Dynamic DNA nanotechnology using strand-displacement reactions

Self-replicating nanomaterials as a new generation of smart nanostructures

Self-replication is the process by which a system or entity autonomously reproduces or generates copies of itself, transmitting hereditary information through its molecular structure. Self-replication can be attractive for various researchers, ranging from biologists focused on uncovering the origin of life, to synthetic chemists and nanotechnologists studying synthetic machines and nanorobots. The capability of a single structure to act as a template to produce multiple copies of itself could allow the bottom-up engineering of progressively complex reaction networks and nanoarchitectures from simple building blocks. Herein, we review nucleic acid-based and amino acid-based self-replicating systems and completely synthetic artificial systems and specially focused on specific aspects of self-replicating nanomaterials. We describe their mechanisms of action and provide a full discussion of the principal requirements for achieving nanostructures capable of self-replication.

Advancements in fluorescent nanobiosensors for HPV detection: from integrating nanomaterials to DNA nanotechnology

Human papillomavirus (HPV) is a leading cause of cervical cancer and other malignancies, necessitating the development of highly sensitive and specific detection tools. This review explores recent advancements in fluorescent nanobiosensors (FNBS) for HPV detection, focusing on the integration of nanomaterials and DNA nanotechnology, highlighting their contributions to improving sensitivity, specificity, and point-of-care (POC) usability. The review critically evaluates a range of nanomaterial-based FNBS, including those employing quantum and carbon dots, nanoclusters, nanosheets, and nanoparticles, discussing their underlying signal amplification mechanisms, target recognition strategies, and limitations related to toxicity, stability, and reproducibility. Furthermore, it examines the application of diverse DNA nanotechnology, such as DNA origami, DNAzyme, catalytic hairpin assembly (CHA), hybridization chain reaction (HCR), and DNA hydrogel in improving FNBS performance. It also addresses the current challenges in clinical translation, emphasizing the necessity for large-scale production methods and thorough clinical validation to ensure biosafety. It also outlines the potential of innovative technologies, such as CRISPR-Cas-based diagnostics and artificial intelligence, to further revolutionize HPV detection and enable accessible, cost-effective screening, particularly in resource-limited settings. This review provides a valuable resource for researchers and clinicians seeking to develop next-generation FNBS for improved HPV diagnostics and cervical cancer prevention.

Application and development of signal amplification strategy in detection of antibiotic residues in food

Food is essential for the proper functioning of the human body, and small molecule contaminants, such as antibiotics, have become a growing concern due to their harmful effects on both biological systems and the environment. These contaminants can enter the food supply through the use of antibiotics in animals, potentially causing significant health and ecological damage. As a result, detecting these pollutants, especially at trace levels, has become increasingly important. Aptamer sensors have gained popularity for this purpose because of their high stability, specificity, ease of modification, and low cost. To improve the sensitivity of these sensors, various signal enhancement strategies are used. These strategies aim to better detect small molecule contaminants, with many relying on nanomaterials and nucleic acid amplification techniques to amplify signals. Nanomaterials, which come in different forms such as zero-dimensional, one-dimensional, two-dimensional, and three-dimensional, play a crucial role in improving the performance of these sensors. This article provides an overview of these signal enhancement approaches, discussing the challenges and potential future directions for the development of aptamers in food contamination detection.

Adenosine-Triggered Dynamic and Transient Aptamer-Based Networks Integrated in Liposome Protocell Assemblies

The development of transient dissipative nucleic-acid-based reaction circuits and constitutional dynamic networks attracts growing interest as a means of emulating native dynamic reaction circuits. Recent efforts applying enzymes, DNAzymes, or light as catalysts controlling the transient, dissipative functions of DNA networks and circuits were reported. Moreover, the integration of the dynamic networks in protocell assemblies and the identification of potential applications are challenging objectives. Here, we introduce the adenosine (AD) aptamer subunit complex coupled with adenosine deaminase (ADA) as a versatile recognition/catalytic framework for driving transient allosterically AD-stabilized DNAzyme circuits or dissipative AD-stabilized constitutional dynamic networks. In addition, the AD/ADA-driven transient frameworks are integrated into liposome assemblies as protocell models. Functionalized liposomes carrying allosterically ATP-stabilized DNAzymes cleaving EGR-1 mRNA are fused with MCF-7 breast cancer cells, demonstrating effective gene therapy and selective apoptosis of cancer cells.

Enzyme- and DNAzyme-Driven Transient Assembly of DNA-Based Phase-Separated Coacervate Microdroplets

An assembly of dissipative, transient, DNA-based microdroplet (MD) coacervates in the presence of auxiliary enzymes (endonucleases and nickases) or MD-embedded DNAzyme is introduced. Two pairs of different Y-shaped DNA core frameworks modified with toehold tethers are cross-linked by complementary toehold-functionalized duplexes, engineered to be cleaved by EcoRI or HindIII endonucleases, or cross-linked by palindromic strands that include pre-engineered Nt.BbvCI or Nb.BtsI nicking sites, demonstrating transient evolution/depletion of phase-separated MD coacervates. By mixing the pairs of endonuclease- or nickase-responsive MDs, programmed or gated transient formation/depletion of MD frameworks is presented. In addition, by cross-linking a pre-engineered Y-shaped core framework with a sequence-designed fuel strand, phase separation of MD coacervates with embedded Mg2+-DNAzyme units is introduced. The DNAzyme-catalyzed cleavage of a ribonucleobase-modified hairpin substrate, generating the waste product of the metabolite fragments, leads to the metabolite-driven separation of the cross-linked coacervates, resulting in the temporal evolution and depletion of the DNAzyme-functionalized MDs. By employing a light-responsive caged hairpin structure, the light-modulated fueled evolution and depletion of the DNAzyme-active MDs are presented. The enzyme- or DNAzyme-catalyzed transient evolution/depletion of the MD coacervates provides protocell frameworks mimicking dynamic transient processes of native cells. The possible application of MDs as functional carriers for the temporal, dose-controlled release of loads is addressed.

Enzyme-free temperature resilient amplification assay with toehold stem-loop probe

Toehold mediated strand displacement reaction (TMSDR) offers a rapid, enzyme-free amplification strategy, providing advantages over traditional methods like RT-PCR, and RT-LAMP. Optimizing TMSDR can significantly enhance sensitivity in point-of-care biosensor applications for target nucleic acid detection. However, achieving optimal performance requires meticulous probe design and stringent quality control. We developed a TMSDR-based system targeting a specific SARS-CoV-2 RNA sequence through testing multiple fluorophore-quencher labeled DNA probes. Following optimization, a probe with a strategically designed: stem, loop, and optimized toehold length emerged as the most effective candidate. Displacer sequence optimization further enhanced amplification efficiency. Ensuring probe purity is crucial, as impurities elevated background noise and diminished sensitivity. This work underscores the importance of rigorous probe quality in achieving reliable and sensitive TMSDR-based viral RNA detection, paving the way for robust point-of-care diagnostic tools.

DNA-Programmed Reaction to Evaluate Specific IgE for Allergy Point-of-Care Testing

A DNA-programmed reaction to evaluate non-nucleic acids inputs with computation speed (≈30 min) and sensitivity (sub-picomolar) suitable for analyzing physiologically relevant biomarkers in a one-pot format and point-of-care testing setting is reported. Specifically, a DNA programme based on the proximity-activation exponential amplification reaction (PEAR) is designed to evaluate specific IgE (sIgE) against Der p 2 implicated in dust mite allergy which affects millions worldwide. In this work, we tailored the molecular components of the input-to-oligo barcode conversion module as an AND gate to detect inputs with binding specificity to Der p 2 antigen and is of an IgE isotype. In addition, an in situ biotinylation method is developed to generate amplified oligo barcodes amendable for direct visualization on a lateral flow format. As a proof-of-concept demonstration of its potential clinical utility, 21 clinical samples are evaluated by the as-developed sIgE PEAR programme using the dual readout modality of real-time fluorescence measurement for precise input quantification and simple lateral flow yes/no answer.

Implementing complex nucleic acid circuits in living cells

Synthetic nucleic acid-based computing has demonstrated complex computational capabilities in vitro. However, translating these circuits into living cells remains challenging because of instability and cellular interference. We introduce an allosteric strand exchange (ASE) strategy for complex intracellular computing. Leveraging conformational cooperativity to regulate strand exchange, ASE offers a modular platform for designing intracellular circuits with flexible programmability. We engineer a scalable circuit architecture based on ASE that can execute AND and OR logic and scale to an eight-input expression. We demonstrate ASE-based circuits can detect messenger RNAs with high specificity in mammalian cells via AND logic computation. The capacity of ASE-based circuits to accept messenger RNAs as inputs enables integration of endogenous cellular information for efficient multi-input information processing, demonstrated by a multi-input molecular classifier monitoring key cell reprogramming events. Reprogramming ASE-based circuit to interface with CRISPR-Cas9 enables programmable control of Cas9-targeting activity for gene editing, highlighting their potential for advancing intracellular biocomputation.

A cofactor mediated supramolecular oligo-adenine triplex for reprogrammable macroscopic hydrogel assembly

Noncanonical DNA structures mediated by low-molecular-weight cofactors significantly enrich the arsenal of the DNA toolbox and expand its functional applications. In this study, cyanuric acid (CA), a cofactor with three thymine-like edges, is employed to assemble adenine-rich strands (A-strands) into a parallel noncanonical A-CA triplex configuration through Watson-Crick and Hoogsteen interactions. This assembly occurs at a system pH value below the pKa of the CA cofactor (6.9), where CA is protonated, while its deprotonation at higher pH levels leads to the dissociation of the A-CA triplex into single A-strands and free CA cofactors. The structural transition is fully pH reversible. The A-CA triplex is further utilized as a crosslinking element for reprogrammable macroscopic object assembly, exemplified by hydrogel cubes (5 × 5 × 5 mm), a topic that has been less explored compared to nano- and microscopic constructs. Controlled, modular assembly and disassembly of various configurations, such as square, line, and T-shape, are demonstrated through reversible pH adjustments. This strategy offers a streamlined approach using a single DNA sequence and cofactor for hydrogel modification and complex construction, providing cost-effective, recyclable, and stimuli-responsive functionality, which inspires the development of versatile and adaptive supramolecular systems in chemistry and materials science.

Isothermal Disorder-to-Order Transitions of DNA Origami Structures Induced by Alternative Component Subsets

DNA origami technology has shown potential across various applications, including the construction of molecular machines. Among these, mimicking the complex structural transitions of natural biomolecules in physiological environments remains a long-standing pursuit. Here, inspired by intrinsically disordered proteins, we propose a strategy for inducing disorder-to-order transitions in DNA origami structures at room temperature using alternative component subsets. In a triangular DNA origami model, we define three subsets of its constitutional DNA staples based on their spatial distributions along the scaffold. Atomic force microscopy and molecular dynamics simulations show that the individual subsets result in metastable assemblies with disordered morphologies and elevated free-energy fluctuations compared with those generated by the complete set of staples. Notably, after the addition of the remaining staples, the irregular structures transform into ordered triangular architectures within 2 h at room temperature, achieving yields of up to ∼60%. These findings suggest that these controlled folding pathways in DNA origami can robustly converge on the global energy minimum at room temperature, thereby providing a promising alternative strategy for engineering biomimetic DNA molecular machines.

Accelerating Toehold-Mediated DNA Strand Displacement Reaction using Polyquaternium

Toehold-mediated strand displacement (TMSD) reaction is a widely used programming language in DNA nanotechnology, but its performance is significantly limited by slow kinetics, especially for low-concentration reactants. Herein, we report on polyquaternium-2 (PQ2) as an effective and efficient accelerator of TMSD reaction. We show that PQ2 could drastically increase the reaction constant of 1-nt TMSD by 105-fold. Significant acceleration of TMSD reactions with sub-nanomolar input has been demonstrated in various TMSD-based catalytic DNA amplifiers. By stabilizing DNA reactants and increasing their effective local concentrations, PQ2 enables much faster reaction kinetics in response to picomolar inputs while eliminating the dependence on toehold length, mitigating the inhibitory effect of secondary structures, maintaining single-base discriminating power, and protecting TMSD system in serum. Also, it improves cascaded signal transmission over an 11-layer circuit with 26 rounds of TMSD reactions, with a half-completion time of only 5.3 minutes. The simple-to-use and low-cost PQ2 offers a promising solution for uncovering the full potential of DNA nanotechnology and will facilitate more efficient and versatile TMSD-based applications from sensitive biosensing to high-performance molecular computing.

Digital Detection of DNA via Impedimetric Tracking of Probe Nanoparticles

CMOS-based nanocapacitor arrays are an emerging technology that permits spatially resolved, high-frequency impedance measurements at the nanoscale. Their capability to detect micro- and nanoscale entities has already been established through nonspecific interactions with the targets. Here, we demonstrate their application in specific macromolecular capture and detection using single-stranded DNA (ssDNA) as a model analyte. While individual ssDNA strands fall below the detection threshold, we employ a strand displacement assay that links DNA hybridization to target ssDNA induced displacement of reporter nanoparticles. This displacement reaction results in distinct electrical signatures with complex spatiotemporal patterns, details that remain unresolved in conventional macroscale impedance spectroscopy techniques due to their limited resolution and signal averaging that obscures localized interactions. The proposed system's massively parallel architecture and the ability to detect complex dynamics of individual nanoparticle-nanoelectrode interactions make it a promising candidate for scalable, portable, and cost-effective biosensing applications in clinical diagnostics and beyond.

Structural stability of wireframe DNA origami: The role of nanocomponent modifications

Wireframe DNA origami nanostructures hold immense potential for diverse applications in nanotechnology. The design of wireframe DNA origami structures traditionally follows a top-down approach. This study introduces a complementary bottom-up approach to investigate the nano-components constituting these nanostructures and their impact on structural stability. To this end, modifications to edge staple crossovers, poly-T bulges, and staple sequences were examined through coarse-grained molecular dynamics. The results reveal that reducing the number of edge staple crossovers slightly alters the distance between the two double-stranded DNA helices forming the edges but maintains adequate structural stability. The removal of poly-T bulges, however, leads to edge opening under specific thermal conditions, whereas structures containing poly-T bulges remain intact, highlighting their critical role in edge stability. Furthermore, changes to the staple sequences, achieved by repositioning the scaffold nick, showed negligible effects on the overall stability of the wireframe DNA origami structures. The incorporation of a bottom-up approach in designing wireframe DNA origami structures can enable the creation of nanostructures with tailored properties for specific applications. These modifications can be adapted for a variety of wireframe DNA origami structures, broadening their potential uses in nanotechnology.

Decoding Complex Biological Milieus: SHINER's Approach to Profiling and Functioning of Extracellular Vesicle Subpopulations

Extracellular vesicles (EVs) are celebrated for their pivotal roles in cellular communication and their potential in disease diagnosis and therapeutic applications. However, their inherent heterogeneity acts as a double-edged sword, complicating the isolation of specific EV subpopulations. Conventional EV isolation methods often fall short, relying on biophysical properties, while affinity-based techniques may compromise EV integrity and utility with harsh recovery conditions. To address these limitations, the SHINER (subpopulation homogeneous isolation and nondestructive EV release) workflow is introduced, which redefines how EVs are isolated and recoverd, featuring the innovative SWITCHER (switchable extracellular vesicle releaser) tool. The SHINER workflow facilitates the precise purification and gentle recovery of target EV subpopulations from complex biological mixtures, preserving their structural integrity and biological functionality. Importantly, SHINER demonstrates exceptional adaptability to multiple markers and clinical applications. It not only enhances the ability to trace EV origins for accurate disease diagnosis but also advances fundamental EV research and provides standardized EV materials for therapeutic innovations. By improving the understanding of EVs and enabling the development of personalized diagnostics and treatments, SHINER propels EV-based science into new frontiers of advanced medicine, offering transformative potential for healthcare.

Intra- and Interbead Communications by an Anchored DNA Structure and Cascaded DNA Reactions

In nature, communication between compartments, such as cells and organelles, gives rise to biological complexity. Two types of chemical communication play important roles in achieving this complexity: intra- and intercompartment communication. Building a bioinspired synthetic system that can exhibit such communication is of interest for realizing microscale artificial robots with the complexity of actual cells. In this study, we aimed to demonstrate intra- and interbead communication using microbeads made of hydrogels as compartments. We employed the diffusion and reaction of programmed DNA molecules as a medium for chemical communication. As a result of the reaction-diffusion dynamics of DNA, the spatiotemporal development of fluorophore-labeled DNAs was observed under fluorescence microscopy, showing both intra- and interbead communication. Our simple, robust, and scalable methodology will accelerate the fabrication of synthetic microsystems that may have complex functionalities from various local interactions.

Bioinspired Nucleic Acid-Based Bandpass Filters and Their Concentration-Adaptive Functions

Natural signaling networks can act as bandpass filters to interpret external stimuli within defined concentration ranges for differential cellular activities. Replicating such a bandpass filtering mechanism by synthetic networks poses a significant challenge. Herein, we introduce a modular design of nucleic acid-based multilayer threshold-gated incoherent feedforward networks as multiband bandpass filters to produce mutually exclusive responses within defined input concentration ranges. In these networks, nucleic acids demonstrate triple functionality by acting as threshold-gated entities to discern input concentration levels, serving as network nodes to assemble incoherent feedforward loops for nonlinear signal processing, and functioning as signal transduction units for coupling downstream functional modules. These modular networks enable the fine-tuning of filtering performance in terms of band position, bandwidth, cascades, and responses. A mathematical simulation model allows us to predict the filtering behaviors under various conditions. Also, the networks are integrated with upstream signal conversion modules to process concentration information on molecules beyond nucleic acids, such as adenosine and its derivatives. Furthermore, connections to downstream functional modules allow the system to regulate various processes in a concentration bandpass manner, realizing concentration-adaptive DNAzyme biocatalysis, tristate logic operations, RNA transcription, and DNA condensate formation. These findings underscore the potential of enzyme-free DNA reaction networks in complex signal processing and lay a solid foundation for developing chemical and material systems with highly adaptive and autonomous behaviors.

Spatiotemporal dynamic and catalytically mediated reconfiguration of compartmentalized cyanuric acid/polyadenine DNA microdroplet condensates

Native cells possess membrane-bound subcompartments, organelles, such as mitochondria and lysosomes, that intercommunicate and regulate cellular functions. Extensive efforts are directed to develop synthetic cells, or protocells, that replicate these structures and functions. Among these approaches, phase-separated coacervate microdroplets composed of polymers, polysaccharides, proteins, or nucleic acids are gaining interest as cell-mimicking systems. Particularly, compartmentalization of the synthetic protocell assemblies and the integration of functional constituents in the containments allowing signaling, programmed transfer of chemical agents, and spatiotemporal controlled catalytic transformations across the protocell subdomains, are challenging goals in developing artificial cells. Here, we report the assembly of compartmentalized, phase-separated cyanuric acid/polyadenine coacervate microdroplets. Hierarchical, co-centric compartmentalization is achieved through the dynamic and competitive spatiotemporal occupation of pre-engineered barcode domains within the polyadenine microdroplet framework by invading DNA strands. By encoding structural and functional information within these DNA-invaded compartments, the light-triggered, switchable reconfiguration of compartments, switchable catalytic reconfiguration of containments, and reversible aggregation/deaggregation of the compartmentalized microdroplets are demonstrated.

Combination of exciton-plasmon interaction and programmable DNA cyclic amplification for electrochemiluminescence/photoelectrochemical sensing of serotonin

A novel dual-mode electrochemiluminescence (ECL)/photoelectrochemistry (PEC) biosensor was developed for sensitive serotonin detection. In this system, the PEC signal was produced by CdS quantum dots (QDs), while the ECL signal originated from L-Au NPs (luminol decorated Au nanoparticles), thereby avoiding the external interference and signal fluctuations that typically arose from using the same materials for both signals. The presence of target serotonin initiated the non-enzymatic toehold-mediated strand displacement reaction (TSDR) on magnetic bead (MB), which was followed by catalytic hairpin assembly (CHA) on the sensing interface, leading to the aggregation of many L-Au NPs. The strong exciton-plasmon interactions (EPI) induced the energy transfer between CdS QDs and Au NPs, causing the significant suppression of the photocurrent. In addition, this design assured that the ECL and PEC respond in opposing manners and that no background ECL signal was detected, thereby greatly improving the sensitivity of the biosensor. Ultimately, the biosensor demonstrated a broad linear range from 5 pM to 1 μM with a detection limit of 1.6 pM, and also could be used for the assay of serum and urine samples with satisfactory results. With the advantages of high sensitivity, selectivity, accuracy and signal stability, this sensing strategy was helpful for disease diagnosis and the fundamental research of neurotransmitters.

Optimal st-PMMA/C60 helical inclusion complexes via tunable energy landscapes for the application of an Ag SERS-active substrate

In bio-inspired systems, the hierarchical structures of biomolecules are mimicked to impart desired functions to self-assembled materials. However, these hierarchical architectures are based on multicomponent systems, which require not only a well defined primary structure of functional molecules but also the programming of self-assembly pathways. In this study, we investigate pathway complexity in the energy landscape of the syndiotactic poly(methyl methacrylate) (st-PMMA)/C60/toluene complex system, where C60 and toluene serve as guests in the st-PMMA helical host. Structural characterization revealed that st-PMMA preferentially wraps around C60, forming a thermodynamically favorable helical inclusion complex (HIC). However, during the preparation of the st-PMMA/C60 HIC, a lengthy guest-exchange pathway was discovered, where the st-PMMA/toluene HIC transformed into the st-PMMA/C60 HIC. This pathway complexity may hinder the formation of the st-PMMA/C60 HIC within a feasible timeframe. Given that the energy landscape can be modulated by temperature, the st-PMMA host can directly wrap around C60 in higher temperature ranges, thereby bypassing the guest-exchange process and increasing the st-PMMA/C60 HIC formation efficiency. Additionally, after self-assembly programming, the st-PMMA/C60 HIC can serve as an excellent photochemical reduction site. The well dispersed nanodomains of the st-PMMA/C60 HICs act as nanoparticle templates for surface-enhanced Raman scattering (SERS) hotspot fabrication. We successfully utilized these HIC templates to synthesize self-assembled SERS-active silver nanoparticle arrays, demonstrating their potential for use in chemical sensing applications. In summary, a clear energy landscape can guide supramolecular engineering to achieve the desired supramolecular architectures by selecting appropriate self-assembly pathways.

A Study of CRISPR Ribonucleoprotein Displacement in Cell-Free Systems

CRISPR/Cas-based transcription factors are a powerful tool for controlling gene expression in living cells and cell-free systems, as their programmable DNA-binding activity makes them a powerful tool for building and scaling up engineered genetic networks. The use of guide RNAs for targeting Cas proteins to desired binding sites opens up the possibility of using RNA engineering techniques to achieve programmable and dynamic control of CRISPR/Cas-based transcription factor activity and hence of gene expression. In this work, we investigate the use of RNA strand displacement systems to remove bound CRISPR/Cas ribonucleoprotein complexes from target DNA in cell-free systems. The binding of catalytically inactive dCas9 is monitored by using CRISPR interference to repress the expression of a reporter protein. We express an antisense RNA complementary to an extended toehold on an engineered guide RNA in an E. coli-based cell-free expression system with the goal of rapidly removing bound CRISPR/Cas ribonucleoproteins via strand displacement. We find that dCas9 appears to be surprisingly resistant to removal via this mechanism, which indicates that other strategies for dynamic removal of bound Cas proteins may prove to be more effective.

DNA Logic Circuit Based on a Toehold-Independent Strand Displacement Reaction Network

DNA strand displacement is widely used in DNA nanotechnology for programming functional DNA circuits. However, many of these systems depend on a single-stranded DNA overhang (toehold). Despite its popularity, eliminating the reliance on a toehold will advance the functionality and practicality of DNA circuits. Herein we develop a toehold-independent DNA strand displacement (TISD) reaction network for DNA logic circuits. Instead of leveraging enthalpic energy provided by the toehold, the TISD reaction employs configurational entropy as the driving force. The working principle, design framework, and practical functionality of the TISD were investigated. TISD-based DNA logic circuits show desirable performances on basic functions like cascaded, fan-in, and fan-out signal transduction. They also exhibit comparable performance on digital computing, including Boolean logic gates, multilayer circuits, and square root computation. As a promising alternative to canonical toehold-dependent systems, TISD will largely expand the design space of DNA-based molecular programming and inspire more versatile DNA-based functional systems.

Tetrahedral DNA framework-directed hybridization chain reaction controlled self-assembly

Nonenzymatic isothermal nucleic acid self-assembly techniques (e.g., the hybridization chain reaction, HCR) hold potential in building materials and biological sensing. However, a traditional HCR is triggered by the random diffusion and disordered conformations of ssDNA initiators, resulting in asynchronous initiation and inherently highly heterogeneous products that do not meet the standards of well-defined nanomaterials. Herein, we developed a nanomechanical restricted strategy directed by tetrahedral DNA frameworks (TDFs) to control HCR self-assembly. We found that the restricted initiator at TDF vertices could induce DNA hairpin assembly to form homogeneous products in solution. Mechanistically, we found that TDFs accelerated the strand displacement rate of the starting H1 and synchronized the assembly process of the HCR. Furthermore, the TDF exhibited strict vertex specificity for HCR controllable assembly, and side extension of the initiator could not result in homogeneous products. This work presents a straightforward and efficient approach for controlling the living self-assembly of macromolecular DNA, thus providing a novel tool for HCR-based nanomanufacturing and quantitative sensing applications.

DNA Nanotechnology in the Undergraduate Laboratory: Toehold-Less Strand Displacement in Switchback DNA

Dynamic DNA nanostructures that reconfigure into different shapes are used in several applications in biosensing, drug delivery, and data storage. One of the ways to produce such structural transformations is by a process called strand displacement. This laboratory experiment demonstrates a strand displacement reaction in a two-stranded DNA nanostructure called switchback DNA by the addition of a third strand. In this process, the difference in the affinity between the component DNA strands is used to convert switchback DNA into conventional duplex DNA. Students are introduced to the concept through gel electrophoresis and quantitative analysis of DNA nanostructure reconfiguration. The experiment presented here is an example of DNA nanotechnology-based exercises in an undergraduate setting and is tailored for adaptation in a chemistry, biology, or biochemistry laboratory with minimal costs.

Thrombin Nanochannel Logic Gate Inspired by BioMemory

The process of "reading" and "writing" in biomemory involves the transmission of electrical signals between neurons, with ligand-gated ion channels assuming a key role. The solid-state nanochannels exhibit certain similarities with neurons. Information transmission can be achieved by controlling the flow of ions within nanochannels, rendering them potentially suitable for simulating neuron behavior. Herein, thrombin (Thr) was chosen as the target protein, and a functionalized nanochannel sensing system was successfully constructed using DNA aptamers, enabling a highly sensitive Thr response with a detection limit of 0.221 fM. Simultaneously, based on Watson-Crick base pairing and programmable chain displacement reactions, controlled release and cyclic response of the target molecule were further achieved. This mechanism elucidates the rules governing specific input-output relationships, innovatively linking them with memory storage and recognition through the Thr-nanochannel logic gate, thereby realizing the reading of biomemory at the hardware level. In summary, the biological hybrid nanofluidic control device of this invention converts molecular events into electrical signals, providing potential avenues for establishing connections between the mechanisms of biomemory and solid-state nanochannel biosensing and recognition in the future.

Dynamic Nanostructure-Based DNA Logic Gates for Cancer Diagnosis and Therapy

DNA logic gates with dynamic nanostructures have made a profound impact on cancer diagnosis and treatment. Through programming the dynamic structure changes of DNA nanodevices, precise molecular recognition with signal amplification and smart therapeutic strategies have been reported. This enhances the specificity and sensitivity of cancer theranostics, and improves diagnosis precision and treatment outcomes. This review explores the basic components of dynamic DNA nanostructures and corresponding DNA logic gates, as well as their applications for cancer diagnosis and therapies. The dynamic DNA nanostructures would contribute to cancer early detection and personalized treatment.

A High-Efficiency Autocatalysis-Oriented Cascade Circuit via Reciprocal Hug-Amplification for Assay-to-Treat Application

Developing a DNA autocatalysis-oriented cascade circuit (AOCC) via reciprocal navigation of two enzyme-free hug-amplifiers might be desirable for constructing a rapid, efficient, and sensitive assay-to-treat platform. In response to a specific trigger (T), seven functional DNA hairpins were designed to execute three-branched assembly (TBA) and three isotropic hybridization chain reaction (3HCR) events for operating the AOCC. This was because three new inducers were reconstructed in TBA arms to initiate 3HCR (TBA-to-3HCR) and periodic T repeats were resultantly reassembled in the tandem nicks of polymeric nanowires to rapidly activate TBA in the opposite direction (3HCR-to-TBA) without steric hindrance, thereby cooperatively manipulating sustainable AOCC progress for exponential hug-amplification (1:3Nn). Our experimental verifications manifested that the T-dependent AOCC amplifier achieved fast input transduction and efficient fluorescence readout. As predicted, the flexible programming of reactive hairpin species endowed the repeating nicks in productive 3HCR nanowires with great possibilities and accessibilities to graft tailored modular elements, such as G-rich AS1411 aptamers capable of adopting G-quadruplex conformations (G4) that readily facilitated the embedding of zinc(II) protoporphyrin IX (ZnPPIX), a kind of heme oxygenase-1 enzyme inhibitor. Thus, the cascading ZnPPIX/G4 entities acted as fluorescent signal reporters, photosensitizers and anticancer drugs, thereby creating an updated AOCC-based assay-to-treat platform for ultrasensitive biosensing, discernible cell imaging and efficient photodynamic therapy of cancer cells. This would offer a new paradigm to advance the rational integration of dynamic DNA assembly and amplifiable recycling circuits for applicable bioassay and theranostics.

Reducing Measurement Deviation by Metastable DNA Probes for Aptamer Thermodynamic Characterization

DNA reaction equilibrium-based calculations have great potential in thermodynamic characterization, but their widespread applications are hindered by significant measurement deviation of equilibrium concentration. Here, we report the advantages of metastable DNA hybridization in reducing quantification deviation of equilibrium concentration and propose a universal and standardized strategy for measuring aptamer binding energy, termed metastable DNA reference calorimetry (MDRC). We built different MDRC-based algorithms tailored to different aptamer binding models, enabling the calculation of thermodynamic parameters for aptamers with one or more binding sites. Our correlative model, considering the cross-effects between different binding sites, showed that for ATP aptamers with two binding sites, binding of the first ATP molecule would decrease its affinity for the second at low temperatures and even completely inhibit this binding at high temperatures. Moreover, the thermodynamic parameters of protein-specific aptamers were calculated to elucidate the universality of the method. The successful analysis of cell-specific aptamers further demonstrated MDRC's applicability in complex biological systems.

Enabling global-scale nucleic acid repositories through versatile, scalable biochemical selection from room-temperature archives

Conventional collection, preservation, and retrieval of nucleic acid specimens, particularly unstable RNA, require costly cold-chain infrastructure and rely on inefficient robotic sample handling, hindering downstream analyses. These generate critical bottlenecks for global pathogen surveillance and genomic biobanking efforts, prohibiting large-scale nucleic acid sample collection and analyses that are needed to empower pathogen tracing, as well as rare disease diagnostics1. Here, we introduce a scalable nucleic acid storage system that enables rapid and precise retrieval on pooled nucleic acid samples-stored at room-temperature with minimal physical footprint2,3-using versatile database-like queries on barcoded, encapsulated samples. Queries can incorporate numerical ranges, categorical filters, and combinations thereof, which is a significant advancement beyond previous demonstrations limited to single-sample retrieval or Boolean classifiers. We apply our system to a pool of ninety-six mock SARS-CoV-2 genomic samples identified with theoretical patient data including patient age, geographic location, and diagnostic state, allowing rapid, multiplexed nucleic acid sample retrieval in a scalable manner to empower genomic analyses. By avoiding expensive and cumbersome freezer storage and retrieval systems, our approach in principle scales to millions of samples without loss of fidelity or throughput, thereby supporting the development of large-scale pathogen and genomic repositories in under-resourced or isolated regions of the US and worldwide.

Photochemically Triggered and Autonomous Oscillatory pH-Modulated Transient Assembly/Disassembly of DNA Microdroplet Coacervates

The assembly of pH-responsive DNA-based, phase-separated microdroplets (MDs) coacervates, consisting of frameworks composed of Y-shaped nucleic acid modules crosslinked by pH-responsive strands, is introduced. The phase-separated MDs reveal dynamic pH-stimulated switchable or oscillatory transient depletion and reformation. In one system, a photoisomerizable merocyanine/spiropyran photoacid is used for the light-induced pH switchable modulation of the reaction medium between the values pH=6.0-4.4. The dynamic transient photochemically-induced switchable depletion/reformation of phase-separated MDs, follows the rhythm of pH changes in solution. In a second system, the Landolt oscillatory reaction mixture pH 7.5→4.2→7.5 is applied to stimulate the oscillatory depletion/reformation of the MDs. The autonomous dynamic oscillation of the assembly/disassembly of the MDs follows the oscillating pH rhythm of the reaction medium.

Applications of Nanotechnology for Spatial Omics: Biological Structures and Functions at Nanoscale Resolution

Spatial omics methods are extensions of traditional histological methods that can illuminate important biomedical mechanisms of physiology and disease by examining the distribution of biomolecules, including nucleic acids, proteins, lipids, and metabolites, at microscale resolution within tissues or individual cells. Since, for some applications, the desired resolution for spatial omics approaches the nanometer scale, classical tools have inherent limitations when applied to spatial omics analyses, and they can measure only a limited number of targets. Nanotechnology applications have been instrumental in overcoming these bottlenecks. When nanometer-level resolution is needed for spatial omics, super resolution microscopy or detection imaging techniques, such as mass spectrometer imaging, are required to generate precise spatial images of target expression. DNA nanostructures are widely used in spatial omics for purposes such as nucleic acid detection, signal amplification, and DNA barcoding for target molecule labeling, underscoring advances in spatial omics. Other properties of nanotechnologies include advanced spatial omics methods, such as microfluidic chips and DNA barcodes. In this review, we describe how nanotechnologies have been applied to the development of spatial transcriptomics, proteomics, metabolomics, epigenomics, and multiomics approaches. We focus on how nanotechnology supports improved resolution and throughput of spatial omics, surpassing traditional techniques. We also summarize future challenges and opportunities for the application of nanotechnology to spatial omics methods.

The Evolution of Nucleic Acid Nanotechnology: From DNA Assembly to DNA-Encoded Library

Deoxyribonucleic acid (DNA), a fundamental biomacromolecule in living organisms, serves as the carrier of genetic information. Beyond its role in encoding biological functions, DNA's inherent ability to hybridize through base pairing has opened new avenues for its application in biological sciences. This review introduces DNA nanotechnology and DNA-encoded library (DEL), and highlights their shared design principles related to DNA assembly. First, a foundational overview of structural DNA nanotechnology, including its design strategies and historical development is provided. Subsequently, various approaches are examined to dynamic DNA nanotechnology, from strand displacement reactions to DNA-templated polymer synthesis. Second, how the principle of DNA assembly has facilitated the development of diverse formats of self-assembly-based DEL synthesis, DNA-template reactions (DTS), and DNA template-mediated proximity induction effects are examined. These advancements are all underpinned by the unique property of DNA assembly. Finally, this review summarizes the common principles shared by DNA nanotechnology and DEL in terms of methodology and design. Additionally, the potential synergies are explored between these two technologies, envisioning future applications where they can be combined to create more versatile and exquisite functionalities.

Spatially Preorganized Hybridization Chain Reaction for the Prompt Diagnosis of Inflammation

Biological systems utilize precise spatial organization to facilitate and regulate information transmission within signaling networks. Inspired by this, artificial scaffolds that enable delicate spatial arrangements are desirable to increase the local concentration of reactants, expedite specific interactions, and minimize undesired interference. In this study, we presented an integrated biosensing nanodevice, termed TRI-HCR, in which hybridization chain reaction (HCR) probes were precisely organized on a triangular DNA origami nanostructure (TRI) with finely-tuned distance, quantity, and pattern. Compared to traditional HCR in the free form, this nanodevice demonstrated increased reaction rate and signal level. We further employed the optimized TRI-HCR for in vivo imaging of a nucleic acid biomarker of inflammatory diseases. In both acute gouty arthritis (AGA) and sepsis-associated acute kidney injury (SA-AKI) model mice, TRI-HCR was capable of diagnosing inflammation in the early stages, significantly earlier than histological examination. We anticipate that this precise spatial preorganization strategy for HCR holds promise for broader applications in early disease detection and monitoring.

Refined design of a DNA logic gate for implementing a DNA-based three-level circuit

DNA computing circuits are favored by researchers because of their high density, high parallelism, and biocompatibility. However, compared with electronic circuits, current DNA circuits have significant errors in understanding the OFF state and logic "0". Nowadays, DNA circuits only have two input states: logic "0" and logic "1", where logic "0" also means the OFF state. Corresponding to an electronic circuit, it is more like an on-off switch than a logic circuit. To correct this conceptual confusion, we propose a three-level circuit. The circuit divides the input signal into three cases: "none", logic "0" and logic "1". In subsequent experiments, 34 input combinations of the primary AND gate, OR gate as well as secondary AND-OR and OR-AND cascade circuits were successfully implemented to perform the operation, which distinguished the OFF state and logic "0" correctly. Based on this, we successfully implemented a more complex voting operation with only 12 strands. We believe that our redefinition of the OFF state and logic "0" will promote tremendous developments in DNA computing circuits.

Programmable DNA Reactions for Advanced Fluorescence Microscopy in Bioimaging

Biological organisms are composed of billions of molecules organized across various length scales. Direct visualization of these biomolecules in situ enables the retrieval of vast molecular information, including their location, species, and quantities, which is essential for understanding biological processes. The programmability of DNA interactions has made DNA-based reactions a major driving force in extending the limits of fluorescence microscopy, allowing for the study of biological complexity at different scales. This review article provides an overview of recent technological advancements in DNA-based fluorescence microscopy, highlighting how these innovations have expanded the technique's capabilities in terms of target multiplexity, signal amplification, super-resolution, and mechanical properties. These advanced DNA-based fluorescence microscopy techniques have been widely used to uncover new biological insights at the molecular level.

Genetically Expressed RNA Strand Displacement for Cellular Manipulation

Nucleic acid strand displacement is a pivotal concept in dynamic nucleic acid nanotechnologies, which has been extensively investigated and applied across various fields. Compared with DNA systems, the genetically expressed RNA strand displacement technology offers unique advantages for construction of genetic circuits in living cells, where RNA expression and modulation may be seamlessly integrated into the genomic network for long-term and stable regulations of diversified biological functionalities. This Concept paper provides an overview of previous efforts on developments of synthetic gene circuits through utilization of RNA strand displacement, including our endeavors in this field. Moreover, future prospects, potential applications and challenges of the genetically expressed RNA strand displacement technology are also discussed.

Blood Screening of Femtomole Level Multiple Alzheimer's Disease Biomarkers by Metal Isotopic DNA Walkers

Aging is a critical global issue that contributes to the high incidence of Alzheimer's disease (AD). Blood screening emerges as the most promising measure for early diagnosis and intervention of AD due to its noninvasive and low cost. However, the practical application of AD blood screening confronts two significant challenges. First, due to the blood-brain barrier, the concentration of AD biomarkers in blood is much lower than that in cerebrospinal fluid. Second, simultaneous quantitative analysis of multiple biomarkers is necessary due to the low specificity of individual biomarkers. Herein, we propose DNAzyme-based 3D DNA walkers for the sensitive and multiplex detection of five AD-associated miRNA biomarkers: hsa-miR-125b, hsa-miR-342-3p, hsa-miR-29b, hsa-miR-191-5p, and hsa-miR-7d-5. The DNAzyme-based 3D DNA walkers provide highly efficient and autonomous amplification of the minimal biomarkers' quantities. The walking-released metal isotopes 89Y, 165Ho, 139La, 140Ce, and 159Tb can be sensitively detected by elemental mass spectrometry without any spectral overlap. The detection limit was achieved to be as low as 1.0 fmol. The proposed method was successfully applied to human serum samples with satisfactory spiked recoveries. With its high sensitivity and multiplexity capabilities, this metal isotope strategy may contribute to the early diagnosis and intervention of AD.

A Single-Tube, Single-Enzyme Clustered Regularly Interspaced Short Palindromic Repeats System (UNISON) with Internal Controls for Accurate Nucleic Acid Detection

Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) proteins have been widely applied in molecular diagnostics. Unlike the Ct value quantification method of PCR, the CRISPR system mainly relies on the rise of the rate of the fluorescence signal to indicate the concentration of the target nucleic acid, which is susceptible to system errors caused by various factors, such as reaction conditions and instrument performance. Therefore, establishing internal controls is essential to improve the accuracy, reliability, and commercial feasibility of the CRISPR system. However, the nonspecific trans-cleavage activity of Cas proteins presents a challenge in establishing internal controls. In this study, we developed unified nucleic acid detection with a single-tube, one-enzyme system (UNISON) for accurate nucleic acid detection with internal controls. By extending the crRNA and modifying it with different fluorophores and quenchers, we achieved that the specific target can only specifically cleave the corresponding folded crRNA and generate a corresponding fluorescence signal. With this design, we established an internal control, achieving accurate and reliable detection of clinical samples of the hepatitis B virus. Integrating internal controls into the CRISPR/Cas system demonstrates significant potential in medical diagnostics and virus monitoring.

Ultrasensitive detection of antimicrobial resistance genes using hybridization chain reaction employing carbon dots

One of the top 10 global concerns include AntiMicrobial Resistance (AMR), which warrants the need to develop materials and methods for detection of AMR genes. Here, we propose a proof-of-concept approach for selective and ultrasensitive detection of AMR gene employing fluorescent carbon dots. Waste pistachio shell derived green emissive carbon dots (PCDs) with a high quantum yield of 24 were prepared via hydrothermal carbonization process and characterised using microscopic and spectroscopic techniques. The fluorescence-based Hybridization Chain Reaction (HCR) mediated sensing studies demonstrated the ability of the PCD sensor to detect AMR gene, compared to random and single mismatch DNA with a limit of detection of 16.17 pM. This strategy of waste valorization to design fluorescent probe offer excellent cost-effective and sustainable alternative for ultra-trace level detection of DNA.

Reconfigurable nanomaterials folded from multicomponent chains of DNA origami voxels

In cells, proteins rapidly self-assemble into sophisticated nanomachines. Bioinspired self-assembly approaches, such as DNA origami, have been used to achieve complex three-dimensional (3D) nanostructures and devices. However, current synthetic systems are limited by low yields in hierarchical assembly and challenges in rapid and efficient reconfiguration between diverse structures. Here, we developed a modular system of DNA origami "voxels" with programmable 3D connections. We demonstrate multifunctional pools of up to 12 unique voxels that can assemble into many shapes, prototyping 50 structures. Programmable switching of local connections between flexible and rigid states achieved rapid and reversible reconfiguration of global structures in three dimensions. Multistep assembly pathways were then explored to increase the yield. Voxels were assembled via flexible chain intermediates into rigid structures, increasing yield up to 100-fold. We envision that foldable chains of DNA origami voxels can achieve increased complexity in reconfigurable nanomaterials, providing modular components for the assembly of nanorobotic systems with future applications in synthetic biology, assembly of inorganic materials, and nanomedicine.

Lateral nanoarchitectonics from nano to life: ongoing challenges in interfacial chemical science

Lateral nanoarchitectonics is a method of precisely designing functional materials from atoms, molecules, and nanomaterials (so-called nanounits) in two-dimensional (2D) space using knowledge of nanotechnology. Similar strategies can be seen in biological systems; in particular, biological membranes ingeniously arrange and organise functional units within a single layer of units to create powerful systems for photosynthesis or signal transduction and others. When our major lateral nanoarchitectural approaches such as layer-by-layer (LbL) assembly and Langmuir-Blodgett (LB) films are compared with biological membranes, one finds that lateral nanoarchitectonics has potential to become a powerful tool for designing advanced functional nanoscale systems; however, it is still rather not well-developed with a great deal of unexplored possibilities. Based on such a discussion, this review article examines the current status of lateral nanoarchitectonics from the perspective of in-plane functional structure organisation at different scales. These include the extension of functions at the molecular level by on-surface synthesis, monolayers at the air-water interface, 2D molecular patterning, supramolecular polymers, macroscopic manipulation and functionality of molecular machines, among others. In many systems, we have found that while the targets are very attractive, the research is still in its infancy, and many challenges remain. Therefore, it is important to look at the big picture from different perspectives in such a comprehensive review. This review article will provide such an opportunity and help us set a direction for lateral nanotechnology toward more advanced functional organization.

Spatial Control over Reactions via Localized Transcription within Membraneless DNA Nanostar Droplets

Biomolecular condensates control where and how fast many chemical reactions occur in cells by partitioning reactants and catalysts, enabling simultaneous reactions in different spatial locations of a cell. Even without a membrane or physical barrier, the partitioning of the reactants can affect the rates of downstream reaction cascades in ways that depend on reaction location. Such effects can enable systems of biomolecular condensates to spatiotemporally orchestrate chemical reaction networks in cells to facilitate complex behaviors such as ribosome assembly. Here, we develop a system for developing such control in synthetic systems. We localize different transcription templates within different phase-separated, membraneless DNA nanostar (NS) droplets─programmable, in vitro liquid-liquid phase separation systems for partitioning of substrates and localization of reactions to membraneless droplets. When RNA produced within such droplets is also degraded in the bulk, droplet-localized transcription creates RNA concentration gradients. Consistent with the formation of these gradients, toehold-mediated strand displacement reactions involving transcripts are 2-fold slower far from the site of transcription than when nearby. We then demonstrate how multiple such gradients can form and be maintained independently by simultaneous transcription reactions occurring in tandem, each localized to different NS droplet types. Our results provide a means for constructing reaction systems in which different reactions are spatially localized and controlled without the need for physical membranes. This system also provides a means for generally studying how localized reactions and the exchange of reaction products might occur between protocells.

Dual-mode, signal-amplified DNA biosensor for label-free, reliable assay of gestational diabetes mellitus-related miRNA (miR-135a)

miR-135a is highly expressed in patients with gestational diabetes mellitus, and its target genes are also involved in insulin signaling pathway, so it is one biomarker for gestational diabetes mellitus. Herein we designed a dual-mode DNA biosensor for reliable assay of miR-135a based on the fluorescence and colorimetric signals. Several experiments were carried out to demonstrate the assay feasibility and mechanism for this dual-mode DNA biosensor. With optimum parameters, this proposed dual-mode biosensor has been realized sensitive and quantitative assay of miR-135a. For the fluorescence and colorimetric signals, the working ranges are 0.56-61 and 8.3-74 nM, while limits of detection are 0.18 and 3.7 nM respectively. This dual-mode strategy allows two independent signals for miR-135a assay, so it can verify each other to show more accurate results with good fidelity. Furthermore, there is a good selectivity in the biosensor for target miR-135a over other nucleotide variants, as well as good anti-interference ability in complex samples. This dual-mode DNA biosensor provides a new approach for miR-135a assay and miRNA expression profiling in gestational diabetes mellitus.

Autocatalytic DNA circuitries

Autocatalysis, a self-sustained replication process where at least one of the products functions as a catalyst, plays a pivotal role in life's evolution, from genome duplication to the emergence of autocatalytic subnetworks in cell division and metabolism. Leveraging their programmability, controllability, and rich functionalities, DNA molecules have become a cornerstone for engineering autocatalytic circuits, driving diverse technological applications. In this tutorial review, we offer a comprehensive survey of recent advances in engineering autocatalytic DNA circuits and their practical implementations. We delve into the fundamental principles underlying the construction of these circuits, highlighting their reliance on DNAzyme biocatalysis, enzymatic catalysis, and dynamic hybridization assembly. The discussed autocatalytic DNA circuitry techniques have revolutionized ultrasensitive sensing of biologically significant molecules, encompassing genomic DNAs, RNAs, viruses, and proteins. Furthermore, the amplicons produced by these circuits serve as building blocks for higher-order DNA nanostructures, facilitating biomimetic behaviors such as high-performance intracellular bioimaging and precise algorithmic assembly. We summarize these applications and extensively address the current challenges, potential solutions, and future trajectories of autocatalytic DNA circuits. This review promises novel insights into the advancement and practical utilization of autocatalytic DNA circuits across bioanalysis, biomedicine, and biomimetics.

Advancements in DNA computing: exploring DNA logic systems and their biomedical applications

DNA computing is regarded as one of the most promising candidates for the next generation of molecular computers, utilizing DNA to execute Boolean logic operations. In recent decades, DNA computing has garnered widespread attention due to its powerful programmable and parallel computing capabilities, demonstrating significant potential in intelligent biological analysis. This review summarizes the latest advancements in DNA logic systems and their biomedical applications. Firstly, it introduces recent DNA logic systems based on various materials such as functional DNA sequences, nanomaterials, and three-dimensional DNA nanostructures. The material innovations driving DNA computing have been summarized, highlighting novel molecular reactions and analytical performance metrics like efficiency, sensitivity, and selectivity. Subsequently, it outlines the biomedical applications of DNA computing-based multi-biomarker analysis in cellular imaging, clinical diagnosis, and disease treatment. Additionally, it discusses the existing challenges and future research directions for the development of DNA computing.

Click-Chemistry-Enabled Functionalization of Cellulose Nanocrystals with Single-Stranded DNA for Directed Assembly

Controlling the self-assembly of cellulose nanocrystals (CNCs) requires precise control over their surface chemistry for the directed assembly of advanced nanocomposites with tailored mechanical, thermal, and optical properties. In this work, in contrast to traditional chemistries, we conducted highly selective click-chemistry functionalization of cellulose nanocrystals with complementary DNA strands via a three-step hybridization-guided process. By grafting terminally functionalized oligonucleotides through copper-free click chemistry, we successfully facilitated the assembly of brushlike DNA-modified CNCs into bundled nanostructures with distinct chiral optical dichroism in thin films. The complexation behavior of grafted DNA chains during the evaporation-driven formation of ultrathin films demonstrates the potential for mediating chiral interactions between the DNA-branched nanocrystals and their assembly into chiral bundles. Furthermore, we discuss the future directions and challenges that include new avenues for the development of functional, responsive, and bioderived nanostructures capable of dynamic reconfiguration via selective complexation, further surface modification strategies, mitigating diverse CNC aggregation, and exploring environmental conditions for the CNC-DNA assembly.

Thermodynamics and Kinetics-Directed Regulation of Nucleic Acid-Based Molecular Recognition

Nucleic acid-based molecular recognition plays crucial roles in various fields like biosensing and disease diagnostics. To achieve optimal detection and analysis, it is essential to regulate the response performance of nucleic acid probes or switches to match specific application requirements by regulating thermodynamics and kinetics properties. However, the impacts of thermodynamics and kinetics theories on recognition performance are sometimes obscure and the relative conclusions are not intuitive. To promote the thorough understanding and rational utilization of thermodynamics and kinetics theories, this review focuses on the landmarks and recent advances of nucleic acid thermodynamics and kinetics and summarizes the nucleic acid thermodynamics and kinetics-based strategies for regulation of nucleic acid-based molecular recognition. This work hopes such a review can provide reference and guidance for the development and optimization of nucleic acid probes and switches in the future, as well as for advancements in other nucleic acid-related fields.

DNA Tetrahedra as Functional Nanostructures: From Basic Principles to Applications

Self-assembled supramolecular DNA tetrahedra composed of programmed sequence-engineered complementary base-paired strands represent elusive nanostructures having key contributions to the development and diverse applications of DNA nanotechnology. By appropriate engineering of the strands, DNA tetrahedra of tuneable sizes and chemical functionalities were designed. Programmed functionalities for diverse applications were integrated into tetrahedra structures including sequence-specific recognition strands (aptamers), catalytic DNAzymes, nanoparticles, proteins, or fluorophore. The article presents a comprehensive review addressing methods to assemble and characterize the DNA tetrahedra nanostructures, and diverse applications of DNA tetrahedra framework are discussed. Topics being addressed include the application of structurally functionalized DNA tetrahedra nanostructure for the assembly of diverse optical or electrochemical sensing platforms and functionalized intracellular sensing and imaging modules. In addition, the triggered reconfiguration of DNA tetrahedra nanostructures and dynamic networks and circuits emulating biological transformations are introduced. Moreover, the functionalization of DNA tetrahedra frameworks with nanoparticles provides building units for the assembly of optical devices and for the programmed crystallization of nanoparticle superlattices. Finally, diverse applications of DNA tetrahedra in the field of nanomedicine are addressed. These include the DNA tetrahedra-assisted permeation of nanocarriers into cells for imaging, controlled drug release, active chemodynamic/photodynamic treatment of target tissues, and regenerative medicine.

Beyond ligand binding: Single molecule observation reveals how riboswitches integrate multiple signals to balance bacterial gene regulation

Riboswitches are specialized RNA structures that orchestrate gene expression in response to sensing specific metabolite or ion ligands, mostly in bacteria. Upon ligand binding, these conformationally dynamic RNA motifs undergo structural changes that control critical gene expression processes such as transcription termination and translation initiation, thereby enabling cellular homeostasis and adaptation. Because RNA folds rapidly and co-transcriptionally, riboswitches make use of the low complexity of RNA sequences to adopt alternative, transient conformations on the heels of the transcribing RNA polymerase (RNAP), resulting in kinetic partitioning that defines the regulatory outcome. This review summarizes single molecule microscopy evidence that has begun to unveil a sophisticated network of dynamic, kinetically balanced interactions between riboswitch architecture and the gene expression machinery that, together, integrate diverse cellular signals.

A Chemo-Mechanically Coupled DNA Origami Clamp Capable of Generating Robust Compression Forces

DNA nanostructures have been utilized to study biological mechanical processes and construct artificial nanosystems. Many application scenarios necessitate nanodevices able to robustly generate large single molecular forces. However, most existing dynamic DNA nanostructures are triggered by probabilistic hybridization reactions between spatially separated DNA strands, which only non-deterministically generate relatively small compression forces (≈0.4 piconewtons (pN)). Here, an intercalator-triggered dynamic DNA origami nanostructure is developed, where large amounts of local binding reactions between intercalators and the nanostructure collectively lead to the robust generation of relatively large compression forces (≈11.2 pN). Biomolecular loads with different stiffnesses, 3, 4, and 6-helix DNA bundles are efficiently bent by the compression forces. This work provides a robust and powerful force-generation tool for building highly chemo-mechanically coupled molecular machines in synthetic nanosystems.

Y-switch: a spring-loaded synthetic gene switch for robust DNA/RNA signal amplification and detection

Nucleic acid tests (NATs) are essential for biomedical diagnostics. Traditional NATs, often complex and expensive, have prompted the exploration of toehold-mediated strand displacement (TMSD) circuits as an economical alternative. However, the wide application of TMSD-based reactions is limited by 'leakage'-the spurious activation of the reaction leading to high background signals and false positives. Here, we introduce the Y-Switch, a new TMSD cascade design that recognizes a custom nucleic acid input and generates an amplified output. The Y-Switch is based on a pair of thermodynamically spring-loaded DNA modules. The binding of a predefined nucleic acid target triggers an intermolecular reaction that activates a T7 promoter, leading to the perpetual transcription of a fluorescent aptamer that can be detected by a smartphone camera. The system is designed to permit the selective depletion of leakage byproducts to achieve high sensitivity and zero-background signal in the absence of the correct trigger. Using Zika virus (ZIKV)- and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-derived nucleic acid sequences, we show that the assay generates a reliable target-specific readout. Y-Switches detect native RNA under isothermal conditions without reverse transcription or pre-amplification, with a detection threshold as low as ∼200 attomole. The modularity of the assay allows easy re-programming for the detection of other targets by exchanging a single sequence domain. This work provides a low-complexity and high-fidelity synthetic biology tool for point-of-care diagnostics and for the construction of more complex biomolecular computations.