Biomedical Engineering Reference
In-Depth Information
one significant question is missing: how to monitor the machinery activation and
function. Fortunately, this is one of the intrinsic advantages of DNA. For example,
DNA is very easy to be modified with luminescent group which can be measured
by photometer or to carry objects that can be imaged by microscopy. There are also
some molecules becoming detectable once interacting with specific DNA motif. All
these pave the way to pull the DNA nanomechanical models out of the dream and
turn them into the actually occurring devices.
Molecular devices made from DNA may be classified into several categories.
According to the type of stimuli that activates the DNA nanodevices, non-DNA
stimuli-driven devices and DNA strands-fueled devices are discriminated. The
former category involves those that can be triggered by environment variations to
switch from one conformation to another. This type of DNA nanodevices shows
high efficiency and reversibility and normally does not produce wastes during
working cycles. The latter category is induced by DNA fuel strands that specifically
bind to the triggering positions, initializing the motion of the devices. The DNA
strands-triggered nanomachines show high specificity and more motions but usually
generate DNA duplex wastes and have longer response time. If cataloged by ways
of mechanical motions or conformational transitions, DNA nanodevices can be
divided into switches, tweezers, rotaries, walkers, motors, etc. In this chapter, we
aim to introduce DNA nanodevices following the track of fueling mechanisms from
non-DNA stimuli to DNA fuel strands. Several applications will also be discussed.
Finally, we will highlight some challenges and prospective.
11.2
Different Structural Motifs of DNA
What makes machines come into being is the integration of the basic structural
elements that possess switchable or movable characteristics. In the case of DNA
nanomachines, different structural motifs utilizing mechanical properties and pro-
grammability of DNA provide diverse building blocks for various design strategies
[
17
](Fig.
11.1
).
Fig. 11.1
Different DNA structural elements. (
a
) Single-strand sticky end; (
b
) duplex; (
c
)hairpin;
(
d
) quadruplex; (
e
) crossover; (
f
)DNAzyme;(
g
) aptamer (Reprinted from Ref. [
17
]. Copyright
2010, with permission from Elsevier)
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