Tetrahedral DNA Nanostructure: A Potential Promoter for Cartilage Tissue Regeneration via Regulating Chondrocyte Phenotype and Proliferation

Programmable biomaterials for bone regeneration

Programmable biomaterials are distinguished by their ability to adjust properties and functions on demand, in a periodic, reversible, or sequential manner. This contrasts with traditional biomaterials, which undergo irreversible, uncontrolled changes. This review synthesizes key advances in programmable biomaterials, examining their design principles, functionalities and applications in bone regeneration. It charts the transition from traditional to programmable biomaterials, emphasizing their enhanced precision, safety and control, which are critical from clinical and biosafety standpoints. We then classify programmable biomaterials into six types: dynamic nucleic acid-based biomaterials, electrically responsive biomaterials, bioactive scaffolds with programmable properties, nanomaterials for targeted bone regeneration, surface-engineered implants for sequential regeneration and stimuli-responsive release materials. Each category is analyzed for its structural properties and its impact on bone tissue engineering. Finally, the review further concludes by highlighting the challenges faced by programmable biomaterials and suggests integrating artificial intelligence and precision medicine to enhance their application in bone regeneration and other biomedical fields.

Tetrahedral Framework Nucleic Acid-Based Delivery of Astaxanthin Suppresses Chondrocyte Pyroptosis and Modulates Oxidative Stress for the Treatment of Osteoarthritis

Worldwide, osteoarthritis (OA) is regarded as the most widespread, distressing, and limiting chronic disease that affects degenerative joints. Currently, there is no treatment available to modify the progression of OA. The pathogenesis of OA is significantly linked with oxidative stress and pyroptosis. Astaxanthin (Ast) is a natural ketocarotenoid pigment with potent antioxidant activity and is shown to effectively alleviate cartilage damage in OA. However, its bioavailability is greatly limited due to poor water solubility, high sensitivity to light, temperature, and pH. In this study, Ast-loaded tetrahedral framework nucleic acids (tFNAs) or tFNA/Ast complexes (TAC) for Ast delivery are developed. Compared with free Ast and tFNA alone, TAC exhibits improved drug stability and cellular uptake. Most importantly, TAC effectively protects chondrocytes against oxidative stress-induced pyroptosis while promoting extracellular matrix anabolism by chondrocytes, and ultimately alleviates cartilage damage in a mouse destabilization of the medial meniscus (DMM) model. Thus, TAC holds great promise for the treatment of OA patients.

Recent advances in the construction strategy, functional properties, and biosensing application of self-assembled triangular unit-based DNA nanostructures

Research on self-assembled deoxyribonucleic acid (DNA) nanostructures with different shapes, sizes, and functions has recently made rapid progress owing to its biocompatibility, programmability, and stability. Among these, triangular unit-based DNA nanostructures, which are typically multi-arm DNA tiles, have been widely applied because of their unique structural rigidity, spatial flexibility, and cell permeability. Triangular unit-based DNA nanostructures are folded from multiple single-stranded DNA using the principle of complementary base pairing. Its shape and size can be determined using pre-set scaffold strands, segmented base complementary regions, and sequence lengths. The resulting DNA nanostructures retain the desired sequence length to serve as binding sites for other molecules and obtain satisfactory results in molecular recognition, spatial orientation, and target acquisition. Therefore, extensive research on triangular unit-based DNA nanostructures has shown that they can be used as powerful tools in the biosensing field to improve specificity, sensitivity, and accuracy. Over the past few decades, various design strategies and assembly techniques have been established to improve the stability, complexity, functionality, and practical applications of triangular unit-based DNA nanostructures in biosensing. In this review, we introduce the structural design strategies and principles of typical triangular unit-based DNA nanostructures, including triangular, tetrahedral, star, and net-shaped DNA. We then summarize the functional properties of triangular unit-based DNA nanostructures and their applications in biosensing. Finally, we critically discuss the existing challenges and future trends.

Progressive cancer targeting by programmable aptamer-tethered nanostructures

Scientific research in recent decades has affirmed an increase in cancer incidence as a cause of death globally. Cancer can be considered a plurality of various diseases rather than a single disease, which can be a multifaceted problem. Hence, cancer therapy techniques acquired more accelerated and urgent approvals compared to other therapeutic approaches. Radiotherapy, chemotherapy, immunotherapy, and surgery have been widely adopted as routine cancer treatment strategies to suppress disease progression and metastasis. These therapeutic approaches have lengthened the longevity of countless cancer patients. Nonetheless, some inherent limitations have restricted their application, including insignificant therapeutic efficacy, toxicity, negligible targeting, non-specific distribution, and multidrug resistance. The development of therapeutic oligomer nanoconstructs with the advantages of chemical solid-phase synthesis, programmable design, and precise adjustment is crucial for advancing smart targeted drug nanocarriers. This review focuses on the significance of the different aptamer-assembled nanoconstructs as multifunctional nucleic acid oligomeric nanoskeletons in efficient drug delivery. We discuss recent advancements in the design and utilization of aptamer-tethered nanostructures to enhance the efficacy of cancer treatment. Valuably, this comprehensive review highlights self-assembled aptamers as the exceptionally intelligent nano-biomaterials for targeted drug delivery based on their superior stability, high specificity, excellent recoverability, inherent biocompatibility, and versatile functions.

Recent advances in DNAzymes for bioimaging, biosensing and cancer therapy

DNAzymes, a class of single-stranded catalytic DNA with good stability, high catalytic activity, and easy synthesis, functionalization and modification properties, have garnered significant interest in the realm of biosensing and bioimaging. Their integration with fluorescent dyes or chemiluminescent moieties has led to remarkable bioimaging outcomes, while DNAzyme-based biosensors have demonstrated robust sensitivity and selectivity in detecting metal ions, nucleic acids, proteins, enzyme activities, exosomes, bacteria and microorganisms. In addition, by delivering DNAzymes into tumor cells, the mRNA therein can be cleaved to regulate the expression of corresponding proteins, which has further propelled the application of DNAzymes in cancer gene therapy and synergistic therapy. This paper reviews the strategies for screening attractive DNAzymes such as SELEX and high-throughput sequencing, and briefly describes the amplification strategies of DNAzymes, which mainly include catalytic hairpin assembly (CHA), DNA walker, hybridization chain reaction (HCR), DNA origami, CRISPR-Cas12a, rolling circle amplification (RCA), and aptamers. In addition, applications of DNAzymes in bioimaging, biosensing, and cancer therapy are also highlighted. Subsequently, the possible challenges of these DNAzymes in practical applications are further pointed out, and future research directions are suggested.

Aptamer-Modified Tetrahedral Framework Nucleic Acid Synergized with TGF-β3 to Promote Cartilage Protection in Osteoarthritis by Enhancing Chondrogenic Differentiation of MSCs

Characterized by progressive and irreversible degeneration of the articular cartilage (AC), osteoarthritis (OA) is the most common chronic joint disease, and there is no cure for OA at present. Recent studies suggest that enhancing the recruitment of endogenous mesenchymal stem cells (MSCs) to damaged cartilage is a promising therapeutic strategy for cartilage repair. Tetrahedral framework nucleic acid (tFNA) is a novel DNA nanomaterial and has shown great potential in the field of biomedical science. Transforming growth factor-beta 3 (TGF-β3), a vital member of the highly conserved TGF-β superfamily, is considered to induce chondrogenesis. A 66-base DNA aptamer named HM69 is reported to identify and recruit MSCs. In this study, aptamer HM69-modified tFNAs were successfully self-assembled and used to load TGF-β3 when the disulfide bonds combined. We confirmed the successful synthesis of the final composition, HM69-tFNA@TGF-β3 (HTT), by PAGE, dynamic light scattering, and atomic force microscopy. The results of in vitro experiments showed that HTT effectively induced MSC proliferation, migration, and chondrogenic differentiation. In addition, HTT-treated MSCs were shown to protect the OA chondrocytes. In DMM mice, the injection of HTT improved the therapeutic outcome of mouse pain symptoms and AC degeneration. In conclusion, this study innovatively used the disulfide bonds combined with TGF-β3 and tFNA, and an additional sequence HM69 was loaded on tFNA for the better-targeted recruitment of MSCs. HTT demonstrated its role in promoting the chondrogenesis of MSCs and cartilage protection, indicating that it might be promising for OA therapy.

Femtosecond Laser Maskless Optical Projection Lithography of Cartilage PCM Inspired 3D Protein Matrix to Chondrocyte Phenotype

Hydrogels containing chondrocytes have exhibited excellent potential in regenerating hyaline cartilage. However, chondrocytes are vulnerable to dedifferentiation during in vitro culture, leading to fibrosis and mechanical degradation of newly formed cartilage. It is proposed to modulate cartilage formation via the developed chondrocyte pericellular matrix (PCM) -like scaffolds for the first time, in which the S, M, and L-sized scaffolds are fabricated by femtosecond laser maskless optical projection lithography (FL-MOPL) of bovine serum albumin-glyceryl methacrylate hydrogel. Chondrocytes on the M PCM-like scaffold can maintain round morphology and synthesize extracellular matrix (ECM) to induce regeneration of hyaline cartilage microtissues by geometrical restriction. A series of M PCM-like scaffolds is fabricated with different stiffness and those with a high Young's modulus are more effective in maintaining the chondrocyte phenotype. The proposed PCM-like scaffolds are effective in modulating cartilage formation influenced by pore size, depth, and stiffness, which will pave the way for a better understanding of the geometric cues of mechanotransduction interactions in regulating cell fate and open up new avenues for tissue engineering.

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.

Heterogeneous DNA hydrogel loaded with Apt02 modified tetrahedral framework nucleic acid accelerated critical-size bone defect repair

Segmental bone defects, stemming from trauma, infection, and tumors, pose formidable clinical challenges. Traditional bone repair materials, such as autologous and allogeneic bone grafts, grapple with limitations including source scarcity and immune rejection risks. The advent of nucleic acid nanotechnology, particularly the use of DNA hydrogels in tissue engineering, presents a promising solution, attributed to their biocompatibility, biodegradability, and programmability. However, these hydrogels, typically hindered by high gelation temperatures (∼46 °C) and high construction costs, limit cell encapsulation and broader application. Our research introduces a novel polymer-modified DNA hydrogel, developed using nucleic acid nanotechnology, which gels at a more biocompatible temperature of 37 °C and is cost-effective. This hydrogel then incorporates tetrahedral Framework Nucleic Acid (tFNA) to enhance osteogenic mineralization. Furthermore, considering the modifiability of tFNA, we modified its chains with Aptamer02 (Apt02), an aptamer known to foster angiogenesis. This dual approach significantly accelerates osteogenic differentiation in bone marrow stromal cells (BMSCs) and angiogenesis in human umbilical vein endothelial cells (HUVECs), with cell sequencing confirming their targeting efficacy, respectively. In vivo experiments in rats with critical-size cranial bone defects demonstrate their effectiveness in enhancing new bone formation. This innovation not only offers a viable solution for repairing segmental bone defects but also opens avenues for future advancements in bone organoids construction, marking a significant advancement in tissue engineering and regenerative medicine.

Multipatterned Chondrocytes' Scaffolds by FL-MOPL with a BSA-GMA Hydrogel to Regulate Chondrocytes' Morphology

Repairing articular cartilage damage is challenging due to its low regenerative capacity. In vitro, cartilage regeneration is a potential strategy for the functional reconstruction of cartilage defects. A hydrogel is an advanced material for mimicking the extracellular matrix (ECM) due to its hydrophilicity and biocompatibility, which is known as an ideal scaffold for cartilage regeneration. However, chondrocyte culture in vitro tends to dedifferentiate, leading to fibrosis and reduced mechanical properties of the newly formed cartilage tissue. Therefore, it is necessary to understand the mechanism of modulating the chondrocytes' morphology. In this study, we synthesize photo-cross-linkable bovine serum albumin-glycidyl methacrylate (BSA-GMA) with 65% methacrylation. The scaffolds are found to be suitable for chondrocyte growth, which are fabricated by homemade femtosecond laser maskless optical projection lithography (FL-MOPL). The large-area chondrocyte scaffolds have holes with interior angles of triangle (T), quadrilateral (Q), pentagon (P), hexagonal (H), and round (R). The FL-MOPL polymerization mechanism, swelling, degradation, and biocompatibility of the BSA-GMA hydrogel have been investigated. Furthermore, cytoskeleton and nucleus staining reveals that the R-scaffold with larger interior angle is more effective in maintaining chondrocyte morphology and preventing dedifferentiation. The scaffold's ability to maintain the chondrocytes' morphology improves as its shape matches that of the chondrocytes. These results suggest that the BSA-GMA scaffold is a suitable candidate for preventing chondrocyte differentiation and supporting cartilage tissue repair and regeneration. The proposed method for chondrocyte in vitro culture by developing biocompatible materials and flexible fabrication techniques would broaden the potential application of chondrocyte transplants as a viable treatment for cartilage-related diseases.

Structural DNA nanotechnology at the nexus of next-generation bio-applications: challenges and perspectives

DNA nanotechnology has significantly progressed in the last four decades, creating nucleic acid structures widely used in various biological applications. The structural flexibility, programmability, and multiform customization of DNA-based nanostructures make them ideal for creating structures of all sizes and shapes and multivalent drug delivery systems. Since then, DNA nanotechnology has advanced significantly, and numerous DNA nanostructures have been used in biology and other scientific disciplines. Despite the progress made in DNA nanotechnology, challenges still need to be addressed before DNA nanostructures can be widely used in biological interfaces. We can open the door for upcoming uses of DNA nanoparticles by tackling these issues and looking into new avenues. The historical development of various DNA nanomaterials has been thoroughly examined in this review, along with the underlying theoretical underpinnings, a summary of their applications in various fields, and an examination of the current roadblocks and potential future directions.

Nanomaterials Modulating the Fate of Dental-Derived Mesenchymal Stem Cells Involved in Oral Tissue Reconstruction: A Systematic Review

The critical challenges in repairing oral soft and hard tissue defects are infection control and the recovery of functions. Compared to conventional tissue regeneration methods, nano-bioactive materials have become the optimal materials with excellent physicochemical properties and biocompatibility. Dental-derived mesenchymal stem cells (DMSCs) are a particular type of mesenchymal stromal cells (MSCs) with great potential in tissue regeneration and differentiation. This paper presents a review of the application of various nano-bioactive materials for the induction of differentiation of DMSCs in oral and maxillofacial restorations in recent years, outlining the characteristics of DMSCs, detailing the biological regulatory effects of various nano-materials on stem cells and summarizing the material-induced differentiation of DMSCs into multiple types of tissue-induced regeneration strategies. Nanomaterials are different and complementary to each other. These studies are helpful for the development of new nanoscientific research technology and the clinical transformation of tissue reconstruction technology and provide a theoretical basis for the application of nanomaterial-modified dental implants. We extensively searched for papers related to tissue engineering bioactive constructs based on MSCs and nanomaterials in the databases of PubMed, Medline, and Google Scholar, using keywords such as "mesenchymal stem cells", "nanotechnology", "biomaterials", "dentistry" and "tissue regeneration". From 2013 to 2023, we selected approximately 150 articles that align with our philosophy.

Tetrahedral framework nucleic acids enhance the chondrogenic potential of human umbilical cord mesenchymal stem cells via the PI3K/AKT axis

The field of regenerative medicine faces a notable challenge in terms of the regeneration of articular cartilage. Without proper treatment, it can lead to osteoarthritis. Based on the research findings, human umbilical cord mesenchymal stem cells (hUMSCs) are considered an excellent choice for regenerating cartilage. However, there is still a lack of suitable biomaterials to control their ability to self-renew and differentiate. To address this issue, in this study using tetrahedral framework nucleic acids (tFNAs) as a new method in an in vitro culture setting to manage the behaviour of hUMSCs was proposed. Then, the influence of tFNAs on hUMSC proliferation, migration and chondrogenic differentiation was explored by combining bioinformatics methods. In addition, a variety of molecular biology techniques have been used to investigate deep molecular mechanisms. Relevant results demonstrated that tFNAs can affect the transcriptome and multiple signalling pathways of hUMSCs, among which the PI3K/Akt pathway is significantly activated. Furthermore, tFNAs can regulate the expression levels of multiple proteins (GSK3β, RhoA and mTOR) downstream of the PI3K-Akt axis to further enhance cell proliferation, migration and hUMSC chondrogenic differentiation. tFNAs provide new insight into enhancing the chondrogenic potential of hUMSCs, which exhibits promising potential for future utilization within the domains of AC regeneration and clinical treatment.

Harnessing Nucleic Acids Nanotechnology for Bone/Cartilage Regeneration

The effective regeneration of weight-bearing bone defects and critical-sized cartilage defects remains a significant clinical challenge. Traditional treatments such as autologous and allograft bone grafting have not been successful in achieving the desired outcomes, necessitating the need for innovative therapeutic approaches. Nucleic acids have attracted significant attention due to their ability to be designed to form discrete structures and programmed to perform specific functions at the nanoscale. The advantages of nucleic acid nanotechnology offer numerous opportunities for in-cell and in vivo applications, and hold great promise for advancing the field of biomaterials. In this review, the current abilities of nucleic acid nanotechnology to be applied in bone and cartilage regeneration are summarized and insights into the challenges and future directions for the development of this technology are provided.

Functional micro-RNA drugs acting as a fate manipulator in the regulation of osteoblastic death

Bone loss is prevalent in clinical pathological phenomena such as osteoporosis, which is characterized by decreased osteoblast function and number, increased osteoclast activity, and imbalanced bone homeostasis. However, current treatment strategies for bone diseases are limited. Regulated cell death (RCD) is a programmed cell death pattern activated by the expression of specific genes in response to environmental changes. Various studies have shown that RCD is closely associated with bone diseases, and manipulating the death fate of osteoblasts could contribute to effective bone treatment. Recently, microRNA-targeting therapy drugs have emerged as a potential solution because of their precise targeting, powerful curative effect, and limited side effects. Nevertheless, their clinical application is limited by their inherent instability, easy enzymatic degradation, and poor membrane penetrability. To address this challenge, a self-assembling tetrahedral DNA nanostructure (TDN)-based microRNA (Tmi) delivery system has been proposed. TDN features excellent biocompatibility, cell membrane penetrability, serum stability, and modification versatility, making it an ideal nucleic acid carrier for miRNA protection and intracellular transport. Once inside cells, Tmi can dissociate and release miRNAs to manipulate key molecules in the RCD signaling pathway, thereby regulating bone homeostasis and curing diseases caused by abnormal RCD activation. In this paper, we discuss the impact of the miRNA network on the initiation and termination of four critical RCD programs in bone tissues: apoptosis, autophagy, pyroptosis, and ferroptosis. Furthermore, we present the Tmi delivery system as a miRNA drug vector. This provides insight into the clinical translation of miRNA nucleic acid drugs and the application of miRNA drugs in bone diseases.

The Current Progress of Tetrahedral DNA Nanostructure for Antibacterial Application and Bone Tissue Regeneration

Recently, programmable assembly technologies have enabled the application of DNA in the creation of new nanomaterials with unprecedented functionality. One of the most common DNA nanostructures is the tetrahedral DNA nanostructure (TDN), which has attracted great interest worldwide due to its high stability, simple assembly procedure, high predictability, perfect programmability, and excellent biocompatibility. The unique spatial structure of TDN allows it to penetrate cell membranes in abundance and regulate cellular biological properties as a natural genetic material. Previous studies have demonstrated that TDNs can regulate various cellular biological properties, including promoting cells proliferation, migration and differentiation, inhibiting cells apoptosis, as well as possessing anti-inflammation and immunomodulatory capabilities. Furthermore, functional molecules can be easily modified at the vertices of DNA tetrahedron, DNA double helix structure, DNA tetrahedral arms or DNA tetrahedral cage structure, enabling TDN to be used as a nanocarrier for a variety of biological applications, including targeted therapies, molecular diagnosis, biosensing, antibacterial treatment, antitumor strategies, and tissue regeneration. In this review, we mainly focus on the current progress of TDN-based nanomaterials for antimicrobial applications, bone and cartilage tissue repair and regeneration. The synthesis and characterization of TDN, as well as the biological merits are introduced. In addition, the challenges and prospects of TDN-based nanomaterials are also discussed.

Recent progress and application of the tetrahedral framework nucleic acid materials on drug delivery

INTRODUCTION

The application of DNA framework nucleic acid materials in the biomedical field has witnessed continual expansion. Among them, tetrahedral framework nucleic acids (tFNAs) have gained significant traction as the foremost biological vectors due to their superior attributes of editability, low immunogenicity, biocompatibility, and biodegradability. tFNAs have demonstrated promising results in numerous in vitro and in vivo applications.

AREAS COVERED

This review summarizes the latest research on tFNAs in drug delivery, including a discussion of the advantages of tFNAs in regulating biological behaviors, and highlights the updated development and advantageous applications of tFNAs-based nanostructures from static design to dynamically responsive design.

EXPERT OPINION

tFNAs possess distinct biological regulatory attributes and can be taken up by cells without the requirement of transfection, differentiating them from other biological vectors. tFNAs can be easily physically/chemically modified and seamlessly incorporated with other functional systems. The static design of the tFNAs-based drug delivery system makes it versatile, reproducible, and predictable. Further use of the dynamic response mechanism of DNA to external stimuli makes tFNAs-based drug delivery more effective and specific, improving the uptake and utilization of the payload by the intended target. Dynamic targeting is poised to become the future primary approach for drug delivery.

Tetrahedral DNA Nanostructure-Engineered Paper-Based Sensor with an Enhanced Antifouling Ability for Photoelectrochemical Sensing

Herein, a newly designed two-in-one tetrahedral DNA (TDN) nanostructure with an antifouling surface and backbone-rigidified interfacial tracks was developed for highly sensitive and selective detection of miRNA-182-5p. The well-regulated TDN tracks were assembled onto the surface of the TiO₂/MIL-125-NH₂-functionalized paper electrode, which efficiently avoided the obstacle of DNA strand tangling and decreased the probability of suspension during the walking process, thus greatly promoting the moving efficiency of DNA walkers. More interestingly, the TDN-modified sensing interfaces demonstrated incomparable antifouling ability against protein samples and interfering miRNAs due to the strong hydrophilic capacity and special molecular conformations, which addressed the dilemma of low sensitivity from traditional antifouling coating strategies. As a proof of concept, the designed bifunctional tetrahedron-modified paper-based photoelectrochemical sensor was successfully used to quantify miRNA-182-5p with a low detection limit of 0.09 fM and high specificity and was validated for monitoring of miRNA-182-5p in real samples. This TDN-engineered biointerface could be used as a universal platform for tracking various targets by substituting the biorecognition events, providing great promise for bioanalysis and clinical diagnosis.

Thermosensitive and biodegradable PCL-based hydrogels: potential scaffolds for cartilage tissue engineering

Due to a lack of sufficient blood supply and unique physicochemical properties, the treatment of injured cartilage is laborious and needs an efficient strategy. Unfortunately, most of the current therapeutic approaches are, but not completely, unable to restore the function of injured cartilage. Tissue engineering-based modalities are an alternative option to reconstruct the injured tissue. Considering the unique structure and consistency of cartilage tissue (osteochondral junction), it is mandatory to apply distinct biomaterials with unique properties slightly different from scaffolds used for soft tissues. PCL is extensively used for the fabrication of fine therapeutic scaffolds to accelerate the restorative process. Thermosensitive PCL hydrogels with distinct chemical compositions have paved the way for sophisticated cartilage regeneration. This review aimed to collect recent findings regarding the application of PCL in hydrogels blended with natural, synthetic materials in the context of cartilage healing.

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.

Degradation-Kinetics-Controllable and Tissue-Regeneration-Matchable Photocross-linked Alginate Hydrogels for Bone Repair

Photocross-linked alginate hydrogels, due to their biodegradability, biocompatibility, strong control for gelling kinetics in space and time, and admirable adaptability for in situ polymerization with a minimally invasive approach in surgical procedures, have created great expectations in bone regeneration. However, hydrogels with suitable degradation kinetics that can match the tissue regeneration process have not been designed, which limits their further application in bone tissue engineering. Herein, we finely developed an oxidation strategy for alginate to obtain hydrogels with more suitable degradation rates and comprehensively explored their physical and biological performances in vitro and in vivo to further advance the clinical application for the hydrogels in bone repair. The physical properties of the gels can be tuned via tailoring the degree of alginate oxidation. In particular, in vivo degradation studies showed that the degradation rates of the gels were significantly increased by oxidizing alginate. The activity, proliferation, initial adhesion, and osteogenic differentiation of rat and rabbit bone marrow stromal cells (BMSCs) cultured with/in the hydrogels were explored, and the results demonstrated that the gels possessed excellent biocompatibility and that the encapsulated BMSCs were capable of osteogenic differentiation. Furthermore, in vivo implantation of rabbit BMSC-loaded gels into tibial plateau defects of rabbits demonstrated the feasibility of hydrogels with appropriate degradation rates for bone repair. This study indicated that hydrogels with increasingly controllable and matchable degradation kinetics and satisfactory bioproperties demonstrate great clinical potential in bone tissue engineering and regenerative medicine and could also provide references for drug/growth-factor delivery therapeutic strategies for diseases requiring specific drug/growth-factor durations of action.

Therapeutic Effects of Self-Assembled Tetrahedral Framework Nucleic Acids on Liver Regeneration in Acute Liver Failure

Liver failure is a serious disease that is characterized by global hepatocyte necrosis. Hepatocyte proliferation and liver regeneration are critically important for the success of treatments for liver disease. Tetrahedral framework nucleic acids (TFNAs), which are widely used antioxidants and anti-inflammatory nanomaterials, activate multiple proliferation and prosurvival pathways. Therefore, the effects of a TFNA on hepatocyte proliferation and liver regeneration in mouse livers injured by 70% partial hepatectomy (PHx), acetaminophen overdose, and carbon tetrachloride were explored in this study. The TFNA, which was successfully self-assembled from four specifically designed ssDNAs, entered the body quickly and was taken up effectively by hepatocytes in the liver and could eventually be cleared by the kidneys. The TFNA promoted hepatocyte proliferation in vitro by activating the Notch and Wnt signaling pathways. In the three in vivo mouse models of liver injury, the TFNA attenuated the injuries and enhanced liver regeneration by regulating the cell cycle and the P53 signaling pathway. Therefore, by promoting hepatocyte proliferation and enhancing liver regeneration, the TFNA shows potential as an effective therapeutic agent for treating acute liver injury induced by 70% PHx and other factors, thereby preventing the progression to acute liver failure and reducing the associated mortality rate.

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.

Cartilage Regeneration Characteristics of Human and Goat Auricular Chondrocytes

Although cartilage regeneration technology has achieved clinical breakthroughs, whether auricular chondrocytes (AUCs) represent optimal seed cells to achieve stable cartilage regeneration is not clear. In this study, we systematically explore biological behaviors of human- and goat-derived AUCs during in vitro expansion as well as cartilage regeneration in vitro and in vivo. To eliminate material interference, a cell sheet model was used to evaluate the feasibility of dedifferentiated AUCs to re-differentiate and regenerate cartilage in vitro and in vivo. We found that the dedifferentiated AUCs could re-differentiate and regenerate cartilage sheets under the chondrogenic medium system, and the generated chondrocyte sheets gradually matured with increased in vitro culture time (2, 4, and 8 weeks). After the implantation of cartilage sheets with different in vitro culture times in nude mice, optimal neocartilage was formed in the group with 2 weeks in vitro cultivation. After in vivo implantation, ossification only occurred in the group with goat-regenerated cartilage sheet of 8 weeks in vitro cultivation. These results, which were confirmed in human and goat AUCs, suggest that AUCs are ideal seed cells for the clinical translation of cartilage regeneration under the appropriate culture system and culture condition.

High-performance bilayer composites for the replacement of osteochondral defects

Two novel bilayer constructs for the repair of osteochondral defects were developed from nanofibers and ceramic particles embedded into PVA matrices, exhibiting multiple promising properties similar to those of corresponding natural tissues.

Delivery of MiR335-5p-Pendant Tetrahedron DNA Nanostructures Using an Injectable Heparin Lithium Hydrogel for Challenging Bone Defects in Steroid-Associated Osteonecrosis

Corticosteroids-induced Dickkopf-1 (DKK1) upregulation and Wnt signaling inhibition result in bone metabolism disorder and steroid-associated osteonecrosis (SAON). Implanting biomaterials to regulate the Wnt pathway is a promising method to repair challenging bone defects associated with SAON. Here, tetrahedral DNA nanostructures (TDNs) are fabricated as gene carriers to deliver MiR335-5p, which targets DKK1 translation. Heparin lithium hydrogel (Li-hep-gel) is synthesized to act as a lithium and MiR@TDNs delivery agent. Finally, the repair effects on challenging bone defect in SAON using a MiR@TDNs/Li-hep-gel composite are assessed in vivo. The results reveal that MiR@TDNs are absorbed by bone mesenchymal stem cells (BMSCs) and increase cell viability and reduce apoptosis. Moreover, MiR@TDNs promote alkaline phosphatase expression and calcium nodular deposition, decrease lipid droplet expression of BMSCs, and improve vascular endothelial growth factor secretion and vascular-like structure formation in vitro. After MiR@TDNs/Li-hep-gel is implanted into the SAON model, the internal bone defect of osteonecrosis is repaired with a large area of new bone accompanied with neovascularization and reduced empty lacunae. In conclusion, MiR@TDNs/Li-hep-gel can provide dual delivery of lithium and MiR@TDNs, which synergistically upregulate the Wnt signaling pathway, enhancing bone regeneration in challenging bone defects, and can be potentially used in SAON repair.

Directed Regeneration of Osteochondral Tissue by Hierarchical Assembly of Spatially Organized Composite Spheroids

The use of engineered scaffolds or stem cells is investigated widely in the repair of injured musculoskeletal tissue. However, the combined regeneration of hierarchical osteochondral tissue remains a challenge due to delamination between cartilage and subchondral bone or difficulty in spatial control over differentiation of transplanted stem cells. Here, two types of composite spheroids are prepared using adipose-derived stem cells (hADSCs) and nanofibers coated with either transforming growth factor-β3 or bone morphogenetic growth factor-2 for chondrogenesis or osteogenesis, respectively. Each type of spheroid is then cultured within a 3D-printed microchamber in a spatially arranged manner to recapitulate the bilayer structure of osteochondral tissue. The presence of inductive factors regionally modulates in vitro chondrogenic or osteogenic differentiation of hADSCs within the biphasic construct without dedifferentiation. Furthermore, hADSCs from each spheroid proliferate and sprout and successfully connect the two layers mimicking the osteochondral interface without apertures. In vivo transplantation of the biphasic construct onto a femoral trochlear groove defect in rabbit knee joint results in 21.2 ± 2.8% subchondral bone volume/total volume and a cartilage score of 25.0 ± 3.7. The present approach can be an effective therapeutic platform to engineer complex tissue.

Application of collagen and mesenchymal stem cells in regenerative dentistry

Collagen is an important macromolecule of extracellular matrix (ECM) in bones, teeth, and temporomandibular joints. Mesenchymal stem cells (MSCs) interact with the components of the ECM such as collagen, proteoglycans, glycosaminoglycans (GAGs), and several proteins on behalf of variable matrix elasticity and bioactive cues. Synthetic collagen-based biomaterials could be effective scaffolds for regenerative dentistry applications due to mimicking of host tissues' ECM. These biomaterials are biocompatible, biodegradable, readily available, and non-toxic to cells whose capability promotes cellular response and wound healing in the craniofacial region. Collagen could incorporate other biomolecules to induce mineralization in calcified tissues such as bone and tooth. Moreover, the addition of these molecules or other polymers to collagen-based biomaterials could enhance mechanical properties, which is important in load-bearing areas such as the mandible. A literature review was performed via reliable internet database (mainly PubMed) based on MeSH keywords. This review first describes the properties of collagen as a key protein in the structure of hard tissues. Then, it introduces different types of collagens, the correlation between collagen and MSCs, and the methods used to modify collagen in regenerative dentistry including recent progression on the regeneration of periodontium, dentin-pulp complex, and temporomandibular joint by applying collagen. Besides, the prospects and challenges of collagen-based biomaterials in the craniofacial region pointes out.

Tetrahedral framework nucleic acids promote the biological functions and related mechanism of synovium-derived mesenchymal stem cells and show improved articular cartilage regeneration activity in situ

Many recent studies have shown that joint-resident mesenchymal stem cells (MSCs) play a vital role in articular cartilage (AC) in situ regeneration. Specifically, synovium-derived MSCs (SMSCs), which have strong chondrogenic differentiation potential, may be the main driver of cartilage repair. However, both the insufficient number of MSCs and the lack of an ideal regenerative microenvironment in the defect area will seriously affect the regeneration of AC. Tetrahedral framework nucleic acids (tFNAs), notable novel nanomaterials, are considered prospective biological regulators in biomedical engineering. Here, we aimed to explore whether tFNAs have positive effects on AC in situ regeneration and to investigate the related mechanism. The results of in vitro experiments showed that the proliferation and migration of SMSCs were significantly enhanced by tFNAs. In addition, tFNAs, which were added to chondrogenic induction medium, were shown to promote the chondrogenic capacity of SMSCs by increasing the phosphorylation of Smad2/3. In animal models, the injection of tFNAs improved the therapeutic outcome of cartilage defects compared with that of the control treatments without tFNAs. In conclusion, this is the first report to demonstrate that tFNAs can promote the chondrogenic differentiation of SMSCs in vitro and enhance AC regeneration in vivo, indicating that tFNAs may become a promising therapeutic for AC regeneration.

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Tetrahedral framework nucleic acids (tFNAs) can promote SMSCs proliferation by activating the Wnt/β-catenin pathway.

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tFNAs can promote SMSCs migration in vitro and vivo.

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tFNAs can promote SMSCs chondrogenic differentiation by regulating the TGF/Smad2/3 signaling pathway.

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tFNAs show improved articular cartilage in situ regeneration activity in vivo.

Functionalizing Framework Nucleic-Acid-Based Nanostructures for Biomedical Application

Strategies for functionalizing diverse tetrahedral framework nucleic acids (tFNAs) have been extensively explored since the first successful fabrication of tFNA by Turberfield. One-pot annealing of at least four DNA single strands is the most common method to prepare tFNA, as it optimizes the cost, yield, and speed of assembly. Herein, the focus is on four key merits of tFNAs and their potential for biomedical applications. The natural ability of tFNA to scavenge reactive oxygen species, along with remarkable enhancement in cellular endocytosis and tissue permeability based on its appropriate size and geometry, promotes cell-material interactions to direct or probe cell behavior, especially to treat inflammatory and degenerative diseases. Moreover, the structural programmability of tFNA enables the development of static tFNA-based nanomaterials via engineering of functional oligonucleotides or therapeutic molecules, and dynamic tFNAs via attachment of stimuli-responsive DNA apparatuses, leading to potential applications in targeted therapies, tissue regeneration, antitumor strategies, and antibacterial treatment. Although there are impressive performance and significant progress, the challenges and prospects of functionalizing tFNA-based nanostructures are still indicated in this review.

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.

The immune regulatory effects of tetrahedral framework nucleic acid on human T cells via the mitogen-activated protein kinase pathway

OBJECTIVES

Autoimmune diseases are a heterogeneous group of diseases which lose the immunological tolerance to self-antigens. It is well recognized that irregularly provoked T cells participate in the pathological immune responses. As a novel nanomaterial with promising applications, tetrahedral framework nucleic acid (TFNA) nanostructure was found to have immune regulatory effects on T cells in this study.

MATERIALS AND METHODS

To verify the successful fabrication of TFNA, the morphology of TFNA was observed by atomic force microscopy (AFM) and dynamic light scattering. The regulatory effect of TFNA was evaluated by flow cytometry after cocultured with CD3+ T cells isolated from healthy donors. Moreover, the associated signaling pathways were investigated. Finally, we verified our results on the T cells from patients with neuromyelitis optica spectrum disorder (NMOSD), which is a typical autoimmune disease induced by T cells.

RESULTS

We revealed the alternative regulatory functions of TFNA in human primary T cells with steady status via the JNK signaling pathway. Moreover, by inhibiting both JNK and ERK phosphorylation, TFNA exhibited significant suppressive effects on IFNγ secretion from provoking T cells without affecting TNF secretion. Similar immune regulatory effects of TFNA were also observed in autoreactive T cells from patients with NMOSD.

CONCLUSIONS

Overall, our results revealed a potential application of TFNA in regulating the adaptive immune system, as well as shed a light on the treatment of T cell-mediated autoimmune diseases.

Tetrahedral Framework Nucleic Acids Loaded with Aptamer AS1411 for siRNA Delivery and Gene Silencing in Malignant Melanoma

siRNA is found to effectively knock down the target gene in cells, which is considered a promising strategy for gene therapy. However, the application of siRNA is limited due to its low efficiency of the cellular uptake. Tetrahedral framework nucleic acids (tFNAs) are synthesized by four single-stranded DNAs and show multiple biological functions in recent studies, especially suitable for drug delivery. More than 60% of malignant melanomas are associated with Braf gene mutation, an attractive therapeutic target for RNA interference. In this study, we modified anti-Braf siRNA (siBraf) with tFNAs to downregulate the target gene. Meanwhile, we directly incorporated AS1411 (a DNA aptamer) to our nanostructure, which assists tFNAs to improve the cellular uptake efficacy of siBraf significantly. The results indicated that tFNAs-AS1411-siBraf exhibited more potent activity to cleave Braf mRNA than free siBraf. This study may provide a new idea for the combination therapy of siRNA and aptamers via DNA nanomaterials to achieve gene silencing.

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.

Controlled Delivery of Growth Factor by Hierarchical Nanostructured Core-Shell Nanofibers for the Efficient Repair of Critical-Sized Rat Calvarial Defect

Electrospun nanofibers have received much attention as bone tissue-engineered scaffolds for their capacity to mimic the structure of natural extracellular matrix (ECM). Most studies have reproduced nanofibers with smooth surface for tissue engineering. This is quite different from the triple-helical nanotopography of natural collagen nanofibrils. In this study, hierarchical nanostructures were coated on the surface of drug-loaded core-shell nanofibers to mimic natural collagen nanofibrils. The nanoshish-kebab (SK) structure was decorated regularly on the surface of the nanofibers, and the inner-loaded bone morphogenetic protein 2 (BMP2) exhibited a gentle release pattern, similar to a zero-order release pattern in kinetics. The in vitro study also showed that the SK structure could accelerate cell proliferation, attachment, and osteogenic differentiation. Four groups of scaffolds were implanted in vivo to repair critical-sized rat calvarial defects: (1) PCL/PVA (control); (2) SK-PCL/PVA; (3) PCL/PVA-BMP2; and (4) SK-PCL/PVA-BMP2. Much more bone was formed in the SK-PCL/PVA group (24.57 ± 3.81%) than in the control group (1.21 ± 0.23%). The BMP2-loaded core-shell nanofibers with nanopatterned structure (SK-PCL/PVA-BMP2) displayed the best repair efficacy (76.38 ± 4.13%), followed by the PCL/PVA-BMP2 group (39.86 ± 5.74%). It was believed that the hierarchical nanostructured core-shell nanofibers could promote osteogeneration and that the SK structure showed synergistic ability with nanofiber-loaded BMP2 in vivo for bone regeneration. Thus, this BMP2-loaded core-shell nanofiber scaffold with hierarchical nanostructure holds great potential for bone tissue engineering applications.

Tetrahedral Framework Nucleic Acid Promotes the Treatment of Bisphosphonate-Related Osteonecrosis of the Jaws by Promoting Angiogenesis and M2 Polarization

Bisphosphonates are often used to treat osteoporosis, malignant bone metastases, and hypercalcemia. However, it can cause serious adverse reactions, bisphosphonate-related osteonecrosis of the jaw (BRONJ), which seriously affects the quality of life of patients. At present, the treatment of BRONJ is still difficult to reach an agreement, and there is no effective treatment. Therefore, it is very important to find effective treatments. Many studies have shown that the occurrence of BRONJ may be due to unbalanced bone turnover, anti-angiogenesis, bacterial infection, direct tissue toxicity, and abnormal immune function. The previous research results show that tetrahedral framework nucleic acids (tFNAs), a new type of nanomaterial, can promote various biological activities of cells, such as cell proliferation, migration, anti-inflammation and anti-oxidation, and angiogenesis. Therefore, we intend to explore the potential of tFNAs in the treatment of BRONJ through this study. The results show that tFNAs can promote the treatment of BRONJ by promoting angiogenesis and promoting M2 polarization in macrophages and inhibiting M1 polarization both in vitro and in vivo. These results provide a theoretical basis for the application of tFNAs in the treatment of BRONJ and also provide new ideas and methods for the treatment of other diseases based on ischemia and immune disorders.

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.

Multi-targeted Antisense Oligonucleotide Delivery by a Framework Nucleic Acid for Inhibiting Biofilm Formation and Virulence

A framework nucleic acid delivery system was developed through self-assembly, which can deliver antisense oligonucleotides against multiple targets in bacterial cells.

The ASOs-tFNAs (750 nM) was found to simultaneously inhibit the expression of gtfBCD, gbpB, and ftf, and significantly reduce the extracellular polysaccharide synthesis and biofilm thickness.

Biofilm formation is responsible for numerous chronic infections and represents a serious health challenge. Bacteria and the extracellular polysaccharides (EPS) cause biofilms to become adherent, toxic, resistant to antibiotics, and ultimately difficult to remove. Inhibition of EPS synthesis can prevent the formation of bacterial biofilms, reduce their robustness, and promote removal. Here, we have developed a framework nucleic acid delivery system with a tetrahedral configuration. It can easily access bacterial cells and functions by delivering antisense oligonucleotides that target specific genes. We designed antisense oligonucleotide sequences with multiple targets based on conserved regions of the VicK protein-binding site. Once delivered to bacterial cells, they significantly decreased EPS synthesis and biofilm thickness. Compared to existing approaches, this system is highly efficacious because it simultaneously reduces the expression of all targeted genes (gtfBCD, gbpB, ftf). We demonstrate a novel nucleic acid-based nanomaterial with multi-targeted inhibition that has great potential for the treatment of chronic infections caused by biofilms.

A lithium-containing biomaterial promotes chondrogenic differentiation of induced pluripotent stem cells with reducing hypertrophy

Background

Induced pluripotent stem cells (iPSCs) exhibit limitless pluripotent plasticity and proliferation capability to provide an abundant cell source for tissue regenerative medicine. Thus, inducing iPSCs toward a specific differentiation direction is an important scientific question. Traditionally, iPSCs have been induced to chondrocytes with the help of some small molecules within 21–36 days. To speed up the differentiation of iPSCs, we supposed to utilize bioactive ceramics to assist chondrogenic-induction process.

Methods

In this study, we applied ionic products (3.125~12.5 mg/mL) of the lithium-containing bioceramic (Li₂Ca₄Si₄O₁₃, L2C4S4) and individual Li⁺ (5.78~23.73 mg/L) in the direct chondrogenic differentiation of human iPSCs.

Results

Compared to pure chondrogenic medium and extracts of tricalcium phosphate (TCP), the extracts of L2C4S4 at a certain concentration range (3.125~12.5 mg/mL) significantly enhanced chondrogenic proteins Type II Collagen (COL II)/Aggrecan/ SRY-Box 9 (SOX9) synthesis and reduced hypertrophic protein type X collagen (COL X)/matrix metallopeptidase 13 (MMP13) production in iPSCs-derived chondrocytes within 14 days, suggesting that these newly generated chondrocytes exhibited favorable chondrocytes characteristics and maintained a low-hypertrophy state. Further studies demonstrated that the individual Li⁺ ions at the concentration range of 5.78~23.73 mg/L also accelerated the chondrogenic differentiation of iPSCs, indicating that Li⁺ ions played a pivotal role in chondrogenic differentiation process.

Conclusions

These findings indicated that lithium-containing bioceramic with bioactive specific ionic components may be used for a promising platform for inducing iPSCs toward chondrogenic differentiation and cartilage regeneration.

Effects of tetrahedral framework nucleic acid/wogonin complexes on osteoarthritis

Osteoarthritis, a disorder characterized by articular cartilage deterioration, varying degrees of inflammation, and chondrocyte apoptosis, is the most common chronic joint disease. To slow or reverse its progression, inflammation should be inhibited, and chondrocyte proliferation should be promoted. Tetrahedral framework nucleic acids can be internalized by chondrocytes (even inflammatory chondrocytes) and can enhance their proliferation and migration. Wogonin, a naturally occurring flavonoid, suppresses oxidative stress and inhibits inflammation. In this study, tetrahedral framework nucleic acids were successfully self-assembled and used to load wogonin. We confirmed the effective formation of tetrahedral framework nucleic acid/wogonin complexes by dynamic light scattering, zeta potential analysis, transmission electron microscopy, and fluorescence spectrophotometry. Tetrahedral framework nucleic acids, wogonin, and especially tetrahedral framework nucleic acid/wogonin complexes effectively alleviated inflammation in vitro and in vivo and prevented cartilage destruction. In addition, these materials remarkably downregulated the expression of inflammatory mediators and matrix metalloproteinases, upregulated chondrogenic markers, and promoted tissue inhibitor of metalloproteinase 1 and B-cell lymphoma 2 expression. In vivo, after treatment with tetrahedral framework nucleic acid/wogonin complexes, the bone mineral density in regenerated tissues was much higher than that found in the untreated groups. Histologically, the complexes enhanced new tissue regeneration, significantly suppressed chondrocyte apoptosis, and promoted chondrogenic marker expression. They also inhibited cell apoptosis, increased chondrogenic marker expression, and suppressed the expression of inflammatory mediators in osteoarthritis. Therefore, we believe that tetrahedral framework nucleic acid/wogonin complexes can be used as an injectable form of therapy for osteoarthritis.

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.

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.

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.

Effect of tetrahedral DNA nanostructures on proliferation and osteogenic differentiation of human periodontal ligament stem cells

OBJECTIVE

To explore the effects and underlying biological mechanisms of tetrahedral DNA nanostructures (TDNs) on the proliferation and osteogenic differentiation of periodontal ligament stem cells (PDLSCs).

MATERIALS AND METHODS

Real-time cell analysis (RTCA) and CCK8 were used to screen the best concentration of TDN for PDLSCs. Cell proliferation and osteogenic differentiation were assessed after PDLSCs were treated with TDN. Data were analysed using one-way ANOVA.

RESULTS

Tetrahedral DNA nanostructures could play a crucial role in accelerating the proliferation of PDLSCs and had the strongest promotive effect on PDLSCs at a concentration of 250 nmol/L. Simultaneously, the osteogenic differentiation of PDLSCs could be promoted significantly by TDNs and the finding displayed that the Wnt/β-catenin signalling pathway might be the underlying biological mechanisms of TDNs on promoting the osteogenic differentiation of PDLSCs.

CONCLUSION

Tetrahedral DNA nanostructure treatment facilitated the proliferation of PDLSCs, significantly promoted osteogenic differentiation by regulating the Wnt/β-catenin signalling pathway. Therefore, TDNs could be a novel nanomaterial with great potential for application to PDLSC-based bone tissue engineering.

Review of craniofacial regeneration in China

AIM

Tissue engineering has been recognised as one of the most effective means to form a new viable tissue for medical purpose. Tissue engineering involves a combination of scaffolds, cells, suitable biochemical and physicochemical factors, and engineering and materials methods. This review covered some biomedicine, such as biomaterials, bioactive factors, and stem cells, and manufacturing technologies used in tissue engineering in the oral maxillofacial region, especially in China.

MATERIALS AND METHODS

Data for this review were identified by searches of Web of Science and PubMed, and references from relevant articles using the search terms "biomaterials", "oral tissue regeneration", "bioactive factors" and "stem cells". Only articles published in English between 2013 and 2018 were included.

CONCLUSION

The combination of stem cells, bioactive factors and 3D scaffolds could be of far-reaching significance for the future therapies in tissue repair or tissue regeneration. Furthermore, the review also mentions issues that need to be solved in the application of these biomedicines.

Nucleic acids and analogs for bone regeneration

With the incidence of different bone diseases increasing, effective therapies are needed that coordinate a combination of various technologies and biological materials. Bone tissue engineering has also been considered as a promising strategy to repair various bone defects. Therefore, different biological materials that can promote stem cell proliferation, migration, and osteoblastic differentiation to accelerate bone tissue regeneration and repair have also become the focus of research in multiple fields. Stem cell therapy, biomaterial scaffolds, and biological growth factors have shown potential for bone tissue engineering; however, off-target effects and cytotoxicity have limited their clinical use. The application of nucleic acids (deoxyribonucleic acid or ribonucleic acid) and nucleic acid analogs (peptide nucleic acids or locked nucleic acids), which are designed based on foreign genes or with special structures, can be taken up by target cells to exert different effects such as modulating protein expression, replacing a missing gene, or targeting specific gens or proteins. Due to some drawbacks, nucleic acids and nucleic acid analogs are combined with various delivery systems to exert enhanced effects, but current studies of these molecules have not yet satisfied clinical requirements. In-depth studies of nucleic acid or nucleic acid analog delivery systems have been performed, with a particular focus on bone tissue regeneration and repair. In this review, we mainly introduce delivery systems for nucleic acids and nucleic acid analogs and their applications in bone repair and regeneration. At the same time, the application of conventional scaffold materials for the delivery of nucleic acids and nucleic acid analogs is also discussed.

Used with an appropriate delivery system, nucleic acids and nucleic acid analogs have excellent potential for bone repair and regeneration. Owing to various challenges with bone tissue regeneration, current research is largely focused on gene therapy, which employs genes to treat or prevent disease, and such new materials as nucleic acids (DNA and RNA) and nucleic acid analogs (compounds structurally similar to naturally occurring nucleic acids). A team headed by Yunfeng Lin at Sichuan University, China conducted a review of delivery systems for nucleic acids and nucleic acid analogs and their application in bone repair and regeneration. The authors identified the use of biomaterial scaffolds (which mimic living tissue) as one of the most important research areas for gene therapy, and that strategy has proven effective with all types of bone regeneration and repair.