DNA Origami Nanostructures - DNA Nanotechnology: From Structure to Function - page 208

8-methoxypsoralen modifications into DNA origami structures [ 37 ], which could
improve the thermal stability of the origami with 30 ı C after photo cross-linking.
To show a representative application of the heat resistance, they performed higher-
temperature self-assembly of the cross-linked origami structures, which markedly
increased the product yield.
Seidel and Liedl et al. measured mechanical properties of 3D DNA origami
using magnetic tweezers (Fig. 10.3 e) [ 38 ]. They directly measured the bending
and torsional rigidities of four- and six-helix bundles assembled by this technique.
Compared to duplex DNA, they found the bending rigidities to be greatly increased
while the torsional rigidities were only moderately augmented. They also presented
a simple mechanical model that can nearly quantitatively describe the observed
behavior. It is expected that this study will be helpful for the application of DNA
origami as noise suppressor in force-based single-molecule experiments.
Some other properties of DNA origami nanostructures were studied by Yan's
group. Firstly, they studied the hybridization behavior of ssDNA target on DNA
origami and found that it was most efficient when probes were located on the edge
rather than in the middle of the DNA origami [ 39 ]. To increase the hybridization
efficiency in the middle, a strategy could be removing the neighboring staples of
the target. They also developed a V-shaped structure [ 39 , 40 ], which contains a
pair of half probes, for the best AFM signal of target binding. Secondly, they
studied the stability of DNA origami in cell lysate [ 41 ]. Several DNA origami
nanostructures of differing shape, size, and probes were used, and their interaction
with lysate obtained from various normal and cancerous cell lines was investigated.
The DNA origami in cell lysate was separated and recovered with agarose gel
and subsequently examined with AFM, TEM, and hybridization studies. It was
found that DNA origami nanostructures were stable in cell lysate and can be easily
separated from lysate mixtures. Thirdly, the effect of DNA hairpin loops on the
twist of planar DNA origami tiles was also systematically studied [ 42 ]. A series
of dumbbell-shaped DNA loops were selectively displayed on the surface of DNA
origami to study the repulsive interactions among the neighboring dumbbell loops
and between the loops and the DNA origami tile on the influence of structural
features of the underlying tiles. They suggested that through the systematic design
and organization of various numbers of dumbbell loops on both surfaces of the tile,
a nearly planar rectangular origami tile could be achieved.

10.5 Scaling Up: Make It Bigger

Although DNA origami technique shows superior ability in preparing arbitrary
nanostructures with high complexity, the size of DNA origami is strictly dependent
on the length of long scaffold strand. In most reported cases, 7-kb M13 strand
was used, and therefore, for 2D DNA origami, its size should be 7,000 nm 3 which
is still too small for possible practical applications. One simple way to solve this
problem is using longer scaffold strand. In a recent publication by Fan's group [ 43 ],