<p>DNA nanotechnology has provided programming construction of
various nanostructures at nanometer-level precision over the last three
decades. DNA self-assembly is usually implemented by annealing process in bulk
solution. In recent several years, a new method thrives by fabricating
two-dimensional (2D) nanostructures on solid surfaces. My researches mainly
focus on this field, surface-assisted DNA assembly driven by base stacking. I
have developed methods to fabricate DNA 2D networks via isothermal assembly on
mica surfaces. I have further explored the applications to realize quasicrystal
fabrication and nanoparticles (NPs) patterning.</p><p><br></p>
<p>In this dissertation, I have developed a strategy to assemble DNA
structures with 1 or 2 pair(s) of blunt ends. Such weak interactions cannot
hold DNA motifs together in solution. However, with DNA-surface attractions,
DNA motifs can assemble into large nanostructures on solid surface. Further
studies reveal that the DNA-surface attractions can be controlled by the
variety and concentration of cation in the bulk solution. Moreover, DNA
nanostructures can be fabricated at very low motif concentrations, at which
traditional solution assembly cannot render large nanostructures. Finally,
assembly time course is also studied to reveal a superfast process for
surface-assisted method compared with solution assembly.</p><p><br></p>
<p>Based on this approach, I have extended my research scope from 1D to 2D
structures assembled from various DNA motifs. In my studies, I have
successfully realized conformational change regulated by DNA-surface
interaction and steric effect. By introduction of DNA duplex “bridges” and
unpaired nucleotide (nt) spacers, we can control the flexibility/rigidity of
DNA nanomotifs, which helps to fabricate more delicate dodecagonal quasicrystals.
The key point is to design the length of spacers. For 6-point-star motif, a
rigid structure is required so that only 1-nt spacers are added. On the other
hand, 3-nt spacers are incorporated to enable an inter-branch angle change from
60° to 90° for a more flexible 5-point-star motif. By tuning the ratio of 5 and
6 -point-star motifs in solution, we can obtain 2D networks from snub square
tiling, dodecagonal tiling, a
mixture of dodecagonal tiling and triangular tiling, and triangular tiling.</p><p><br></p>
Finally,
I have explored the
applications of my assembly method for patterning NPs. Tetragonal and hexagonal
DNA 2D networks have been fabricated on mica surfaces and served as templates.
Then modify the surfaces with positively-charged “glues”, <i>e.g.</i> poly-L-lysine (PLL) or Ni<sup>2+</sup>. After that, various
NPs have been patterned into designated lattices, including individual DNA
nanomotifs, gold NPs (AuNPs), proteins, and silica complexes. Observed NP
lattices and fast Fourier Transform (FFT) patterns have demonstrated the DNA
networks’ patterning effect on NPs.
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7985189 |
| Date | 10 June 2019 |
| Creators | Longfei Liu (6581096) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/DNA_SELF-ASSEMBLY_DRIVEN_BY_BASE_STACKING/7985189 |
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