Methods to Characterize the Oligonucleotide Functionalization of Quantum Dots

Amphiphilic and Biocompatible DNA Origami-Based Emulsion Formation and Nanopore Release for Anti-Melanogenesis Therapy

Programmable engineered DNA origami provides infinite possibilities for customizing nanostructures with controllable precision and configurable functionality. Here, a strategy for fabricating an amphiphilic triangular DNA origami with a central nanopore that integrates phase-stabilizing, porous-gated, and affinity-delivering effects is presented. By introducing the DNA origami as a single-component surfactant, the water-in-oil-in-water (W/O/W) emulsion is effectively stabilized with decreased interfacial tension. Microscopic observation validates the attachment of the DNA origami onto the water-in-oil and oil-in-water interfaces. Furthermore, fluorescence studies and molecular docking simulations indicate the binding interactions of DNA origami with arbutin and coumaric acid at docking sites within central nanopores. These central nanopores are functionalized as molecular gates and affinity-based scaffold for the zero-order release of arbutin and coumaric acid at a constant rate regardless of concentration gradient throughout the whole releasing period. In vivo zebrafish results illustrate the advantages of this zero-order release for anti-melanogenesis therapy over direct exposure or Fickian diffusion. The DNA origami-based W/O/W emulsion presents anti-melanogenic effects against UV-B exposure without cardiotoxicity or motor toxicity. These results demonstrate that this non-toxic amphiphilic triangular DNA origami is capable of solely stabilizing the W/O/W emulsion as well as serving as nanopore gates and affinity-based scaffold for constant release.

DNA-Mediated Self-Assembly and Metallization of Semiconductor Nanorods for the Fabrication of Nanoelectronic Interfaces

DNA nanostructures provide a powerful platform for the programmable assembly of nanomaterials. Here, this approach is extended to semiconductor nanorods that possess interesting electrical properties and could be utilized for the bottom-up fabrication of nanoelectronic building blocks. The assembly scheme is based on an efficient DNA functionalization of the nanorods. A complete coverage of the rod surface with DNA ensures a high colloidal stability while maintaining the rod size and shape. It furthermore supports the assembly of the nanorods at defined docking positions of a DNA origami platform with binding efficiencies of up to 90 % as well as the formation of nanorod dimers with defined relative orientations. By incorporating orthogonal binding sites for gold nanoparticles, defined metal-semiconductor heterostructures can be fabricated. Subsequent application of a seeded growth procedure onto the gold nanoparticles (AuNPs) allows for to establish a direct metal-semiconductor interface as a crucial basis for the integration of semiconductors in self-assembled nanoelectronic devices.

DNA-Assembled Plasmonic Waveguides for Nanoscale Light Propagation to a Fluorescent Nanodiamond

Plasmonic waveguides consisting of metal nanoparticle chains can localize and guide light well below the diffraction limit, but high propagation losses due to lithography-limited large interparticle spacing have impeded practical applications. Here, we demonstrate that DNA-origami-based self-assembly of monocrystalline gold nanoparticles allows the interparticle spacing to be decreased to ∼2 nm, thus reducing propagation losses to 0.8 dB per 50 nm at a deep subwavelength confinement of 62 nm (∼λ/10). We characterize the individual waveguides with nanometer-scale resolution by electron energy-loss spectroscopy. Light propagation toward a fluorescent nanodiamond is directly visualized by cathodoluminescence imaging spectroscopy on a single-device level, thereby realizing nanoscale light manipulation and energy conversion. Simulations suggest that longitudinal plasmon modes arising from the narrow gaps are responsible for the efficient waveguiding. With this scalable DNA origami approach, micrometer-long propagation lengths could be achieved, enabling applications in information technology, sensing, and quantum optics.

Tunable Fluorescence of a Semiconducting Polythiophene Positioned on DNA Origami

A novel approach for the integration of π-conjugated polymers (CPs) into DNA-based nanostructures is presented. Using the controlled Kumada catalyst-transfer polycondensation, well-defined thiophene-based polymers with controllable molecular weight, specific end groups, and water-soluble oligoethylene glycol-based side chains were synthesized. The end groups were used for the easy but highly efficient click chemistry-based attachment of end-functionalized oligodeoxynucleotides (ODNs) with predesigned sequences. As demonstrated by surface plasmon resonance spectroscopy, the prepared block copolymers (BCPs), P3(EO)₃T-b-ODN, comprising different ODN lengths and specific or repetitive sequences, undergo specific hybridization with complementary, thiol-functionalized ODNs immobilized on a gold surface. Furthermore, the site-specific attachment of the BCPs to DNA origami structures is studied. We demonstrate that a nanoscale object, that is, a single BCP with a single ODN handle, can be directed and bound to the DNA origami with reasonable yield, site-specificity, and high spatial density. On the basis of these results, we are able to demonstrate for the first time that optical properties of CP molecules densely immobilized on DNA origami can be locally fine-tuned by controlling the attractive π-π-stacking interactions between the CPs. In particular, we show that the fluorescence of the immobilized CP molecules can be significantly enhanced by surfactant-induced breakup of π-π-stacking interactions between the CP's backbones. Such molecular control over the emission intensity of the CPs can be valuable for the construction of sophisticated switchable nanophotonic devices and nanoscale biosensors.