DNA-Based Nanoscale Self-Assembly

One of the crucial challenges in nanoscience is gaining control over the formation of the desired nanoscale structures. Such structural control provides access to the novel material functions. While many functional nanoscale blocks are inorganic, soft matter components, i.e. surfactants, macromolecules, polymers, and biopolymers, can play an important role in defining structures formed from those blocks via self-Assembly. In recent years DNA-based self-Assembly approaches emerged as powerful means for nanoscale fabrications: DNA can direct inter-particle binding, can be used as a scaffold for particle positioning and can regulate a structural self-Assembly. We review here the major areas of DNA-based nanoscale selfassembly, including systems formed purely from the DNA strands and structures formed by particles with the help of DNA. The methods for particles functionalized with DNA are elaborated. The assembly approaches that exploit DNA programmability for the creation of desired clusters, lattices and dynamically tunable systems are discussed

Quantum Efficiency Modification Of Organic Fluorophores Using Gold Nanoparticles On Dna Origami Scaffolds

We used DNA origami as a platform to coassemble a 20 nm gold nanoparticle (AuNP) and an organic fluorophore (TAMRA) and studied the distance-dependent plasmonic interactions between the particle and the dye using steady state fluorescence and lifetime measurements. Greater fluorescence quenching was found at smaller dye-particle distances, which was accompanied by an enhancement of the decay rate. We also fabricated 20 and 30 nm AuNP homodimers using DNA origami scaffolds and positioned a Cy3 fluorophore between the AuNPs in both assemblies. For each particle size, three different interparticle distances were investigated. Up to 50% enhancement of the Cy3 fluorescence quantum efficiency was observed for the dye between the 30 nm AuNPs. These results are in good agreement with the theoretical simulations. © 2013 American Chemical Society

Dna Directed Self-Assembly Of Anisotropic Plasmonic Nanostructures

Programmable positioning of one-dimensional (1D) gold nanorods (AuNRs) was achieved by DNA directed self-assembly. AuNR dimer structures with various predetermined inter-rod angles and relative distances were constructed with high efficiency. These discrete anisotropic metallic nanostructures exhibit unique plasmonic properties, as measured experimentally and simulated by the discrete dipole approximation method. © 2011 American Chemical Society

Selective transformations between nanoparticle superlattices via the reprogramming of DNA-mediated interactions

The rapid development of self-assembly approaches has enabled the creation of materials with desired organization of nanoscale components. However, achieving dynamic control, wherein the system can be transformed on demand into multiple entirely different states, is typically absent in atomic and molecular systems and has remained elusive in designed nanoparticle systems. Here, we demonstrate with in situ small-angle X-ray scattering that, by using DNA strands as inputs, the structure of a three-dimensional lattice of DNA-coated nanoparticles can be switched from an initial ‘mother’ phase into one of multiple ‘daughter’ phases. The introduction of different types of reprogramming DNA strands modifies the DNA shells of the nanoparticles within the superlattice, thereby shifting interparticle interactions to drive the transformation into a particular daughter phase. Moreover, we mapped quantitatively with free-energy calculations the selective reprogramming of interactions onto the observed daughter phases.by Yugang Zhang, Suchetan Pal, Babji Srinivasan, Thi Vo, Sanat Kumar and Oleg Gan

Construction of bi-functional inorganic–organic hybrid nanocomposites

Single system bi-functional inorganic–organic hybrid nanocomposites, PB@SiO<SUB>2</SUB>@BTC@Ln (PB = Prussian blue, BTC = benzene tricarboxylate; Ln = Tb(III)/Sm(III)) having a PB magnetic core and a luminescent lanthanide probe, show superparamagnetic behavior and significant enhancement in luminescence intensities

Stoichiometric control of DNA-grafted colloid self-assembly

There have been recent surges of interest in understanding the self-assembly of DNA-grafted colloids into different crystallographic lattices, namely CsCl, AlB2, Cr3Si, and Cs6C60. Conventional approaches view the number of grafted linkers and effective size of each colloid as the major governing design parameters. It is generally assumed that the mixed stoichiometries need to match those defined by the target structures in order to obtain the desired lattice. Thus, contributions from stoichiometry are considered secondary and its exact effects on lattice formation remains an open question. Theoretical extensions to the popular complementary contact model show that the equilibrium lattice structure can be tuned through direct control of stoichiometry. Our results are also validated through experimental observations of the equilibrium crystal morphologies at differing stoichiometric ratios. These findings strongly suggest that stoichiometry is a new handle that can be used to control DNA-grafted colloidal self-assembly.by Babji Srinivasan et al.by Babji Srinivasanby Babji Srinivasan et al.

Probing Aberrantly Glycosylated Mucin 1 in Breast Cancer Extracellular Vesicles

Aberrantly glycosylated mucin 1 is a critical prognostic biomarker in breast epithelial cancers. Hypoglycosylated mucin 1 coats the surface of the cancer cells, where O-glycans are predominantly linked via an N-acetylgalactosamine moiety (GalNAc). Cancer cell-derived extracellular vesicles (EVs) carry biomarkers from parent cancer cells to the recipient cells and, therefore, could potentially be leveraged for diagnostics and noninvasive disease monitoring. We devised a label-free approach for identifying glycoprotein mucin 1 overexpression on breast cancer EVs. While exploring a plethora of biochemical (enzyme-linked immunosorbent assay, flow cytometry, and SDS-PAGE) and label-free biophysical techniques (circular dichroism and infrared spectroscopy (IR)) along with multivariate analysis, we discovered that mucin 1 is significantly overexpressed in breast cancer EVs and aberrant glycosylation in mucin 1 could be critically addressed using IR and multivariate analysis targeting the GalNAc sugar. This approach emerges as a convenient and comprehensive method of distinguishing cancer EVs from normal samples and holds potential for nonintrusive breast cancer liquid biopsy screening