Tunable DNA Origami Motors Translocate Ballistically Over μm Distances at nm/s Speeds

Inspired by biological motor proteins, that efficiently convert chemical fuel to unidirectional motion, there has been considerable interest in developing synthetic analogues. Among the synthetic motors created thus far, DNA motors that undertake discrete steps on RNA tracks have shown the greatest promise. Nonetheless, DNA nanomotors lack intrinsic directionality, are low speed and take a limited number of steps prior to stalling or dissociation. Herein, we report the first example of a highly tunable DNA origami motor that moves linearly over micron distances at an average speed of 40 nm/min. Importantly, nanomotors move unidirectionally without intervention through an external force field or a patterned track. Because DNA origami enables precise testing of nanoscale structure-function relationships, we were able to experimentally study the role of motor shape, chassis flexibility, leg distribution, and total number of legs in tuning performance. An anisotropic rigid chassis coupled with a high density of legs maximizes nanomotor speed and endurance.     

Bioinspired Chemical Communication between Synthetic Nanomotors

While chemical communication plays a key role in diverse natural processes, the intelligent chemical communication between synthetic nanomotors remains unexplored. The design and operation of bioinspired synthetic nanomotors is presented. Chemical communication between nanomotors is possible and has an influence on propulsion behavior. A chemical “message” is sent from a moving activator motor to a nearby activated (receiver) motor by release of Ag⁺ ions from a Janus polystyrene/Ni/Au/Ag activator motor to the activated Janus SiO₂/Pt nanomotor. The transmitted silver signal is translated rapidly into a dramatic speed change associated with the enhanced catalytic activity of activated motors. Selective and successive activation of multiple nanomotors is achieved by sequential localized chemical communications. The concept of establishing chemical communication between different synthetic nanomotors paves the way to intelligent nanoscale robotic systems that are capable of cooperating with each other.     

Achieving Control in Micro-/Nanomotor Mobility

Unprecedented opportunities exist for the generation of advanced nanotechnologies based on synthetic micro/nanomotors (MNMs), such as active transport of medical agents or the removal of pollutants. In this regard, great efforts have been dedicated toward controlling MNM motion (e.g., speed, directionality). This was generally performed by precise engineering and optimizing of the motors′ chassis, engine, powering mode (i.e., chemical or physical), and mechanism of motion. Recently, new insights have emerged to control motors mobility, mainly by the inclusion of different modes that drive propulsion. With high degree of synchronization, these modes work providing the required level of control. In this Minireview, we discuss the diverse factors that impact motion; these include MNM morphology, modes of mobility, and how control over motion was achieved. Moreover, we highlight the main limitations that need to be overcome so that such motion control can be translated into real applications.     

Fuel‐Free Micro‐/Nanomotors as Intelligent Therapeutic Agents

There are many efficient biological motors in Nature that perform complex functions by converting chemical energy into mechanical motion. Inspired by this, the development of their synthetic counterparts has aroused tremendous research interest in the past decade. Among these man‐made motor systems, the fuel‐free (or light, magnet, ultrasound, or electric field driven) motors are advantageous in terms of controllability, lifespan, and biocompatibility concerning bioapplications, when compared with their chemically powered counterparts. Therefore, this review will highlight the latest biomedical applications in the versatile field of externally propelled micro‐/nanomotors, as well as elucidating their driving mechanisms. A perspective into the future of the micro‐/nanomotors field and a discussion of the challenges we need to face along the road towards practical clinical translation of external‐field‐propelled micro‐/nanomotors will be provided.     

Complexing DNA Origami Frameworks through Sequential Self‐Assembly Based on Directed Docking

Ordered DNA origami arrays have the potential to compartmentalize space into distinct periodic domains that can incorporate a variety of nanoscale objects. Herein, we used the cavities of a preassembled 2D DNA origami framework to incorporate square‐shaped DNA origami structures (SQ‐origamis). The framework was self‐assembled on a lipid bilayer membrane from cross‐shaped DNA origami structures (CR‐origamis) and subsequently exposed to the SQ‐origamis. High‐speed AFM revealed the dynamic adsorption/desorption behavior of the SQ‐origamis, which resulted in continuous changing of their arrangements in the framework. These dynamic SQ‐origamis were trapped in the cavities by increasing the Mg²⁺ concentration or by introducing sticky‐ended cohesions between extended staples, both from the SQ‐ and CR‐origamis, which enabled the directed docking of the SQ‐origamis. Our study offers a platform to create supramolecular structures or systems consisting of multiple DNA origami components.     

High‐Throughput Design of Biocompatible Enzyme‐Based Hydrogel Microparticles with Autonomous Movement

Micro‐ and nanomotors and their use for biomedical applications have recently received increased attention. However, most designs use top‐down methods to construct inorganic motors, which are labour‐intensive and not suitable for biomedical use. Herein, we report a high‐throughput design of an asymmetric hydrogel microparticle with autonomous movement by using a microfluidic chip to generate asymmetric, aqueous, two‐phase‐separating droplets consisting of poly(ethylene glycol) diacrylate (PEGDA) and dextran, with the biocatalyst placed in the PEGDA phase. The motor is propelled by enzyme‐mediated decomposition of fuel. The speed of the motors is influenced by the roughness of the PEGDA surface after diffusion of dextran and was tuned by using higher molecular weight dextran. This roughness allows for easier pinning of oxygen bubbles and thus higher speeds of the motors. Pinning of bubbles occurs repeatedly at the same location, thereby resulting in constant circular or linear motion.     

The Art of Designing DNA Nanostructures with CAD Software

Since the arrival of DNA nanotechnology nearly 40 years ago, the field has progressed from its beginnings of envisioning rather simple DNA structures having a branched, multi-strand architecture into creating beautifully complex structures comprising hundreds or even thousands of unique strands, with the possibility to exactly control the positions down to the molecular level. While the earliest construction methodologies, such as simple Holliday junctions or tiles, could reasonably be designed on pen and paper in a short amount of time, the advent of complex techniques, such as DNA origami or DNA bricks, require software to reduce the time required and propensity for human error within the design process. Where available, readily accessible design software catalyzes our ability to bring techniques to researchers in diverse fields and it has helped to speed the penetration of methods, such as DNA origami, into a wide range of applications from biomedicine to photonics. Here, we review the historical and current state of CAD software to enable a variety of methods that are fundamental to using structural DNA technology. Beginning with the first tools for predicting sequence-based secondary structure of nucleotides, we trace the development and significance of different software packages to the current state-of-the-art, with a particular focus on programs that are open source.     

Motion Control of Polymeric Nanomotors Based on Host–Guest Interactions

Controlling the motion of artificial self‐propelled micro‐ and nanomotors independent of the fuel concentration is still a great challenge. Here we describe the first report of speed manipulation of supramolecular nanomotors via blue light‐responsive valves, which can regulate the access of hydrogen peroxide fuel into the motors. Light‐sensitive polymeric nanomotors are built up via the self‐assembly of functional block copolymers, followed by bowl‐shaped stomatocyte formation and incorporation of platinum nanoparticles. Subsequent addition of β‐cyclodextrin (β‐CD) leads to the formation of inclusion complexes with the trans‐isomers of the azobenzene derivatives grafted from the surfaces of the stomatocytes. β‐CDs attachment decreases the diffusion rate of hydrogen peroxide into the cavities of the motors because of partly blocking of the openings of the stomatocyte. This results in a lowering of the speed of the nanomotors. Upon blue light irradiation, the trans‐azobenzene moieties isomerize to the cis‐form, which lead to the detachment of the β‐CDs due to their inability to form complexes with the cis‐isomer. As a result, the speed of the nanomotors increases accordingly. Such a conformational change provides us with the unique possibility to control the speed of the supramolecular nanomotor via light‐responsive host–guest complexation. We envision that such artificial responsive nano‐systems with controlled motion could have potential applications in drug delivery.     

Block Copolymer Micellization as a Protection Strategy for DNA Origami

DNA nanotechnology enables the synthesis of nanometer‐sized objects that can be site‐specifically functionalized with a large variety of materials. For these reasons, DNA‐based devices such as DNA origami are being considered for applications in molecular biology and nanomedicine. However, many DNA structures need a higher ionic strength than that of common cell culture buffers or bodily fluids to maintain their integrity and can be degraded quickly by nucleases. To overcome these deficiencies, we coated several different DNA origami structures with a cationic poly(ethylene glycol)–polylysine block copolymer, which electrostatically covered the DNA nanostructures to form DNA origami polyplex micelles (DOPMs). This straightforward, cost‐effective, and robust route to protect DNA‐based structures could therefore enable applications in biology and nanomedicine where unprotected DNA origami would be degraded.     

DNA Origami Post‐Processing by CRISPR‐Cas12a

Customizable nanostructures built through the DNA‐origami technique hold tremendous promise in nanomaterial fabrication and biotechnology. Despite the cutting‐edge tools for DNA‐origami design and preparation, it remains challenging to separate structural components of an architecture built from—thus held together by—a continuous scaffold strand, which in turn limits the modularity and function of the DNA‐origami devices. To address this challenge, here we present an enzymatic method to clean up and reconfigure DNA‐origami structures. We target single‐stranded (ss) regions of DNA‐origami structures and remove them with CRISPR‐Cas12a, a hyper‐active ssDNA endonuclease without sequence specificity. We demonstrate the utility of this facile, selective post‐processing method on DNA structures with various geometrical and mechanical properties, realizing intricate structures and structural transformations that were previously difficult to engineer. Given the biocompatibility of Cas12a‐like enzymes, this versatile tool may be programmed in the future to operate functional nanodevices in cells.     

Universal optimal working cycles of molecular motors

Molecular motors capable of directional track-walking or rotation are abundant in living cells, and inspire the emerging field of artificial nanomotors. Some biomotors can convert 90% of free energy from chemical fuels into usable mechanical work, and the same motors still maintain a speed sufficient for cellular functions. This study exposed a new regime of universal optimization that amounts to a thermodynamically best working regime for molecular motors but is unfamiliar in macroscopic engines. For the ideal case of zero energy dissipation, the universally optimized working cycle for molecular motors is infinitely slow like Carnot cycle for heat engines. But when a small amount of energy dissipation reduces energy efficiency linearly from 100%, the speed is recovered exponentially due to Boltzmann's law. Experimental data on a major biomotor (kinesin) suggest that the regime of universal optimization has been largely approached in living cells, underpinning the extreme efficiency-speed trade-off in biomotors. The universal optimization and its practical approachability are unique thermodynamic advantages of molecular systems over macroscopic engines in facilitating motor functions. The findings have important implications for the natural evolution of biomotors as well as the development of artificial counterparts.     

Vesicle Tubulation with Self‐Assembling DNA Nanosprings

A major goal of nanotechnology and bioengineering is to build artificial nanomachines capable of generating specific membrane curvatures on demand. Inspired by natural membrane‐deforming proteins, we designed DNA‐origami curls that polymerize into nanosprings and show their efficacy in vesicle deformation. DNA‐coated membrane tubules emerge from spherical vesicles when DNA‐origami polymerization or high membrane‐surface coverage occurs. Unlike many previous methods, the DNA self‐assembly‐mediated membrane tubulation eliminates the need for detergents or top‐down manipulation. The DNA‐origami design and deformation conditions have substantial influence on the tubulation efficiency and tube morphology, underscoring the intricate interplay between lipid bilayers and vesicle‐deforming DNA structures.     

Light-Activated Assembly of DNA Origami into Dissipative Fibrils

Hierarchical DNA nanostructures offer programmable functions at scale, but making these structures dynamic, while keeping individual components intact, is challenging. Here we show that the DNA A-motif—protonated, self-complementary poly(adenine) sequences—can propagate DNA origami into one-dimensional, micron-length fibrils. When coupled to a small molecule pH regulator, visible light can activate the hierarchical assembly of our DNA origami into dissipative fibrils. This system is recyclable and does not require DNA modification. By employing a modular and waste-free strategy to assemble and disassemble hierarchical structures built from DNA origami, we offer a facile and accessible route to developing well-defined, dynamic, and large DNA assemblies with temporal control. As a general tool, we envision that coupling the A-motif to cycles of dissipative protonation will allow the transient construction of diverse DNA nanostructures, finding broad applications in dynamic and non-equilibrium nanotechnology.     

Fabrication of Self-Propelled Micro- and Nanomotors Based on Janus Structures

Delicate molecular and biological motors are tiny machines capable of achieving numerous vital tasks in biological processes. To gain a deeper understanding of their mechanism of motion, researchers from multiple backgrounds have designed and fabricated artificial micro- and nanomotors. These nano-/microscale motors can self-propel in solution by exploiting different sources of energy; thus showing tremendous potential in widespread applications. As one of the most common motor systems, Janus motors possess unique asymmetric structures and integrate different functional materials onto two sides. This review mainly focuses on the fabrication of different types of micro- and nanomotors based on Janus structures. Furthermore, some challenges still exist in the implementation of Janus motors in the biomedical field. With such common goals in mind, it is expected that the elaborate and multifunctional design of Janus motors will overcome their challenges in the near future.     

Cargo-towing synthetic nanomachines: towards active transport in microchip devices

This review article discusses the use of synthetic catalytic nano motors for cargo manipulations and for developing miniaturized lab-on-chip systems based on autonomous transport. The ability of using chemically-powered artificial nanomotors to capture, transport and release therapeutic payloads or nanostructured biomaterials represents one of the next major prospects for nanomotor development. The increased cargo-towing force of such self-propelled nanomotors, along with their precise motion control within microchannel networks, versatility and facile functionalization, pave the way to new integrated functional lab-on-a-chip powered by active transport and perform a series of tasks. Such use of cargo-towing artificial nanomotors has been inspired by on-chip kinesin molecular shuttles. Functionalized nano/microscale motors can thus be used to pick a selected nano/microscale chemical or biological payload target at the right place, transport and deliver them to a target location in a timely manner. Key challenges for using synthetic nanomachines for driving transport processes along microchannel networks are discussed, including loading and unloading of cargo and precise motion control, along with recent examples of related cargo manipulation processes and guided transport in lab-on-a-chip formats. The exciting research area of cargo-carrying catalytic man-made nanomachines is expected to grow rapidly, to lead to new lab-on-a-chip formats and to provide a wide range of future microchip opportunities.     

Surface‐Assisted Large‐Scale Ordering of DNA Origami Tiles

The arrangement of DNA‐based nanostructures into extended higher order assemblies is an important step towards their utilization as functional molecular materials. We herein demonstrate that by electrostatically controlling the adhesion and mobility of DNA origami structures on mica surfaces by the simple addition of monovalent cations, large ordered 2D arrays of origami tiles can be generated. The lattices can be formed either by close‐packing of symmetric, non‐interacting DNA origami structures, or by utilizing blunt‐end stacking interactions between the origami units. The resulting crystalline lattices can be readily utilized as templates for the ordered arrangement of proteins.     

On the Stability of DNA Origami Nanostructures in Low‐Magnesium Buffers

DNA origami structures have great potential as functional platforms in various biomedical applications. Many applications, however, are incompatible with the high Mg²⁺ concentrations commonly believed to be a prerequisite for maintaining DNA origami integrity. Herein, we investigate DNA origami stability in low‐Mg²⁺ buffers. DNA origami stability is found to crucially depend on the availability of residual Mg²⁺ ions for screening electrostatic repulsion. The presence of EDTA and phosphate ions may thus facilitate DNA origami denaturation by displacing Mg²⁺ ions from the DNA backbone and reducing the strength of the Mg²⁺–DNA interaction, respectively. Most remarkably, these buffer dependencies are affected by DNA origami superstructure. However, by rationally selecting buffer components and considering superstructure‐dependent effects, the structural integrity of a given DNA origami nanostructure can be maintained in conventional buffers even at Mg²⁺ concentrations in the low‐micromolar range.     

Multivalent Aptamer-modified DNA Origami as Drug Delivery System for Targeted Cancer Therapy

In spite of great development in nanoparticle-based drug delivery systems(DDSs)for improved therapeutic efficacy,it remains challenging for effective delivery of chemotherapeutic drugs to targeted tumor cells.In this work,we report a triangle DNA origami as targeted DDS for cancer therapy.DNA origami shows excellent biocompatibility and stability in cell culture medium for 24 h.In addition,the DNA origami structures conjugated with multivalent aptamers enable for efficient delivery of anticancer drug doxorubicin(Dox)into targeted cancer cell due to their targeting function,reducing side effects associated with nonspecific distribution.Moreover,we also demonstrated that the multivalent aptamer-modified DNA origami loading Dox exhibits prominent therapeutic efficacy in vitro.Accordingly,this work provides a good paradigm for the development of DNA origami nanostructure-based targeted DDS for cancer therapy.     

Fabrication of Defined Polydopamine Nanostructures by DNA Origami‐Templated Polymerization

A versatile, bottom‐up approach allows the controlled fabrication of polydopamine (PD) nanostructures on DNA origami. PD is a biosynthetic polymer that has been investigated as an adhesive and promising surface coating material. However, the control of dopamine polymerization is challenged by the multistage‐mediated reaction mechanism and diverse chemical structures in PD. DNA origami decorated with multiple horseradish peroxidase‐mimicking DNAzyme motifs was used to control the shape and size of PD formation with nanometer resolution. These fabricated PD nanostructures can serve as “supramolecular glue” for controlling DNA origami conformations. Facile liberation of the PD nanostructures from the DNA origami templates has been achieved in acidic medium. This presented DNA origami‐controlled polymerization of a highly crosslinked polymer provides a unique access towards anisotropic PD architectures with distinct shapes that were retained even in the absence of the DNA origami template.