Self-Assembled DNA-Inorganic Nanoparticle Structures - DNA Nanotechnology: From Structure to Function - page 195

impressive chiral plasmonic optical property that promisingly enlarges the research
area in plasmonics. Yan achieved stacked ring, single spiral, double spiral, and
nested spiral 3-D nanopatterns of AuNPs through different ways for the edge tiles
association in their DNA tile system [ 54 ]. The distribution of tube types was suc-
cessfully tuned by changing the size of AuNPs used. In another work, Yan utilized
DNA origami cage as scaffold for precise placement of gold nanoparticles into 3-D
nanostructures [ 55 ]. The outer dimensions of the cage are 41 nm 30 nm 20 nm,
and the inner cavity dimensions are 10 nm 10 nm 21 nm (Fig. 9.7 c). The
inner cavity provides space for encapsulation of nanoparticles. Rational design
of DNA probes located at different position on the inside and outside cage
surface, which are complimentary to the nanoparticles capping, allows for 3-D NPs
arrangement.
As compared to the 3-D DNA-directed discrete gold nanostructures mentioned
above, 3-D AuNPs superlattices, which instead have polyvalent DNA nanocon-
jugates as building blocks, are also of great significance in the research area of
DNA-based rationally designed materials. Mirkin [ 7 ] reported the first example of
AuNPs macroscopic materials by assembling two sets of polyvalent DNA-modified
AuNPs with a linking DNA duplex, which contains single-strand DNA respectively
complimentary to the AuNP-bound DNA at the two ends. The assembled products
were macroscopic amorphous aggregates but not crystal lattices. Later, Mirkin
group developed this strategy involving DNA polyvalent functionalization to con-
struct highly ordered macroscopic materials [ 56 ]. They achieved face-centered cubic
gold crystal structure that results from the assembly of single-component particle
with one sequence DNA linker and body-centered cubic gold crystal structure
that arises from the assembly of binary-component particle with two different
DNA linkers. And it was pointed that the crystallization maximizing the DNA
duplex formation dominates the crystallography symmetry. Almost at the same time,
Gang prepared body-centered cubic gold crystal lattice by assembling two sets of
DNA-capped AuNPs via base-pair recognition between the outer complimentary
sequences of DNA capping [ 57 ]. Soon they reported external DNA linker-assisted
assembly of BCC crystalline ordered phase of polyvalent gold nanoconjugates
[ 58 ]. The sequence and resulting flexibility of DNA linker were found to play
an important role in the formation of well-defined crystalline structures from
both of their works. Most of these programmable crystalline lattices are statistic
without versatile manipulation. Gang added a loop sequence to the DNA linker
in the assembly of nanoparticles into 3-D superlattices [ 59 ], thus gave rise to the
structural reversibility through hybridization or dehybridization of the loop strand
with external strand. The reconfiguration of nanostructures allows for dynamic
tunability of the optical property as a result. Except for gold nanosphere acting
as building blocks, anisotropic as well as hollow nanoparticles were also reported
in the programmable assembly of well-defined crystalline superlattices [ 60 , 61 ].
Whereas, the edge- and size-selective functionalization of the anisotropic nanoscale
building blocks is fundamental in the rational assembly of anisotropic nanoparticles
into discrete nanoarchitectures, (Fig. 9.7 d) but remains a great challenge.