The fabrication of biomimetic biphasic CAN-PAC hydrogel with a seamless interfacial layer applied in osteochondral defect repair

Cartilage tissue engineering based on biomimetic scaffolds has become a rapidly developing strategy for repairing cartilage defects. In this study, a biphasic CAN-PAC hydrogel for osteochondral defect(OCD)regeneration was fabricated based on the density difference between the two layers via a thermally reactive,rapid cross-linking method. The upper hydrogel was cross-linked by CSMA and NIPAm, and the lower hydrogel was composed of PECDA, AAm and PEGDA. The interface between the two layers was first grafted by the physical cross-linking of calcium gluconate and alginate, followed by the chemical cross-linking of the carbon-carbon double bonds in the other components. The pore sizes of the upper and lower hydrogels were ~ 187.4 and ~ 112.6 μm, respectively. The moduli of the upper and lower hydrogels were ~ 0.065 and~ 0.261 MPa. This prepared bilayer hydrogel exhibited the characteristics of mimetic composition, mimetic structure and mimetic stiffness, which provided a microenvironment for sustaining cell attachment and viability. Meanwhile, the biodegradability and biocompatibility of the CAN-PAC hydrogel were examined in vivo. Furthermore, an osteochondral defect model was developed in rabbits, and the bilayer hydrogels were implanted into the defect. The regenerated tissues in the bilayer hydrogel group exhibited new translucent cartilage and repaired subchondral bone, indicating that the hydrogel can enhance the repair of osteochondral defects.

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 selfassembled 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.

Tetrahedral Framework Nucleic Acid-Based Delivery of Resveratrol Alleviates Insulin Resistance:From Innate to Adaptive Immunity

Obesity-induced insulin resistance is the hallmark of metabolic syndrome,and chronic,low-grade tissue inflammation links obesity to insulin resistance through the activation of tissue-infiltrating immune cells.Current therapeutic approaches lack efficacy and immunomodulatory capacity.Thus,a new therapeutic approach is needed to prevent chronic inflammation and alleviate insulin resistance.Here,we synthesized a tetrahedral framework nucleic acid(tFNA)nanoparticle that carried resveratrol(RSV)to inhibit tissue inflammation and improve insulin sensitivity in obese mice.The prepared nanoparticles,namely tFNAs-RSV,possessed the characteristics of simple synthesis,stable properties,good water solubility,and superior biocompatibility.The tFNA-based delivery ameliorated the lability of RSV and enhanced its therapeutic efficacy.In high-fat diet(HFD)-fed mice,the administration of tFNAs-RSV ameliorated insulin resistance by alleviating inflammation status.tFNAs-RSV could reverse M1 phenotype macrophages in tissues to M2 phenotype macrophages.As for adaptive immunity,the prepared nanoparticles could repress the activation of Th1 and Th17 and promote Th2 and Treg,leading to the alleviation of insulin resistance.Furthermore,this study is the first to demonstrate that tFNAs,a nucleic acid material,possess immunomodulatory capacity.Collectively,our findings demonstrate that tFNAs-RSV alleviate insulin resistance and ameliorate inflammation in HFD mice,suggesting that nucleic acid materials or nucleic acid-based delivery systems may be a potential agent for the treatment of insulin resistance and obesity-related metabolic diseases.

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(t FNAs), 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, t FNAs have been widely applied in the biomedical field as threedimensional DNA nanomaterials. Surprisingly, t FNAs 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,t FNAs 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 t FNAs also have potential applications in controlled and targeted therapies. This review summarized the latest progress in pure/modified/dynamic t FNAs 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.

Correction to:Tetrahedral Framework Nucleic Acid‑Based Delivery of Resveratrol Alleviates Insulin Resistance:From Innate to Adaptive Immunity

Correction to:Nano‑Micro Lett.(2021)13:86 https://doi.org/10.1007/s40820-021-00614-6 The Nano-Micro Letters(2021)13:86,article by Li et al.,entitled“Tetrahedral Framework Nucleic Acid‐Based Delivery of Resveratrol Alleviates Insulin Resistance:From Innate to Adaptive Immunity”(Nano-Micro Lett.https://doi.org/10.1007/s40820-021-00614-6),was published online 06 March,2020,with errors.

Transdermal treatment for malignant melanoma by aptamer-modified tetrahedral framework nucleic acid delivery of vemurafenib

Melanoma is one of the most malignant skin tumors, whose high invasion is generally associated with BRAF gene mutation. Although new chemotherapeutic drugs, such as vemurafenib, have been developed to inhibit the growth of melanoma, these drugs are usually administered intravenously or orally, resulting in toxic side effects on major tissues and organs. Tetrahedral framework nucleic acids(tFNAs) are a novel type of DNA nanostructures with excellent biocompatibility and versatility which have been proven to penetrate through skin barrier with ease. In this study, we prepared t FNAs with vemurafenib and connected DNA aptamer AS1411 at the apex of t FNAs(AS1411-tFNAs/vemurafenib). On one hand, AS1411-tFNAs/vemurafenib could kill melanoma cells by blocking the mutated BRAF gene in vitro. Compared with free vemurafenib, AS1411-tFNAs/vemurafenib had no obvious toxicity to normal cells. On the other hand,AS1411-tFNAs could transfer vemurafenib to cross through the skin barrier and permeate into tumor tissues. In vivo, transdermal delivery of AS1411-t FNAs/vemurafenib could inhibit the growth of human A375melanoma, whose inhibiting effect was stronger than intravenous administration of vemurafenib. These results demonstrated the application prospects of tFNAs combined with chemotherapeutic drugs in skin tumors.

A novel mesenchymal stem cell-targeting dual-miRNA delivery system based on aptamer-functionalized tetrahedral framework nucleic acids:Application to endogenous regeneration of articular cartilage

Articular cartilage injury(ACI)remains one of the key challenges in regenerative medicine,as current treatment strategies do not result in ideal regeneration of hyaline-like cartilage.Enhancing endogenous repair via micro-RNAs(miRNAs)shows promise as a regenerative therapy.miRNA-140 and miRNA-455 are two key and promising candidates for regulating the chondrogenic differentiation of mesenchymal stem cells(MSCs).In this study,we innovatively synthesized a multifunctional tetrahedral framework in which a nucleic acid(tFNA)-based targeting miRNA codelivery system,named A-T-M,was used.With tFNAs as vehicles,miR-140 and miR-455 were connected to and modified on tFNAs,while Apt19S(a DNA aptamer targeting MSCs)was directly integrated into the nanocomplex.The relevant results showed that A-T-M efficiently delivered miR-140 and miR-455 into MSCs and subsequently regulated MSC chondrogenic differentiation through corresponding mechanisms.Interestingly,a synergistic effect between miR-140 and miR-455 was revealed.Furthermore,A-T-M successfully enhanced the endogenous repair capacity of articular cartilage in vivo and effectively inhibited hypertrophic chondrocyte formation.A-T-M provides a new perspective and strategy for the regeneration of articular cartilage,showing strong clinical application value in the future treatment of ACI.

A tetrahedral framework nucleic acid based multifunctional nanocapsule for tumor prophylactic mRNA vaccination

Synthetic antigen-encoding mRNA plays an increasingly significant role in tumor vaccine technology owing to its antigen-specific immune-activation. However, its immune efficacy is challenged by inferior delivery efficiency and demand for suitable adjuvants. Here, we develop a novel mRNA nanovaccine based on a multifunctional nanocapsule, which is a dual-adjuvant formulation composed of cytosine-phosphateguanine motifs loaded tetrahedral framework nucleic acid(CpG-tFNA) and an immunopeptide murine β-defensin 2(mDF2β). This m RNA nanovaccine successfully achieves intracellular delivery, antigen expression and presentation of dendritic cells, and proliferation of antigen-specific T cells. In a tumor prophylactic vaccination model, it exerts an excellent inhibitory effect on lymphoma occurrence through cellular immunity. This mRNA nanovaccine has promising prophylactic applications in tumors and many other diseases.

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.

Tetrahedral framework nucleic acids regulate osteogenic differentiation potential of osteoporotic adipose-derived stem cells

Osteoporosis(OP)is a noncommunicable bone disease caused by a shift in the balance between os-teoblasts and osteoclasts,and can severely affect the health of elderly persons.Autologous stem-cell transplantation can improve reduced bone density and weakened fracture healing abilities in patients with OP.However,OP can adversely affect the osteogenesis and proliferation abilities of autologous adipose-derived stem cells(ASCs).Therefore,an effective drug is required to facilitate autologous ASCs to recover their osteogenic and proliferative potential.Tetrahedral framework nucleic acid(tFNA)is a new type of nanomaterial that has ability to regulate the biological behavior of cells effectively and en-hance the bioactivity of stem cells.In this study,we examine the effects of tFNAs on the osteogenic differentiation and proliferation abilities of ASCs in rats with OP.The results indicate that the 250 nmol/L tFNAs can considerably increase the expression of osteogenesis-related markers,effectively promote the proliferation and osteogenic differentiation of osteoporotic ASCs(OP-ASCs),and help them to regain their osteogenic and proliferative potential.In short,tFNAs can enable OP-ACSs to recover their osteogenic po-tential and promote their proliferation and,therefore,can play a key regulatory role in autologous ASC transplantation.