Chiral plasmonic metasurface assembled by DNA origami.

Chiral materials are essential to perceive photonic devices that control the helicity of light. However, the chirality of natural materials is rather weak, and relatively thick films are needed for noticeable effects. To overcome this limitation, artificial photonic materials were suggested to affect the chiral response in a much more substantial manner. Ideally, a single layer of such a material, a metasurface, should already be sufficient. While various structures fabricated with top-down nanofabrication technologies have already been reported, here we propose to utilize scaffolded DNA origami technology, a scalable bottom-up approach for metamolecule production, to fabricate a chiral metasurface. We introduce a chiral plasmonic metamolecule in the shape of a tripod and simulate its optical properties. By fixing the metamolecule to a rectangular planar origami, the tripods can be assembled into a 2D DNA origami crystal that forms a chiral metasurface. We simulate the optical properties but also fabricate selected devices to assess the experimental feasibility of the suggested approach critically.

Piggybacking functionalized DNA nanostructures into live cell nuclei.

DNA origami (DO) are promising tools for in vitro or in vivo applications including drug delivery; biosensing, detecting biomolecules; and probing chromatin sub-structures. Targeting these nanodevices to mammalian cell nuclei could provide impactful approaches for probing visualizing and controlling important biological processes in live cells. Here we present an approach to deliver DO strucures into live cell nuclei. We show that labelled DOs do not undergo detectable structural degradation in cell culture media or human cell extracts for 24 hr. To deliver DO platforms into the nuclei of human U2OS cells, we conjugated 30 nm long DO nanorods with an antibody raised against the largest subunit of RNA Polymerase II (Pol II), a key enzyme involved in gene transcription. We find that DOs remain structurally intact in cells for 24hr, including within the nucleus. Using fluorescence microscopy we demonstrate that the electroporated anti-Pol II antibody conjugated DOs are efficiently piggybacked into nuclei and exihibit sub-diffusive motion inside the nucleus. Our results reveal that functionalizing DOs with an antibody raised against a nuclear factor is a highly effective method for the delivery of nanodevices into live cell nuclei.

Versatile computer-aided design of free-form DNA nanostructures and assemblies.

Recent advances in structural DNA nanotechnology have been facilitated by design tools that continue to push the limits of structural complexity while simplifying an often-tedious design process. We recently introduced the software MagicDNA, which enables design of complex 3D DNA assemblies with many components; however, the design of structures with free-form features like vertices or curvature still required iterative design guided by simulation feedback and user intuition. Here, we present an updated design tool, MagicDNA 2.0, that automates the design of free-form 3D geometries, leveraging design models informed by coarse-grained molecular dynamics simulations. Our GUI-based, stepwise design approach integrates a high level of automation with versatile control over assembly and subcomponent design parameters. We experimentally validated this approach by fabricating a range of DNA origami assemblies with complex free-form geometries, including a 3D Nozzle, G-clef, and Hilbert and Trifolium curves, confirming excellent agreement between design input, simulation, and structure formation.

Thermally reversible pattern formation in arrays of molecular rotors.

Control over the mesoscale to microscale patterning of materials is of great interest to the soft matter community. Inspired by DNA origami rotors, we introduce a 2D nearest-neighbor lattice of spinning rotors that exhibit discrete orientational states and interactions with their neighbors. Monte Carlo simulations of rotor lattices reveal that they exhibit a variety of interesting ordering behaviors and morphologies that can be modulated through rotor design parameters. The rotor arrays exhibit diverse patterns including closed loops, radiating loops, and bricklayer structures in their ordered states. They exhibit specific heat peaks at very low temperatures for small system sizes, and some systems exhibit multiple order-disorder transitions depending on inter-rotor interaction design. We devise an energy-based order parameter and show via umbrella sampling and histogram reweighting that this order parameter captures well the order-disorder transitions occurring in these systems. We fabricate real DNA origami rotors which themselves can order via programmable DNA base-pairing interactions and demonstrate both ordered and disordered phases, illustrating how rotor lattices may be realized experimentally and used for responsive organization. This work establishes the feasibility of realizing structural nanomaterials that exhibit locally mediated microscale patterns which could have applications in sensing and precision surface patterning.

High-yield genome engineering in primary cells using a hybrid ssDNA repair template and small-molecule cocktails.

Enhancing CRISPR-mediated site-specific transgene insertion efficiency by homology-directed repair (HDR) using high concentrations of double-stranded DNA (dsDNA) with Cas9 target sequences (CTSs) can be toxic to primary cells. Here, we develop single-stranded DNA (ssDNA) HDR templates (HDRTs) incorporating CTSs with reduced toxicity that boost knock-in efficiency and yield by an average of around two- to threefold relative to dsDNA CTSs. Using small-molecule combinations that enhance HDR, we could further increase knock-in efficiencies by an additional roughly two- to threefold on average. Our method works across a variety of target loci, knock-in constructs and primary human cell types, reaching HDR efficiencies of >80-90%. We demonstrate application of this approach for both pathogenic gene variant modeling and gene-replacement strategies for IL2RA and CTLA4 mutations associated with Mendelian disorders. Finally, we develop a good manufacturing practice (GMP)-compatible process for nonviral chimeric antigen receptor-T cell manufacturing, with knock-in efficiencies (46-62%) and yields (>1.5 × 109 modified cells) exceeding those of conventional approaches.

Probing the Mechanical Properties of DNA Nanostructures with Metadynamics.

Molecular dynamics simulations are often used to provide feedback in the design workflow of DNA nanostructures. However, even with coarse-grained models, the convergence of distributions from unbiased simulation is slow, limiting applications to equilibrium structural properties. Given the increasing interest in dynamic, reconfigurable, and deformable devices, methods that enable efficient quantification of large ranges of motion, conformational transitions, and mechanical deformation are critically needed. Metadynamics is an automated biasing technique that enables the rapid acquisition of molecular conformational distributions by flattening free energy landscapes. Here we leveraged this approach to sample the free energy landscapes of DNA nanostructures whose unbiased dynamics are nonergodic, including bistable Holliday junctions and part of a bistable DNA origami structure. Taking a DNA origami-compliant joint as a case study, we further demonstrate that metadynamics can predict the mechanical response of a full DNA origami device to an applied force, showing good agreement with experiments. Our results exemplify the efficient computation of free energy landscapes and force response in DNA nanodevices, which could be applied for rapid feedback in iterative design workflows and generally facilitate the integration of simulation and experiments. Metadynamics will be particularly useful to guide the design of dynamic devices for nanorobotics, biosensing, or nanomanufacturing applications.

CRISPR-Cas9-mediated nuclear transport and genomic integration of nanostructured genes in human primary cells.

DNA nanostructures are a promising tool to deliver molecular payloads to cells. DNA origami structures, where long single-stranded DNA is folded into a compact nanostructure, present an attractive approach to package genes; however, effective delivery of genetic material into cell nuclei has remained a critical challenge. Here, we describe the use of DNA nanostructures encoding an intact human gene and a fluorescent protein encoding gene as compact templates for gene integration by CRISPR-mediated homology-directed repair (HDR). Our design includes CRISPR-Cas9 ribonucleoprotein binding sites on DNA nanostructures to increase shuttling into the nucleus. We demonstrate efficient shuttling and genomic integration of DNA nanostructures using transfection and electroporation. These nanostructured templates display lower toxicity and higher insertion efficiency compared to unstructured double-stranded DNA templates in human primary cells. Furthermore, our study validates virus-like particles as an efficient method of DNA nanostructure delivery, opening the possibility of delivering nanostructures in vivo to specific cell types. Together, these results provide new approaches to gene delivery with DNA nanostructures and establish their use as HDR templates, exploiting both their design features and their ability to encode genetic information. This work also opens a door to translate other DNA nanodevice functions, such as biosensing, into cell nuclei.

A quantitative model for a nanoscale switch accurately predicts thermal actuation behavior.

Manipulation of temperature can be used to actuate DNA origami nano-hinges containing gold nanoparticles. We develop a physical model of this system that uses partition function analysis of the interaction between the nano-hinge and nanoparticle to predict the probability that the nano-hinge is open at a given temperature. The model agrees well with experimental data and predicts experimental conditions that allow the actuation temperature of the nano-hinge to be tuned over a range of temperatures from 30 °C to 45 °C. Additionally, the model identifies microscopic interactions that are important to the macroscopic behavior of the system, revealing surprising features of the system. This combination of physical insight and predictive potential is likely to inform future designs that integrate nanoparticles into dynamic DNA origami structures or use strand binding interactions to control dynamic DNA origami behavior. Furthermore, our modeling approach could be expanded to consider the incorporation, stability, and actuation of other types of functional elements or actuation mechanisms integrated into nucleic acid devices.

Sites of high local frustration in DNA origami.

The self-assembly of a DNA origami structure, although mostly feasible, represents indeed a rather complex folding problem. Entropy-driven folding and nucleation seeds formation may provide possible solutions; however, until now, a unified view of the energetic factors in play is missing. Here, by analyzing the self-assembly of origami domains with identical structure but different nucleobase composition, in function of variable design and experimental parameters, we identify the role played by sequence-dependent forces at the edges of the structure, where topological constraint is higher. Our data show that the degree of mechanical stress experienced by these regions during initial folding reshapes the energy landscape profile, defining the ratio between two possible global conformations. We thus propose a dynamic model of DNA origami assembly that relies on the capability of the system to escape high structural frustration at nucleation sites, eventually resulting in the emergence of a more favorable but previously hidden state.

Three-Dimensional DNA Origami as Programmable Anchoring Points for Bioreceptors in Fiber Optic Surface Plasmon Resonance Biosensing.

Many challenges in biosensing originate from the fact that the all-important nanoarchitecture of the biosensor surface, including precise density and orientation of bioreceptors, is not entirely comprehended. Here, we introduced a three-dimensional DNA origami as a bioreceptor carrier to functionalize the fiber optic surface plasmon resonance (FO-SPR) sensor with nanoscale precision. Starting from a 24-helix bundle, two distinct DNA origami structures were designed to position thrombin-specific aptamers with different densities and distances (27 and 113 nm) from the FO-SPR surface. The origami-based biosensors not only proved to be capable of reproducible, label-free thrombin detection but revealed also valuable innovative features: (1) a significantly better performance in the absence of backfilling, known as essential in the biosensing field, suggesting improved bioreceptor orientation and accessibility, and (2) a wider linear range compared to previously reported thrombin biosensors. We envisage that our method will be beneficial for both scientists and clinicians looking for new surface (bio)chemistry and improved diagnostics.

Synthetic DNA filaments: from design to applications.

Natural filaments, such as microtubules and actin filaments, are fundamental components of the cell. Despite their relatively simple linear structure, filaments play a number of crucial roles in living organisms, from scaffolding to cellular adhesion and motility. The mechanical properties of natural filaments mostly rely on the structural features of the component units and on the way they are connected together, thus providing an ideal molecular model for emulation purposes. In this review, we describe the progresses done in this field using DNA for the rational design of synthetic filamentous-like materials with tailored structural and physical characteristics. We firstly survey the strategies that have been adopted until now for the construction of individual DNA building components and their programmable self-assembly into linear oligomeric structures. We then describe the theoretical models of polymer elasticity applied to calculate the bending strength of DNA filaments, expressed in terms of persistence length. Finally, we report some of the most exciting examples of truly biomimetic DNA filaments, which are capable of mimicking not only the sophisticated structural features of their natural counterparts but also their responsiveness to external stimuli, thus resulting in active motion and growing networks between distant loci.

Hierarchical Assembly of DNA Filaments with Designer Elastic Properties.

The elastic features of protein filaments are encoded in their component units and in the way they are connected, thus defining a biunivocal relationship between the monomer and the result of its self-assembly. Using DNA origami approaches, we constructed a reconfigurable module, composed of two quasi-independent domains and four possible interfaces, capable of facial and lateral growing through specific recognition patterns. Whereas the flexibility of the intra-domains region can be regulated by switchable DNA motifs, the inter-domain interfaces feature mutually and self-complementary shapes, whose pairwise association leads to filaments of programmable periodicity and variable persistence length. Thus, we show here that the assembly pathway leading to oligomeric chains can be finely tuned and fully controlled, enabling the emulation of protein-like filaments using a single construction principle. Our approach results in artificial materials with a large variety of ultrastructures and bending strengths comparable, or even superior, to their natural counterparts.

From Nano to Macro through Hierarchical Self-Assembly: The DNA Paradigm.

From atoms to molecules and bio-macromolecules, from organelles to cells, tissues, to the whole living system, nature shows us that the formation of complex systems with emergent properties originates from the hierarchical self-assembly of single components in guided bottom-up processes. By using DNA as a fundamental building block with well-known self-recognition properties, scientists have developed design rules and physical-chemical approaches for the fully programmable construction of highly organized structures with nanosized features. This review highlights the basic principles of hierarchical self-assembly in terms of type and number of distinguishable components and their interaction energies. Such general concepts are then applied to DNA-based systems. After a brief overview of the strategies used until now for the construction of individual DNA units, such as DNA tile motifs and origami structures, their self-association into assemblies of higher order is discussed. Particular emphasis is given to the forces involved in the self-assembly process, understanding and rational combination of which might help to coordinate the single elements of hierarchical structures both in space and time, thus advancing our efforts towards the creation of devices that mimic the complexity and functionality of natural systems.

Temozolomide added to whole brain radiotherapy in patients with multiple brain metastases of non-small-cell lung cancer: a multicentric Austrian phase II study.

BACKGROUND: This multicentric randomized phase II study investigated the feasibility and toxicity of temozolomide (TMZ) added to whole brain radiotherapy (WBRT) followed by adjuvant TMZ in patients with multiple brain metastases of non-small-cell lung cancer (NSCLC). METHODS: Patients with multiple brain metastases from NSCLC aged ≥ 18 years, classified according to recursive partitioning analysis class I or II and with adequate organ functions were eligible. Treatment consisted of WBRT + TMZ 75 mg/m² for 2 weeks followed at day 28 by TMZ 100 mg/m²/day 2 weeks on/2 weeks off for up to 6 months (radiochemotherapy, RCT) or WBRT alone (radiotherapy, RT). RESULTS: The study enrolled only 35 patients (22 patients in RCT and 13 in RT) and had to be closed prematurely due to poor accrual. The toxicity was mainly due to TMZ with WHO grade 3 and 4 thrombocytopenia in 3/22 versus 0/13, leucocytopenia in 1/22 versus 0/13 and lymphocytopenia in 7/22 versus 12/13 patients in RCT and RT respectively. Thirteen patients in RCT and six in RT progressed systemically and dropped out before first restaging of the response in brain. Median time to progression (TTP) was 2.4 months (95 % CI: 2-2.6 months) and 2.0 months (95 % CI: 0.5-3.5 months), median overall survival (OAS) was 3 months (95% CI: 1.7-3.1 months) and 6.3.months (95 % CI: 0.2-7.6 months) in RCT and RT, respectively. CONCLUSIONS: Like other studies before on patients with brain metastases, insufficient number of recruited patients does not allow conclusions on efficacy and toxicity as the study closed prematurely.

Pemetrexed with or without matuzumab as second-line treatment for patients with stage IIIB/IV non-small cell lung cancer.

INTRODUCTION: This randomized phase II study investigated pemetrexed in combination with the epidermal growth factor receptor (EGFR)-targeting monoclonal antibody matuzumab compared with pemetrexed alone as second-line therapy for patients with advanced non-small cell lung cancer. METHODS: Patients received pemetrexed 500 mg/m every 3 weeks either alone (n = 50) or in combination with matuzumab at either 800 mg weekly (n = 51) or 1600 mg every 3 weeks (n = 47). The primary end point was objective response, as assessed by an independent review committee. RESULTS: Tumor EGFR expression was detected in 87% of randomized patients. The objective response rate for the pooled matuzumab-treated arms was 11% compared with 5% for pemetrexed alone (p = 0.332). Apart from one patient in the pemetrexed alone group, all responses occurred in patients whose tumors expressed EGFR. The objective response rate for patients receiving weekly matuzumab was 16% compared with 2% for those receiving matuzumab every 3 weeks. There was also a trend for improved overall survival in patients receiving matuzumab weekly versus every 3 weeks (12.4 months versus 5.9 months, respectively, versus 7.9 months for pemetrexed alone). The combination of pemetrexed and matuzumab demonstrated an acceptable safety profile, with the most common grade 3/4 adverse event being neutropenia. CONCLUSION: Although the analysis on the pooled matuzumab-treated arms did not demonstrate a statistically significant improvement in objective response for the addition of matuzumab to pemetrexed compared with pemetrexed alone, the trends for improvement in objective response and overall survival for pemetrexed plus weekly matuzumab compared with pemetrexed alone warrant confirmation in additional clinical trials.