Tuning Ratios, Densities, and Supramolecular Spacing in Bifunctional DNA‐Modified Gold Nanoparticles

Abstract

Methods for combining multiple functions into well-defined nanomaterials are still lacking, despite their need in nanomedicine and within the broader field of nanotechnology. Here several strategies for controlling the amount and the ratio of combinations of labeled DNA on 13-nm gold nanoparticles using self-assembly of thiolated DNA and/or DNA-directed assembly are explored. It is found that the self-assembly of mixtures of fluorescently labeled DNA can lead to a higher amount of labeled DNA per particle; however, the ratio of fluorophores on the nanoparticles differs greatly from that in the self-assembly solution. In contrast, when fluorescently labeled DNA are hybridized to DNA-modified gold nanoparticles, the fluorophore ratio on the nanoparticles is much closer to their ratio in solution. The use of bifunctional DNA-doublers in self-assembly and DNA-directed assembly is also explored to increase the complexity of these materials and control their composition. Finally, tuning the distance between the labels from 2.9 to 5.4 nm was achieved using different hybridized DNA clamp complexes. Fluorescent results suggest that assembling these clamps on nanoparticle surfaces may be possible, although the resulting label spacing could not be quantified.

Triplet‐State‐Mediated Super‐Resolution Imaging of Fluorophore‐Labeled Gold Nanorods

“…19 However, if cooperative binding occurs, such that binding of one type of DNA (unlabeled single stranded or labeled double stranded) leads to increased local binding of that same type, then we might expect to observe asymmetric binding in our frequency histograms 30. 31 A second possible reason for the apparent binding asymmetry is that the fluorescently labeled ligands on one end of the nanorod were excited more efficiently than the ligands on the other end; this would lead to a higher frequency of TAMRA emission events at one end. One possible explanation for this theory is that a slight out‐of plane tilt could lead to asymmetric ligand excitation; however, later examples will refute this theory.…”

Interaction of colloidal nanoparticles with their local environment: the (ionic) nanoenvironment around nanoparticles is different from bulk and determines the physico-chemical properties of the nanoparticles

“…Thus, in order to determine the ion concentration profile around NPs, ion-sensitive fluorophores (and the reference fluorophores) need to be immobilized at different distances R to the NP surface. This can be conveniently done by using molecular spacers such as DNA [143][144][145] or PEG [55][56][57]. In order to obtain spacers providing controlled distances R, the trick lies in saturating the NP surface.…”

Directed Assembly of Nucleic Acid-Based Polymeric Nanoparticles from Molecular Tetravalent Cores

“…The size and distributions of these novel nanomaterials can be modulated by tuning the SMDH concentration, the assembly time/temperature, and the NaCl concentration, demonstrating a systematic strategy for constructing nucleic acid nanoparticles from purely organic building blocks without the need for a template or scaffold. 31–34 These nucleic acid-based polymeric nanoparticles exhibit enhanced cellular internalization and can be functionalized to have highly enhanced resistance against DNase I compared to the SMDH 4 building blocks. Together with the ability to transform these particles into SNAs, while still maintaining active surface groups for further functionalization, these novel materials have the potential to become useful in areas spanning both diagnostics and therapeutics.…”