Biomedical Engineering Reference
In-Depth Information
and programmable step-by-step assembly controls. This proximity-based strategy
exactly mimicked an industrial assembly line, providing great promise to assemble
a highly complicated nanosystem with different DNA nanorobots programmed to
work cooperatively.
8.4
Emerging Nanomaterials for DNA-Guided Self-Assembly
The development of DNA-programmable functional nanophase materials has been
bottlenecked by the limited availability of suitable material building blocks, which
is seriously unbalanced with the very rich diversity of the materials world. So far,
gold nanoparticles have been the first choice as a model material to demonstrate
a self-assembly strategy. Apart from AuNPs, silver nanoparticles (AgNPs) are
probably the only other metal-based materials that have been employed in DNA-
directed self-assembly [
40
,
41
]. There is a clear need to introduce more materials
to this research field. The pursuits along this direction have recently achieved
some important progresses. Various DNA-conjugated nanomaterials other than
the gold nanoparticles have been obtained and verified to be effective for DNA-
programmable assembly, including carbon nanotubes, quantum dots, graphene,
platinum, and silver nanoparticles. The emergence of these materials will be able
to bring novel functions and applications to DNA-based nanophase materials.
8.4.1
Quantum Dots
Quantum dots are a special form of fluorescent semiconductor nanoparticles that
have found important applications in sensing and bioimaging as well as photonic
and optoelectronic materials. DNA conjugation of quantum dots has been attempted
by several research groups. For example, by forming a streptavidin coating on the
quantum dots, a biotinylated DNA could be easily attached through streptavidin-
biotin interaction [
42
,
43
]. Kelley et al. developed a more convenient strategy for
the preparation of DNA-conjugated quantum dots by direct nanoparticle synthesis
in the presence of a “diblock” DNA ligand [
40
,
44
] bearing a PS (phosphorothioate)
linkage domain for the surface anchoring of quantum dots [
45
].
Upon further development, the Kelley group was able to prepare stable
DNA-functionalized CdTe quantum dots bearing a specified number of DNA
ligands, based on which a valence-controllable assembly of various quantum
dot complexes was demonstrated (Fig.
8.8
)[
46
]. The DNA ligands used in this
experiment consisted of three structural domains of different functions: a quantum-
dot-binding domain containing phosphorothioate linkages that contributed to the
high affinity to the metal part of the chalcogenide quantum dot, a spacer containing
regular phosphodiester linkages, and a DNA-hybridization domain. The size and
the fluorescence emission of the quantum dot were related to the length and base
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