Cuboid Vesicles Formed by Frame‐Guided Assembly on DNA Origami Scaffolds

DNA-based nanostructures for RNA delivery

RNA-based therapeutics have emerged as a promising approach for the treatment of various diseases, including cancer, genetic disorders, and infectious diseases. However, the delivery of RNA molecules into target cells has been a major challenge due to their susceptibility to degradation and inefficient cellular uptake. To overcome these hurdles, DNA-based nano technology offers an unprecedented opportunity as a potential delivery platform for RNA therapeutics. Due to its excellent characteristics such as programmability and biocompatibility, these DNA-based nanostructures, composed of DNA molecules assembled into precise and programmable structures, have garnered significant attention as ideal building materials for protecting and delivering RNA payloads to the desired cellular destinations. In this review, we highlight the current progress in the design and application of three DNA-based nanostructures: DNA origami, lipid-nanoparticle (LNP) technology related to frame guided assembly (FGA), and DNA hydrogel for the delivery of RNA molecules. Their biomedical applications are briefly discussed and the challenges and future perspectives in this field are also highlighted.

DNA Origami: From Molecular Folding Art to Drug Delivery Technology

DNA molecules that store genetic information in living creatures can be repurposed as building blocks to construct artificial architectures, ranging from the nanoscale to the microscale. The precise fabrication of self-assembled DNA nanomaterials and their various applications have greatly impacted nanoscience and nanotechnology. More specifically, the DNA origami technique has realized the assembly of various nanostructures featuring rationally predesigned geometries, precise addressability, and versatile programmability, as well as remarkable biocompatibility. These features have elevated DNA origami from academic interest to an emerging class of drug delivery platform for a wide range of diseases. In this minireview, the latest advances in the burgeoning field of DNA-origami-based innovative platforms for regulating biological functions and delivering versatile drugs are presented. Challenges regarding the novel drug vehicle's safety, stability, targeting strategy, and future clinical translation are also discussed.

Programming Intracellular Clustering of Spiky Nanoparticles via Liposome Encapsulation

The intracellular clustering of anisotropic nanoparticles is crucial to the improvement of the localized surface plasmon resonance (LSPR) for phototherapy applications. Herein, we programmed the intracellular clustering process of spiky nanoparticles (SNPs) by encapsulating them into an anionic liposome via a frame-guided self-assembly approach. The liposome-encapsulated SNPs (lipo-SNPs) exhibited distinct and enhanced lysosome-triggered aggregation behavior while maintaining excellent monodispersity, even in acidic or protein-rich environments. We explored the enhancement of the photothermal therapy performance for SNPs as a proof of concept. The photothermal conversion efficiency of lipo-SNPs clusters significantly increased 15 times compared to that of single lipo-SNPs. Upon accumulation in lysosomes with a 2.4-fold increase in clustering, lipo-SNPs resulted in an increase in cell-killing efficiency to 45% from 12% at 24 μg/mL. These findings indicated that liposome encapsulation provides a promising approach to programing nanoparticle clustering at the target site, which facilitates advances in the development of smart nanomedicine with programmable enhancement in LSPR.

Programming Aggregate States of DNA Nanorods with Sub-10 nm Hydrophobic Patterns for Tunable Cell Entry

The intracellular application of DNA nanodevices is challenged by their inadequate cellular entry efficiency, which may be addressed by the development of amphiphilic DNA nanostructures. However, the impact of the spatial distribution of hydrophobicity in cell entry has not been fully explored. Here, we program a spectrum of amphiphilic DNA nanostructures displaying diverse sub-10 nm patterns of cholesterol, which result in distinct aggregate states in the aqueous solution and thus varied cell entry efficiencies. We find that the hydrophobic patterns can lead to discrete aggregate states, from monomers to low-number oligomers (n = 1-6). We demonstrate that the monomers or oligomers with moderate hydrophobic density are preferred for cell entry, with up to ∼174-fold improvement relative to unmodified ones. Our study provides a new clue for the rational design of amphiphilic DNA nanostructures for intracellular applications.

Recent Advances in DNA Origami-Engineered Nanomaterials and Applications

DNA nanotechnology is a unique field, where physics, chemistry, biology, mathematics, engineering, and materials science can elegantly converge. Since the original proposal of Nadrian Seeman, significant advances have been achieved in the past four decades. During this glory time, the DNA origami technique developed by Paul Rothemund further pushed the field forward with a vigorous momentum, fostering a plethora of concepts, models, methodologies, and applications that were not thought of before. This review focuses on the recent progress in DNA origami-engineered nanomaterials in the past five years, outlining the exciting achievements as well as the unexplored research avenues. We believe that the spirit and assets that Seeman left for scientists will continue to bring interdisciplinary innovations and useful applications to this field in the next decade.

Single-Molecular Poly(propylene oxide) (PPO) Nucleus-Guided Assembly for Hydrophobicity-Dependent Molecular Transport in the Nanopore

By combining DNA nanotechnology and solid-phase nanopore technology, the aggregation behavior of polymer guided by a single-molecular poly(propylene) (PPO) nucleus in a 3D DNA network has been studied. At low temperature, the PPO chain is evenly dispersed in the rigid 3D DNA network; at higher temperature, the PPO chain self-collapses to a single-molecular nucleus; and upon addition of amphiphilic block copolymers below the critical micelle concentration (CMC), the chains tend to aggregate on the isolated hydrophobic nucleus through intermolecular hydrophobic interactions. The process has been characterized by a rheological test and an electrochemical test. This study not only provides a preliminary understanding of the nucleation and growth process of block copolymers but also offers a theoretical basis for the study of protein self-folding and aggregation in the future. On this basis, utilizing this nucleation and growth event, a novel smart nanopore has been developed for hydrophobicity-dependent molecular transport.

Binding and Characterization of DNA Origami Nanostructures on Lipid Membranes

DNA origami is an extremely versatile nanoengineering tool with widespread applicability in various fields of research, including membrane physiology and biophysics. The possibility to easily modify DNA strands with lipophilic moieties enabled the recent development of a variety of membrane-active DNA origami devices. Biological membranes, as the core barriers of the cells, display vital structural and functional roles. Therefore, lipid bilayers are widely popular targets of DNA origami nanotechnology for synthetic biology and biomedical applications. In this chapter, we summarize the typical experimental methods used to investigate the interaction of DNA origami with synthetic membrane models. Herein, we present detailed protocols for the production of lipid model membranes and characterization of membrane-targeted DNA origami nanostructures using different microscopy approaches.

Frame-Guided Assembly of Amphiphiles

ConspectusAmphiphiles tend to self-assemble into various structures and morphologies in aqueous environments (e.g., micelles, tubes, fibers, vesicles, and lamellae). These assemblies and their properties have made significant impact in traditional chemical industries, e.g., increasing solubility, decreasing surface tension, facilitating foaming, etc. It is well-known that the molecular structure and its environment play a critical role in the assembly process, and many theories, including critical packing factor, thermodynamic models, etc., have been proposed to explain and predict the assembly morphology. It has been recognized that the morphology of the amphiphilic assembly plays important roles in determining the functions, such as curvature-dependent biophysical (e.g., liposome fusion and fission) and biochemical (e.g., lipid metabolism and membrane protein trafficking) processes, size-related EPR (enhanced permeability and retention) effects, etc. Meanwhile, various nanomaterials have promised great potential in directing the arrangement of molecules, thus generating unique functions. Therefore, control over the amphiphilic morphology is of great interest to scientists, especially in nanoscale with the assistance of functional nanomaterials. However, how to precisely manipulate the sizes and shapes of the assemblies is challenged by the entropic nature of the hydrophobic interaction. Inspired by the "cytoskeleton-membrane protein-lipid bilayer" principle of the cell membrane, a strategy termed "frame-guided assembly (FGA)" has been proposed and developed to direct the arrangement of amphiphiles. The FGA strategy welcomes various nanomaterials with precisely controlled properties to serve as scaffolds. By introducing scattered hydrophobic molecules, which are defined as either leading hydrophobic groups (LHGs) or nucleation seeds onto a selected scaffold, a discontinuous hydrophobic trace along the scaffold can be outlined, which will further guide the amphiphiles in the system to grow and form customized two- or three-dimensional (2D/3D) membrane geometries.Topologically, the supporting frame can be classified as three types including inner-frame, outer-frame, and planar-frame. Each type of FGA assembly possesses particular advantages: (1) The inner-frame, similar to endoskeletons of many cellular structures, steadily supports the membrane from the inside and exposes the full surface area outside. (2) The outer-frame, on the other hand, molds and constrains the membrane-wrapped vesicles to regulate their size and shape. It also allows postengineering of the frame to precisely decorate and dynamically manipulate the membrane. (3) The planar-frame mediates the growth of the 2D membrane that profits from the scanning-probe microscopic characterization and benefits the investigation of membrane proteins.In this Account, we introduce the recent progress of frame-guided assembly strategy in the preparation of customized amphiphile assemblies, evaluate their achievements and limitations, and discuss prospective developments and applications. The basic principle of FGA is discussed, and the morphology controllability is summarized in the inner-, outer-, and planar-frame categories. As a versatile strategy, FGA is able to guide different types of amphiphiles by designing specific LHGs for given molecular structures. The mechanism of FGA is then discussed systematically, including the driving force of the assembly, density and distribution of the LHGs, amphiphile concentration, and the kinetic process. Furthermore, the applications of FGA have been developed for liposome engineering, membrane protein incorporation, and drug delivery, which suggest the huge potential of FGA in fabricating novel and functional complexes.

Boosted Productivity in Single-Tile-Based DNA Polyhedra Assembly by Simple Cation Replacement

Cations such as divalent magnesium ion (Mg²⁺ ) play an essential role in DNA self-assembly. However, the strong electrostatic shielding effect of Mg²⁺ would be disadvantageous in some situations that require relatively weak interactions to allow a highly reversible error-correcting mechanism in the process of assembly. Herein, by substituting the conventional divalent Mg²⁺ with monovalent sodium ion (Na⁺ ), we have achieved one-pot high-yield assembly of tile-based DNA polyhedra at micromolar concentration of tiles, at least 10 times higher than the DNA concentrations reported previously. This strategy takes advantage of coexisting counterions and is expected to surmount the major obstacle to potential applications of such DNA nanostructures: large-scale production.

Frame-guided assembly from a theoretical perspective

The molecular self-assembly of various structures such as micelles and vesicles has been the subject of comprehensive studies. Recently, a new approach to design these structures, the frame-guided assembly, has been developed to progress towards fabrics of predefined shape and size, following an initially provided frame of guiding elements. Here we study frame-guided assembly into a two-dimensional membrane via computer simulations, based on a single-bead coarse grained surfactant model in continuous space. In agreement with the experiment the assembly process already starts for surfactant concentrations below the critical micelle concentration. Furthermore, upon increasing temperature the formation process gets more delocalized. Additionally, the assembly process of the resulting membrane plane is modelled by a lattice gas model. It displays a similar phenomenology but additionally allows the derivation of analytical mean-field predictions. In this way a fundamental understanding of frame-guided assembly can be gained.

Tumor-targeting [2]catenane-based grid-patterned periodic DNA monolayer array for in vivo theranostic application

DNA nanotechnology is often used to build various nano-structures for signaling and/or drug delivery, but it essentially suffers from several major limitations, such as a large number of DNA strands and limited targeting ligands. Moreover, there is no report on in vivo two-dimensional DNA arrays because of various technical challenges. By cross-catenating two palindromic DNA rings, herein, we demonstrate a catenane-based grid-patterned periodic DNA monolayer array ([2]GDA) capable of preferentially accumulating in tumor tissues without any targeting ligands, with a thickness equal to the double-helical DNA monolayer (nearly 2 nm). The structural flexibility of [2]GDA enabled it to fold into a spherical object in solution, favoring cellular uptake. Thus, its cellular internalization activity was comparable with that of the commercial lipofectamine 3000. Moreover, [2]GDA retained the structural integrity over 24 h incubation in biological solutions, achieving a 360-fold improvement in in vivo stability. Significantly, anticancer drug-loaded [2]GDA exhibits desirable therapeutic efficacy in tumor-bearing animals without detectable side effects.

Multi-Wavelength Photopolymerization of Stable Poly(Catecholamines)-DNA Origami Nanostructures

The synthesis of multicomponent polymer hybrids with nanometer precision is chemically challenging in the bottom‐up synthesis of complex nanostructures. Here, we leverage the fidelity of the DNA origami technique to install a multiple wavelength responsive photopolymerization system with nanometer resolution. By precisely immobilizing various photosensitizers on the origami template, which are only activated at their respective maximum wavelength, we can control sequential polymerization processes. In particular, the triggered photosensitizers generate reactive oxygen species that in turn initiate the polymerization of the catecholamines dopamine and norepinephrine. We imprint polymeric layers at designated positions on DNA origami, which modifies the polyanionic nature of the DNA objects, thus promoting their uptake into living cells while preserving their integrity. Our herein proposed method provides a rapid platform to access complex 3D nanostructures by customizing material and biological interfaces.

Functional DNA-Polymer Conjugates

DNA nanotechnology has seen large developments over the last 30 years through the combination of solid phase synthesis and the discovery of DNA nanostructures. Solid phase synthesis has facilitated the availability of short DNA sequences and the expansion of the DNA toolbox to increase the chemical functionalities afforded on DNA, which in turn enabled the conception and synthesis of sophisticated and complex 2D and 3D nanostructures. In parallel, polymer science has developed several polymerization approaches to build di- and triblock copolymers bearing hydrophilic, hydrophobic, and amphiphilic properties. By bringing together these two emerging technologies, complementary properties of both materials have been explored; for example, the synthesis of amphiphilic DNA-polymer conjugates has enabled the production of several nanostructures, such as spherical and rod-like micelles. Through both the DNA and polymer parts, stimuli-responsiveness can be instilled. Nanostructures have consequently been developed with responsive structural changes to physical properties, such as pH and temperature, as well as short DNA through competitive complementary binding. These responsive changes have enabled the application of DNA-polymer conjugates in biomedical applications including drug delivery. This review discusses the progress of DNA-polymer conjugates, exploring the synthetic routes and state-of-the-art applications afforded through the combination of nucleic acids and synthetic polymers.

Tuning lipid layer formation on particle surfaces by using DNA-containing recruiter molecules

Biofunctional interfaces containing DNA-conjugated molecules have been explored for various bioengineering applications. However, there is still a lack of understanding of the interaction between DNA conjugates and surrounding biomolecules. In this study, we prepare DNA-containing recruiter molecules and incorporate them onto DNA immobilized gold nanoparticles through DNA hybridization. Liposomes composed of different phospholipids are then applied to investigate supported lipid layer formation on these recruiter-containing surfaces. We find that the morphology and the amount of lipid layers formed are determined by both the liposome concentration and the type of recruiter molecule. When liposomes are applied in excess above a critical concentration, surface chemistry determines the lipid layers formed, leading to lipid multilayers on hydrophilic DNA recruiter containing surfaces and lipid monolayers on hydrophobic DNA-lipid recruiter containing surfaces. When the liposome concentration is below the critical value, the surface molecules take on a more direct role and recruit lipids through hydrophobic interaction. The total amount of the lipid layers formed is further modulated by the overall charge and the fluidity of the liposomes applied. These results provide quantitative analysis on the interaction of DNA conjugates with lipid molecules and introduce a new approach to fine-tune lipid layer formation behavior.

Recent Progress of DNA Nanostructures on Amphiphilic Membranes

Employing DNA nanostructures mimicking membrane proteins on artificial amphiphilic membranes have been widely developed to understand the structures and functions of the natural membrane systems. In this review, the recent developments in artificial systems constructed by amphiphilic membranes and DNA nanostructures are summarized. First, the preparations and properties of the amphipathic bilayer models are introduced. Second, the interactions are discussed between the membrane and the DNA nanostructures, as well as their coassembly behaviors. Next, the alternative systems related to membrane protein-mediated signal transmission, selective distribution, transmembrane channels, and membrane fusion are also introduced. Moreover, the constructions of membrane skeleton protein-mimicking DNA nanostructures are also highlighted.

3D DNA Nanostructures: The Nanoscale Architect

Structural DNA nanotechnology is a pioneering biotechnology that presents the opportunity to engineer DNA-based hardware that will mediate a profound interface to the nanoscale. To date, an enormous library of shaped 3D DNA nanostructures have been designed and assembled. Moreover, recent research has demonstrated DNA nanostructures that are not only static but can exhibit specific dynamic motion. DNA nanostructures have thus garnered significant research interest as a template for pursuing shape and motion-dependent nanoscale phenomena. Potential applications have been explored in many interdisciplinary areas spanning medicine, biosensing, nanofabrication, plasmonics, single-molecule chemistry, and facilitating biophysical studies. In this review, we begin with a brief overview of general and versatile design techniques for 3D DNA nanostructures as well as some techniques and studies that have focused on improving the stability of DNA nanostructures in diverse environments, which is pivotal for its reliable utilization in downstream applications. Our main focus will be to compile a wide body of existing research on applications of 3D DNA nanostructures that demonstrably rely on the versatility of their mechanical design. Furthermore, we frame reviewed applications into three primary categories, namely encapsulation, surface templating, and nanomechanics, that we propose to be archetypal shape- or motion-related functions of DNA nanostructures found in nanoscience applications. Our intent is to identify core concepts that may define and motivate specific directions of progress in this field as we conclude the review with some perspectives on the future.

DNA Origami Meets Polymers: A Powerful Tool for the Design of Defined Nanostructures

The combination of DNA origami nanostructures and polymers provides a new possibility to access defined structures in the 100 nm range. In general, DNA origami serves as a versatile template for the highly specific arrangement of polymer chains. Polymer-DNA hybrid nanostructures can either be created by growing the polymer from the DNA template or by attaching preformed polymers to the DNA scaffold. These conjugations can be of a covalent nature or be based on base-pair hybridization between respectively modified polymers and DNA origami. Furthermore, the negatively charged DNA backbone permits interaction with positively charged polyelectrolytes to form stable complexes. The combination of polymers with tuneable characteristics and DNA origami allows the creation of a new class of hybrid materials, which could offer exciting applications for controlled energy transfer, nanoscale organic circuits, or the templated synthesis of nanopatterned polymeric structures.

Recent Advances of DNA Nanostructure-Based Cell Membrane Engineering

Materials that can regulate the composition and structure of the cell membrane to fabricate engineered cells with defined functions are in high demand. Compared with other biomolecules, DNA has unique advantages in cell membrane engineering due to its excellent programmability and biocompatibility. Especially, the near-atomic scale precision of DNA nanostructures facilitates the investigation of structure-property relations on the cell membrane. In this review, first the state of the art of functional DNA nanostructures is summarized, and then the overview of the use of DNA nanostructures to engineer the cell membrane is presented. Subsequently, applications of DNA nanostructures in modifying cell membrane morphology, controlling ions transport, and synthesizing high precise liposomes are highlighted. Finally, the challenges and outlook on using DNA nanostructures for cell membrane engineering are discussed.

Reversible membrane deformations by straight DNA origami filaments

Membrane-active cytoskeletal elements, such as FtsZ, septin or actin, form filamentous polymers able to induce and stabilize curvature on cellular membranes. In order to emulate the characteristic dynamic self-assembly properties of cytoskeletal subunits in vitro, biomimetic synthetic scaffolds were here developed using DNA origami. In contrast to our earlier work with pre-curved scaffolds, we specifically assessed the potential of origami mimicking straight filaments, such as actin and microtubules, by origami presenting cholesteryl anchors for membrane binding and additional blunt end stacking interactions for controllable polymerization into linear filaments. By assessing the interaction of our DNA nanostructures with model membranes using fluorescence microscopy, we show that filaments can be formed, upon increasing MgCl2 in solution, for structures displaying blunt ends; and can subsequently depolymerize, by decreasing the concentration of MgCl2. Distinctive spike-like membrane protrusions were generated on giant unilamellar vesicles at high membrane-bound filament densities, and the presence of such deformations was reversible and shown to correlate with the MgCl2-triggered polymerization of DNA origami subunits into filamentous aggregates. In the end, our approach reveals the formation of membrane-bound filaments as a minimal requirement for membrane shaping by straight cytoskeletal-like objects.

Synthesis and applications of anisotropic nanoparticles with precisely defined dimensions

Shape and size play powerful roles in determining the properties of a material; controlling these aspects with precision is therefore an important, fundamental goal of the chemical sciences. In particular, the introduction of shape anisotropy at the nanoscale has emerged as a potent way to access new properties and functionality, enabling the exploration of complex nanomaterials across a range of applications. Recent advances in DNA and protein nanotechnology, inorganic crystallization techniques, and precision polymer self-assembly are now enabling unprecedented control over the synthesis of anisotropic nanoparticles with a variety of shapes, encompassing one-dimensional rods, dumbbells and wires, two-dimensional and three-dimensional platelets, rings, polyhedra, stars, and more. This has, in turn, enabled much progress to be made in our understanding of how anisotropy and particle dimensions can be tuned to produce materials with unique and optimized properties. In this Review, we bring these recent developments together to critically appraise the different methods for the bottom-up synthesis of anisotropic nanoparticles enabling exquisite control over morphology and dimensions. We highlight the unique properties of these materials in arenas as diverse as electron transport and biological processing, illustrating how they can be leveraged to produce devices and materials with otherwise inaccessible functionality. By making size and shape our focus, we aim to identify potential synergies between different disciplines and produce a road map for future research in this crucial area.

Engineering spatiotemporal organization and dynamics in synthetic cells

Constructing synthetic cells has recently become an appealing area of research. Decades of research in biochemistry and cell biology have amassed detailed part lists of components involved in various cellular processes. Nevertheless, recreating any cellular process in vitro in cell-sized compartments remains ambitious and challenging. Two broad features or principles are key to the development of synthetic cells-compartmentalization and self-organization/spatiotemporal dynamics. In this review article, we discuss the current state of the art and research trends in the engineering of synthetic cell membranes, development of internal compartmentalization, reconstitution of self-organizing dynamics, and integration of activities across scales of space and time. We also identify some research areas that could play a major role in advancing the impact and utility of engineered synthetic cells. This article is categorized under: Biology-Inspired Nanomaterials > Lipid-Based Structures Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Hydrophobic Interaction: A Promising Driving Force for the Biomedical Applications of Nucleic Acids

The comprehensive understanding and proper use of supramolecular interactions have become critical for the development of functional materials, and so is the biomedical application of nucleic acids (NAs). Relatively rare attention has been paid to hydrophobic interaction compared with hydrogen bonding and electrostatic interaction of NAs. However, hydrophobic interaction shows some unique properties, such as high tunability for application interest, minimal effect on NA functionality, and sensitivity to external stimuli. Therefore, the widespread use of hydrophobic interaction has promoted the evolution of NA-based biomaterials in higher-order self-assembly, drug/gene-delivery systems, and stimuli-responsive systems. Herein, the recent progress of NA-based biomaterials whose fabrications or properties are highly determined by hydrophobic interactions is summarized. 1) The hydrophobic interaction of NA itself comes from the accumulation of base-stacking forces, by which the NAs with certain base compositions and chain lengths show properties similar to thermal-responsive polymers. 2) In conjugation with hydrophobic molecules, NA amphiphiles show interesting self-assembly structures with unique properties in many new biosensing and therapeutic strategies. 3) The working-mechanisms of some NA-based complex materials are also dependent on hydrophobic interactions. Moreover, in recent attempts, NA amphiphiles have been applied in organizing macroscopic self-assembly of DNA origami and controlling the cell-cell interactions.

Controlling Matter at the Molecular Scale with DNA Circuits

In recent years, a diverse set of mechanisms have been developed that allow DNA strands with specific sequences to sense information in their environment and to control material assembly, disassembly, and reconfiguration. These sequences could serve as the inputs and outputs for DNA computing circuits, enabling DNA circuits to act as chemical information processors to program complex behavior in chemical and material systems. This review describes processes that can be sensed and controlled within such a paradigm. Specifically, there are interfaces that can release strands of DNA in response to chemical signals, wavelengths of light, pH, or electrical signals, as well as DNA strands that can direct the self-assembly and dynamic reconfiguration of DNA nanostructures, regulate particle assemblies, control encapsulation, and manipulate materials including DNA crystals, hydrogels, and vesicles. These interfaces have the potential to enable chemical circuits to exert algorithmic control over responsive materials, which may ultimately lead to the development of materials that grow, heal, and interact dynamically with their environments.

DNA-Mediated Step-Growth Polymerization of Bottlebrush Macromonomers

Herein, we report the DNA-mediated self-assembly of bivalent bottlebrush polymers, a process akin to the step-growth polymerization of small molecule monomers. In these "condensation reactions", the polymer serves as a steric guide to limit DNA hybridization in a fixed direction, while the DNA serves as a functional group equivalent, connecting complementary brushes to form well-defined, one-dimensional nanostructures. The polymerization was studied using spectroscopy, microscopy, and scattering techniques and was modeled numerically. The model made predictions of the degree of polymerization and size distribution of the assembled products, and suggested the potential for branching at hybridization junctions, all of which were confirmed experimentally. This study serves as a theoretical basis for the polymer-assembly approach which has the potential to open up new possibilities for suprapolymers with controlled architecture, macromonomer sequence, and end-group functionalities.

DNA-Programmed Chemical Synthesis of Polymers and Inorganic Nanomaterials

DNA nanotechnology, based on sequence-specific DNA recognition, could allow programmed self-assembly of sophisticated nanostructures with molecular precision. Extension of this technique to the preparation of broader types of nanomaterials would significantly improve nanofabrication technique to lower nanometer scale and even achieve single molecule operation. Using such exquisite DNA nanostructures as templates, chemical synthesis of polymer and inorganic nanomaterials could also be programmed with unprecedented accuracy and flexibility. This review summarizes recent advances in the synthesis and assembly of polymer and inorganic nanomaterials using DNA nanostructures as templates, and discusses the current challenges and future outlook of DNA templated nanotechnology.

Gene/paclitaxel co-delivering nanocarriers prepared by framework-induced self-assembly for the inhibition of highly drug-resistant tumors

While drug resistance has been recognized as the main cause of unsuccessful chemotherapy, the efficient inhibition of highly drug-resistant tumors still remains a significant challenge, especially for in vivo treatments. Drug resistance has been associated with the high expression of the multi-drug resistance gene 1 (MDR1), which can encode an efflux transporter known as P-glycoprotein (P-gp) that is located in the cellular membrane. Therefore, the combined delivery of MDR1-inhibited genes and chemotherapeutic drugs is anticipated to enable the effective inhibition of drug-resistant tumors. Herein, highly paclitaxel (PTX)-resistant ovarian (OV) cancer with a drug resistance index reaching up to ~ 60 was chosen to evaluate the performance of an efficient gene/drug co-delivery nanocarrier. Inspired by the self-assembly that occurs in cells and exosomes, we designed a biomimetic lipid/dextran hybrid nanocarrier with a diameter of ~ 100 nm to enhance the endocytosis and the efficiency of drug/gene release within the cells. This nanocarrier was fabricated via the frame-guided self-assembly of lipid amphiphiles on the surfaces of redox-cleavable dextran-based nanogels. The anionic MDR1-siRNA and the hydrophobic drug PTX were respectively loaded into the cationic lipid shell and the hydrophobic internal core of the hybrid nanocarriers. MDR1-siRNA can knock down MDR1, promoting the accumulation of PTX in cells, and thus is expected to achieve an efficient inhibitory effect against highly PTX-resistant cancer cells. Both in vitro and in vivo studies revealed that this dual-delivery system significantly enhanced the therapeutic effect in comparison with that provided by a PTX-only system. Thus, the construction of gene/chemo co-delivered lipid/dextran nanocarriers provides a new strategy to inhibit highly drug-resistant tumors both in vitro and in vivo. In addition, this work will contribute toward the development of urgently needed tumor nanotherapy that is able to overcome drug resistance while also offering an unmatched range of effective therapeutic nanocarriers. STATEMENT OF SIGNIFICANCE: The biomimetic lipid/dextran hybrid nanocarrier with a diameter of ~ 100 nm, which was fabricated via the frame-guided self-assembly of lipid amphiphiles onto the surface of redox-cleavable dextran-based nanogels, provides a model carrier to co-deliver MDR1-siRNA and PTX.  The MDR1-siRNA/PTX co-loaded biomimetic lipid/dextran hybrid nanocarriers demonstrate good capability in overcoming the PTX-resistance in highly chemo-resistant human ovarian (OV) cancer cells both in vitro and in vivo.

Artificial Phospholipids and Their Vesicles

Phospholipids are at the heart and origin of life on this planet. The possibilities in terms of phospholipid self-assembly and biological functions seem limitless. Nonetheless, nature exploits only a small fraction of the available chemical space of phospholipids. Using chemical synthesis, artificial phospholipid structures become accessible, and the study of their biophysics may reveal unprecedented properties. In this article, the recent advances by our work group in the field of chemical lipidology are summarized. The family of diamidophospholipids is discussed in detail from monolayer characterization to the formation of faceted vesicles, culminating in the template-free self-assembly of phospholipid cubes and the possible applications of vesicle origami in modern personalized medicine.

Branched DNA Architectures Produced by PCR-Based Assembly as Gene Compartments for Cell-Free Gene-Expression Reactions

The physical distance between genes plays important roles in controlling gene expression reactions in vivo. Herein, we report the design and synthesis of a branched gene architecture in which three transcription units are integrated into one framework through assembly based on the polymerase chain reaction (PCR), together with the exploitation of these constructs as "gene compartments" for cell-free gene expression reactions, probing the impact of this physical environment on gene transcription and translation. We find that the branched gene system enhances gene expression yields, in particular at low concentrations of DNA and RNA polymerase (RNAP); furthermore, in a crowded microenvironment that mimics the intracellular microenvironment, gene expression from branched genes maintains a relatively high level. We propose that the branched gene assembly forms a membrane-free gene compartment that resembles the nucleoid of prokaryotes and enables RNAP to shuttle more efficiently between neighboring transcription units, thus enhancing gene expression efficiency. Our branched DNA architecture provides a valuable platform for studying the influence of "cellular" physical environments on biochemical reactions in simplified cell-free systems.

From DNA Nanotechnology to Material Systems Engineering

In the past 35 years, DNA nanotechnology has grown to a highly innovative and vibrant field of research at the interface of chemistry, materials science, biotechnology, and nanotechnology. Herein, a short summary of the state of research in various subdisciplines of DNA nanotechnology, ranging from pure "structural DNA nanotechnology" over protein-DNA assemblies, nanoparticle-based DNA materials, and DNA polymers to DNA surface technology is given. The survey shows that these subdisciplines are growing ever closer together and suggests that this integration is essential in order to initiate the next phase of development. With the increasing implementation of machine-based approaches in microfluidics, robotics, and data-driven science, DNA-material systems will emerge that could be suitable for applications in sensor technology, photonics, as interfaces between technical systems and living organisms, or for biomimetic fabrication processes.

3D Lattice Engineering of Nanoparticles by DNA Shells

With the development of structural DNA nanotechnology, DNA has now far exceeded its original function: as a genetic code. It can, in principle, self-assemble into desired shapes with accurate size. Moreover, it can perform as a functional linker to program other materials by grafting DNA onto these materials. Nanoparticles, both inorganic and organic, can now be programmatically assembled into complex 3D superlattices with high order when guided by DNA. By encoding functions into the as-assembled nanoparticles, materials with excellent collective effects may be invented. Here, how nanoparticles with different shapes or functions are successfully fabricated into 3D lattices with the help of DNA shells coated on the surface and how scientists can produce desired lattices by design are reviewed. The cases to achieve dynamic superlattices of nanoparticles by affecting the environment where DNA survives are also discussed.

DNA-Based Nanofabrication: Pathway to Applications in Surface Engineering

This Concept provides an overview of recent developments of DNA-based nanofabrication and discusses its potential applications in the area of surface engineering. The first part of the paper discusses the strength and limitations of existing DNA-based nanofabrication methods. The second part highlights several examples of surface engineering applications involving nano- and microscale surface textures. It finishes with a discussion of the opportunities and remaining challenges of applying DNA-based nanofabrication in surface engineering applications.

Dynamic Nanostructures from DNA-Coupled Molecules, Polymers, and Nanoparticles

Dynamic and reconfigurable systems that can sense and react to physical and chemical signals are ubiquitous in nature and are of great interest in diverse areas of science and technology. DNA is a powerful tool for fabricating such smart materials and devices due to its programmable and responsive molecular recognition properties. For the past couple of decades, DNA-based self-assembly is actively explored to fabricate various DNA-organic and DNA-inorganic hybrid nanostructures with high-precision structural control. Building upon past development, researchers have recently begun to design and assemble dynamic nanostructures that can undergo an on-demand transformation in the structure, properties, and motion in response to various external stimuli. In this Review, recent advances in dynamic DNA nanostructures, focusing on hybrid structures fabricated from DNA-conjugated molecules, polymers, and nanoparticles, are introduced, and their potential applications and future perspectives are discussed.

Synthetic cell division via membrane-transforming molecular assemblies

Reproduction, i.e. the ability to produce new individuals from a parent organism, is a hallmark of living matter. Even the simplest forms of reproduction require cell division: attempts to create a designer cell therefore should include a synthetic cell division machinery. In this review, we will illustrate how nature solves this task, describing membrane remodelling processes in general and focusing on bacterial cell division in particular. We discuss recent progress made in their in vitro reconstitution, identify open challenges, and suggest how purely synthetic building blocks could provide an additional and attractive route to creating artificial cell division machineries.

DNA Nanotechnology Enters Cell Membranes

DNA is more than a carrier of genetic information: It is a highly versatile structural motif for the assembly of nanostructures, giving rise to a wide range of functionalities. In this regard, the structure programmability is the main advantage of DNA over peptides, proteins, and small molecules. DNA amphiphiles, in which DNA is covalently bound to synthetic hydrophobic moieties, allow interactions of DNA nanostructures with artificial lipid bilayers and cell membranes. These structures have seen rapid growth with great potential for medical applications. In this Review, the current state of the art of the synthesis of DNA amphiphiles and their assembly into nanostructures are first summarized. Next, an overview on the interaction of these DNA amphiphiles with membranes is provided, detailing on the driving forces and the stability of the interaction. Moreover, the interaction with cell surfaces in respect to therapeutics, biological sensing, and cell membrane engineering is highlighted. Finally, the challenges and an outlook on this promising class of DNA hybrid materials are discussed.

Emerging Biomimetic Applications of DNA Nanotechnology

Re-engineering cellular components and biological processes has received great interest and promised compelling advantages in applications ranging from basic cell biology to biomedicine. With the advent of DNA nanotechnology, the programmable self-assembly ability makes DNA an appealing candidate for rational design of artificial components with different structures and functions. This Forum Article summarizes recent developments of DNA nanotechnology in mimicking the structures and functions of existing cellular components. We highlight key successes in the achievements of DNA-based biomimetic membrane proteins and discuss the assembly behavior of these artificial proteins. Then, we focus on the construction of higher-order structures by DNA nanotechnology to recreate cell-like structures. Finally, we explore the current challenges and speculate on future directions of DNA nanotechnology in biomimetics.

Placing and shaping liposomes with reconfigurable DNA nanocages

The diverse structure and regulated deformation of lipid bilayer membranes are among a cell's most fascinating features. Artificial membrane-bound vesicles, known as liposomes, are versatile tools for modelling biological membranes and delivering foreign objects to cells. To fully mimic the complexity of cell membranes and optimize the efficiency of delivery vesicles, controlling liposome shape (both statically and dynamically) is of utmost importance. Here we report the assembly, arrangement and remodelling of liposomes with designer geometry: all of which are exquisitely controlled by a set of modular, reconfigurable DNA nanocages. Tubular and toroid shapes, among others, are transcribed from DNA cages to liposomes with high fidelity, giving rise to membrane curvatures present in cells yet previously difficult to construct in vitro. Moreover, the conformational changes of DNA cages drive membrane fusion and bending with predictable outcomes, opening up opportunities for the systematic study of membrane mechanics.

Cationic Albumin Encapsulated DNA Origami for Enhanced Cellular Transfection and Stability

DNA nanostructures, owing to their controllable and adaptable nature, have been considered as highly attractive nanoplatforms for biomedical applications in recent years. However, their use in the biological environment has been restricted by low cellular transfection efficiency in mammalian cells, weak stability under physiological conditions, and endonuclease degradation. Herein, we demonstrate an effective approach to facilitate fast transfection of DNA nanostructures and enhance their stability by encapsulating DNA origami with a biocompatible cationic protein (cHSA) via electrostatic interaction. The coated DNA origami is found to be stable under physiological conditions. Moreover, the cHSA coating could significantly improve the cellular transfection efficiency of DNA origami, which is essential for biological applications.

Chemistries for DNA Nanotechnology

The predictable nature of DNA interactions enables the programmable assembly of highly advanced 2D and 3D DNA structures of nanoscale dimensions. The access to ever larger and more complex structures has been achieved through decades of work on developing structural design principles. Concurrently, an increased focus has emerged on the applications of DNA nanostructures. In its nature, DNA is chemically inert and nanostructures based on unmodified DNA mostly lack function. However, functionality can be obtained through chemical modification of DNA nanostructures and the opportunities are endless. In this review, we discuss methodology for chemical functionalization of DNA nanostructures and provide examples of how this is being used to create functional nanodevices and make DNA nanostructures more applicable. We aim to encourage researchers to adopt chemical modifications as part of their work in DNA nanotechnology and inspire chemists to address current challenges and opportunities within the field.