Dynamics of DNA Origami Lattices

Electronic Properties of DNA Origami Nanostructures Revealed by In Silico Calculations

DNA origami is a pioneering approach for producing complex 2- or 3-D shapes for use in molecular electronics due to its inherent self-assembly and programmability properties. The electronic properties of DNA origami structures are not yet fully understood, limiting the potential applications. Here, we conduct a theoretical study with a combination of molecular dynamics, first-principles, and charge transmission calculations. We use four separate single strand DNAs, each having 8 bases (4 × G4C4 and 4 × A4T4), to form two different DNA nanostructures, each having two helices bundled together with one crossover. We also generated double-stranded DNAs to compare electronic properties to decipher the effects of crossovers and bundle formations. We demonstrate that density of states and band gap of DNA origami depend on its sequence and structure. The crossover regions could reduce the conductance due to a lack of available states near the HOMO level. Furthermore, we reveal that, despite having the same sequence, the two helices in the DNA origami structure could exhibit different electronic properties, and electrode position can affect the resulting conductance values. Our study provides better understanding of the electronic properties of DNA origamis and enables us to tune these properties for electronic applications such as nanowires, switches, and logic gates.

Life at the interface: Engineering bio-nanomaterials through interfacial molecular self-assembly

Interfacial self-assembly describes the directed organization of molecules and colloids at phase boundaries. Believed to be fundamental to the inception of primordial life, interfacial assembly is exploited by a myriad of eukaryotic and prokaryotic organisms to execute physiologic activities and maintain homeostasis. Inspired by these natural systems, chemists, engineers, and materials scientists have sought to harness the thermodynamic equilibria at phase boundaries to create multi-dimensional, highly ordered, and functional nanomaterials. Recent advances in our understanding of the biophysical principles guiding molecular assembly at gas-solid, gas-liquid, solid-liquid, and liquid-liquid interphases have enhanced the rational design of functional bio-nanomaterials, particularly in the fields of biosensing, bioimaging and biotherapy. Continued development of non-canonical building blocks, paired with deeper mechanistic insights into interphase self-assembly, holds promise to yield next generation interfacial bio-nanomaterials with unique, and perhaps yet unrealized, properties. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Dynamic Interface-Assisted Rapid Self-Assembly of DNA Origami-Framed Anisotropic Nanoparticles

The ordered arrangement of nanoparticles can generate unique physicochemical properties, rendering it a pivotal direction in the field of nanotechnology. DNA-based chemical encoding has emerged as an unparalleled strategy for orchestrating precise and controlled nanoparticle assemblies. Nonetheless, it is often time-consuming and has limited assembly efficiency. In this study, we developed a strategy for the rapid and ordered assembly of DNA origami-framed nanoparticles assisted by dynamic interfaces. By assembling Au nanoparticles (AuNPs) onto DNA origami with different sticky ends in various directions, we endowed them with anisotropic specific affinities. After assembling DNA origami-framed AuNPs onto supported lipid bilayers with freely diffusing single-stranded DNA via DNA hybridization, we found that DNA origami-framed AuNPs could form larger ordered assemblies than those in 3D solution within equivalent time frames. Furthermore, we also achieved rapid and ordered assembly of liposome nanoparticles by employing the aforementioned strategy. Our work provides a novel avenue for efficient and rapid assembly of nanoparticles across two-dimensional interfaces, which is expected to promote the application of ordered nanoparticle assemblies in sensor and biomimetic system construction.

Computation-aided Design of Rod-Shaped Janus Base Nanopieces for Improved Tissue Penetration and Therapeutics Delivery

Despite the development of various drug delivery technologies, there remains a significant need for vehicles that can improve targeting and biodistribution in "hard-to-penetrate" tissues. Some solid tumors, for example, are particularly challenging to penetrate due to their dense extracellular matrix (ECM). In this study, we have formulated a new family of rod-shaped delivery vehicles named Janus base nanopieces (Rod JBNps), which are more slender than conventional spherical nanoparticles, such as lipid nanoparticles (LNPs). These JBNp nanorods are formed by bundles of DNA-inspired Janus base nanotubes (JBNts) with intercalated delivery cargoes. To develop this novel family of delivery vehicles, we employed a computation-aided design (CAD) methodology that includes molecular dynamics and response surface methodology. This approach precisely and efficiently guides experimental designs. Using an ovarian cancer model, we demonstrated that JBNps markedly improve penetration into the dense ECM of solid tumors, leading to better treatment outcomes compared to FDA-approved spherical LNP delivery. This study not only successfully developed a rod-shaped delivery vehicle for improved tissue penetration but also established a CAD methodology to effectively guide material design.

Cation-dependent assembly of hexagonal DNA origami lattices on SiO2 surfaces

DNA origami nanostructures have emerged as functional materials for applications in various areas of science and technology. In particular, the transfer of the DNA origami shape into inorganic materials using established silicon lithography methods holds great promise for the fabrication of nanostructured surfaces for nanoelectronics and nanophotonics. Using ordered DNA origami lattices directly assembled on the oxidized silicon surface instead of single nanostructures would enable the fabrication of functional nanopatterned surfaces with macroscopic dimensions. Here, we thus investigate the assembly of hexagonal DNA lattices from DNA origami triangles on RCA-cleaned silicon wafers with hydroxylated surface oxide by time-lapse atomic force microscopy (AFM). Lattice assembly on the SiO2 surface is achieved by a competition of monovalent and divalent cations at elevated temperatures. Ca2+ is found to be superior to Mg2+ in promoting the assembly of ordered lattices, while the presence of Mg2+ rather results in DNA origami aggregation and multilayer formation at the comparably high Na+ concentrations of 200 to 600 mM. Furthermore, Na+ concentration and temperature have a similar effect on lattice order, so that a reduction of temperature can be compensated to some extent by an increase in Na+ concentration. However, even under optimized conditions, the DNA origami lattices assembled on the SiO2 surface exhibit a lower degree of order than equivalent lattices assembled on mica, which is attributed to a higher desorption rate of the DNA origami nanostructures. Even though this high desorption rate also complicates any post-assembly treatment, the formed DNA origami lattices could successfully be transferred into the dry state, which is an important prerequisite for further processing steps.

Reconfigurable pH-Responsive DNA Origami Lattices

DNA nanotechnology enables straightforward fabrication of user-defined and nanometer-precise templates for a cornucopia of different uses. To date, most of these DNA assemblies have been static, but dynamic structures are increasingly coming into view. The programmability of DNA not only allows for encoding of the DNA object shape but also it may be equally used in defining the mechanism of action and the type of stimuli-responsiveness of the dynamic structures. However, these "robotic" features of DNA nanostructures are usually demonstrated for only small, discrete, and device-like objects rather than for collectively behaving higher-order systems. Here, we show how a large-scale, two-dimensional (2D) and pH-responsive DNA origami-based lattice can be assembled into two different configurations ("open" and "closed" states) on a mica substrate and further switched from one to the other distinct state upon a pH change of the surrounding solution. The control over these two configurations is achieved by equipping the arms of the lattice-forming DNA origami units with "pH-latches" that form Hoogsteen-type triplexes at low pH. In short, we demonstrate how the electrostatic control over the adhesion and mobility of the DNA origami units on the surface can be used both in the large lattice formation (with the help of directed polymerization) and in the conformational switching of the whole lattice. To further emphasize the feasibility of the method, we also demonstrate the formation of pH-responsive 2D gold nanoparticle lattices. We believe this work can bridge the nanometer-precise DNA origami templates and higher-order large-scale systems with the stimuli-induced dynamicity.

Programmed Self-Assembly of DNA Nanosheets with Discrete Single-Molecule Thickness and Interfacial Mechanics: Design, Simulation, and Characterization

DNA is programmed to hierarchically self-assemble into superstructures spanning from nanometer to micrometer scales. Here, we demonstrate DNA nanosheets assembled out of a rationally designed flexible DNA unit (F-unit), whose shape resembles a Feynman diagram. F-units were designed to self-assemble in two dimensions and to display a high DNA density of hydrophobic moieties. oxDNA simulations confirmed the planarity of the F-unit. DNA nanosheets with a thickness of a single DNA duplex layer and with large coverage (at least 30 μm × 30 μm) were assembled from the liquid phase at the solid/liquid interface, as unambiguously evidenced by atomic force microscopy imaging. Interestingly, single-layer nanodiscs formed in solution at low DNA concentrations. DNA nanosheet superstructures were further assembled at liquid/liquid interfaces, as demonstrated by the fluorescence of a double-stranded DNA intercalator. Moreover, the interfacial mechanical properties of the nanosheet superstructures were measured as a response to temperature changes, demonstrating the control of interfacial shear mechanics based on DNA nanostructure engineering. The rational design of the F-unit, along with the presented results, provide an avenue toward the controlled assembly of reconfigurable/responsive nanosheets and membranes at liquid/liquid interfaces, to be potentially used in the characterization of biomechanical processes and materials transport.

Dynamic RNA synthetic biology: new principles, practices and potential

An increased appreciation of the role of RNA dynamics in governing RNA function is ushering in a new wave of dynamic RNA synthetic biology. Here, we review recent advances in engineering dynamic RNA systems across the molecular, circuit and cellular scales for important societal-scale applications in environmental and human health, and bioproduction. For each scale, we introduce the core concepts of dynamic RNA folding and function at that scale, and then discuss technologies incorporating these concepts, covering new approaches to engineering riboswitches, ribozymes, RNA origami, RNA strand displacement circuits, biomaterials, biomolecular condensates, extracellular vesicles and synthetic cells. Considering the dynamic nature of RNA within the engineering design process promises to spark the next wave of innovation that will expand the scope and impact of RNA biotechnologies.