Biological membranes fulfill many important tasks within living organisms. In addition to separating cellular volumes, membranes confine the space available to membrane-associated proteins to two dimensions (2D), which greatly increases their probability to interact with each other and assemble into multiprotein complexes. We here employed two DNA origami structures functionalized with cholesterol moieties as membrane anchors—a three-layered rectangular block and a Y-shaped DNA structure—to mimic membrane-assisted assembly into hierarchical superstructures on supported lipid bilayers and small unilamellar vesicles. As designed, the DNA constructs adhered to the lipid bilayers mediated by the cholesterol anchors and diffused freely in 2D with diffusion coefficients depending on their size and number of cholesterol modifications. Different sets of multimerization oligonucleotides added to bilayer-bound origami block structures induced the growth of either linear polymers or two-dimensional lattices on the membrane. Y-shaped DNA origami structures associated into triskelion homotrimers and further assembled into weakly ordered arrays of hexagons and pentagons, which resembled the geometry of clathrin-coated pits. Our results demonstrate the potential to realize artificial self-assembling systems that mimic the hierarchical formation of polyhedral lattices on cytoplasmic membranes.

Self-assembled DNA nanostructures have been used to create man-made transmembrane channels in lipid bilayers. Here, we present a DNA-tile structure with a nominal subnanometer channel and cholesterol-tags for membrane anchoring. With an outer diameter of 5 nm and a molecular weight of 45 kDa, the dimensions of our synthetic nanostructure are comparable to biological ion channels. Because of its simple design, the structure self-assembles within a minute, making its creation scalable for applications in biology. Ionic current recordings demonstrate that the tile structures enable ion conduction through lipid bilayers and show gating and voltage-switching behavior. By demonstrating the design of DNA-based membrane channels with openings much smaller than that of the archetypical six-helix bundle, our work showcases their versatility inspired by the rich diversity of natural membrane components.

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Mechanical properties and biological inertness of titanium provide potential in orthopedic and dental implants. However, integration of titanium-based implants into the existing tissue is a major problem. Herein, we demonstrate biofunctionalization of titanium surfaces through a mussel-inspired adhesion mechanism conjugated to self-assembled peptide nanofibers in order to overcome biocompatibility issues. A Dopa conjugated peptide nanofiber coating was used along with bioactive peptide sequences for osteogenic activity to enhance osseointegration of medical grade titanium surface, TiAl6V4 alloy. Dopa-mediated immobilization of osteogenic peptide nanofibers on titanium surfaces created an osteoconductive interface between osteoblast-like cells and inhibited adhesion and viability of soft tissue forming fibroblasts compared to the uncoated titanium substrate. This biofunctionalization strategy can be extended into other surface immobilization systems owing to the versatile adhesive properties of Dopa and the ease of ligand conjugation to peptide amphiphile molecules. © 2012 The Royal Society of Chemistry