Biomedical Engineering Reference
In-Depth Information
for assembling 13 nm AuNPs rationally and reversibly into macroscopic
aggregates [76]. As shown in Fig. 11c, two non-complementary oligonu-
cleotides are separately coupled to gold particles by thiol adsorption. Subse-
quently, as a linker, a DNA duplex with “sticky ends” that are complemen-
tary to the two oligonucleotides on the particles was added to the mixture.
Then, the oligonucleotide-modified nanoparticles self-assemble into aggre-
gates (Fig. 11c). This process is reversible by thermal denaturation. Following
this initial work, the 3D self-assembly through complemented hybridization
of DNA has been used to aggregate other particles such as polystyrene latex
microspheres [77], micron-sized colloids [78, 79], and protein-encapsulated
iron oxide (ferritin) [80].
DNA templated protein arrays with predictable control at the nanometer
scale could lead to single-molecule detection in proteomics studies. Individ-
ual proteins placed at unique locations on the nanoarray could be detected
with single molecule imaging techniques such as recognition imaging, in
which specific antibodies are attached to the scanning probe cantilever.
Aptamers are DNA or RNA molecules that can bind other molecules such
as other nucleic acids, proteins, small organic compounds, and even entire or-
ganisms [81]. Yan et al. incorporated aptamer sequences into a rationally de-
signed DNA nanostructure, and successfully used the aptamer-bearing DNA
nanostructure for the directed assembly of thrombin protein arrays [82].
They succeed in the use of a TX DNA tile as the template to direct the assem-
bly of an aptamer and its subsequent organization of proteins into periodic
1D arrays. AFM images show that aptamers on the DNA array are mostly
occupied by thrombin. The results clearly demonstrated that the thrombin
binding aptamer still functions as the protein-binding moiety upon incor-
poration into a complex DNA nanostructure. In similar works [83, 84], the
ability to use self-assembled DNA nanostructures to precisely control the
spatial location of both streptavidin protein molecules and their nanogold
conjugates has also been demonstrated.
Furthermore, by constructing a family of DNA tiles known as four-by-four
DNA tiles, a precise control of periodic spacing between individual protein
molecules was successfully demonstrated on two types of DNA nanoassem-
blies, the 2D nanogrid and the 1D nanotrack [85].
3.3
DNA Device
The DNA strand stacking is not only available to build supramolecular struc-
tures, it is also able to drive nanoscale movements. The first DNA nanoscale
device is a simple example that drives a molecular device by changing the con-
centration of a small molecule [86]. This device consists of two DX molecules
connected by a shaft with a special sequence that could be converted from the
normal right-handed B-DNA to the left-handed Z-DNA. The transition can
