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.

DNA-based self-assembled nanostructures are widely used to position organic and inorganic objects with nanoscale precision. A particular promising application of DNA structures is their usage as programmable carrier systems for targeted drug delivery. To provide DNA-based templates that are robust against degradation at elevated temperatures, low ion concentrations, adverse pH conditions, and DNases, we built 6-helix DNA tile tubes consisting of 24 oligonucleotides carrying alkyne groups on their 3'-ends and azides on their 5'-ends. By a mild click reaction, the two ends of selected oligonucleotides were covalently connected to form rings and interlocked DNA single strands, so-called DNA catenanes. Strikingly, the structures stayed topologically intact in pure water and even after precipitation from EtOH. The structures even withstood a temperature of 95 °C when all of the 24 strands were chemically interlocked.

In self-assembly, the information for the overall shape and functionality of the resulting structure is encoded in its multiple subunits. A promising path to the successful construction of self-assembling objects is DNA nanotechnology, where the hybridization specifi city of complementary sequences is employed to create nanoscale objects of defi ned shapes. [ 1 , 2 ] Driven by the hope to rival conventional top-down lithography methods, a lot of effort went into the spatial arrangement of metal nanoparticles [3][4][5][6] and the metallization of individual DNA double strands (dsDNA) or DNA multihelical bundles which were presented as promising scaffolds for nanoelectronic applications. [7][8][9][10][11][12][13] However, one reason why metallized DNA structures have yet found little application in nanoelectronics and nanooptics might be the limited control over the fi nal 3D shape of the metallized objects. With the establishment of DNA origami, [ 14 , 15 ] where a long, singlestranded DNA scaffold is folded into shape by the help of hundreds of short staple oligonucleotides, new possibilities for the positioning of nanoparticles in defi ned confi rmations [16][17][18] and the creation of metallized objects of unprecedented shapes have arisen. [ 19 ] Besides the spatial labeling precision which is offered by this technique, [ 20 ] DNA origami structures can assemble hierarchically into multimeric architectures with dimensions of several micrometers. [ 15 , 21 , 22 ] This offers the possibility to create complex and large-scale spatial arrangements of anisotropic optical and electronic components.Here we show that DNA origami structures can be used to attract and template positively charged gold particles in desired conformations and that by further electroless deposition of metal ions from solution such structures can be converted into continuously metallized objects. In contrast to previous work, where DNA nanostructures were metallized via a glutaraldehyde-based method, [ 19 ] we use 1.4 nm gold clusters coated with positively charged amines, which bind to negatively charged DNA origami structures, as seeding sites for the gold cluster growth ( Figure 1 ). Such metal-seeded objects can then grow further into continuously metallized objects of arbitrary shapes such as gold nanocuboids, nanodonuts, or polymerized nanorods of micrometer length.To demonstrate the principle of our strategy, 428 nm-long six-helix bundles [ 23 ] were converted into gold nanorods of defi ned length. First, the DNA objects were assembled in a one-pot reaction where 10 n m of scaffold (p7560 and p8634) is mixed with ≈ 200 oligonucleotides of 100 n m each in a 1 m m Tris-EDTA buffer and 15 m m MgCl 2 . After a thermal annealing process, the objects were purifi ed by electrophoresis followed by physical gel extraction. For the metallization process, Au clusters of 1.4 nm diameter covered with positively charged amines (Nanoprobes, USA) are deposited on the negatively charged backbones of the DNA strands of the origami structures. The A...

Rigid particles as well as soft capsules can be ingested by cells and stored in acidic compartments around the nucleus. TEM and fluorescence images show that the rigid particles retain their original spherical shape whereas the hollow and thus more flexible capsules are deformed and squeezed upon the incorporation process. Though soft capsules are deformed upon uptake, the cargo loaded into the capsules is not released into the cytosol.