Explore the vast range of titles available.

We demonstrate that discrete three-dimensional (3D) DNA components can specifically self-assemble in solution on the basis of shape-complementarity and without base pairing. Using this principle, we produced homo- and heteromultimeric objects, including micrometer-scale one- and two-stranded filaments and lattices, as well as reconfigurable devices, including an actuator, a switchable gear, an unfoldable nanobook, and a nanorobot. These multidomain assemblies were stabilized via short-ranged nucleobase stacking bonds that compete against electrostatic repulsion between the components' interfaces. Using imaging by electron microscopy, ensemble and single-molecule fluorescence resonance energy transfer spectroscopy, and electrophoretic mobility analysis, we show that the balance between attractive and repulsive interactions, and thus the conformation of the assemblies, may be finely controlled by global parameters such as cation concentration or temperature and by an allosteric mechanism based on strand-displacement reactions.

By using DNA sequence information to encode the shapes of DNA origami building blocks, shape-programmable assemblies can be created, with sizes and complexities similar to those of viruses. DNA origami by design In nature, large and complex structures such as viruses assemble with ease, but building such large and complex artificial objects remains a grand challenge. Hendrik Dietz and colleagues now show that large and discrete objects can be created efficiently by using DNA sequence information to encode the shapes of individual DNA origami building blocks, and the geometry and details of the interactions between these building blocks to control their copy numbers, positions and orientations within higher-order assemblies. The team create planar rings reaching 350 nanometres in diameter, tubes the size of some bacilli, and three-dimensional polyhedral cages 450 nanometres in diameter, which strikingly illustrate the capability of this method. The technique can in principle be adjusted to create other assemblies that might find use in drug delivery, as scaffolds or for creating complex machine-like objects. Three related papers is this issue report further advances in DNA origami, and all four are summarized in a News & Views. Natural biomolecular assemblies such as molecular motors, enzymes, viruses and subcellular structures often form by self-limiting hierarchical oligomerization of multiple subunits 1 , 2 , 3 . Large structures can also assemble efficiently from a few components by combining hierarchical assembly and symmetry, a strategy exemplified by viral capsids 4 . De novo protein design 5 , 6 , 7 , 8 , 9 and RNA 10 , 11 and DNA nanotechnology 12 , 13 , 14 aim to mimic these capabilities, but the bottom-up construction of artificial structures with the dimensions and complexity of viruses and other subcellular components remains challenging. Here we show that natural assembly principles can be combined with the methods of DNA origami 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 to produce gigadalton-scale structures with controlled sizes. DNA sequence information is used to encode the shapes of individual DNA origami building blocks, and the geometry and details of the interactions between these building blocks then control their copy numbers, positions and orientations within higher-order assemblies. We illustrate this strategy by creating planar rings of up to 350 nanometres in diameter and with atomic masses of up to 330 megadaltons, micrometre-long, thick tubes commensurate in size to some bacilli, and three-dimensional polyhedral assemblies with sizes of up to 1.2 gigadaltons and 450 nanometres in diameter. We achieve efficient assembly, with yields of up to 90 per cent, by using building blocks with validated structure and sufficient rigidity, and an accurate design with interaction motifs that ensure that hierarchical assembly is self-limiting and able to proceed in equilibrium to allow for error correction. We expect that our method, which enables the self-assembly of structures with sizes approaching that of viruses and cellular organelles, can readily be used to create a range of other complex structures with well defined sizes, by exploiting the modularity and high degree of addressability of the DNA origami building blocks used.

Molecular self-assembly with DNA is an attractive route for building nanoscale devices. The development of sophisticated and precise objects with this technique requires detailed experimental feedback on the structure and composition of assembled objects. Here we report a sensitive assay for the quality of assembly. The method relies on measuring the content of unpaired DNA bases in self-assembled DNA objects using a fluorescent de-Bruijn probe for three-base ‘codons’, which enables a comparison with the designed content of unpaired DNA. We use the assay to measure the quality of assembly of several multilayer DNA origami objects and illustrate the use of the assay for the rational refinement of assembly protocols. Our data suggests that large and complex objects like multilayer DNA origami can be made with high strand integration quality up to 99%. Beyond DNA nanotechnology, we speculate that the ability to discriminate unpaired from paired nucleic acids in the same macromolecule may also be useful for analysing cellular nucleic acids. Sequence-programmable self-assembly of DNA enables the formation of a variety of complex structures; however, determining the quality of these multi-chain structures is challenging. Here the authors address this problem by using a fluorescent probe to measure the amount of unpaired bases in the DNA assemblies.

Multispecific antibodies have emerged as versatile therapeutic agents, and therefore, approaches to optimize and streamline their design and assembly are needed. Here we report on the modular and programmable assembly of IgG antibodies, F(ab) and scFv fragments on DNA origami nanocarriers. We screened 105 distinct quadruplet antibody variants in vitro for the ability to activate T cells in the presence of target cells. T-cell engagers were identified, which in vitro showed the specific and efficient T-cell-mediated lysis of five distinct target cell lines. We used these T-cell engagers to target and lyse tumour cells in vivo in a xenograft mouse tumour model. Our approach enables the rapid generation, screening and testing of bi- and multispecific antibodies to facilitate preclinical pharmaceutical development from in vitro discovery to in vivo proof of concept. A synthetic nanocarrier based on DNA origami chassis offers control over valency, orientation and spatial arrangement of antibodies for simultaneously engaging immune signalling pathways, checkpoint inhibition and targeted co-stimulation in anticancer immunotherapy in vivo.