications, biological sensors, responsive materials and bionanotechnology. My research interests are to develop new mechanism for DNA motors, combining antisense technology in cell delivery and gene silencing and rational design for three dimensional self-assembly of DNA crystals. We have designed a metastable left-handed DNA architecture, which has four domains of half turn of normal-right handed B-DNA. This DNA conformation can be transformed to a continuous right-handed double helix when the regular complementary strand is present. The advantage is that such strand displacement occurs without toehold. This strategy has been successfully applied to power a DNA motor, proved by gel electrophoresis and FRET. The application of DNA/RNA nanostructure in biosystem has a short history around ten years. We incorporated antisense DNA or siRNA into DNA nanostructures and delivered into cancer cells. Folate labeling can enhance the delivery efficiency, but doesn't seem to improve gene knockdown. siRNA with a tail showed a better gene silencing efficiency and longer effect. We also found some of the nanostructures were more toxic than simple duplex when combining with lipofectamine2000, and the toxicity was evaluated by cell viability assays. DNA crystals with rationally designed symmetry and cell parameters were obtained. 3-fold or 4-fold screw axis was from stacking of DX molecules with different sizes. Both crystals showed up with good shape, and X-ray diffraction of 4-fold crystal could go to 7-Å resolution, while 3-fold one had poor diffraction. Preliminary diffraction data processing agrees with our design, and some modifications of the design, such as changing the sticky end strength, elongating the motif, and increasing the symmetry order, didn’t improve the diffraction resolution.




Mao, Purdue University.

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