Self-Assembled DNA-Inorganic Nanoparticle Structures - DNA Nanotechnology: From Structure to Function - page 191

of the Tollens reaction: that is, one aldehyde sugar molecule can reduce two Ag C
ions to Ag 0 . These Ag clusters could then act as nucleation sites for further Ag
deposition under mild reductive conditions. Tethering of the sugar functional groups
to DNA offers stabilization of the synthesized AgNCs, and the DNA strands could
serve as addressable points for further sequence-specific DNA hybridization. TEM
imaging and energy-dispersive X-ray spectroscopy further confirmed the presence
of Ag on the DNA scaffold (Fig. 9.6 b). They [ 46 ] further succeeded in assembling
AuNRs together with AuNPs onto a DNA origami scaffold in a predetermined
orientation. The principle for functionalizing AuNRs is similar to the AuNPs via
the interaction of Au-S bond. They obtained a series of structures consisting of
AuNRs. The first AuNR was attached onto one of the arms of the triangular DNA
origami structure, and the second AuNR was immobilized onto another arm to form
a relative angle ranging from zero angle (side by side arrangement) to 60 angle,
90 angle, and 180 angle (end-to-end arrangement). Each AuNR dimer exhibits
distinct resonance peak shift in the extinction spectra which is reasonably agreed
with the predicted result. This work opened new avenues to characterize the effect
of interparticle distance and orientation-dependent photonic interactions between
AuNRs and other nanophotonic elements (Fig. 9.6 c). Winfree [ 47 ] reported another
highlight work that used DNA origami to arrange two crossover single carbon
nanotubes to fabricate a field-effect transistor. They assembled a rectangular origami
template that displays two lines of single-stranded DNA “hooks” in a cross pattern
with 6-nm resolution. The perpendicular lines of hooks serve as sequence-specific
binding sites for two types of nanotubes, each functionalized noncovalently with a
different DNA linker molecule. The hook-binding domain of each linker is protected
to ensure efficient hybridization. When origami templates and DNA-functionalized
nanotubes are mixed, strand displacement-mediated deprotection and subsequent
selective binding align the nanotubes into cross junctions (Fig. 9.6 d). The devices
exhibited stable field-effect transistor-like behavior. It is a milestone work in the
application of DNA origami self-assembly. In 2012, DNA origami was also used for
pattering streptavidin-functionalized QDs reported by Ko et al. [ 48 ]. They choose
the specific affinity of streptavidin-functionalized QDs to biotinylated sites on DNA
origami as a model system because the streptavidin-biotin interaction is strong,
generally applicable, and well studied (Fig. 9.6 e).
Fig. 9.5 (continued) of AuNPs with different sizes. ( c ) “DNA slit” structure and introduction
of AuNPs into the DNA slit. AFM images of AuNP-attached DNA slits, in which AuNPs were
introduced onto the mica surface. ( d ) Process for assembling 2-D nanoparticle arrays (Part ( a )
reprinted with permission from Ref. [ 42 ]. Copyright 2008 American Chemical Society. Part ( b )
reprinted with permission from Ref. [ 13 ]. Copyright 2010 American Chemical Society. Part ( c )
reproduced from Ref. [ 43 ] with permission of The Royal Society of Chemistry. Part ( d ) reprinted
with permission from Macmillan Publishers Ltd: Ref. [ 44 ], copyright 2010)