DNA nanotechnology offers unparalleled precision and programmability for the bottom-up organization of materials. This approach relies on pre-assembling a DNA scaffold, typically containing hundreds of different strands, and using it to position functional components. A particularly attractive strategy is to employ DNA nanostructures not as permanent scaffolds, but as transient, reusable templates to transfer essential information to other materials. To our knowledge, this approach, akin to top-down lithography, has not been examined. Here we report a molecular printing strategy that chemically transfers a discrete pattern of DNA strands from a three-dimensional DNA structure to a gold nanoparticle. We show that the particles inherit the DNA sequence configuration encoded in the parent template with high fidelity. This provides control over the number of DNA strands and their relative placement, directionality and sequence asymmetry. Importantly, the nanoparticles produced exhibit the site-specific addressability of DNA nanostructures, and are promising components for energy, information and biomedical applications.

DNA nanotubes have great potential as nanoscale scaffolds for the organization of materials and the templation of nanowires and as drug delivery vehicles. Current methods for making DNA nanotubes either rely on a tile-based step-growth polymerization mechanism or use a large number of component strands and long annealing times. Step-growth polymerization gives little control over length, is sensitive to stoichiometry, and is slow to generate long products. Here, we present a design strategy for DNA nanotubes that uses an alternative, more controlled growth mechanism, while using just five unmodified component strands and a long enzymatically produced backbone. These tubes form rapidly at room temperature and have numerous, orthogonal sites available for the programmable incorporation of arrays of cargo along their length. As a proof-of-concept, cyanine dyes were organized into two distinct patterns by inclusion into these DNA nanotubes.

Polymer-bearing surfaces are of particular interest because of their thermal and solvent response, 1,2 their prospective use as protein and cell adhesive platforms, 3À5 or as self-biolubricating substrates, among others. 6 Surface-tethered polymer chains provide the means to tailor the surface properties by undergoing externally stimulated conformational changes. This is particularly true for polyelectrolyte polymers such as poly(acrylic acid) (PAA) whose degree of ionization is highly influenced by pH, ionic strength, and the presence of multivalent species. 7,8 Various polymer conformations including pancake and brushes are possible with end-tethered polyelectrolytes by varying surface density and the media. 9 The control of conformational properties have allowed for advances in areas such as surface friction modulation, switchable wettability, autophobicity, 10À12 antifouling 13À16 and lubricity, 6,17À21 to name but a few.Surface-bound polymers of well-defined discrete degrees of polymerization and high surface homogeneity are desired for ensuring control of surface properties and reversible surface response with external stimuli such as temperature, pH and ionic strength. These polymers can be obtained by controlled polymerization with an ATRP initiator chemically linked to the substrate. For silica substrates, the substrateÀinitiator linkage (Si substrate ÀOÀSi initiator bond) is generally robust enough for both sustaining the reaction conditions required for ATRP and subsequent polymer brush formation and characterization. We recently showed that PAA brushes built on mica by anchoring polystyrene-poly(acrylic acid)(PS-b-PAA) diblock copolymers in a polystyrene monolayer covalently attached to OH-activated mica surfaces resist to cleavage at pH 5.5 with added salt for several days. 22 However, there is still uncertainty regarding the robustness of the substrateÀpolymer bond and whether it is resistant to the extreme pH and ionic strengths that are required for conformational analyses of polyelectrolyte brushes. It is unknown whether these extreme conditions hydrolyze the SiÀOÀSi bond and cleave the polymer from the substrate leading to undesired decrease in polymer grafting density, similar to what was reported for poly(methacrylic acid) brushes and PAA brushes grafted from silica-based substrates. 23À25 Knowing the conditions under which undesired polymer cleavage occurs is pivotal for accurate surface-property studies. They are also important for controlling reversible polymer conformational changes, while preventing polymer degrafting. Although we previously provided indirect evidence for polymer cleavage from mica at high pH and salt concentrations, 23 determining the exact conditions under which PAA cleavage occurred was not possible. Also, unequivocal evidence for polymer degrafting from silica substrates has not yet been demonstrated.ABSTRACT: Poly(acrylic acid) (PAA) covalently immobilized on glass substrates was made fluorescent by grafting a BODIPY derivative (PMOH) via an ester linkage. Although...

Using highly functional 'building-blocks' of AuNPs mono-conjugated to three-dimensional DNA 'rung' structures, both discrete and extended linear assemblies are controllably prepared via addition of various templating backbone strands. This unique approach presents a facile alternative to other methods of AuNP organization through DNA, and has potential utility in the fields of nanophotonics and nanoelectronics.

Given its highly predictable self-assembly properties, DNA has proven to be an excellent template toward the design of functional materials. Prominent examples include the remarkable complexity provided by DNA origami and single-stranded tile (SST) assemblies, which require hundreds of unique component strands. However, in many cases, the majority of the DNA assembly is purely structural, and only a small "working area" needs to be aperiodic. On the other hand, extended lattices formed by DNA tile motifs require only a few strands; but they suffer from lack of size control and limited periodic patterning. To overcome these limitations, we adopt a templation strategy, where an input strand of DNA dictates the size and patterning of resultant DNA tile structures. To prepare these templating input strands, a sequential growth technique developed in our lab is used, whereby extended DNA strands of defined sequence and length may be generated simply by controlling their order of addition. With these, we demonstrate the periodic patterning of size-controlled double-crossover (DX) and triple-crossover (TX) tile structures, as well as intentionally designed aperiodicity of a DX tile structure. As such, we are able to prepare size-controlled DNA structures featuring aperiodicity only where necessary with exceptional economy and efficiency.

Fluorescent nanoparticles were prepared via adsorption of the conjugated polyelectrolyte poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene] (MPS-PPV) onto 50 and 100 nm aminosilane functionalized silica beads. The particles were investigated via ensemble and single-molecule or -particle spectroscopy techniques to quantify the effect of the silica bead core on the exciton migration efficiency within the polymer. Ensemble emission spectra and ensemble fluorescence quenching studies with methyl viologen are consistent with good exciton migration along the polymer in the polymer-coated bead. The silica nanobead scaffolding preserves the sensitivity of the free polymer and provides a controllable architecture that minimizes nonspecific interactions. Single-particle spectroscopy studies were conducted on particles immobilized onto the positively charged surface of glass cover slips. Particle immobilization enabled us to monitor the effect of oxygen scavenger solutions on individual particles by changing the surrounding solution. The intensity–time trajectories of individual beads provide a mechanism of signal transduction with potential applications in multiplexing studies. Hundreds of individual beads can be imaged in a rapid parallel fashion.

The morphology of supramolecular materials is usually dictated by directional intermolecular interactions. However, the impact of the precise monomer sequence – their order along the polymer chain, localization, and number...

The site-specific incorporation of transition-metal complexes within DNA duplexes, followed by their immobilization on a gold surface, was studied by electrochemistry to characterize their ability to mediate charge. Cyclic voltammetry, square-wave voltammetry, and control experiments were carried out on fully matched and mismatched DNA strands that are mono- or bis-labeled with transition-metal complexes. These experiments are all consistent with the ability of the metal centers to act as a redox probe that is well coupled to the DNA π-stack, allowing DNA-mediated charge transport.