3D Hybrid Nanofiber Aerogels Combining with Nanoparticles Made of a Biocleavable and Targeting Polycation and MiR-26a for Bone Repair

Janus Nanofibrous Patch with In Situ Grown Superlubricated Skin for Soft Tissue Repair with Inhibited Postoperative Adhesion

The patch with a superlubricated surface shows great potential for the prevention of postoperative adhesion during soft tissue repair. However, the existing patches suffer from the destruction of topography during superlubrication coating and lack of pro-healing capability. Herein, we demonstrate a facile and versatile strategy to develop a Janus nanofibrous patch (J-NFP) with antiadhesion and reactive oxygen species (ROS) scavenging functions. Specifically, sequential electrospinning is performed with initiators and CeO2 nanoparticles (CeNPs) embedded on the different sides, followed by subsurface-initiated atom transfer radical polymerization for grafting zwitterionic polymer brushes, introducing superlubricated skin on the surface of single nanofibers. The poly(sulfobetaine methacrylate) brush-grafted patch retains fibrous topography and shows a coefficient of friction of around 0.12, which is reduced by 77% compared with the pristine fibrous patch. Additionally, a significant reduction in protein, platelet, bacteria, and cell adhesion is observed. More importantly, the CeNPs-embedded patch enables ROS scavenging as well as inhibits pro-inflammatory cytokine secretion and promotes anti-inflammatory cytokine levels. Furthermore, the J-NFP can inhibit tissue adhesion and promote repair of both rat skin wounds and intrauterine injuries. The present strategy for developing the Janus patch exhibits enormous prospects for facilitating soft tissue repair.

New dimensions of electrospun nanofiber material designs for biotechnological uses

Electrospinning technology has garnered wide attention over the past few decades in various biomedical applications including drug delivery, cell therapy, and tissue engineering. This technology can create nanofibers with tunable fiber diameters and functionalities. However, the 2D membrane nature of the nanofibers, as well as the rigidity and low porosity of electrospun fibers, lower their efficacy in tissue repair and regeneration. Recently, new avenues have been explored to resolve the challenges associated with 2D electrospun nanofiber membranes. This review discusses recent trends in creating different electrospun nanofiber microstructures from 2D nanofiber membranes by using various post-processing methods, as well as their biotechnological applications.

Mechanically resilient hybrid aerogels containing fibers of dual-scale sizes and knotty networks for tissue regeneration

The structure and design flexibility of aerogels make them promising for soft tissue engineering, though they tend to come with brittleness and low elasticity. While increasing crosslinking density may improve mechanics, it also imparts brittleness. In soft tissue engineering, resilience against mechanical loads from mobile tissues is paramount. We report a hybrid aerogel that consists of self-reinforcing networks of micro- and nanofibers. Nanofiber segments physically entangle microfiber pillars, allowing efficient stress distribution through the intertwined fiber networks. We show that optimized hybrid aerogels have high specific tensile moduli (~1961.3 MPa cm3 g-1) and fracture energies (~7448.8 J m-2), while exhibiting super-elastic properties with rapid shape recovery (~1.8 s). We demonstrate that these aerogels induce rapid tissue ingrowth, extracellular matrix deposition, and neovascularization after subcutaneous implants in rats. Furthermore, we can apply them for engineering soft tissues via minimally invasive procedures, and hybrid aerogels can extend their versatility to become magnetically responsive or electrically conductive, enabling pressure sensing and actuation.

Advanced Synthetic Scaffolds Based on 1D Inorganic Micro-/Nanomaterials for Bone Regeneration

Inorganic nanoparticulate biomaterials, such as calcium phosphate and bioglass particles, with chemical compositions similar to that of the inorganic component of natural bone, and hence having excellent biocompatibility and bioactivity, are widely used for the fabrication of synthetic bone graft substitutes. Growing evidence suggests that structurally anisotropic, or 1D inorganic micro-/nanobiomaterials are superior to inorganic nanoparticulate biomaterials in the context of mechanical reinforcement and construction of self-supporting 3D network structures. Therefore, in the past decades, efforts have been devoted to developing advanced synthetic scaffolds for bone regeneration using 1D micro-/nanobiomaterials as building blocks. These scaffolds feature extraordinary physical and biological properties, such as enhanced mechanical properties, super elasticity, multiscale hierarchical architecture, extracellular matrix-like fibrous microstructure, and desirable biocompatibility and bioactivity, etc. In this review, an overview of recent progress in the development of advanced scaffolds for bone regeneration is provided based on 1D inorganic micro-/nanobiomaterials with a focus on their structural design, mechanical properties, and bioactivity. The promising perspectives for future research directions are also highlighted.

The translational potential of miR-26 in atherosclerosis and development of agents for its target genes ACC1/2, COL1A1, CPT1A, FBP1, DGAT2, and SMAD7

Atherosclerosis is one of the leading causes of death worldwide. miR-26 is a potential biomarker of atherosclerosis. Standardized diagnostic tests for miR-26 (MIR26-DX) have been developed, but the fastest progress has been in predicting the efficacy of IFN-α therapy for hepatocellular carcinoma (HCC, phase 3). MiR-26 slows atherosclerosis development by suppressing ACC1/2, ACLY, ACSL3/4, ALDH3A2, ALPL, BMP2, CD36, COL1A1, CPT1A, CTGF, DGAT2, EHHADH, FAS, FBP1, GATA4, GSK3β, G6PC, Gys2, HMGA1, HMGB1, LDLR, LIPC, IL-1β, IL-6, JAG2, KCNJ2, MALT1, β-MHC, NF-κB, PCK1, PLCβ1, PYGL, RUNX2, SCD1, SMAD1/4/5/7, SREBF1, TAB3, TAK1, TCF7L2, and TNF-α expression. Many agents targeting these genes, such as the ACC1/2 inhibitors GS-0976, PF-05221304, and MK-4074; the DGAT2 inhibitors IONIS-DGAT2Rx, PF-06427878, PF-0685571, and PF-07202954; the COL1A1 inhibitor HT-100; the stimulants 68Ga-CBP8 and RCT-01; the CPT1A inhibitors etomoxir, perhexiline, and teglicar; the FBP1 inhibitors CS-917 and MB07803; and the SMAD7 inhibitor mongersen, have been investigated in clinical trials. Interestingly, miR-26 better reduced intima-media thickness (IMT) than PCSK9 or CT-1 knockout. Many PCSK9 inhibitors, including alirocumab, evolocumab, inclisiran, AZD8233, Civi-007, MK-0616, and LIB003, have been investigated in clinical trials. Recombinant CT-1 was also investigated in clinical trials. Therefore, miR-26 is a promising target for agent development. miR-26 promotes foam cell formation by reducing ABCA1 and ARL4C expression. Multiple materials can be used to deliver miR-26, but it is unclear which material is most suitable for mass production and clinical applications. This review focuses on the potential use of miR-26 in treating atherosclerosis to support the development of agents targeting it.

In Situ Deposition of Drug and Gene Nanoparticles on a Patterned Supramolecular Hydrogel to Construct a Directionally Osteochondral Plug

The integrated repair of bone and cartilage boasts advantages for osteochondral restoration such as a long-term repair effect and less deterioration compared to repairing cartilage alone. Constructing multifactorial, spatially oriented scaffolds to stimulate osteochondral regeneration, has immense significance. Herein, targeted drugs, namely kartogenin@polydopamine (KGN@PDA) nanoparticles for cartilage repair and miRNA@calcium phosphate (miRNA@CaP) NPs for bone regeneration, were in situ deposited on a patterned supramolecular-assembled 2-ureido-4 [lH]-pyrimidinone (UPy) modified gelation hydrogel film, facilitated by the dynamic and responsive coordination and complexation of metal ions and their ligands. This hydrogel film can be rolled into a cylindrical plug, mimicking the Haversian canal structure of natural bone. The resultant hydrogel demonstrates stable mechanical properties, a self-healing ability, a high capability for reactive oxygen species capture, and controlled release of KGN and miR-26a. In vitro, KGN@PDA and miRNA@CaP promote chondrogenic and osteogenic differentiation of mesenchymal stem cells via the JNK/RUNX1 and GSK-3β/β-catenin pathways, respectively. In vivo, the osteochondral plug exhibits optimal subchondral bone and cartilage regeneration, evidenced by a significant increase in glycosaminoglycan and collagen accumulation in specific zones, along with the successful integration of neocartilage with subchondral bone. This biomaterial delivery approach represents a significant toward improved osteochondral repair.

Attributes of Nanomaterials and Nanotopographies for Improved Bone Tissue Engineering and Regeneration

Bone tissue engineering (BTE) is a multidisciplinary area that can solve the limitation of conventional grafting methods by developing viable and biocompatible bone replacements. The three essential components of BTE, i.e., Scaffold material and Cells and Growth factors altogether, facilitate support and guide for bone formation, differentiation of the bone tissues, and enhancement in the cellular activities and bone regeneration. However, there is a scarcity of the appropriate materials that can match the mechanical property as well as functional similarity to native tissue, considering the bone as hard tissue. In such scenarios, nanotechnology can be leveraged upon to achieve the desired aspects of BTE, and that is the key point of this review article. This review article examines the significant areas of nanotechnology research that have an impact on regeneration of bone: (a) scaffold with nanomaterials helps to enhance physicochemical interactions, biocompatibility, mechanical stability, and attachment; (b) nanoparticle-based approaches for delivering bioactive chemicals, growth factors, and genetic material. The article begins with the introduction of components and healing mechanisms of bone and the factors associated with them. The focus of this article is on the various nanotopographies that are now being used in scaffold formation, by describing how they are made, and how these nanotopographies affect the immune system and potential underlying mechanisms. The advantages of 4D bioprinting in BTE by using nanoink have also been mentioned. Additionally, we have investigated the importance of an in silico approach for finding the interaction between drugs and their related receptors, which can help to formulate suitable systems for delivery. This review emphasizes the role of nanoscale approach and how it helps to increase the efficacy of parameters of scaffold as well as drug delivery system for tissue engineering and bone regeneration.

The osteogenic and angiogenic potential of microRNA-26a delivered via a non-viral delivery peptide for bone repair

Bone-related injuries and diseases are among the most common causes of morbidity worldwide. Current bone-regenerative strategies such as auto- and allografts are invasive by nature, with adverse effects such as pain, infection and donor site morbidity. MicroRNA (miRNA) gene therapy has emerged as a promising area of research, with miRNAs capable of regulating multiple gene pathways simultaneously through the repression of post-transcriptional mRNAs. miR-26a is a key regulator of osteogenesis and has been found to be upregulated following bone injury, where it induces osteodifferentiation of mesenchymal stem cells (MSCs) and facilitates bone formation. This study demonstrates, for the first time, that the amphipathic, cell-penetrating peptide RALA can efficiently deliver miR-26a to MSCs in vitro to regulate osteogenic signalling. Transfection with miR-26a significantly increased expression of osteogenic and angiogenic markers at both gene and protein level. Using a rat calvarial defect model with a critical size defect, RALA/miR-26a NPs were delivered via an injectable, thermo-responsive Cs-g-PNIPAAm hydrogel to assess the impact on both rate and quality of bone healing. Critical defects treated with the RALA/miR-26a nanoparticles (NPs) had significantly increased bone volume and bone mineral density at 8 weeks, with increased blood vessel formation and mechanical properties. This study highlights the utility of RALA to deliver miR-26a for the purpose of bone healing within an injectable biomaterial, warranting further investigation of dose-related efficacy of the therapeutic across a range of in vivo models.

Aerogel-Based Materials in Bone and Cartilage Tissue Engineering-A Review with Future Implications

Aerogels are fascinating solid materials known for their highly porous nanostructure and exceptional physical, chemical, and mechanical properties. They show great promise in various technological and biomedical applications, including tissue engineering, and bone and cartilage substitution. To evaluate the bioactivity of bone substitutes, researchers typically conduct in vitro tests using simulated body fluids and specific cell lines, while in vivo testing involves the study of materials in different animal species. In this context, our primary focus is to investigate the applications of different types of aerogels, considering their specific materials, microstructure, and porosity in the field of bone and cartilage tissue engineering. From clinically approved materials to experimental aerogels, we present a comprehensive list and summary of various aerogel building blocks and their biological activities. Additionally, we explore how the complexity of aerogel scaffolds influences their in vivo performance, ranging from simple single-component or hybrid aerogels to more intricate and organized structures. We also discuss commonly used formulation and drying methods in aerogel chemistry, including molding, freeze casting, supercritical foaming, freeze drying, subcritical, and supercritical drying techniques. These techniques play a crucial role in shaping aerogels for specific applications. Alongside the progress made, we acknowledge the challenges ahead and assess the near and far future of aerogel-based hard tissue engineering materials, as well as their potential connection with emerging healing techniques.

Elevating nucleic acid delivery via a stable anionic peptide-dextran ternary system

Nucleic acid-based therapies hold promise for treating previously intractable diseases but require effective delivery vectors to protect the therapeutic agents and ensure efficient transfection. Cationic polymeric vectors are particularly notable for their adaptability, high transfection efficiency, and low cost, but their positive charge often attracts blood proteins, causing aggregation and reduced transfection efficiency. Addressing this, we designed an anionic peptide-grafted dextran (Dex-LipE5H) to serve as a cross-linkable coating to bolster the stability of cationic polymer/nucleic acid complexes. The Dex-LipE5H was synthesized through a Michael addition reaction, combining an anionic peptide (LipE5H) with dextran modified by divinyl sulfone. We demonstrated Dex-lipE5H utility in a novel ternary nucleic acid delivery system, CDex-LipE5H/PEI/nucleic acid. CDex-LipE5H/PEI/nucleic acid demonstrated lower cytotoxicity and superior anti-protein absorption ability compared to PEI/pDNA and Dex-LipE5H/PEI/pDNA. Most notably, the crosslinked CDex-LipE5H/PEI/pDNA demonstrated remarkable transfection performance in HepG2 cells, which poses significant transfection challenges, even in a medium with 20% serum. This system's effective siRNA interference performance was further validated through a PCSK9 gene knockdown assay. This investigation provides novel insights and contributes to the design of cost-effective, next-generation nucleic acid delivery systems with enhanced blood stability and transfection efficiency.

Biomedical applications of nanomaterials in the advancement of nucleic acid therapy: Mechanistic challenges, delivery strategies, and therapeutic applications

In the past few decades, substantial advancement has been made in nucleic acid (NA)-based therapies. Promising treatments include mRNA, siRNA, miRNA, and anti-sense DNA for treating various clinical disorders by modifying the expression of DNA or RNA. However, their effectiveness is limited due to their concentrated negative charge, instability, large size, and host barriers, which make widespread application difficult. The effective delivery of these medicines requires safe vectors that are efficient & selective while having non-pathogenic qualities; thus, nanomaterials have become an attractive option with promising possibilities despite some potential setbacks. Nanomaterials possess ideal characteristics, allowing them to be tuned into functional bio-entity capable of targeted delivery. In this review, current breakthroughs in the non-viral strategy of delivering NAs are discussed with the goal of overcoming challenges that would otherwise be experienced by therapeutics. It offers insight into a wide variety of existing NA-based therapeutic modalities and techniques. In addition to this, it provides a rationale for the use of non-viral vectors and a variety of nanomaterials to accomplish efficient gene therapy. Further, it discusses the potential for biomedical application of nanomaterials-based gene therapy in various conditions, such as cancer therapy, tissue engineering, neurological disorders, and infections.

CHIR99021-Treated Osteocytes with Wnt Activation in 3D-Printed Module Form an Osteogenic Microenvironment for Enhanced Osteogenesis and Vasculogenesis

Finding a bone implant that has high bioactivity that can safely drive stem cell differentiation and simulate a real in vivo microenvironment is a challenge for bone tissue engineering. Osteocytes significantly regulate bone cell fate, and Wnt-activated osteocytes can reversely regulate bone formation by regulating bone anabolism, which may improve the biological activity of bone implants. To achieve a safe application, we used the Wnt agonist CHIR99021 (C91) to treat MLO-Y4 for 24 h, in a co-culture with ST2 for 3 days after withdrawal. We found that the expression of Runx2 and Osx increased, promoted osteogenic differentiation, and inhibited adipogenic differentiation in the ST2 cells, and these effects were eliminated by the triptonide. Therefore, we hypothesized that C91-treated osteocytes form an osteogenic microenvironment (COOME). Subsequently, we constructed a bio-instructive 3D printing system to verify the function of COOME in 3D modules that mimic the in vivo environment. Within PCI3D, COOME increased the survival and proliferation rates to as high as 92% after 7 days and promoted ST2 cell differentiation and mineralization. Simultaneously, we found that the COOME-conditioned medium also had the same effects. Therefore, COOME promotes ST2 cell osteogenic differentiation both directly and indirectly. It also promotes HUVEC migration and tube formation, which can be explained by the high expression of Vegf. Altogether, these results indicate that COOME, combined with our independently developed 3D printing system, can overcome the poor cell survival and bioactivity of orthopedic implants and provide a new method for clinical bone defect repair.

Bone ECM-inspired biomineralization chitin whisker liquid crystal hydrogels for bone regeneration

As a particular cell niche, natural bone extracellular matrix (ECM) is an organic-inorganic composite material formed by mineralization of liquid crystal (LC) collagen fiber network. However, designing bone repair materials that highly imitate the LC characteristic and composite components of natural bone ECM is a great challenge. Here, we report a novel kind of bone ECM-inspired biomineralization chitin whisker LC hydrogels. First, photocurable chitin whisker LC hydrogels with bone ECM-like chiral nematic LC state and viscoelasticity are created. Next, biomineralization, guided by LC hydrogels, is carried out to truly mimic the mineralization process of natural bone, so as to obtain the organic-inorganic composite materials with bone ECM-like microenvironment. The chitin whisker LC hydrogels exhibit superior biomineralization, protein adsorption and osteogenesis ability, more importantly, LC hydrogel with negatively charged -COOH groups is more conducive to biomineralization and shows more desirable osteogenic activity than that with positively charged -NH₂ groups. Notably, compared with the pristine LC hydrogels, the biomineralization LC hydrogels display more favorable osteogenesis ability due to their bone ECM-like LC texture and bone-like hydroxyapatite. This study opens an avenue toward the design of bone ECM-inspired biomineralization chitin whisker LC hydrogels for bone regeneration.

Remote control of the recruitment and capture of endogenous stem cells by ultrasound for in situ repair of bone defects

Stem cell-based tissue engineering has provided a promising platform for repairing of bone defects. However, the use of exogenous bone marrow mesenchymal stem cells (BMSCs) still faces many challenges such as limited sources and potential risks. It is important to develop new approach to effectively recruit endogenous BMSCs and capture them for in situ bone regeneration. Here, we designed an acoustically responsive scaffold (ARS) and embedded it into SDF-1/BMP-2 loaded hydrogel to obtain biomimetic hydrogel scaffold complexes (BSC). The SDF-1/BMP-2 cytokines can be released on demand from the BSC implanted into the defected bone via pulsed ultrasound (p-US) irradiation at optimized acoustic parameters, recruiting the endogenous BMSCs to the bone defected or BSC site. Accompanied by the daily p-US irradiation for 14 days, the alginate hydrogel was degraded, resulting in the exposure of ARS to these recruited host stem cells. Then another set of sinusoidal continuous wave ultrasound (s-US) irradiation was applied to excite the ARS intrinsic resonance, forming highly localized acoustic field around its surface and generating enhanced acoustic trapping force, by which these recruited endogenous stem cells would be captured on the scaffold, greatly promoting them to adhesively grow for in situ bone tissue regeneration. Our study provides a novel and effective strategy for in situ bone defect repairing through acoustically manipulating endogenous BMSCs.

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We designed ARS and embedded it into SDF-1/BMP-2 loaded hydrogel to form BSC.

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The BSC can release SDF-1/BMP-2 by p-US irradiation for recruitment of endogenous BMSCs and capture them by s-US irradiation.

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The in situ repair of bone defects were successfully realized by US-mediated control of the recruitment and capture of BMSCs.

Natural silk nanofibers as building blocks for biomimetic aerogel scaffolds

Protein nanofibers offer great promise for tissue engineering scaffolds owing to biomimetic architecture and exceptional biocompatibility. Natural silk nanofibrils (SNFs) are promising but unexplored protein nanofibers for biomedical applications. In this study, the SNF-assembled aerogel scaffolds with ECM-mimicking architecture and ultra-high porosity are developed based on a polysaccharides-assisted strategy. The SNFs exfoliated from silkworm silks can be utilized as building blocks to construct 3D nanofibrous scaffolds with tunable densities and desirable shapes on a large scale. We demonstrate that the natural polysaccharides can regulate SNF assembly through multiple binding modes, endowing the scaffolds with structural stability in water and tunable mechanical properties. As a proof of concept, the biocompatibility and biofunctionality of the chitosan-assembled SNF aerogels were investigated. The nanofibrous aerogels have excellent biocompatibility, and their biomimetic structure, ultra-high porosity, and large specific surface area endow the scaffolds with enhanced cell viability to mesenchymal stem cells. The nanofibrous aerogels were further functionalized by SNF-mediated biomineralization, demonstrating their potential as a bone-mimicking scaffold. Our results show the potential of natural nanostructured silks in the field of biomaterials and provide a feasible strategy to construct protein nanofiber scaffolds.

A novel decellularized matrix of Wnt signaling-activated osteocytes accelerates the repair of critical-sized parietal bone defects with osteoclastogenesis, angiogenesis, and neurogenesis

Cell source is the key to decellularized matrix (DM) strategy. This study compared 3 cell types, osteocytes with/without dominant active Wnt/β-catenin signaling (daCO and WTO) and bone marrow stromal cells (BMSCs) for their DMs in bone repair. Decellularization removes all organelles and >95% DNA, and retained >74% collagen and >71% GAG, maintains the integrity of cell basement membrane with dense boundaries showing oval and honeycomb structure in osteocytic DM and smooth but irregular shape in the BMSC-DM. DM produced higher cell survival rate (90%) and higher proliferative activity. In vitro, daCO-DM induces more and longer stress fibers in BMSCs, conducive to cell adhesion, spreading, and osteogenic differentiation. 8-wk after implantation of the critical-sized parietal bone defect model, daCO-DM formed tight structures, composed of a large number of densely-arranged type-I collagen under polarized light microscope, which is similar to and integrated with host bone. BV/TV (>54%) was 1.5, 2.9, and 3.5 times of WTO-DM, BMSC-DM, and none-DM groups, and N.Ob/T.Ar (3.2 × 10²/mm²) was 1.7, 2.9, and 3.3 times. At 4-wk, daCO-DM induced osteoclastogenesis, 2.3 times higher than WTO-DM; but BMSC-DM or none-DM didn't. daCO-DM increased the expression of RANKL and MCSF, Vegfa and Angpt1, and Ngf in BMSCs, which contributes to osteoclastogenesis, angiogenesis, and neurogenesis, respectively. daCO-DM promoted H-type vessel formation and nerve markers β3-tubulin and NeuN expression. Conclusion: daCO-DM produces metabolic and neurovascularized organoid bone to accelerate the repair of bone defects. These features are expected to achieve the effect of autologous bone transplantation, suitable for transformation application.

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Decellularized matrix of osteocytes with dominant-active β-catenin (daCO-DM) promotes osteogenesis for regenerative repair.

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daCO-DM induces BMSCs to form stress fibers, conducive to cell adhesion, spreading, and differentiation towards osteoblasts.

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daCO-DM-induced osteoblasts have strong activity secreting dense and orderly-arranged type I collagen as host bone’s.

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daCO-DM induces BMSCs to express pre-osteoclastogenic cytokine RANKL and MCSF for osteoclastogenesis of marrow monocytes.

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daCO-DM enhances BMSCs to express angiogenic Vegfa and Angpt1, and neurogenic Ngf potentially for neurovascularization.

Nanofiber Aerogels with Precision Macrochannels and LL-37-Mimic Peptides Synergistically Promote Diabetic Wound Healing

Fast healing of diabetic wounds remains a major clinical challenge. Herein, this work reports a strategy to combine nanofiber aerogels containing precision macrochannels and the LL-37-mimic peptide W379 for rapid diabetic wound healing. Nanofiber aerogels consisting of poly(glycolide-co-lactide) (PGLA 90:10)/gelatin and poly-p-dioxanone (PDO)/gelatin short electrospun fiber segments were prepared by partially anisotropic freeze-drying, crosslinking, and sacrificial templating with three-dimensional (3D)-printed meshes, exhibiting nanofibrous architecture and precision micro-/macrochannels. Like human cathelicidin LL-37, W379 peptide at a concentration of 3 μg/mL enhanced the migration and proliferation of keratinocytes and dermal fibroblasts in a cell scratch assay and a proliferation assay. In vivo studies show that nanofiber aerogels with precision macrochannels can greatly promote cell penetration compared to aerogels without macrochannels. Relative to control and aerogels with and without macrochannels, adding W379 peptides to aerogels with precision macrochannels shows the best efficacy in healing diabetic wounds in mice in terms of cell infiltration, neovascularization, and re-epithelialization. The fast re-epithelization could be due to upregulation of phospho-extracellular signal-regulated kinase (p38 MAPK) after treatment with W379. Together, the approach developed in this work could be promising for the treatment of diabetic wounds and other chronic wounds.

MicroRNA-loaded biomaterials for osteogenesis

The large incidence of bone defects in clinical practice increases not only the demand for advanced bone transplantation techniques but also the development of bone substitute materials. A variety of emerging bone tissue engineering materials with osteogenic induction ability are promising strategies for the design of bone substitutes. MicroRNAs (miRNAs) are a class of non-coding RNAs that regulate intracellular protein expression by targeting the non-coding region of mRNA3′-UTR to play an important role in osteogenic differentiation. Several miRNA preparations have been used to promote the osteogenic differentiation of stem cells. Therefore, multiple functional bone tissue engineering materials using miRNA as an osteogenic factor have been developed and confirmed to have critical efficacy in promoting bone repair. In this review, osteogenic intracellular signaling pathways mediated by miRNAs are introduced in detail to provide a clear understanding for future clinical treatment. We summarized the biomaterials loaded with exogenous cells engineered by miRNAs and biomaterials directly carrying miRNAs acting on endogenous stem cells and discussed their advantages and disadvantages, providing a feasible method for promoting bone regeneration. Finally, we summarized the current research deficiencies and future research directions of the miRNA-functionalized scaffold. This review provides a summary of a variety of advanced miRNA delivery system design strategies that enhance bone regeneration.

Recent Advances in Designing Fibrous Biomaterials for the Domain of Biomedical, Clinical, and Environmental Applications

Unique properties and potential applications of nanofibers have emerged as innovative approaches and opportunities in the biomedical, healthcare, environmental, and biosensor fields. Electrospinning and centrifugal spinning strategies have gained considerable attention among all kinds of strategies to produce nanofibers. These techniques produce nanofibers with high porosity and surface area, adequate pore architecture, and diverse chemical compositions. The extraordinary characteristics of nanofibers have unveiled new gates in nanomedicine to establish innovative fiber-based formulations for biomedical use, healthcare, and a wide range of other applications. The present review aims to provide a comprehensive overview of nanofibers and their broad range of applications, including drug delivery, biomedical scaffolds, tissue/bone-tissue engineering, dental applications, and environmental remediation in a single place. The review begins with a brief introduction followed by potential applications of nanofibers. Finally, the future perspectives and current challenges of nanofibers are demonstrated. This review will help researchers to engineer more efficient multifunctional nanofibers with improved characteristics for their effective use in broad areas. We strongly believe this review is a reader's delight and will help in dealing with the fundamental principles and applications of nanofiber-based scaffolds. This review will assist students and a broad range of scientific communities to understand the significance of nanofibers in several domains of nanotechnology, nanomedicine, biotechnology, and environmental remediation, which will set a benchmark for further research.

Electrospun Nanofibers for Bone Regeneration: From Biomimetic Composition, Structure to Function

In recent years, a variety of novel materials and processing technologies have been developed to prepare tissue engineering scaffolds for bone defect repair. Among them, nanofibers fabricated via electrospinning technology...

Osteogenic Property Regulation of Stem Cells by a Hydroxyapatite 3D-Hybrid Scaffold With Cancellous Bone Structure

Cancellous bone plays an indispensable role in the skeletal system due to its various functions and high porosity. In this work, chitosan and hydroxyapatite nanowires (CS@HAP NWs) hybrid nanostructured scaffolds with suitable mechanical properties, high porosity and a fine porous structure were prepared to simulate the 3-dimensional structure of cancellous bone. The 3D-hybrid scaffolds promote cell adhesion and the migration of human adipose-derived stem cells (hADSCs) inside the scaffolds. The cavities in the scaffolds provide space for the hADSCs proliferation and differentiation. Moreover, the various contents of HAP and the induced mechanical property changes regulate the differentiation of hADSCs toward osteoblasts. Overall, cellular fate regulation of hADSCs via rationally engineered HAP-based hybrid scaffolds is a facile and effective approach for bone tissue engineering.

MiRNA-Nanofiber, the Next Generation of Bioactive Scaffolds for Bone Regeneration: A Review

Scaffold-based bone tissue engineering has been introduced as an alternative treatment option for bone grafting due to limitations in the allograft. Not only physical conditions but also biological conditions such as gene expression significantly impact bone regeneration. Scaffolds in composition with bioactive molecules such as miRNA mimics provide a platform to enhance migration, proliferation, and differentiation of osteoprogenitor cells for bone regeneration. Among scaffolds, fibrous structures showed significant advantages in promoting osteogenic differentiation and bone regeneration via delivering bioactive molecules over the past decade. Here, we reviewed the bone and bone fracture healing considerations for the impact of miRNAs on bone regeneration. We also examined the methods used to improve miRNA mimics uptake by cells, the fabrication of fibrous scaffolds, and the effective delivery of miRNA mimics using fibrous scaffold and their processes for bone development. Finally, we offer our view on the principal challenges of miRNA mimics delivery by nanofibers for bone tissue engineering.

Biomaterial-based delivery of nucleic acids for tissue regeneration

Gene therapy is a promising novel method of tissue regeneration by stimulating or inhibiting key signaling pathways. However, their therapeutic applications in vivo are largely limited by several physiological obstacles, such as degradation of nucleases, impermeability of cell membranes, and transport to the desired intracellular compartments. Biomaterial-based gene delivery systems can overcome the problems of stability and local drug delivery, and can temporarily control the overexpression of therapeutic genes, leading to the local production of physiologically relevant levels of regulatory factors. But the gene delivery of biomaterials for tissue regeneration relies on multi-factor design. This review aims to outline the impact of gene delivery methods, therapeutic genes and biomaterials selection on this strategy, emphatically introduce the latest developments in the design of gene delivery vehicles based on biomaterials, summarize the mechanism of nucleic acid for tissue regeneration, and explore the strategies of nucleic acid delivery vehicles for various tissue regeneration.

Biomaterials with structural hierarchy and controlled 3D nanotopography guide endogenous bone regeneration

Biomaterials without exogenous cells or therapeutic agents often fail to achieve rapid endogenous bone regeneration with high quality. Here, we reported a class of three-dimensional (3D) nanofiber scaffolds with hierarchical structure and controlled alignment for effective endogenous cranial bone regeneration. 3D scaffolds consisting of radially aligned nanofibers guided and promoted the migration of bone marrow stem cells from the surrounding region to the center in vitro. These scaffolds showed the highest new bone volume, surface coverage, and mineral density among the tested groups in vivo. The regenerated bone exhibited a radially aligned fashion, closely recapitulating the scaffold's architecture. The organic phase in regenerated bone showed an aligned, layered, and densely packed structure, while the inorganic mineral phase showed a uniform distribution with smaller pore size and an even distribution of stress upon the simulated compression. We expect that this study will inspire the design of next-generation biomaterials for effective endogenous bone regeneration with desired quality.

Pharmaceutical electrospinning and 3D printing scaffold design for bone regeneration

Bone regenerative engineering provides a great platform for bone tissue regeneration covering cells, growth factors and other dynamic forces for fabricating scaffolds. Diversified biomaterials and their fabrication methods have emerged for fabricating patient specific bioactive scaffolds with controlled microstructures for bridging complex bone defects. The goal of this review is to summarize the points of scaffold design as well as applications for bone regeneration based on both electrospinning and 3D bioprinting. It first briefly introduces biological characteristics of bone regeneration and summarizes the applications of different types of material and the considerations for bone regeneration including polymers, ceramics, metals and composites. We then discuss electrospinning nanofibrous scaffold applied for the bone regenerative engineering with various properties, components and structures. Meanwhile, diverse design in the 3D bioprinting scaffolds for osteogenesis especially in the role of drug and bioactive factors delivery are assembled. Finally, we discuss challenges and future prospects in the development of electrospinning and 3D bioprinting for osteogenesis and prominent strategies and directions in future.

Freeze-Casting with 3D-Printed Templates Creates Anisotropic Microchannels and Patterned Macrochannels within Biomimetic Nanofiber Aerogels for Rapid Cellular Infiltration

A new approach is described for fabricating 3D poly(ε-caprolactone) (PCL)/gelatin (1:1) nanofiber aerogels with patterned macrochannels and anisotropic microchannels by freeze-casting with 3D-printed sacrificial templates. Single layer or multiple layers of macrochannels are formed through an inverse replica of 3D-printed templates. Aligned microchannels formed by partially anisotropic freezing act as interconnected pores between templated macrochannels. The resulting macro-/microchannels within nanofiber aerogels significantly increase preosteoblast infiltration in vitro. The conjugation of vascular endothelial growth factor (VEGF)-mimicking QK peptide to PCL/gelatin/gelatin methacryloyl (1:0.5:0.5) nanofiber aerogels with patterned macrochannels promotes the formation of a microvascular network of seeded human microvascular endothelial cells. Moreover, nanofiber aerogels with patterned macrochannels and anisotropic microchannels show significantly enhanced cellular infiltration rates and host tissue integration compared to aerogels without macrochannels following subcutaneous implantation in rats. Taken together, this novel class of nanofiber aerogels holds great potential in biomedical applications including tissue repair and regeneration, wound healing, and 3D tissue/disease modeling.

3D PCL/Gelatin/Genipin Nanofiber Sponge as Scaffold for Regenerative Medicine

Recent advancements in tissue engineering and material science have radically improved in vitro culturing platforms to more accurately replicate human tissue. However, the transition to clinical relevance has been slow in part due to the lack of biologically compatible/relevant materials. In the present study, we marry the commonly used two-dimensional (2D) technique of electrospinning and a self-assembly process to construct easily reproducible, highly porous, three-dimensional (3D) nanofiber scaffolds for various tissue engineering applications. Specimens from biologically relevant polymers polycaprolactone (PCL) and gelatin were chemically cross-linked using the naturally occurring cross-linker genipin. Potential cytotoxic effects of the scaffolds were analyzed by culturing human dermal fibroblasts (HDF) up to 23 days. The 3D PCL/gelatin/genipin scaffolds produced here resemble the complex nanofibrous architecture found in naturally occurring extracellular matrix (ECM) and exhibit physiologically relevant mechanical properties as well as excellent cell cytocompatibility. Samples cross-linked with 0.5% genipin demonstrated the highest metabolic activity and proliferation rates for HDF. Scanning electron microscopy (SEM) images indicated excellent cell adhesion and the characteristic morphological features of fibroblasts in all tested samples. The three-dimensional (3D) PCL/gelatin/genipin scaffolds produced here show great potential for various 3D tissue-engineering applications such as ex vivo cell culturing platforms, wound healing, or tissue replacement.