Neuroprotective Effect of Tetrahedral DNA Nanostructures in a Cell Model of Alzheimer's Disease

Harnessing DNA origami's therapeutic potential for revolutionizing cardiovascular disease treatment: A comprehensive review

DNA origami is a cutting-edge nanotechnology approach that creates precise and detailed 2D and 3D nanostructures. The crucial feature of DNA origami is how it is created, which enables precise control over its size and shape. Biocompatibility, targetability, programmability, and stability are further advantages that make it a potentially beneficial technique for a variety of applications. The preclinical studies of sophisticated programmable nanomedicines and nanodevices that can precisely respond to particular disease-associated triggers and microenvironments have been made possible by recent developments in DNA origami. These stimuli, which are endogenous to the targeted disorders, include protein upregulation, pH, redox status, and small chemicals. Oncology has traditionally been the focus of the majority of past and current research on this subject. Therefore, in this comprehensive review, we delve into the intricate world of DNA origami, exploring its defining features and capabilities. This review covers the fundamental characteristics of DNA origami, targeting DNA origami to cells, cellular uptake, and subcellular localization. Throughout the review, we emphasised on elucidating the imperative for such a therapeutic platform, especially in addressing the complexities of cardiovascular disease (CVD). Moreover, we explore the vast potential inherent in DNA origami technology, envisioning its promising role in the realm of CVD treatment and beyond.

Tetrahedral framework nucleic acids inhibit pathological neovascularization and vaso-obliteration in ischaemic retinopathy via PI3K/AKT/mTOR signalling pathway

This study aimed to explore the effect and the molecular mechanism of tetrahedral framework nucleic acids (tFNAs), a novel self-assembled nanomaterial with excellent biocompatibility and superior endocytosis ability, in inhibition of pathological retinal neovascularization (RNV) and more importantly, in amelioration of vaso-obliteration (VO) in ischaemic retinopathy. tFNAs were synthesized from four single-stranded DNAs (ssDNAs). Cell proliferation, wound healing and tube formation assays were performed to explore cellular angiogenic functions in vitro. The effects of tFNAs on reducing angiogenesis and inhibiting VO were explored by oxygen-induced retinopathy (OIR) model in vivo. In vitro, tFNAs were capable to enter endothelial cells (ECs), inhibit cell proliferation, tube formation and migration under hypoxic conditions. In vivo, tFNAs successfully reduce RNV and inhibit VO in OIR model via the PI3K/AKT/mTOR/S6K pathway, while vascular endothelial growth factor fusion protein, Aflibercept, could reduce RNV but not inhibit VO. This study provides a theoretical basis for the further understanding of RNV and suggests that tFNAs might be a novel promising candidate for the treatment of blind-causing RNV.

Center backbone-rigidified DNA polygonal nanostructures and bottom face-templated polyhedral pyramids with structural stability in a complex biological medium

Due to the sequence programmability, good biocompatibility, versatile functionalities and vast sequence space, DNA oligonucleotides are considered to be ideal building blocks for the assembly of diverse nanostructures in one, two and three dimensions that are capable of engineering of multiple functional nucleic acids into a useful tool to implement intended tasks in biological and medical field. However, the construction of wireframe nanostructures consisting of only a few DNA strands remains quite challenging mainly because of the molecular flexibility-based uncontrollability of size and shape. In this contribution, utilizing gel electrophoretic analysis and atomic force microscopy, we demonstrate the modeling assembly technique for the construction of wireframe DNA nanostructures that can be divided into two categories: rigid center backbone-guided modeling (RBM) and bottom face-templated assembly (BTA) that are responsible for the construction of DNA polygons and polyhedral pyramids, respectively. The highest assembly efficiency (AE) is about 100%, while the lowest AE is not less than 50%. Moreover, when adding one edge for polygons or one side face for pyramids, we only need to add one oligonucleotide strand. Especially, the advanced polygons (e.g., pentagon and hexagon) of definite shape are for the first time constructed. Along this line, introduction of cross-linking strands enables the hierarchical assembly of polymer polygons and polymer pyramids. These wireframe DNA nanostructures exhibit the substantially enhanced resistance to nuclease degradation and maintain their structural integrity in fetal bovine serum for several hours even if the vulnerable nicks are not sealed. The proposed modeling assembly technique represents important progress toward the development of DNA nanotechnology and is expected to promote the application of DNA nanostructures in biological and biomedical fields. STATEMENT OF SIGNIFICANCE: DNA oligonucleotides are considered to be ideal building blocks for the assembly of diverse nanostructures. However, the construction of wireframe nanostructures consisting of only a few DNA strands remains quite challenging. In this contribution, we demonstrate the modeling technique for the construction of different wireframe DNA nanostructures: rigid center backbone-guided modeling (RBM) and bottom face-templated assembly (BTA) that are responsible for the assembly of DNA polygons and polyhedral pyramids, respectively. Moreover, cross-linking strands enables the hierarchical assembly of polymer polygons and polymer pyramids. These wireframe DNA nanostructures exhibit the substantially enhanced resistance to nuclease degradation and maintain their structural integrity in fetal bovine serum for several hours, promoting the application of DNA nanostructures in biological and biomedical fields.

DNA Nano Trihedron Exhibits an Inhibitory Effect on Breast Cancer Cells

As a new type of nanomaterial, DNA nanomaterials show great potential in biomedical applications because of their high precision, high controllability, and high biocompatibility among other characteristics. Therapeutic drugs based on DNA nanomaterials have been shown to have beneficial therapeutic effects on a variety of diseases. The application of DNA nanomedicines in the treatment of diseases has become a rapidly developing area of study. However, the instability of DNA nanomaterials greatly limits their clinical application. Therefore, we designed and synthesized a stable topological DNA nanostructure: DNA Nano Trihedron (DNT). We demonstrated that DNT could enter MCF-7 cells without the transfection agent. In addition, DNT could induce dramatic changes in gene expression and produce significant inhibitory effects on MCF-7 cells. DNT after two months of storage still had an inhibitory effect on MCF-7 cells.

Interlacing the relevance of caspase activation in the onset and progression of Alzheimer's disease

Caspases, a family of cysteine proteases is a renowned regulator of apoptosis. Members of this family are responsible for the proteolytic dismantling of numerous cellular structures. Apart from apoptosis, caspases remarkably contribute to a diverse range of molecular processes. Being the imperative members of several cellular cascades their abnormal activation/deactivation has severe implications and also leads to various diseased conditions. Similar aberrant activation of caspases is one of the several causes of neuropathologies associated with Alzheimer's disease (AD), a form of dementia severely affecting neuropsychiatric and cognitive functions. Emerging studies are providing deeper insights into the mechanisms of caspase action in the progression of AD. Current article is an attempt to review these studies and present the action mechanisms of different mammalian caspases in the advancement of AD associated neuropathologies.

Advances in regenerative medicine applications of tetrahedral framework nucleic acid-based nanomaterials: an expert consensus recommendation

With the emergence of DNA nanotechnology in the 1980s, self-assembled DNA nanostructures have attracted considerable attention worldwide due to their inherent biocompatibility, unsurpassed programmability, and versatile functions. Especially promising nanostructures are tetrahedral framework nucleic acids (tFNAs), first proposed by Turberfield with the use of a one-step annealing approach. Benefiting from their various merits, such as simple synthesis, high reproducibility, structural stability, cellular internalization, tissue permeability, and editable functionality, tFNAs have been widely applied in the biomedical field as three-dimensional DNA nanomaterials. Surprisingly, tFNAs exhibit positive effects on cellular biological behaviors and tissue regeneration, which may be used to treat inflammatory and degenerative diseases. According to their intended application and carrying capacity, tFNAs could carry functional nucleic acids or therapeutic molecules through extended sequences, sticky-end hybridization, intercalation, and encapsulation based on the Watson and Crick principle. Additionally, dynamic tFNAs also have potential applications in controlled and targeted therapies. This review summarized the latest progress in pure/modified/dynamic tFNAs and demonstrated their regenerative medicine applications. These applications include promoting the regeneration of the bone, cartilage, nerve, skin, vasculature, or muscle and treating diseases such as bone defects, neurological disorders, joint-related inflammatory diseases, periodontitis, and immune diseases.

Golgi-Targeted Fluorescent Probe for Imaging NO in Alzheimer's Disease

Nitric oxide (NO) is a crucial neurotransmitter participating in many biological processes via nitrosylation reaction. NO produced in diverse subcellular regions also regulates the function of cells in different manners. A Golgi apparatus is rich in nitric oxide synthase and may serve as a potential therapeutic target for Alzheimer's disease (AD). However, due to the lack of an effective tool, it is difficult to reveal the relationship between Golgi-NO and AD. Herein, we report Golgi-NO as the first Golgi-targeted fluorescent probe for sensing and imaging NO in the Golgi apparatus. The probe is designed and synthesized by incorporating 4-sulfamoylphenylamide as a Golgi-targeted moiety to 6-carboxyrhodamine B, generating a fluorophore of Golgi-RhB with modifiable carboxyl, which is then combined with the NO recognition moiety of o-diaminobenzene. The probe shows superior analytical performance including accurate Golgi-targeted ability and high selectivity for NO. Moreover, using the probe, we disclose a significant increase of NO in Golgi apparatus in the AD model. This study provides a competent tool for studying the function and nitrosylation of NO in the Golgi apparatus in related diseases.

Self-Fluorescent Lone Tryptophan Nanoparticles as Theranostic Agents Against Alzheimer's Disease

Aggregation of β-amyloid (Aβ42) peptide in the neural extracellular space leads to cellular dysfunction, resulting in Alzheimer's disease (AD). The hydrophobic core of the amyloidogenic Aβ42 peptide contains aromatic residues that play an important role in the self-assembly and subsequent aggregation of the peptide. Hence, targeting these hydrophobic core residues by potent low molecular agents can be a promising therapeutic approach toward AD. In the current work, we have developed self-fluorescent solo tryptophan nanoparticles (TNPs) as nanotheranostic systems against AD. We demonstrated that TNPs could significantly inhibit as well as disrupt the fibrils formed by both Aβ42 peptide and another reductionist approach-based amyloid model dipeptide, phenylalanine-phenylalanine (FF). More importantly, these nanostructures were nontoxic to neural cells and could protect the neurons from Aβ42 peptide and FF aggregate-induced cytotoxicity. In addition, efficacy studies performed in animal model further revealed that the TNPs could rescue spatial and learning memory in intracerebroventricular streptozotocin-administration-induced AD phenotype in rats. Moreover, our pharmacokinetics study further established the BBB permeability and brain delivery potency of TNPs. The inherent excellent fluorescent properties of these nanoparticles could be exploited further to use them as imaging modalities for tagging and detecting FF and Aβ42 peptide fibrils. Overall, our results clearly illustrated that the solo TNPs could serve as promising nanotheranostic agents for AD therapy.

Applications of tetrahedral DNA nanostructures in wound repair and tissue regeneration

Tetrahedral DNA nanostructures (TDNs) are molecules with a pyramidal structure formed by folding four single strands of DNA based on the principle of base pairing. Although DNA has polyanionic properties, the special spatial structure of TDNs allows them to penetrate the cell membrane without the aid of transfection agents in a caveolin-dependent manner and enables them to participate in the regulation of cellular processes without obvious toxic side effects. Because of their stable spatial structure, TDNs resist the limitations imposed by nuclease activity and innate immune responses to DNA. In addition, TDNs have good editability and biocompatibility, giving them great advantages for biomedical applications. Previous studies have found that TDNs have a variety of biological properties, including promoting cell migration, proliferation and differentiation, as well as having anti-inflammatory, antioxidant, anti-infective and immune regulation capabilities. Moreover, we confirmed that TDNs can promote the regeneration and repair of skin, blood vessels, muscles and bone tissues. Based on these findings, we believe that TDNs have broad prospects for application in wound repair and regeneration. This article reviews recent progress in TDN research and its applications.

Therapeutic Applications of Programmable DNA Nanostructures

Deoxyribonucleic acid (DNA) nanotechnology, a frontier in biomedical engineering, is an emerging field that has enabled the engineering of molecular-scale DNA materials with applications in biomedicine such as bioimaging, biodetection, and drug delivery over the past decades. The programmability of DNA nanostructures allows the precise engineering of DNA nanocarriers with controllable shapes, sizes, surface chemistries, and functions to deliver therapeutic and functional payloads to target cells with higher efficiency and enhanced specificity. Programmability and control over design also allow the creation of dynamic devices, such as DNA nanorobots, that can react to external stimuli and execute programmed tasks. This review focuses on the current findings and progress in the field, mainly on the employment of DNA nanostructures such as DNA origami nanorobots, DNA nanotubes, DNA tetrahedra, DNA boxes, and DNA nanoflowers in the biomedical field for therapeutic purposes. We will also discuss the fate of DNA nanostructures in living cells, the major obstacles to overcome, that is, the stability of DNA nanostructures in biomedical applications, and the opportunities for DNA nanostructure-based drug delivery in the future.

A DNA Nanostructure-Based Neuroprotectant against Neuronal Apoptosis via Inhibiting Toll-like Receptor 2 Signaling Pathway in Acute Ischemic Stroke

Ischemic stroke is a main cause of cognitive neurological deficits and disability worldwide due to a plethora of neuronal apoptosis. Unfortunately, numerous neuroprotectants for neurons have failed because of biological toxicity, severe side effects, and poor efficacy. Tetrahedral framework nucleic acids (tFNAs) possess excellent biocompatibility and various biological functions. Here, we tested the efficacy of a tFNA for providing neuroprotection against neuronal apoptosis in ischemic stroke. The tFNA prevented apoptosis of neurons (SHSY-5Y cells) caused by oxygen-glucose deprivation/reoxygenation through interfering with ischemia cascades (excitotoxicity and oxidative stress) in vitro. It effectively ameliorated the microenvironment of the ischemic hemisphere by upregulating expression of erythropoietin and inhibiting inflammation, which reversed neuronal loss, alleviated cell apoptosis, significantly shrank the infarction volume from 33.9% to 2.7%, and attenuated neurological deficits in transient middle cerebral artery occlusion (tMCAo) rat models in vivo. In addition, blocking the TLR2-MyD88-NF-κB signaling pathway is a potential mechanism of the neuroprotection by tFNA in ischemic stroke. These findings indicate that tFNA is a safe pleiotropic nanoneuroprotectant and a promising therapeutic strategy for ischemic stroke.

Application of Programmable Tetrahedral Framework Nucleic Acid-Based Nanomaterials in Neurological Disorders: Progress and Prospects

Tetrahedral framework nucleic acid (tFNA), a special DNA nanodevice, is widely applied in diverse biomedical fields. Due to its high programmability, biocompatibility, tissue permeability as well as its capacity for cell proliferation and differentiation, tFNA presents a powerful tool that could overcome potential barriers in the treatment of neurological disorders. This review evaluates recent studies on the use and progress of tFNA-based nanomaterials in neurological disorders.

The biological applications of DNA nanomaterials: current challenges and future directions

DNA, a genetic material, has been employed in different scientific directions for various biological applications as driven by DNA nanotechnology in the past decades, including tissue regeneration, disease prevention, inflammation inhibition, bioimaging, biosensing, diagnosis, antitumor drug delivery, and therapeutics. With the rapid progress in DNA nanotechnology, multitudinous DNA nanomaterials have been designed with different shape and size based on the classic Watson-Crick base-pairing for molecular self-assembly. Some DNA materials could functionally change cell biological behaviors, such as cell migration, cell proliferation, cell differentiation, autophagy, and anti-inflammatory effects. Some single-stranded DNAs (ssDNAs) or RNAs with secondary structures via self-pairing, named aptamer, possess the ability of targeting, which are selected by systematic evolution of ligands by exponential enrichment (SELEX) and applied for tumor targeted diagnosis and treatment. Some DNA nanomaterials with three-dimensional (3D) nanostructures and stable structures are investigated as drug carrier systems to delivery multiple antitumor medicine or gene therapeutic agents. While the functional DNA nanostructures have promoted the development of the DNA nanotechnology with innovative designs and preparation strategies, and also proved with great potential in the biological and medical use, there is still a long way to go for the eventual application of DNA materials in real life. Here in this review, we conducted a comprehensive survey of the structural development history of various DNA nanomaterials, introduced the principles of different DNA nanomaterials, summarized their biological applications in different fields, and discussed the current challenges and further directions that could help to achieve their applications in the future.

Tetrahedral framework nucleic acids facilitate neurorestoration of facial nerves by activating the NGF/PI3K/AKT pathway

The facial nerve is a crucial nerve in the maxillofacial region and is vulnerable to damage. As a consequence of the complications during nerve restoration, existing remedies have certain limitations, thus the treatment of facial nerve injury is always a perplexing task for people. Regulation of Schwann cells is always the breakpoint of neurorestoration since Schwann cells count a great deal in injured nerve repair. In this study, we presented proof that tetrahedral framework nucleic acids (tFNAs), a kind of nucleic acid nanomaterial, were capable of regulating the neurorestorative pathway NGF/PI3 K/AKT, resulting in the activation of a series of cell behaviors related to injured nerve restoration such as proliferation and migration. In vivo experiments also proved that tFNAs enhanced the expressions of axon and myelin marker proteins, impelled histological recovery, promoted the efficient restoration of nerve conduction and muscle movement. Additionally, tFNAs possessed excellent biocompatibility and superior endocytosis ability. Thus, there is good potential for tFNAs to be applied in the therapy of facial nerve injury or even peripheral nerve injury.

Application of Nanomaterials in Neurodegenerative Diseases

Neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Huntington's disease are very harmful brain lesions. Due to the difficulty in obtaining therapeutic drugs, the best treatment for neurodegenerative diseases is often not available. In addition, the bloodbrain barrier can effectively prevent the transfer of cells, particles and macromolecules (such as drugs) in the brain, resulting in the failure of the traditional drug delivery system to provide adequate cellular structure repair and connection modes, which are crucial for the functional recovery of neurodegenerative diseases. Nanomaterials are designed to carry drugs across the blood-brain barrier for targets. Nanotechnology uses engineering materials or equipment to interact with biological systems at the molecular level to induce physiological responses through stimulation, response and target site interactions, while minimizing the side effects, thus revolutionizing the treatment and diagnosis of neurodegenerative diseases. Some magnetic nanomaterials play a role as imaging agents or nanoprobes for Magnetic Resonance Imaging to assist in the diagnosis of neurodegenerative diseases. Although the current research on nanomaterials is not as useful as expected in clinical applications, it achieves a major breakthrough and guides the future development direction of nanotechnology in the application of neurodegenerative diseases. This review briefly discusses the application and advantages of nanomaterials in neurodegenerative diseases. Data for this review were identified by searches of PubMed, and references from relevant articles published in English between 2015 and 2019 using the search terms "nanomaterials", "neurodegenerative diseases" and "blood-brain barrier".

Rationally Programming Nanomaterials with DNA for Biomedical Applications

DNA is not only a carrier of genetic information, but also a versatile structural tool for the engineering and self-assembling of nanostructures. In this regard, the DNA template has dramatically enhanced the scalability, programmability, and functionality of the self-assembled DNA nanostructures. These capabilities provide opportunities for a wide range of biomedical applications in biosensing, bioimaging, drug delivery, and disease therapy. In this review, the importance and advantages of DNA for programming and fabricating of DNA nanostructures are first highlighted. The recent progress in design and construction of DNA nanostructures are then summarized, including DNA conjugated nanoparticle systems, DNA-based clusters and extended organizations, and DNA origami-templated assemblies. An overview on biomedical applications of the self-assembled DNA nanostructures is provided. Finally, the conclusion and perspectives on the self-assembled DNA nanostructures are presented.

DNA Nanostructures in the Fight Against Infectious Diseases

Throughout history, humanity has been threatened by countless epidemic and pandemic outbreaks of infectious diseases, from the Justinianic Plague to the Spanish flu to COVID-19. While numerous antimicrobial and antiviral drugs have been developed over the last 200 years to face these threats, the globalized and highly connected world of the 21st century demands for an ever-increasing efficiency in the detection and treatment of infectious diseases. Consequently, the rapidly evolving field of nanomedicine has taken up the challenge and developed a plethora of strategies to fight infectious diseases with the help of various nanomaterials such as noble metal nanoparticles, liposomes, nanogels, and virus capsids. DNA nanotechnology represents a comparatively recent addition to the nanomedicine arsenal, which, over the past decade, has made great progress in the area of cancer diagnostics and therapy. However, the past few years have seen also an increasing number of DNA nanotechnology-related studies that particularly focus on the detection and inhibition of microbial and viral pathogens. Herein, a brief overview of this rather young research field is provided, successful concepts as well as potential challenges are identified, and promising directions for future research are highlighted.

Silenced lncRNA H19 and up-regulated microRNA-129 accelerates viability and restrains apoptosis of PC12 cells induced by Aβ25-35 in a cellular model of Alzheimer's disease

Accumulating data manifest that long non-coding RNA (lncRNAs) are involved in all kinds of neurodegenerative disorders, consisting of the onset and progression of Alzheimer's disease (AD). The study was for the research of the mechanism of lncRNA H19 (H19) in viability and apoptosis of PC12 cells induced by Aβ_25-35 in a cellular model of AD with the regulation of microRNA (miR)-129 and high mobility group box-1 protein (HMGB1). An AD cellular model of PC12 cells was established using Aβ_25-35. The Aβ_25-35-induced PC12 cells were transfected with si-H19 or miR-129 mimic to figure their roles in cell viability,apoptosis, mitochondrial membrane potential dysfunction and oxidative stress in AD. Luciferase reporter assay and RNA-pull down assay were employed for verification of the binding relationship between H19 and miR-129 and the targeting relationship between miR-129 and HMGB1. An AD mouse model was induced and brain tissues were collected. H19, miR-129 and HMGB1 were detected in Aβ_25-35-treated cells and brain tissues of AD mice. Elevated H19, HMGB1 and decreased miR-129 were found in Aβ_25-35-treated PC12 cells as well as in brain tissues of AD mice. Silenced H19 or elevated miR-129 promoted viability, inhibited apoptosis, prevented mitochondrial membrane potential dysfunction and decreased oxidative stress in Aβ_25-35-treated PC12 cells. H19 could specifically bind to miR-129. MiR-129 specifically suppressed HMGB1 expression. This study suggests that silenced H19 and up-regulated miR-129 accelerates viability and represses apoptosis of PC12 cells stimulated by Aβ_25-35 in AD, which is beneficial for AD treatment.

Effect of lncRNA WT1-AS regulating WT1 on oxidative stress injury and apoptosis of neurons in Alzheimer's disease via inhibition of the miR-375/SIX4 axis

Objective: To study the effect of lncRNA WT1-AS on oxidative stress injury (OSI) and apoptosis of neurons in Alzheimer's disease (AD) and its specific mechanisms related to the microRNA-375 (miR-375)/SIX4 axis and WT1 expression.

Results: After bioinformatic prediction, WT1-AS was found to be downregulated in Aβ_25-35treated SH-SY5Y cells, and WT1-AS overexpression inhibited WT1 expression. WT1 could target miR-375 to promote its expression. miR-375 bound to SIX4, and miR-375 overexpression inhibited SIX4 expression. WT1-AS inhibited OSI and apoptosis, while WT1 and miR-375 overexpression or SIX4 silencing reversed the WT1-AS effect on OSI and apoptosis. In vivo experiments revealed that WT1-AS improved learning/memory abilities and inhibited OSI and apoptosis in AD mice.

Conclusion: Overexpression of WT1-AS can inhibit the miR-375/SIX4 axis, OSI and neuronal apoptosis in AD by inhibiting WT1 expression.

Methods: Related lncRNAs were identified, and miR-375 downstream targets were predicted. WT1-AS, WT1, miR-375 and SIX4 expression was detected in a cell model induced by Aβ_25-35. The binding of WT1 with miR-375 and that of miR-375 with SIX4 were further confirmed. Adenosine triphosphate (ATP), reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and lactate dehydrogenase (LDH) activities, and apoptosis levels were tested after mitochondrial membrane potential observation. Learning/memory abilities and neuronal apoptosis were tested in a mouse model.

Designer, Programmable 3D DNA Nanodevices to Probe Biological Systems

DNA nanotechnology is a unique field that provides simple yet robust design techniques for self-assembling nanoarchitectures with extremely high potential for biomedical applications. Though the field began to exploit DNA to build various nanoscale structures, it has now taken a different path, diverging from the creation of complex structures to functional DNA nanodevices that explore various biological systems and mechanisms. Here, we present a brief overview of DNA nanotechnology, summarizing the key strategies for construction of various DNA nanodevices, with special focus on three-dimensional (3D) nanocages or polyhedras. We then discuss biological applications of 3D DNA nanocages, particularly tetrahedral DNA cages, in their ability to program and modulate cellular systems, in biosensing, and as tools for targeted therapeutics. We conclude with a final discussion on challenges and perspectives of 3D DNA nanodevices in biomedical applications.

Progress in Biomedical Applications of Tetrahedral Framework Nucleic Acid-Based Functional Systems

The past decades have witnessed the development of DNA nanotechnology and the emergence of various spatial DNA nanostructures, from two-dimensions to three-dimensions. The typical example is the tetrahedral framework nucleic acid (tFNA). In this review, we summarize the progress in fabrication, modification of tFNA-based functional systems and their potentials in biomedical applications. Through a one-step assembly process, tFNA is synthesized via four single stranded DNAs with three short sequences complementary to the other sequence of another single strand. Characterizations including polyacrylamide gel electrophoresis, atomic force microscopy, and dynamic light scattering measurement show tFNA as a pyramid-like nanostructure with the size of around 10 nm. Feathered with intrinsic biocompatibility and satisfactory cellular membrane permeability, the first generation of tFNA shows promising capacities in regulating cell biological behavior, promoting tissue regeneration, and immunomodulation. Along with excellent editability and relative biostability in complicated conditions, tFNA could be modified via hanging functional domains on the vertex or side arm and incorporating small-molecular-weight drugs to form the second generation, for reversing multidrug resistance in tumor cells or microorganisms, target therapy, anticancer and antibacterial treatments. The third generation of tFNA is currently tried via a multistep assembly process for stimuli-response and precise drug release. Although tFNAs show promising potentials in cargo delivery, massive efforts still need to be made to improve biostability, maximal load, and structural controllability.

Design, fabrication and applications of tetrahedral DNA nanostructure-based multifunctional complexes in drug delivery and biomedical treatment

Although organic nanomaterials and inorganic nanoparticles possess inherent flexibility, facilitating functional modification, increased intracellular uptake and controllable drug release, their underlying cytotoxicity and lack of specificity still cause safety concerns. Owing to their merits, which include natural biocompatibility, structural stability, unsurpassed programmability, ease of internalization and editable functionality, tetrahedral DNA nanostructures show promising potential as an alternative vehicle for drug delivery and biomedical treatment. Here, we describe the design, fabrication, purification, characterization and potential biomedical applications of a self-assembling tetrahedral DNA nanostructure (TDN)-based multifunctional delivery system. First, relying on Watson-Crick base pairing, four single DNA strands form a simple and typical pyramid structure via one hybridization step. Then, the protocol details four different modification approaches, including replacing a short sequence of a single DNA strand by an antisense peptide nucleic acid, appending an aptamer to the vertex, direct incubation with small-molecular-weight drugs such as paclitaxel and wogonin and coating with protective agents such as cationic polymers. These modified TDN-based complexes promote the intracellular uptake and biostability of the delivered molecules, and show promise in the fields of targeted therapy, antibacterial and anticancer treatment and tissue regeneration. The entire duration of assembly and characterization depends on the cargo type and modification method, which takes from 2 h to 3 d.

The Application of Tetrahedral Framework Nucleic Acids as a Drug Carrier in Biomedicine Fields

In recent years, tetrahedral Framework Nucleic Acids(tFNAs) have become a hot topic in the field of DNA nanostructures because of their stable structures, nanoscale size, superior mechanical properties and convenient synthesis with high yield. tFNAs are considered promising drug delivery carriers because they can pass through the cellular membrane without any help and they have a good biocompatibility and biodegradability. Besides, they have rich modification sites, they can be modified by kinds of functional groups. The functionalization molecules can be modified on the vertexes, embedded between the double-stranded DNA of the tetrahedron edges, hanged on the edges, or encapsulated in the cage-like structure of the tetrahedron. The structure of tetrahedron can also be intelligently controlled through smart design, such as integrating DNA hairpin loop structure onto the edges. Nowadays, DNA tetrahedron will have a broader development prospect in the application of drug transport carriers and intelligent drug carriers. Therefore, DNA material is a new carrier material with great advantages and has a very broad application prospect in the construction of an intelligent drug transport system.

Treatment of Alzheimer's disease with framework nucleic acids

OBJECTIVES

To provide a new research direction for nerve regeneration and strategy for Alzheimer's disease treatment, tetrahedral DNA nanostructures (TDNs)-novel tetrahedral framework nucleic acid molecule nanoparticles (tFNA) that can inhibit the apoptosis of nerve cells are employed in the experiment.

MATERIALS AND METHODS

To verify the successful preparation of TDNs, the morphology of TDNs was observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The expression of apoptosis-related genes and proteins was investigated by confocal microscope, flow cytometry, PCR and Western blot to detect the impact of TDNs on the Alzheimer's model. And finally, Morris water maze experiment was used to test behavioural changes and Nissl stain was detected to observe the morphology and quantity of neurons in the hippocampus. Immunofluorescence stain was used to observe the Aβ stain, and TUNEL dyeing was utilized to observe neuronal apoptosis.

RESULTS

In vitro and in vivo experiments confirm that TDNs, in a specific concentration range, have no toxic or side effects on nerve cells, can effectively inhibit apoptosis in an Alzheimer's disease cell model and effectively improve memory and learning ability in a rat model of Alzheimer's disease.

CONCLUSIONS

These findings suggest that TDNs may be a promising drug for the treatment of Alzheimer's disease.

Enhanced Neural Regeneration with a Concomitant Treatment of Framework Nucleic Acid and Stem Cells in Spinal Cord Injury

Spinal cord injury (SCI), began with a primary injury including contusion and compression, is a common disease caused by various pathogenesis. Characterized disruption of axons and irreversible loss of neurons in SCI, and further damage in spinal cord tissue caused by following secondary injuries, such as the formation of glial scar and inflammation, makes it even harder to recover for affected patients. Tetrahedral framework nucleic acid (tFNA), which possesses the capability of promoting neuroprotection and neuroregeneration in vitro, might alleviate the injuries, and facilitate the neural tissue regeneration in experimental animal models of SCI. Here, we developed a concomitant treatment of tFNA and neural stem cells (NSCs) for the synergistic therapy in treating the injury of the spinal cord. We first observed that tFNA could promote cell proliferation of NSCs then verified that the concomitant treatment of tFNA and NSCs showed the neuroprotective actions by increasing the survival of transplanted NSCs. Furthermore, the recovery of motor function and the tissue regeneration in the lesion site of the spinal cord achieved the best performance in the SCI rats treated with the combination of tFNA and NSCs than others, and the formation of glial scar was the least. Our findings provide novel evidence of a promising strategy for synergistic treatment of SCI in the future.

MicroRNA-214-3p modified tetrahedral framework nucleic acids target survivin to induce tumour cell apoptosis

Objectives

Due to the instability of microRNAs, the applications of microRNA are currently limited. Thus, we utilized tetrahedral framework nucleic acids and a targeted microRNAs to form a stable nanocomposite to explore whether this nanocomposite can promote apoptosis of tumour cells.

Materials and methods

In our study, the survivin gene, which is expressed only in tumour cells and embryonic cells, was selected as the target gene; miRNA‐214‐3p, which can reduce the expression of survivin, was modified onto tetrahedral framework nucleic acid, thereby producing a reduction in the expression of survivin upon intracellular delivery and eventually leading to tumour cell apoptosis.

Results

By comparing the stability of microRNAs with that of microRNA‐tetrahedral framework nucleic acid, we proved the superiority of this carrier system. The results of flow cytometry showed that after treated with this complex, the ratio of A549 cells in both late and early period of apoptosis in miRNA‐214‐3p‐tetrahedral framework nucleic acid group had doubled and the cell cycle in the G2‐M phase had declined. The decrease in the expression of anti‐apoptotic protein and the increase in the expression of pro‐apoptotic protein indicate that the ability of this complex to function in cells also makes it attractive as a new targeted therapy for cancer.

Conclusion

The unique expression of survivin in tumour cells and embryonic cells makes microRNA‐tetrahedral framework nucleic acid a new targeted therapy. In addition, due to the functional diversity of microRNAs, this delivery system approach can be applied to a wide variety of fields, such as targeted therapy and tissue regeneration.

Enhanced Efficacy of Temozolomide Loaded by a Tetrahedral Framework DNA Nanoparticle in the Therapy for Glioblastoma

Glioblastoma (GBM) is one of the deadliest primary brain malignant tumors with a bleak prognosis. Craniotomy surgical resection followed by radiotherapy and chemotherapy was still the standard therapeutic strategy for GBM. As a target alkylating agent, temozolomide (TMZ) was utilized in the therapy of GBM for decades. However, effective treatment for GBM is stymied by rapid acquired resistance and bone marrow suppression. Here, we synthesize a tetrahedral framework nucleic acid (tFNA) nanoparticle that can carry TMZ to enhance the lethality on four GBM cell lines via activating the cell apoptosis and autophagy pathway. Our nanoparticle, namely, tFNA-TMZ, shows a more obvious efficacy in killing TMZ-sensitive cells (A172 and U87) than single-agent TMZ. Besides, tFNA-TMZ was able to attenuate drug resistance in TMZ-resistant cells (T98G and LN-18) via downregulating the expression of O6-methylguanine-DNA-methyltransferase. Furthermore, we modified the tFNA with GS24, a DNA aptamer that can specially bind to transferrin receptor in the cerebral vascular endothelial cell of mouse and enable the tFNA nanoparticle to cross the blood-brain barrier. In summary, our results demonstrated that tFNA-TMZ has a promising role as a nanoscale vehicle to deliver TMZ to enhance the efficacy of GBM.

Cardioprotection of Tetrahedral DNA Nanostructures in Myocardial Ischemia-Reperfusion Injury

Acute myocardial infarction, which can be extremely difficult to treat, is the worst deadly disease around the world. Reperfusion is expedient to reverse myocardial ischemia. However, during reperfusion, reactive oxygen species (ROS) produced by myocardial ischemia-reperfusion injury (MIRI) and further cell apoptosis are the most serious challenges to cardiomyocytes. Therefore, searching for reagents that can simultaneously reduce oxidative damage and MIRI-induced apoptosis is the pivotal strategy to rescue injured cardiomyocytes. Nevertheless, current cardioprotective drugs have some shortcomings, such as cardiotoxicity, inadequate intravenous administration, or immature technology. Previous studies have shown that tetrahedral DNA nanostructures (TDNs) have biological safety with promising anti-inflammatory and antioxidative potential. However, the progress that TDNs have made in the biological behavior of cardiomyocytes has not been explored. In this experiment, a cellular model of MIRI was first established. Then, confirmed by a series of experiments, our study indicates that TDNs can significantly decrease oxidative damage and apoptosis by limiting the overexpression of ROS, along with effecting the expression of apoptosis-related proteins. In addition, Western blot analysis demonstrated that TDNs could activate the Akt/Nrf2 signaling pathway to improve the myocardial injury induced by MIRI. Above all, the antioxidant and antiapoptotic capacities of TDNs make them a potential therapeutic drug for MIRI. This study provides new ideas and directions for more homogeneous diseases induced by oxidative damage.

Potent anti-angiogenesis and anti-tumour activity of pegaptanib-loaded tetrahedral DNA nanostructure

Objectives

Pegaptanib might be a promising anti‐tumour drug targeting VEGF to inhibit tumour vascular endothelial cell proliferation. However, the poor biostability limited its application. In this study, we took tetrahedron DNA nanostructures (TDNs) as drug nanocarrier for pegaptanib to explore the potent anti‐angiogenesis and anti‐tumour activity of this drug delivery system.

Materials and methods

The successful synthesis of TDNs and pegaptanib‐TDNs was determined by 8% polyacrylamide gel electrophoresis (PAGE), capillary electrophoresis and dynamic light scattering (DLS). The cytotoxicity of pegaptanib alone and pegaptanib‐TDNs on HUVECs and Cal27 was evaluated by the cell count kit‐8 (CCK‐8) assay. The effect of pegaptanib and pegaptanib‐TDNs on proliferation, migration and tube formation of HUVECs induced by VEGF was examined by CCK‐8 assay, wound healing assay and tubule formation experiment. The cell binding capacity and serum stability were detected by flow cytometry and PAGE, respectively.

Results

Pegaptanib‐TDNs had stronger killing ability than pegaptanib alone, and the inhibiting effect was in a concentration‐dependent manner. What's more, pegaptanib‐loaded TDNs could effectively enhance the ability of pegaptanib to inhibit proliferation, migration and tube formation of HUVECs induced by VEGF. These might attribute to the stronger binding affinity to the cell membrane and greater serum stability of pegaptanib‐TDNs.

Conclusions

These results suggested that pegaptanib‐TDNs might be a novel strategy to improve anti‐angiogenesis and anti‐tumour ability of pegaptanib.

PEGylated Protamine-Based Adsorbing Improves the Biological Properties and Stability of Tetrahedral Framework Nucleic Acids

Recently, many researchers have reported that DNA nanostructures, such as tetrahedral framework nucleic acids (tFNAs), have great potential to be useful tools in clinical and laboratory applications due to their programmable shapes, functional sites, and biological responses. However, finite endocytosis and stability in cells and body fluids compromise the functions of DNA nanostructures as a result of various adverse factors. In this study, we successfully synthesized PEGylated protamine, and tFNAs were adsorbed to it in a proper ratio of nitrogen in protamine to phosphorus in tFNAs (N/P ratio) as the functional complex. Furthermore, we demonstrated that PEGylated protamine-adsorbed tFNAs show a more prominent positive effect on cell viability and proliferation than naked tFNAs do. An increase in endocytosis can be observed in three different tissue-derived cells with the PEG-protamine-tFNA (PPT) complex. The increased endocytic ability is mediated by multiple pathways; moreover, the stimulatory effect of the PPT complex on the endocytic ability is dramatically blocked by the inhibition of the caveola-dependent pathway. Consistently, when tFNAs are stabilized by PEGylated protamine, they often tend to escape from lysosomes and survive for a longer period in biological fluids rather than being rapidly eliminated from the kidneys. The in vitro and in vivo results of our study demonstrate that the PPT complex method is a feasible, potent, and low-cost strategy that improves tFNA biocompatibility, stability, and internalization. This study provides evidence supporting the possibility of implementing PPTs for use in drug delivery, bioimaging, and gene transfection in the future.

Targeted and effective glioblastoma therapy via aptamer-modified tetrahedral framework nucleic acid-paclitaxel nanoconjugates that can pass the blood brain barrier

Targeted DNA nanoparticles have been identified as one of the most promising nanocarriers in anti-glioma drug delivery. We established a multifunctional nanosystem for targeted glioma therapy. Tetrahedral framework nucleic acid (tFNA), entering U87MG cells and bEnd.3 cells, was chosen to deliver two aptamers, GMT8 and Gint4.T, and paclitaxel. GMT8 and Gint4.T, which specifically bind with U87MG cells and with PDGFRβ, were linked with tFNA, to form Gint4.T-tFNA-GMT8 (GTG). GTG was efficiently internalized by U87MG and bEnd.3 cells and penetrated an in-vitro blood-brain-barrier model. GTG loaded with paclitaxel (GPC) had potentiated anti-glioma efficacy. It inhibited the proliferation, migration, and invasion of U87MG cells, and enhanced apoptosis induction in these cells. The expression of apoptosis-related proteins was significantly changed after treatment with GPC, confirming apoptosis induction. Our study demonstrated that the combination of GTG and paclitaxel has great potential for glioma treatment and tFNA shows great promise for use in drug delivery.

Tetrahedral Framework Nucleic Acids Promote Corneal Epithelial Wound Healing in Vitro and in Vivo

Poor post-traumatic wound healing can affect the normal function of damaged tissues and organs. For example, poor healing of corneal epithelial injuries may lead to permanent visual impairment. It is of great importance to find a therapeutic way to promote wound closure. Tetrahedral framework nucleic acids (tFNAs) are new promising nanomaterials, which can affect the biological behavior of cells. In the experiment, corneal wound healing is used as an example to explore the effect of tFNAs on wound healing. Results show that the proliferation and migration of human corneal epithelial cells are enhanced by exposure to tFNAs in vitro, possibly relevant to the activation of P38 and ERK1/2 signaling pathway. An animal model of corneal alkali burn is established to further identify the facilitation effect of tFNAs on corneal wound healing in vivo. Clinical evaluations and histological analyses show that tFNAs can improve the corneal transparency and accelerate the re-epithelialization of wounds. Both in vitro and in vivo experiments show that tFNAs can play a positive role in corneal epithelial wound healing.

An Intelligent DNA Nanorobot with in Vitro Enhanced Protein Lysosomal Degradation of HER2

DNA nanorobots have emerged as new tools for nanomedicine with the potential to ameliorate the delivery and anticancer efficacy of various drugs. DNA nanostructures have been considered one of the most promising nanocarriers. In the present study, we report a DNA framework-based intelligent DNA nanorobot for selective lysosomal degradation of tumor-specific proteins on cancer cells. We site-specifically anchored an anti-HER2 aptamer (HApt) on a tetrahedral framework nucleic acid (tFNA). This DNA nanorobot (HApt-tFNA) could target HER2-positive breast cancer cells and specifically induce the lysosomal degradation of the membrane protein HER2. An injection of the DNA nanorobot into a mouse model revealed that the presence of tFNA enhanced the stability and prolonged the blood circulation time of HApt, and HApt-tFNA could therefore drive HER2 into lysosomal degradation with a higher efficiency. The formation of the HER2-HApt-tFNA complexes resulted in the HER2-mediated endocytosis and digestion in lysosomes, which effectively reduced the amount of HER2 on the cell surfaces. An increased HER2 digestion through HApt-tFNA further induced cell apoptosis and arrested cell growth. Hence, this novel DNA nanorobot sheds new light on targeted protein degradation for precision breast cancer therapy.

DNA-Based Nanomedicine with Targeting and Enhancement of Therapeutic Efficacy of Breast Cancer Cells

Recently, a DNA tetrahedron has been reported to be a novel nanomedicine and promising drug vector because of its compactness, biocompatibility, biosafety, and editability. Here, we modified the DNA tetrahedron with a DNA aptamer (AS1411) as a DNA-based delivery system, which could bind to nucleolin for its cancer cell selectivity. Nucleolin is a specific biomarker protein overexpressed on membranes of malignant cancer cells and its deregulation is implicated in cell proliferation. The antimetabolite drug 5-fluorouracil (5-FU) is an extensively used anticancer agent; however, its major limitation is the lack of target specificity. Cyanine 5 (Cy5), a fluorescent probe, can be used to label DNA tetrahedron and enhance photostability with minimal effects on its basic functions. In this study, we additionally attached 5-FU to the DNA-based delivery system as a new tumor-targeting nanomedicine (AS1411-T-5-FU) to enhance the therapeutic efficacy and targeting of breast cancer. We examined the difference of the cellular uptake of AS1411-T-5-FU between breast cancer cells and normal breast cells and concluded that AS1411-T-5-FU had a better targeting ability to kill breast cancer cells than 5-FU. We further evaluated the expressions of cell apoptosis-related proteins and genes, which are associated with the mitochondrial apoptotic pathway. Ultimately, our results suggest the potential of DNA tetrahedron in cancer therapies, and we develop a novel approach to endow 5-FU with targeting property.