Synthesis and Internal Structure of Finite-Size DNA–Gold Nanoparticle Assemblies

Abstract

Spatially defined networks of 15 nm-sized DNA-functionalized gold nanoparticles (DNA–AuNPs) were studied using dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), as well as optical extinction spectroscopy (OES). We use a combination of these techniques with Monte Carlo simulations of pair-distance distribution function (PDDF) curves and generalized Mie theory simulations as well as in situ-transmission electron microscopy (in situ-TEM) to analyze the internal structure of the finite-size assemblies. The DLS data show that monodisperse, spherical networks with hydrodynamic radii of ca. 30 nm are found for reaction mixtures of complementarily functionalized DNA–AuNPs between 1:15 and 1:20. Different interparticle distances within these assemblies are identified and quantified. By controlling the network morphology through selection of the reaction mixture, center-shell geometries are obtained. The number of shell-AuNPs surrounding each center-AuNP is determined from the SAXS data and Monte Carlo simulations. This number is quantified to be ca. 10, with the exact number depending on the linking DNA double strand. The optical spectra of the networks are found to be consistent with the structural properties. The structural information gained here enables a quantitative description of optical and other physical properties, which is expected to prove useful for the construction and application of such systems, for example, in drug release, gene regulation, or external-stimuli-responsive materials.

The Structure of Gold-Nanoparticle Networks Cross-Linked by Di- and Multifunctional RAFT Oligomers

“…35,37,45 The disappearance of the structure factor peak for samples 2a NC −3e NC , with inserted styrene monomer, therefore probably reflects the dispersity of the particle linker as well as its conformational degrees of freedom, since polystyrene is much less rigid compared with DNA.…”

Non-Cross-Linking Aggregation of DNA-Carrying Polymer Micelles Triggered by Duplex Formation

“…Addition of salts to an aqueous dispersion of charged hydrophobic colloids induces their spontaneous aggregation, which can be quantitatively described by the DLVO theory . When the surfaces of colloids are modified with biomolecules such as proteins, their colloidal behaviors are highly complicated, mainly due to the fact that intrinsic properties of the surface-bound molecules greatly affect the colloidal stability. − For example, DNA-functionalized particles, including microbeads, − gold nanoparticles, − silver nanoparticles, − and quantum dots − are readily aggregated by using DNA duplex formation in a cross-linking manner. Both turbidity changes and solution color changes induced by colloidal aggregation allow the naked-eye detection of DNA duplex formation. − Therefore, such particles can be used as a powerful tool in medical diagnosis.…”

Stimulus-Responsive Planet–Satellite Nanostructures as Colloidal Actuators: Reversible Contraction and Expansion of the Planet–Satellite Distance

“…These differences can be best understood by comparison of the small-angle data in real space: The PDDFs in Figure reveal a second peak at larger r values together with a peak centered at around 8 nm. The peak at approximately 8 nm contains contributions from the individual planet and satellite particles, where the planet particles dominate however due to their size (see for comparison also the PDDF for individual planet particles in Figure ); the peak at larger r contains contributions from planet–satellite distances. , Hence, information about the planet–satellite (and satellite–satellite) distances in these nanostructures are contained in these PDDFs, and we had recently described how this information can be extracted together with the average number of satellite particles per planet . We performed such analysis for SAXS measurements in which the temperature was repeatedly switched between 20 and 40 °C (Figure B).…”