Biomedical Engineering Reference
In-Depth Information
The aforementioned higher-order self-assembly strategies vary a lot in design
principles. However, they all share a common and basic feature, that is, the
connections between adjacent DNA origami units are based on sequence-dependent
base pairing. While looking into Rothemund's original paper, it is not difficult to
find that he met a big problem, that is, the unanticipated random aggregations
caused by blunt-end stacking. Surprisingly, in one of his recent papers [
56
], they
showed a revolutionary design of programming the geometric arrangement of blunt-
end stacking interactions for enabling higher-order molecular recognitions between
DNA origami units (Fig.
10.4
g). They showed that both binary codes and shape
complementarity can serve as a basis for such stacking bonds. Orthogonal stacking
bonds were used to connect five distinct DNA origami units. It is believed that
this strategy may not only create diverse bonds for DNA origami higher-order self-
assembly but also shed light on new molecular recognition in systems beyond DNA
nanostructures.
10.6
Marriage with Top-Down
As mentioned above, DNA origami technique has succeeded in building exquisite
artificial nano-shapes with an amazing resolution of 6 nm. This ability has already
been utilized to organize nano-objects, for example, proteins [
57
-
59
], enzymes [
60
],
metal nanoparticles [
61
-
63
], polymers [
64
], and carbon nanotubes [
65
,
66
], into
arrays precisely. However, on the other hand, when DNA origami itself binds to
surface, these DNA big tiles only generate randomly dispersed patterns without any
organization. Therefore, in order to fully harness the potential of DNA origami as a
universal building block for nanodevice, it is also important to control the position
and orientation of the origami itself on solid supports.
An ideal solution to this problem is to combine bottom-up DNA origami with
top-down fabrications. The first success in this direction is the aforementioned
Kuzyk's dielectrophoresis trapping method [
32
], in which they showed a single
DNA origami smiley or rectangle could be trapped between two nanoelectrode, and
this technique has also been used to measure the conductivity of DNA origami.
However, it looks that the trapped DNA origami deformed severely and new
effective approaches are critically needed.
Towards this goal, Soh and Yan et al. tested the immobilization of DNA
origami on gold surfaces pre-functionalized with a carboxylic acid terminated
self-assembled monolayer [
67
]. The carboxylic acid groups on gold surface could
concentrate and chelate Mg
2C
ions and are thereby helpful for the absorption of
negatively charged DNA origami. Importantly, DNA origami could not be absorbed
on SiO
2
surface without gold coating. Based on this selective immobilization
technique, they succeeded in the delivery of individual DNA origami structures to
70-nm-diameter gold patterns which were fabricated by electron beam lithography
(EBL). In another work reported by Lieberman's group [
68
], it seems also possible
to use positively charged APTES patterns, although the authors only tested small
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