An instantly fixable and self-adaptive scaffold for skull regeneration by autologous stem cell recruitment and angiogenesis

Endogenous dual-responsive and self-adaptive silk fibroin-based scaffold with enhancement of immunomodulation for skull regeneration

Despite the current biomaterials (e.g. titanium mesh and polyether ether ketone) have been applied to clinical skull repair, the limitations on mechanical match, shape adaptability, bioactivity and osteointegration have greatly limited their clinical application. In this work, we constructed a water and inflammatory microenvironment dual-responsive self-adaptive silk fibroin-magnesium oxide-based scaffold with the matrix metalloproteinase-2-responsive gelatin-methacryloyl-interleukin-4 (IL-4) coating, which presented good mechanical compliance, quickly shape matching and intraoperative reprocessability. With the capability of responding to an acute inflammation microenvironment followed by a triggered on-demand release of the IL-4, the combination of immunoactive IL-4 and Mg2+ co-ordinately facilitated metabolic reprogramming by suppressing glycolysis, promoting mitochondrial oxidative phosphorylation and modulating adenosine 5'-monophosphate-activated protein kinase (AMPK) signalling pathways in macrophages, resulting in significantly facilitating M2 macrophage activation. During the stage of tissue remodelling, the sustained release of Mg2+ further promoted macrophage M2 polarization and the expression of anti-inflammatory cytokines, significantly reduced immune response and improved ectopic osteogenesis ability. Meanwhile, the cranial defect models of male rats demonstrated that this scaffold could significantly enhance biomineralized deposition and vascularisation, and achieve good bone regeneration of cranial defects. Overall, the bioactive scaffold provides a promising biomaterial and alternative repair strategy for critical-size skull defect repair.

Sequential simulation of regeneration-specific microenvironments using scaffolds loaded with nanoplatelet vesicles enhances bone regeneration

Bone regeneration is a complex and coordinated physiological process, and the different stages of this process have corresponding microenvironments to support cell development and physiological activities. However, biological scaffolds that provide different three-dimensional environments during different stages of bone regeneration are lacking. In this study, we report a novel composite scaffold (NPE@DCBM) inspired by the stages of bone regeneration; this scaffold was composed of a fibrin hydrogel loaded with nanoplatelet vesicles (NPVs), designated as NPE, and decellularized cancellous bone matrix (DCBM) microparticles. Initially, the NPE rapidly established a temporary microenvironment conducive to cell migration and angiogenesis. Subsequently, the DCBM simulated the molecular structure of bone and promoted new bone formation. In vitro, the NPVs regulated lipid metabolism in bone marrow mesenchymal stem cells (BMSCs), reprogramed the fate of BMSCs by activating the PI3K/AKT and MAPK/ERK positive feedback pathways, and increased BMSC functions, including proliferation, migration and proangiogenic potential. In vivo, NPV@DCBM accelerated bone tissue regeneration and repair. Initially, the NPE rapidly induced angiogenesis between DCBM microparticles, and subsequently, BMSCs differentiated into osteoblasts with DCBM microparticles at their core. In summary, the design of this composite scaffold that sequentially mimics different bone regeneration microenvironments may provide a promising strategy for bone regeneration, with clinical translational potential.

Hierarchical interconnected porous scaffolds with regulated interfacial nanotopography exhibit antimicrobial, alleviate inflammation, neovascularization, and tissue integration for bone regeneration

Novel interconnected porous scaffolds featuring suitable micro-interface structures hold significance in bone regeneration. Therefore, a hierarchical interconnected porous scaffold with nanotopography interface of pores, mimicking natural bone structure and extracellular matrix microenvironment, are designed to enhance bone regeneration by improving cell adhesion, proliferation, alleviate inflammation, and tissue integration capabilities. The scaffold is fabricated through Pickering emulsion templating method, with aminated gelatin and copper-hydroxyapatite nanoparticles serving as co-stabilizers. This process results in a dual nanoparticles-decorated interface, which could provide ample anchoring points for cells. Adjusting the ratio of the two nanoparticles leads to scaffold with different interfacial roughness. The resultant scaffold increases the number of cellular focal adhesions, enhancing cell adhesion, while its high porosity supports cell recruitment, proliferation and immunomodulation. Copper-hydroxyapatite adsorption at the pore interface reduces copper ion usage and exposes nanoparticles for direct cell contact, endowing the scaffold with enhanced antibacterial and angiogenic properties. An initial burst release phase of copper ions exerts inhibitory effects on mRNA expression, followed by a sustained and optimal release phase that promotes osteogenesis. The molecular mechanism underlying the scaffold of osteogenic potential has been elucidated through RNA sequencing analysis, along with the regulation of inflammatory cytokine expression. In vitro and in vivo studies alike verify its neovascularization-promoting capacity. The efficacy shown in a rat model with critical cranial defects underscores its clinical promise for bone regeneration, as Cu-doped scaffolds retain osteoinductive qualities after 10 weeks in vivo. This study innovates a manufacturing method for a novel scaffold in bone tissue engineering.

Spatiotemporally Programming Microenvironment to Recapitulate Endochondral Ossification via Greenhouse-Inspired Bionic Niche

Various biomaterials have been developed to address challenging critical-sized bone defects. However, most of them focus on intramembranous ossification (IMO) rather than endochondral ossification (ECO), often resulting in suboptimal therapeutic outcomes. Drawing inspiration from the functionality of the greenhouse ecosystem, herein a bionic niche is innovatively crafted to recapitulate the ECO process. This niche consists of three hierarchical components: an embedded microchannel network that facilitates cell infiltration and matter exchange, a polydopamine surface modification layer with immunomodulatory functions, and an ECO-targeted delivery system based on mesoporous silica nanoparticles. Through spatiotemporally programming of the microenvironment, the bionic niche effectively recapitulates the key stages of ECO. Notably, even in the rat calvaria, a region well-known for IMO, the bionic niche is capable of initiating ECO, evident by cartilage template formation, leading to efficient bone regeneration. Taken together, this study introduces prospective concepts for designing next-generation ECO-driven biomaterials for bone tissue engineering.

3D-bioprinted functional scaffold based on synergistic induction of i-PRF and laponite exerts efficient and personalized bone regeneration via miRNA-mediated TGF-β/Smads signaling

BACKGROUND

Limited stem cells, low vascularization efficiency, and weak osteoinductive activity plague the repair and reconstruction of bone defects with cell-free scaffolds.

METHODS

Herein, injectable platelet-rich fibrin (i-PRF) was loaded into a alginate methacryloyl (AlgMA)/gelatin methacryloyl (GelMA)-methylcellulose (AGM) bioink system and constructed a porous hydrogel scaffold by 3D bioprinting. The addition of nanosilicate-laponite (Lap) further enhanced this scaffold and synergized with i-PRF to promote efficient and personalized cranial regeneration.

RESULTS

At the biochemical level, Lap significantly enhanced the ability of the scaffold to retard growth factor release, and multiple physiologically proportional growth factors in the scaffold synergistically promoted rapid neoangiogenesis and concomitantly recruited endogenous bone marrow mesenchymal stem cells (BMSCs). More importantly, the bioactive ions released by Lap markedly promoted the proliferation of BMSCs and consistently induced the osteogenic differentiation of BMSCs. At the immunological level, i-PRF-AGM@Lap significantly attenuates the inflammatory response by promoting macrophage M2 polarization. Mechanistically, miRNA sequencing and functional validation experiments demonstrated that bioactive ions released by Lap could synergize with growth factors in i-PRF to promote osteogenic differentiation of BMSCs through the miR-21 and miR-125a-mediated transforming growth factor-β/Smads signaling pathway.

CONCLUSION

The results of this study provide a new idea for the personalized treatment of bone defects.

E7 peptide modified poly(ε-caprolactone)/silk fibroin/octacalcium phosphate nanofiber membranes with "recruitment-osteoinduction" potentials for effective guided bone regeneration

Effective membranes that have the osteogneic potential and the ability to recruit osteoblast precursor cells challenged guided bone regeneration (GBR). Herein, we engineered multifunctional nanofiber membranes by using eletrospun poly(ε-caprolactone) (PCL) and silk fibroin (SF), incorporated with octacalcium phosphate (OCP) and BMSCs-affine peptide (E7) to form the PCL/SF/OCP/E7 (PSOE) nanofiber, wherein the E7 peptide enhances the enrichment of BMSCs, and OCP as osteogenesis promoter. The composite membranes enhance the recruitment and biomineralization processes essential for bone regeneration. Notably, the dual functionality of BMSC recruitment and osteoinduction provides a "recruitment-osteoinduction" strategy that significantly improves bone repair. In vitro analyses confirmed that the PSOE nanofibers have superior hydrophilicity and biocompatibility, and significantly upregulated the expression of osteogenic genes in mesenchymal stem cells, thereby facilitating osteogenic differentiation. In vivo studies using a rat tibial defect model revealed that PSOE nanofibers promoted bone repair within 8 weeks, as validated by micro-CT and histological evaluations. This study highlights the PSOE nanofiber's potential as a promising synthetic periosteum substitute for effective bone regeneration.

Regulation Energy Metabolism of Fiber Scaffolds Orchestrates Osteoimmunomodulation and Angio/Osteogenesis

Bone formation is a highly metabolic process, involving extensive biosynthesis and biomineralization, both of which require substantial amounts of energy. Additionally, the regulation of the immune microenvironment and the development of a neovascularization network are equally crucial in bone formation. Inspired by the high energy demands of the bone formation process, a core-shell electrospun fiber scaffold (PFC/PCK) capable of sustainably releasing a metabolic regulator (αKG) and biomineralizing ions (CaP) is developed. In vitro experiments show that the PFC/PCK fiber scaffolds can induce hyperpolarization of mitochondrial membrane potential in bone marrow mesenchymal stem cells (BMSCs), increase energy supply, effectively regulate immune microenvironment, and remarkably promote expression of angiogenesis and osteogenesis markers. In vivo evaluation further confirms the outstanding immunoregulatory and osteo/angio-genesis capabilities of the fabricated fiber scaffolds. Importantly, transcriptome analysis identifies that the fiber scaffolds upregulate genes and signaling pathways associated with M2 macrophage activation, energy generation, angiogenesis, and osteogenesis. Additionally, metabolomics analysis confirms that the fiber scaffolds enhance bone formation by promoting the expression of osteogenic metabolites. The versatile fiber scaffolds developed in current study demonstrates a new strategy for functional bone regeneration.

Evolving biomaterials design from trial and error to intelligent innovation

The design and exploration of biomaterials plays a pivotal role in many fields, including medical and engineering. The prevailing approach to biomaterials discovery relies on orthogonal experiments, with repeated attempts to optimize experimental conditions. This method has proven invaluable in gaining experience, but it is also inefficient and challenging to predict the behavior of complex systems. The advent of high-throughput screening (HTS) techniques has led to a notable enhancement in the efficiency of biomaterials development, enabling researchers to assess a vast array of material combinations within a relatively short timeframe. Nevertheless, the emergence of artificial intelligence (AI) has been the catalyst for a new era in biomaterials design. AI has markedly accelerated the development of new materials by enabling the prediction of material properties through machine learning (ML) and deep learning models, as well as optimizing the design pipeline. This review will present a systematic overview of the development of biomaterials design technology. It will also explore the integration of AI with HTS technology and envisage the potential of AI-driven materials design in biomaterials for the future. STATEMENT OF SIGNIFICANCE: The design and synthesis of biomaterials have undergone substantial shifts, reflecting evolving research paradigms. High-throughput screening has emerged as a broad and efficient alternative to traditional free-form combination methods in biomaterial design. The advent of artificial intelligence (AI) enables personalized biomaterial design and, as a transformative tool in biomaterial development, is poised to redefine the field and offer long-term solutions for its advancement. Building on these advancements, this review systematically summarizes the evolution of biomaterial design, offering insights into the future trajectory of the field.

3D-Printed Scaffolds for Cranial Bone Regeneration: A Systematic Review of Design, Materials, and Computational Optimization

Cranial bone defects from trauma, congenital conditions, or surgery are challenging to treat due to the skull's limited regeneration. Traditional methods like autografts and allografts have drawbacks, including donor site issues and poor integration. 3D-printed scaffolds provide a patient-specific alternative, improving bone regeneration and integration. This review evaluates advancements in 3D-printed scaffolds for cranial bone regeneration, focusing on fabrication techniques, material innovations, and structural optimization while assessing their preclinical and clinical potential. A systematic literature search (2014-2024) was conducted using PubMed and other databases. Studies addressing scaffold properties such as porosity, pore interconnectivity, and mechanical stability were included, while non-cranial scaffold studies were excluded. Advances in 3D printing have enabled patient-specific scaffolds with optimized architecture to enhance bone regeneration, mechanical support, and nutrient transport. Bioceramics, polymers, and composites mimic native bone properties, while bioactive coatings further improve osteogenesis. However, limited clinical translation and insufficient customization remain challenges. Further preclinical and clinical trials are crucial to overcoming barriers in mechanical optimization and patient-specific scaffold fabrication, bridging the gap between research and clinical applications.

NIR-programmable 3D-printed shape-memory scaffold with dual-thermal responsiveness for precision bone regeneration and bone tumor management

Clinically, intraoperative treatment of bone tumors presents several challenges, including the effective inactivation of tumors and filling of irregular bone defects after tumor removal. In this study, intelligent thermosensitive composite materials with shape-memory properties were constructed using polylactic acid (PLA) and polycaprolactone (PCL), which have excellent biocompatibility and degradability. Additionally, beta-tricalcium phosphate (β-TCP), with its osteogenic properties, and magnesium (Mg) powder, with its photothermal and bone-promoting abilities, were incorporated to improve the osteogenic potential of the composite and enable the material to respond intelligently to near-infrared (NIR) light. Utilizing 3D printing technology, the composite material was prepared into an NIR-responsive shape-memory bone-filling implant that deforms when the scaffold temperature increases to 48 ℃ under NIR laser irradiation. Moreover, at a lower temperature of 42 ℃, mild photothermal therapy promotes macrophage polarization toward the M2 phenotype. This process regulates the secretion of interleukin (IL)-4, IL-10, tumor necrosis factor-α, IL-6, and bone morphogenetic protein (BMP)-2, reducing local inflammation, enhancing the release of pro-healing factors, and improving osteogenesis. Overall, this innovative scaffold is a promising and efficient treatment for filling irregular bone defects after bone tumor surgery.

Hydrogels with programmed spatiotemporal mechanical cues for stem cell-assisted bone regeneration

Hydrogels are extensively utilized in stem cell-based tissue regeneration, providing a supportive environment that facilitates cell survival, differentiation, and integration with surrounding tissues. However, designing hydrogels for regenerating hard tissues like bone presents significant challenges. Here, we introduce macroporous hydrogels with spatiotemporally programmed mechanical properties for stem cell-driven bone regeneration. Using liquid-liquid phase separation and interfacial supramolecular self-assembly of protein fibres, the macroporous structure of hydrogels provide ample space to prevent contact inhibition during proliferation. The rigid protein fibre-coated pore shell provides sustained mechanical cues for guiding osteodifferentiation and protecting against mechanical loads. Temporally, the hydrogel exhibits tunable degradation rates that can synchronize with new tissue deposition to some extent. By integrating localized mechanical heterogeneity, macroporous structures, surface chemistry, and regenerative degradability, we demonstrate the efficacy of these stem cell-encapsulated hydrogels in rabbit and porcine models. This marks a substantial advancement in tailoring the mechanical properties of hydrogels for stem cell-assisted tissue regeneration.

Biopolymer-based bone scaffold for controlled Pt (IV) prodrug release and synergistic photothermal-chemotherapy and immunotherapy in osteosarcoma

Achieving bone defect repair while preventing tumor recurrence after osteosarcoma surgery has consistently posed a clinical challenge. Local treatment with 3D-printed scaffolds loaded with chemotherapeutic drugs can exert certain effects in tumor inhibition and bone regeneration. However, the non-specific activation of chemotherapeutic drugs leads to high local toxic side effects and the formation of an immunosuppressive tumor microenvironment, thereby limiting their clinical application and therapeutic efficacy. To address this, we designed a Pt (IV) prodrug with low toxicity and minimal side effects, which releases Pt (II) in response to glutathione. This prodrug was grafted onto polydopamine (PDA) through an amidation reaction, resulting in a composite nanomaterial (PDA@Pt) that possesses both photothermal synergistic chemotherapy and immuno-oncological properties. Subsequently, we innovatively employed selective laser sintering technology to incorporate PDA@Pt into a poly (L-lactic acid)/bioactive glass matrix, successfully constructing a composite scaffold with dual anti-tumor and bone repair capabilities. The study revealed that the composite scaffold significantly inhibited the growth of osteosarcoma cells and activated the cGAS-STING pathway by inducing DNA damage, ultimately converting the 'cold tumor' into a 'hot tumor.' Additionally, the composite scaffold could induce osteogenic differentiation of bone marrow mesenchymal stem cells and exhibited excellent bone repair capabilities in vivo.

Biomimetic Intrafibrillar Mineralization of Hierarchically Structured Amyloid-Like Fibrils

Intrafibrillar mineralization is essential not only as a fundamental process in forming biological hard tissues but also as a foundation for developing advanced composite fibril-based materials for innovative applications. Traditionally, only natural collagen fibrils have been shown to enable intrafibrillar mineralization, presenting a challenge in designing ordered hierarchical fibrils from common protein aggregation that exhibit similar high intrafibrillar mineralization activity. In this study, a mechanically directed two-step transformation method is developed that converts phase-transitioned protein nanofilms into crystalline, hierarchical amyloid-like fibrils with multilayer structures, which effectively control the growth and lateral organization of hydroxyapatite within adaptive gaps. The resulting mineralized HSAF achieves a hardness of 0.616 ± 0.007 GPa and a modulus of 19.06 ± 3.54 GPa-properties closely resembling native hard tissues-and exhibits exceptionally high bioactivity in promoting both native bone tissue growth and further intrafibrillar mineralization, achieving 76.9% repair in a mice cranial defect model after 8 weeks and outperforming other regenerative materials. This remarkable performance, stemming from the unique structure and composition of the fibers, positions HSAF as a promising candidate for biomedical and engineering applications. These findings advance the understanding of biomineralization mechanisms and establish a foundation for developing high-bioactivity materials for hard tissue regeneration.

Natural collagen scaffold with intrinsic piezoelectricity for enhanced bone regeneration

Materials-mediated piezoelectric signals have been widely applied in bone regeneration. Collagen is the most abundant protein in the human body, and native collagen with complete tertiary structure shows efficient piezoelectricity. However, the traditional collagen scaffolds are lack of piezoelectricity due to the destruction of the complete tertiary structure. Here, natural collagen scaffolds with the complete tertiary structure were prepared. Alkali treatment made the collagen scaffold lose piezoelectricity. The collagen with/without piezoelectricity (PiezoCol/NCol) scaffolds both possessed good cytocompatibility and promoted cell adhesion. After being implanted subcutaneously, the NCol scaffold almost did not affect bone regeneration with/without ultrasound treatment. However, under ultrasound treatment, the PiezoCol scaffold promoted the new bone formation with enhanced osteogenic differentiation, angiogenesis, and neural differentiation, meaning that piezoelectricity endows collagen with satisfactory promotion for bone regeneration. Meanwhile, the PiezoCol scaffold can also accelerate bone formation without ultrasound treatment, which should be attributed to the daily exercise-caused weak piezoelectric stimulation. Further, the proteomic analysis revealed the mechanism by which the PiezoCol scaffold promoted bone tissue formation via mainly upregulating the PI3K-Akt signaling pathway. This study provides a new strategy to enhance the osteoinduction of collagen scaffold for bone regeneration by maintaining intrinsic piezoelectricity.

3D printed shape-memory piezoelectric scaffolds with in-situ self-power properties for bone defect repair

Electrical stimulation has been shown to regulate early immunity and late-stage osteogenesis in bone repair. However, achieving in-situ electrical stimulation in the form of self-power in vivo during the initial postoperative stages when the patients have limited mobility remains challenging. In this study, we developed a 3D-printed in-situ self-powered composite scaffold composed of shape memory polyurethane elastomers (SMPU) and polyvinylidene fluoride (PVDF) piezoelectric nanofibers. The composite scaffold demonstrates excellent shape memory performance, allowing for minimally invasive implantation. During the shape memory process, the composite scaffold can provide mechanical force stimulation to PVDF nanofibers to generate charge. Therefore, self-power was achieved through the integration of the shape memory process and piezoelectric effects, and it can be used for in-situ electrical stimulation during the initial postoperative period. Additionally, the composite scaffold can output voltage under continuous mechanical force stimulation, indicating that the patients can apply sustained mechanical force stimulation to the composite scaffold to output voltage through rehabilitation exercises when the patients regain mobility. Both cell experiments and animal studies confirmed that this composite scaffold can effectively regulate the immune microenvironment and enhance osteogenesis. This study successfully achieves in-situ electrical stimulation in the form of self-power by integrating the shape memory process and piezoelectric effects, which is expected to be an effective repair strategy for bone tissue engineering.

3D printed scaffolds with multistage osteogenic activity for bone defect repair

The bone defect repair is a complex process including immune regulation, stem cell osteogenic differentiation and extracellular matrix mineralization. Current bone tissue engineering approaches often fail to adapt throughout the above osteogenic process, resulting in suboptimal repair outcomes. To address this problem, a 3D-printed scaffold with multistage osteogenic activity based on shape-memory elastomer and electroactive material is developed. The scaffold exhibits excellent shape memory performance and can trigger shape recovery by physiological temperature. The physiological temperature-triggered shape-memory behavior makes the scaffold promising for minimally invasive implantation. After electric field polarization, the scaffold's surface carries the negative charge, which can activate the PI3K/Akt signaling pathway to promote the polarization of macrophages to M2 phenotype and activate the FAK/ERK signaling pathway to promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), indicating that the scaffold can effectively participate in immune microenvironment regulation and stem cell osteogenic differentiation. Additionally, the negative charge on the scaffold's surface can attract calcium and phosphate ions, forming a mineralized matrix and promoting late-stage extracellular matrix mineralization by continuously supplying mineralizing ions such as calcium and phosphate. Overall, this study introduces a 3D-printed scaffold with multistage osteogenic activity, offering a promising strategy for bone defect repair.

Polydopamine Nanocomposite Hydrogel for Drug Slow-Release in Bone Defect Repair: A Review of Research Advances

In recent years, hydrogels have emerged as promising candidates for bone defect repair due to their excellent biocompatibility, high porosity, and water-retentive properties. However, conventional hydrogels face significant challenges in clinical translation, including brittleness, low mechanical strength, and poorly controlled drug degradation rates. To address these limitations, as a multifunctional polymer, polydopamine (PDA) has shown great potential in both bone regeneration and drug delivery systems. Its robust adhesive properties, biocompatibility, and responsiveness to photothermal stimulation make it an ideal candidate for enhancing hydrogel performance. Integrating PDA into conventional hydrogels not only improves their mechanical properties but also creates an environment conducive to cell adhesion, proliferation, and differentiation, thereby promoting bone defect repair. Moreover, PDA facilitates controlled drug release, offering a promising approach to optimizing treatment outcomes. This paper first explores the mechanisms through which PDA promotes bone regeneration, laying the foundation for its clinical translation. Additionally, it discusses the application of PDA-based nanocomposite hydrogels as advanced drug delivery systems for bone defect repair, providing valuable insights for both research and clinical translation.

Engineering next-generation oxygen-generating scaffolds to enhance bone regeneration

In bone, an adequate oxygen (O2) supply is crucial during development, homeostasis, and healing. Oxygen-generating scaffolds (OGS) have demonstrated significant potential to enhance bone regeneration. However, the complexity of O2 delivery and signaling in vivo makes it challenging to tailor the design of OGS to precisely meet this biological requirement. We review recent advances in OGS and analyze persisting engineering and translational hurdles. We also discuss the potential of computational and machine learning (ML) models to facilitate the integration of novel imaging data with biological readouts and advanced biomanufacturing technologies. By elucidating how to tackle current challenges using cutting-edge technologies, we provide insights for transitioning from traditional to next-generation OGS to improve bone regeneration in patients.

Osteomimix: A Multidimensional Biomimetic Cascade Strategy for Bone Defect Repair

Despite advancements in biomimetic mineralization techniques, the repair of large-scale bone defects remains a significant challenge. Inspired by the bone formation process, a multidimensional biomimetic cascade strategy is developed by replicating the biomineralization cascade, emulating the hierarchical structure of bone, and biomimicking its biological functions for efficient bone regeneration. This strategy involves the photocrosslinking of sodium methacrylate carboxymethyl cellulose-stabilized amorphous magnesium-calcium phosphate with methacrylate-modified type I collagen to create a self-mineralizing hydrogel. The hydrogel is then integrated with either naturally derived or synthetic oriented bulk scaffolds. The resulting composite, named Osteomimix, provides excellent mechanical support and can be customized for irregular bone defects using CAD/CAM technology. Through in vitro and in vivo studies, this work finds that Osteomimix exhibits spontaneous in situ biomimetic mineralization in a cell-free environment, while modulating immune responses and promoting vascularized bone formation in a cell-dependent manner. Built on bone-specific insights, this strategy achieves biomimicry across temporal, spatial, and functional dimensions, facilitating the seamless integration of artificial constructs with the natural tissue repair dynamics.

Bifunctional mesoporous HMUiO-66-NH2 nanoparticles for bone remodeling and ROS scavenging in periodontitis therapy

Periodontal bone defects represent an irreversible consequence of periodontitis associated with reactive oxygen species (ROS). However, indiscriminate removal of ROS proves to be counterproductive for tissue repair and insufficient for addressing existing bone defects. In the treatment of periodontitis, it is crucial to rationally alleviate local ROS while simultaneously promoting bone regeneration. In this study, Zr-based large-pore hierarchical mesoporous metal-organic framework (MOF) nanoparticles (NPs) HMUiO-66-NH2 were successfully proposed as bifunctional nanomaterials for bone regeneration and ROS scavenging in periodontitis therapy. HMUiO-66-NH2 NPs demonstrated outstanding biocompatibility both in vitro and in vivo. Significantly, these NPs enhanced the osteogenic differentiation of bone mesenchymal stem cells (BMSCs) under normal and high ROS conditions, upregulating osteogenic gene expression and mitigating oxidative stress. Furthermore, in vivo imaging revealed a gradual degradation of HMUiO-66-NH2 NPs in periodontal tissues. Local injection of HMUiO-66-NH2 effectively reduced bone defects and ROS levels in periodontitis-induced C57BL/6 mice. RNA sequencing highlighted that differentially expressed genes (DEGs) are predominantly involved in bone tissue development, with notable upregulation in Wnt and TGF-β signaling pathways. In conclusion, HMUiO-66-NH2 exhibits dual functionality in alleviating oxidative stress and promoting bone repair, positioning it as an effective strategy against bone resorption in oxidative stress-related periodontitis.

A Functionalized 3D-Printed Ti6Al4V "Cell Climbing Frame" Inspired by Marine Sponges to Recruit and Rejuvenate Autologous BMSCs in Osteoporotic Bone Repair

Osteoporosis, characterized by low bone mass and high fracture risk, challenges orthopedic implant design. Conventional 3D-printed Ti6Al4V scaffolds are mechanically robust but suffer from poor bone regeneration in osteoporotic patients due to stress shielding and cellular senescence. In this study, a functionalized 3D-printed Ti6Al4V "Cell Climbing Frame" is developed, aiming to adapt to the mechanical microenvironment of osteoporosis, effectively recruit and support the adhesion and growth of autologous bone marrow mesenchymal stem cells (BMSCs), while rejuvenating senescent cells for improved bone regeneration. Inspired by marine sponges, the processing accuracy limitations of selective laser melting (SLM) technology is broke through innovatively constructing a hierarchical porous structure with macropores and micropores nested within each other. Results demonstrate that the unique hierarchical porous scaffold reduces the elastic modulus, facilitates blood penetration, and enhances cell adhesion and growth. Further surface functionalization with E7 peptides and exosomes promotes the attraction and rejuvenation of BMSCs and boosts migration, proliferation, and osteogenic differentiation in vitro. In vivo, the functionalized "Cell Climbing Frame" accelerates bone repair in osteoporotic rats, while delaying surrounding bone loss, enabling robust multi-stage osseointegration. This innovation advances 3D-printed regenerative implants for osteoporotic bone repair.

Multienzyme-Activity Sulfur Quantum Dot Nanozyme-Mediated Cascade Reactions in Whole-Stage Symptomatic Therapy of Infected Bone Defects

Integrating the therapeutic efficacy of early bacterial clearance, midstage inflammatory remission, and late-stage effective tissue healing is considered a pivotal challenge in symptomatic treatment of infected bone defects (IBDs). Herein, a microenvironment-adaptive nanoplatform based on a sulfur quantum dot (SQD) nanozyme was proposed for whole-stage symptomatic therapy of IBDs by mediating the sequence of enzyme cascade reactions. The SQD nanozyme prepared by a size-engineering modification strategy exhibits enhanced multienzyme activity compared to conventional micrometer- and nanometer-sized sulfur particles. In the early stages of bacterial infection, the SQD nanozyme self-activates superoxide dismutase-peroxidase activity, resulting in the production of reactive oxygen species (ROS) that effectively eliminate bacteria. After disinfection, the SQD nanozyme self-switched to superoxide dismutase-catalase mimetic behavior and eliminated excess ROS, efficiently promoting macrophage polarization to an anti-inflammatory phenotype in the midinflammatory microenvironment. Importantly, SQD nanozyme-mediated M2 macrophage polarization significantly improved the damaged bone immune microenvironment, accelerating bone repair at late-stage tissue healing. Therefore, this strategy offers a promising and viable approach for the treatment of infectious tissue healing by developing multienzyme-activity nanozymes that respond intelligently to the microenvironment at different stages, effectively fighting bacteria, reducing inflammation, and promoting tissue regeneration for whole-stage symptomatic therapy.

Enhanced hemostatic efficacy of cryogel with copper ion-loaded mesoporous bioactive glasses for acute and persistent bleeding

Uncontrolled acute and persistent bleeding, as well as with infection, is a great challenge because of the high mortality during treating the patients with injuries, complex surgery or bone marrow failure. Here, we develop an external form of natural components which is based on phosphorylated methacrylated gelatin (GelMA, G) cryogel (GP) loaded with tannic acid (TA)-mixed copper ion (Cu2+) mesoporous bioactive glasses (MBG), named after GP@MBG-Cu-TA cryogel, to address the goals of reduce persistent bleeding and enhance antibacterial activity. Structurally, GP@MBG-Cu-TA cryogel is based on GP, MBG loaded with TA and Cu2+ adheres to GP via hydrogen bonding. In vitro, GP@MBG-Cu-TA cryogel displays a good biocompatibility, hemostatic and antimicrobial capability. In vivo studies, GP@MBG-Cu-TA cryogel can enhance the hemostatic effect in the liver injury in SD rats for the acute bleeding, as well as in the aplastic anemia and hemophilia A mice with tail amputation for the persistent bleeding. In addition, GP@MBG-Cu-TA cryogel accelerates the skin wound repair in the mice with the bacterial contamination at the injury site. In sum, GP@MBG-Cu-TA cryogel is not only endowed with dual function of hemostatic and antimicrobial capability, but also can stop bleeding of the objects with either normal or abnormal coagulation function. Thus, GP@MBG-Cu-TA cryogel provides a promising candidate dressing for managing bleeding and bacterial complications in clinic.

A review of self-healing hydrogels for bone repair and regeneration: Materials, mechanisms, and applications

Bone defects, which arise from various factors such as trauma, tumor resection, and infection, present a significant clinical challenge. There is an urgent need to develop new biomaterials capable of repairing a wide array of damage and defects in bone tissue. Self-healing hydrogels, a groundbreaking advancement in the field of biomaterials, displaying remarkable ability to regenerate damaged connections after partial severing, thus offering a promising solution for bone defect repair. This review first presents a comprehensive overview of the progress made in the design and preparation of these hydrogels, focusing on the self-healing mechanisms based on physical non-covalent interactions and dynamic chemical covalent bonds. Subsequently, the applications of self-healing hydrogels including natural polymers, synthetic polymers, and nano-hybrid materials, are discussed in detail, emphasizing their mechanisms in promoting bone tissue regeneration. Finally, the review addresses current challenges as well as future prospects for the use of hydrogels in bone repair and regeneration, identifying osteogenic properties, mechanical performance, and long-term biocompatibility as key areas for further improvement. In summary, this paper provides an in-depth analysis of recent advances in self-healing hydrogels for bone repair and regeneration, underscoring their immense potential for clinical application.

A microenvironment responsive polyetheretherketone implant with antibacterial and osteoimmunomodulatory properties facilitates osseointegration

Failure of intraosseous prostheses is primarily attributed to implant loosening and infections. Current primary therapeutic modalities, such as antibiotics and local debridement, not only face challenges in thoroughly eliminating obstinate adhered bacteria but also encounter difficulties in ameliorating undue inflammatory reactions and regenerating impaired peri-implant bone tissues. Polyetheretherketone (PEEK) has excellent mechanical and physicochemical characteristics and has been used extensively as a medical biomaterial. However, the limited bactericidal and osseointegrative activities of bioinert PEEK restrict its clinical application. Herein, a microenvironment responsive coating with immobilised immunomodulatory magnesium ions (Mg2+) and disinfectant cerium oxide nanoparticles (CNPs) is designed via ion coordination mediated by polydopamine (PDA) and electrospinning based on collagen structure-bionic silk fibroin (SF). By utilising the pH responsiveness of SF, CNPs exhibit potent antibacterial effects in an acidic environment (pH 5.0) caused by local bacterial infection. Due to the chelation interaction with PDA and the constraint of SF, Mg2+ is slowly released, ameliorating the local immune microenvironment and boosting osteogenesis by upregulating M2 phenotype macrophages. Bioinformatics analysis indicates that the inflammation is suppressed via the NF-κB signaling pathway. Overall, this SF-based coating maximizes the synergistic effect of CNPs and Mg2+, offering enhanced antibacterial and osteoimmunomodulatory bioactivity for successful implantation.

Chitosan/Sodium Tripolyphosphate/Sodium Alginate/miRNA-34c-5p Antagomir Scaffolds Promote the Functionality of Rabbit Cranial Parietal Repair

Purpose

MicroRNA-34c-5p (miR-34c-5p) plays a pivotal role in bone remodeling, yet its therapeutic potential is hindered by challenges such as instability, limited cellular internalization, and immune responses. This study was aimed at developing innovative scaffolds capable of efficiently delivering microRNAs (miRNAs), specifically miR-34c-5p.

Methods

Chitosan (CS)/sodium tripolyphosphate (STPP)/sodium alginate (SA) scaffolds, referred to as CTS scaffolds, were synthesized at a specific ratio and characterized using dynamic light scattering and scanning electron microscopy (SEM). Cytotoxicity assessments were conducted through cell activity staining. The loading capacity and releasing performance of miRNAs were quantified using spectrophotometry. Subsequently, the in vivo efficacy of miR-34c-5p Agomir/Antagomir in regulating bone repair was evaluated in the rabbit cranial bone defect model, with micro-CT scanning and histological analysis conducted at 4, 8, and 12 weeks.

Results

CTS scaffolds with a composition ratio of 1:0.2:0.1 were successfully synthesized, exhibiting a mean particle size of 360.1 nm. SEM revealed scaffolds had the porous spongy structure. Cell activity staining confirmed the excellent biocompatibility of the CTS scaffolds. Spectrophotometry demonstrated miR-34c-5p Antagomir were continually released, reaching 91.41% within 30 days. Differential new bone formation was observed between the miR-34c-5p Agomir and Antagomir groups. Micro-CT imaging and histological staining revealed varying degrees of bone regeneration, with notable improvements in the miR-34c-5p Antagomir group.

Conclusion

CTS scaffolds with a composition ratio of 1:0.2:0.1 demonstrate favorable biocompatibility and enable efficient loading and sustained release of miR-34c-5p Antagomir. The study suggests potential applications of miR-34c-5p Antagomir in promoting bone repair and highlights the promise of innovative scaffolds for therapeutic miRNAs administration in bone regeneration.

Photoactivated Hydrogel Therapeutic System with MXene-Based Nanoarchitectonics Potentiates Endogenous Bone Repair Through Reshaping the Osteo-Vascularization Network

The repair and reconstruction of large-scale bone defects face enormous challenges because of the failure to reconstruct the osteo-vascularization network. Herein, a near-infrared (NIR) light-responsive hydrogel system is reported to achieve programmed tissue repair and regeneration through the synergetic effects of on-demand drug delivery and mild heat stimulation. The spatiotemporal hydrogel system (HG/MPa) composed of polydopamine-coated Ti3C2Tx MXene (MP) nanosheets decorated with acidic fibroblast growth factor (aFGF, a potent angiogenic drug) and hydroxypropyl chitosan/gelatin (HG) hydrogel is developed to orchestrate the reconstruction of the osteo-vascularization network and boost bone regeneration. Upon exposure to NIR light irradiation, the engineered HG/MPa hydrogel can achieve the initial complete release of aFGF to induce rapid angiogenesis and provide sufficient blood supply, maximizing its biofunction in the defect area. This integrated hydrogel system demonstrated good therapeutic efficacy in promoting cell adhesion, proliferation, migration, angiogenesis, and osteogenic differentiation through periodic NIR irradiation. In vivo, animal experiments further revealed that the spatiotemporalized hydrogel platform synergized with mild photothermal treatment significantly accelerated critical-sized bone defect healing by increasing the osteo-vascularization network density, recruiting endogenous stem cells, and facilitating the production of osteogenesis/angiogenesis-related factors. Overall, smart-responsive hydrogel could enhance the reconstruction of the osteo-vascularization network in bone regeneration.

Framework Nucleic Acid-Based Selective Cell Catcher for Endogenous Stem Cell Recruitment

Cell-surface engineering holds great promise in boosting endogenous stem cell attraction for tissue regeneration. However, challenges such as cellular internalization of ligand and the dynamic nature of cell membranes often complicate ligand-receptor interactions. The aim of this study is to harness the innovative potential of programmable tetrahedral framework nucleic acid (tFNA) to enable precise, tunable ligand-receptor interactions, thereby improving stem cell recruitment efficiency. This approach involves experimental screening and theoretical analysis using dissipative particle dynamics. The results demonstrate that altering the flexibility and topology of ligands on tFNA changes their cellular internalization and membrane binding efficiency. Furthermore, optimizing the distribution of the mesenchymal stem cell (MSC)-binding aptamer 19S (Apt19S) on the tFNA enhances the stem cell capture efficiency. Following successful in vitro MSC capture, Apt19S-modified tFNA is chemically linked to a hyaluronic acid hydrogel, forming an efficient "stem cell catcher" system. Subsequent in vivo experiments demonstrate that this system effectively promotes early stem cell recruitment and accelerates bone regeneration in different bone healing scenarios, including cranial and maxillary defects.

Recent Strategies and Advances in Hydrogel-Based Delivery Platforms for Bone Regeneration

Bioactive molecules have shown great promise for effectively regulating various bone formation processes, rendering them attractive therapeutics for bone regeneration. However, the widespread application of bioactive molecules is limited by their low accumulation and short half-lives in vivo. Hydrogels have emerged as ideal carriers to address these challenges, offering the potential to prolong retention times at lesion sites, extend half-lives in vivo and mitigate side effects, avoid burst release, and promote adsorption under physiological conditions. This review systematically summarizes the recent advances in the development of bioactive molecule-loaded hydrogels for bone regeneration, encompassing applications in cranial defect repair, femoral defect repair, periodontal bone regeneration, and bone regeneration with underlying diseases. Additionally, this review discusses the current strategies aimed at improving the release profiles of bioactive molecules through stimuli-responsive delivery, carrier-assisted delivery, and sequential delivery. Finally, this review elucidates the existing challenges and future directions of hydrogel encapsulated bioactive molecules in the field of bone regeneration.

Implantable Self-Powered Systems for Electrical Stimulation Medical Devices

With the integration of bioelectronics and materials science, implantable self-powered systems for electrical stimulation medical devices have emerged as an innovative therapeutic approach, garnering significant attention in medical research. These devices achieve self-powering through integrated energy conversion modules, such as triboelectric nanogenerators (TENGs) and piezoelectric nanogenerators (PENGs), significantly enhancing the portability and long-term efficacy of therapeutic equipment. This review delves into the design strategies and clinical applications of implantable self-powered systems, encompassing the design and optimization of energy harvesting modules, the selection and fabrication of adaptable electrode materials, innovations in systematic design strategies, and the extensive utilization of implantable self-powered systems in biological therapies, including the treatment of neurological disorders, tissue regeneration engineering, drug delivery, and tumor therapy. Through a comprehensive analysis of the latest research progress, technical challenges, and future directions in these areas, this paper aims to provide valuable insights and inspiration for further research and clinical applications of implantable self-powered systems.

Microenvironment-optimized gastrodin-functionalized scaffolds orchestrate asymmetric division of recruited stem cells in endogenous bone regeneration

The regeneration of osteoporotic bone defects remains challenging as the critical stem cell function is impaired by inflammatory microenvironment. Synthetic materials that intrinsically direct osteo-differentiation versus self-renewal of recruited stem cell represent a promising alternative strategy for endogenous bone formation. Therefore, a microenvironmentally optimized polyurethane (PU) /n-HA scaffold to enable sustained delivery of gastrodin is engineered to study its effect on the osteogenic fate of stem cells. It exhibited interconnected porous networks and an elevated sequential gastrodin release pattern to match immune-osteo cascade concurrent with progressive degradation of materials. In a critical-sized femur defect model of osteoporotic rat, 5% gastrodin-PU/n-HA potently promoted neo-bone regeneration by facilitating M2 macrophage polarization and CD146+ host stem cell recruitment to defective site. The implantation time-dependently increased the bone marrow mesenchymal stem cell (BMSC) population, and further culture of BMSCs showed a robust ability of proliferation, migration, and mitochondrial resurgence. Of note, some of cell pairs produced one stemness daughter cell while the other committed to osteogenic lineage in an asymmetric cell division (ACD) manner, and a much more compelling ACD response was triggered when 5% gastrodin-PU/n-HA implanted. Further investigation revealed that one-sided concentrated presentation of aPKC and β-catenin in dividing cells effectively induced asymmetric distribution, which polarized aPKC biased the response of the daughter cells to Wnt signal. The asymmetric cell division in skeletal stem cells (SSCs) was mechanically comparable to BMSCs and also governed by distinct aPKC and β-catenin biases. Concomitantly, delayed bone loss adjacent to the implant partly alleviated development of osteoporosis. In conclusion, our findings provide insight into the regulation of macrophage polarization combined with osteogenic commitment of recruited stem cells in an ACD manner, advancing scaffold design strategy for endogenous bone regeneration.

A novel multifunctional nanocomposite hydrogel orchestrates the macrophage reprogramming-osteogenesis crosstalk to boost bone defect repair

Repairing bone defects is a complex cascade reaction process, as immune system regulation, vascular growth, and osteogenic differentiation are essential. Thus, developing a tissue-engineered biomaterial that caters to the complex healing process of bone regeneration remains a major clinical challenge. In the study, Ca2+-TA-rGO (CTAG)/GelMA hydrogels were synthesized by binding Ca2+ using metal chelation to graphene oxide (GO) nanosheets reduced by tannic acid (TA-rGO) and doping them into gelatin methacrylate (GelMA) hydrogels. TA and rGO exhibited biocompatibility and immunomodulatory properties in this composite, while Ca2+ promoted bone formation and angiogenesis. This novel nanocomposite hydrogel demonstrated good mechanical properties, degradability, and conductivity, and it could achieve slow Ca2+ release during bone regeneration. Both in vitro and in vivo experiments revealed that CTAG/GelMA hydrogel modulated macrophage reprogramming and induced a shift from macrophages to healing-promoting M2 macrophages during the inflammatory phase, promoted vascular neovascularization, and facilitated osteoblast differentiation during bone formation. Moreover, CTAG/GelMA hydrogel could downregulate the NF-κB signaling pathway, offering new insights into regulating macrophage reprogramming-osteogenic crosstalk. Conclusively, this novel multifunctional nanocomposite hydrogel provides a multistage treatment for bone and orchestrates macrophage reprogramming-osteogenic crosstalk to boost bone repair.

Electron-donable heterojunctions with synergetic Ru-Cu pair sites for biocatalytic microenvironment modulations in inflammatory mandible defects

The clinical treatments of maxillofacial bone defects pose significant challenges due to complex microenvironments, including severe inflammation, high levels of reactive oxygen species (ROS), and potential bacterial infection. Herein, we propose the de novo design of an efficient, versatile, and precise electron-donable heterojunction with synergetic Ru-Cu pair sites (Ru-Cu/EDHJ) for superior biocatalytic regeneration of inflammatory mandible defects and pH-controlled antibacterial therapies. Our studies demonstrate that the unique structure of Ru-Cu/EDHJ enhances the electron density of Ru atoms and optimizes the binding strength of oxygen species, thus improving enzyme-like catalytic performance. Strikingly, this biocompatible Ru-Cu/EDHJ can efficiently switch between ROS scavenging in neutral media and ROS generation in acidic media, thus simultaneously exhibiting superior repair functions and bioadaptive antibacterial properties in treating mandible defects in male mice. We believe synthesizing such biocatalytic heterojunctions with exceptional enzyme-like capabilities will offer a promising pathway for engineering ROS biocatalytic materials to treat trauma, tumors, or infection-caused maxillofacial bone defects.

Multifunctional injectable hydrogel system as a mild photothermal-assisted therapeutic platform for programmed regulation of inflammation and osteo-microenvironment for enhanced healing of diabetic bone defects in situ

Background: Factor-free biomaterial scaffolds play an increasingly important role in promoting in situ bone reconstruction and regeneration. However, the complicated and variable pathophysiological microenvironments of the injury sites under diabetic conditions, including the vicious cycle of oxidative stress and inflammatory response, impaired osteo/angiogenesis function and hyperactive osteoclastogenesis, as well as increased susceptibility to bacterial infection, may largely weaken the therapeutic potential of implanted scaffolds, leading to uncontrolled and poor outcomes of bone defect healing. Methods and Results: To tackle the aforementioned challenges, a mild photothermal-assisted multifunctional therapeutic platform (denoted as GAD/MC) that integrates copper-containing two-dimensional Ti3C2Tx MXene nanosheets, gelatin methacrylate, and alginate-graft-dopamine was proposed to achieve efficient and synergistic therapy for diabetic bone defects. Thereinto, copper-decorated MXene (MC) nanosheets were employed as both functional crosslinkers and nanofillers to participate in the construction of an interpenetrating polymer network structure through multiple covalent and noncovalent bonds, which conferred the hydrogel with advantageous traits like enhanced mechanical properties, injectability and moldability, strong bone tissue adhesion and self-healing ability, as well as excellent anti-swelling and near-infrared (NIR) photothermal conversion capabilities. On account of the NIR/pH dual-responsive properties, the resulting hydrogel system was capable of achieving the controlled and stimuli-responsive release of bioactive Cu2+, allowing on-demand delivery at the site of injury. Moreover, with the assistance of mild photothermal effects, this integrated hydrogel system demonstrated remarkable antibacterial and antioxidant properties. It effectively scavenged excessive reactive oxygen species (ROS), inhibited inflammatory responses, and promoted macrophage polarization towards the pro-healing M2 phenotype. Such characteristics were beneficial for recreating an optimized microenvironment that supported the adhesion, proliferation, migration, and differentiation of osteoblasts and endothelial cells, while concurrently inhibiting osteoclast function. In a critical-sized cranial defect model using diabetic rats, the injectable GAD/MC hydrogel system combined with on-demand mild hyperthermia further synergistically accelerated new bone formation and bone healing processes by eliminating intracellular ROS, ameliorating inflammation, orchestrating M2 macrophage polarization, promoting osteo/angiogenesis, and suppressing osteoclastogenesis. Conclusions: Overall, the constructed multifunctional injectable hydrogel system has emerged as a promising therapeutic candidate for addressing complex bone-related challenges by remodeling the disordered immune microenvironment and expediting the bone healing process.

Exploration of bone metabolism status in the distal femur of mice at different growth stages

The mouse femur, particularly the distal femur, is commonly utilized in orthopedic research. Despite its significance, little is known about the key events involved in the postnatal development of the distal femur. Therefore, investigating the development process of the mouse distal femur is of great importance. In this study, distal femurs of CD-1 mice aged 1, 2, 4, 6, and 8 weeks were examined. We found that the width and height of the distal femur continued to increase till the 4th week, followed with stabilization. Notably, the width to height ratio remained relatively consistent with age. Micro computed tomography analysis demonstrated gradual increases in bone volume/tissue volume, trabecular number, and trabecular thickness from 1 to 6 weeks, alongside a gradual decrease in trabecular separation. Histological analysis further indicated the appearance of the secondary ossification center at approximately 2 weeks, with ossification mostly completed by 4 weeks, leading to the formation of a prototype epiphyseal plate. Subsequently, the epiphyseal plate gradually narrowed at 6 and 8 weeks. Moreover, the thickness and maturity of the bone cortex surrounding the epiphyseal plate increased over time, reaching peak cortical bone density at 8 weeks. In conclusion, to enhance model stability and operational ease, we recommend constructing conventional mouse models of the distal femur between 4 and 8 weeks old.

Hierarchical Integration of Curcumin-Loaded CaCO3 Nanoparticles and Black Phosphorus Nanosheets in Core/Shell Nanofiber for Cranial Defect Repair

Reconstruction and healing of large craniofacial bone defects are major clinical challenges due to high risk of chronic inflammation and reduced cell mineralization levels. Herein, a core-shell nanofiber-based implant with significant pro-osteogenesis capability for treating skull defects is reported, which is hierarchically integrated with curcumin-loaded calcium carbonate nanoparticles (CaCO3@Cur NPs) in the outer layers and black phosphorus nanosheets (BPNSs) in the core compartments. The radical alignment of the integrated nanocomponents allows the sequential in situ release of the therapeutic agents in a controlled manner after implantation. Curcumin can repolarize M1 macrophages into M2 phenotypes for anti-inflammation purposes. Meanwhile, the released calcium and phosphate ions can promote the biomineralization of hydroxyapatite at the defect site and facilitate bone regeneration. Evaluations on cranial defect-bearing rat models demonstrated that the electrospun fibers in the present study substantially promoted restoration of the damaged skulls and inhibited inflammation in the wound bed. This strategy provides a new idea for the treatment of skull defects in the clinic.

Graphene Oxide Quantum Dots-Preactivated Dental Pulp Stem Cells/GelMA Facilitates Mitophagy-Regulated Bone Regeneration

Background

In bone tissue engineering (BTE), cell-laden scaffolds offer a promising strategy for repairing bone defects, particularly when host cell regeneration is insufficient due to age or disease. Exogenous stem cell-based BTE requires bioactive factors to activate these cells. Graphene oxide quantum dots (GOQDs), zero-dimensional derivatives of graphene oxide, have emerged as potential osteogenic nanomedicines. However, constructing biological scaffolds with GOQDs and elucidating their biological mechanisms remain critical challenges.

Methods

We utilized GOQDs with a particle size of 10 nm, characterized by a surface rich in C-O-H and C-O-C functional groups. We developed a gelatin methacryloyl (GelMA) hydrogel incorporated with GOQDs-treated dental pulp stem cells (DPSCs). These constructs were transplanted into rat calvarial bone defects to estimate the effectiveness of GOQDs-induced DPSCs in repairing bone defects while also investigating the molecular mechanism underlying GOQDs-induced osteogenesis in DPSCs.

Results

GOQDs at 5 μg/mL significantly enhanced the osteogenic differentiation of DPSCs without toxicity. The GOQDs-induced DPSCs showed active osteogenic potential in three-dimensional cell culture system. In vivo, transplantation of GOQDs-preactivated DPSCs/GelMA composite effectively facilitated calvarial bone regeneration. Mechanistically, GOQDs stimulated mitophagy flux through the phosphatase-and-tensin homolog-induced putative kinase 1 (PINK1)/Parkin E3 ubiquitin ligase (PRKN) pathway. Notably, inhibiting mitophagy with cyclosporin A prevented the osteogenic activity of GOQDs.

Conclusion

This research presents a well-designed bionic GOQDs/DPSCs/GelMA composite scaffold and demonstrated its ability to promote bone regeneration by enhancing mitophagy. These findings highlight the significant potential of this composite for application in BTE and underscore the crucial role of mitophagy in promoting the osteogenic differentiation of GOQDs-induced stem cells.

Engineering Injectable Coassembled Hydrogel by Photothermal Driven Chitosan-Stabilized MoS2 Nanosheets for Infected Wound Healing

The application of enzyme-like molybdenum disulfide (MoS2) in tissue repair was confronted with stable dispersion, solubilization, and biotoxicity. Here, the injectable self-healing hydrogel was successfully designed using a step-by-step coassembly of chitosan and MoS2. Polyphenolic chitosan as a "structural stabilizer" of MoS2 nanosheets reconstructed well-dispersed MoS2@CSH nanosheets, which improved the biocompatibility of traditional MoS2, and strengthened its photothermal conversion and enzyme-like activities, guaranteeing highly efficient radical scavenging and antimicrobial properties. Furthermore, the polyphenol chitosan was employed again as a "molecular cross-linking agent" to form the injectable NIR-responsive MoS2@CSH hydrogel by accelerating hydrogen-bond interaction among chitosan and the multicross-linking reaction among polyphenols. The rapid self-healing ability was conducive to wound closure and dynamic adaptability. An experimental study on infected wound healing demonstrated that MoS2@CSH hydrogel could substantially eradicate bacteria and accelerate the angiogenesis of infected wounds. The photothermal-driven coassembly of MoS2 and polycation provided an alternative strategy for infected wound healing.

Fabricating oxygen self-supplying 3D printed bioactive hydrogel scaffold for augmented vascularized bone regeneration

Limited cells and factors, inadequate mechanical properties, and necrosis of defects center have hindered the wide clinical application of bone-tissue engineering scaffolds. Herein, we construct a self-oxygenated 3D printed bioactive hydrogel scaffold by integrating oxygen-generating nanoparticles and hybrid double network hydrogel structure. The hydrogel scaffold possesses the characteristics of extracellular matrix; Meanwhile, the fabricated hybrid double network structure by polyacrylamide and CaCl2-crosslinked sodium carboxymethylcellulose endows the hydrogel favorable compressive strength and 3D printability. Furthermore, the O2 generated by CaO2 nanoparticles encapsulated in ZIF-8 releases steadily and sustainably because of the well-developed microporous structure of ZIF-8, which can significantly promote cell viability and proliferation in vitro, as well as angiogenesis and osteogenic differentiation with the assistance of Zn2+. More significantly, the synergy of O2 and 3D printed pore structure can prevent necrosis of defects center and facilitate cell infiltration by providing cells the nutrients and space they need, which can further induce vascular network ingrowth and accelerate bone regeneration in all areas of the defect in vivo. Overall, this work provides a new avenue for preparing cell/factor-free bone-tissue engineered scaffolds that possess great potential for tissue regeneration and clinical alternative.

Multiscale engineered artificial compact bone via bidirectional freeze-driven lamellated organization of mineralized collagen microfibrils

Bone, renowned for its elegant hierarchical structure and unique mechanical properties, serves as a constant source of inspiration for the development of synthetic materials. However, achieving accurate replication of bone features in artificial materials with remarkable structural and mechanical similarity remains a significant challenge. In this study, we employed a cascade of continuous fabrication processes, including biomimetic mineralization of collagen, bidirectional freeze-casting, and pressure-driven fusion, to successfully fabricate a macroscopic bulk material known as artificial compact bone (ACB). The ACB material closely replicates the composition, hierarchical structures, and mechanical properties of natural bone. It demonstrates a lamellated alignment of mineralized collagen (MC) microfibrils, similar to those found in natural bone. Moreover, the ACB exhibits a similar high mineral content (70.9 %) and density (2.2 g/cm3) as natural cortical bone, leading to exceptional mechanical properties such as high stiffness, hardness, and flexural strength that are comparable to those of natural bone. Importantly, the ACB also demonstrates excellent mechanical properties in wet, outstanding biocompatibility, and osteogenic properties in vivo, rendering it suitable for a broad spectrum of biomedical applications, including orthopedic, stomatological, and craniofacial surgeries.

Multifunctional vitamin D-incorporated PLGA scaffold with BMP/VEGF-overexpressed tonsil-derived MSC via CRISPR/Cas9 for bone tissue regeneration

Guiding endogenous regeneration of bone defects using biomaterials and regenerative medicine is considered an optimal strategy. One of the effective therapeutic approaches involves using transgene-expressed stem cells to treat tissue destruction and replace damaged parts. Among the various gene editing techniques for cells, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) is considered as a promising method owing to the increasing therapeutic potential of cells by targeting specific sites. Herein, a vitamin D-incorporated poly(lactic-co-glycolic acid) (PLGA) scaffold with bone morphogenetic protein 2 (BMP2)/vascular endothelial growth factor (VEGF)-overexpressed tonsil-derived MSCs (ToMSCs) via CRISPR/Cas9 was introduced for bone tissue regeneration. The optimized seeding ratio of engineered ToMSCs on the scaffold demonstrated favorable immunomodulatory function, angiogenesis, and osteogenic activity in vitro. The multifunctional scaffold could potentially support stem cell in vivo and induce the transition from M1 to M2 macrophage with magnesium hydroxide and vitamin D. This study highlights the improved synergistic effect of a vitamin D-incorporated PLGA scaffold and a gene-edited ToMSCs for bone tissue engineering and regenerative medicine.

From the microspheres to scaffolds: advances in polymer microsphere scaffolds for bone regeneration applications

The treatment and repair of bone tissue damage and loss due to infection, tumours, and trauma are major challenges in clinical practice. Artificial bone scaffolds offer a safer, simpler, and more feasible alternative to bone transplantation, serving to fill bone defects and promote bone tissue regeneration. Ideally, these scaffolds should possess osteoconductive, osteoinductive, and osseointegrative properties. However, the current first-generation implants, represented by titanium alloys, have shown poor bone-implant integration performance and cannot meet the requirements for bone tissue repair. This has led to increased research on second and third generation artificial bone scaffolds, which focus on loading bioactive molecules and cells. Polymer microspheres, known for their high specific surface areas at the micro- and nanoscale, exhibit excellent cell and drug delivery behaviours. Additionally, with their unique rigid structure, microsphere scaffolds can be constructed using methods such as thermal sintering, injection, and microsphere encapsulation. These scaffolds not only ensure the excellent cell drug loading performance of microspheres but also exhibit spatial modulation behaviour, aiding in bone repair within a three-dimensional network structure. This article provides a summary and discussion of the use of polymer microsphere scaffolds for bone repair, focusing on the mechanisms of bone tissue repair and the current status of clinical bone grafts, aimed at advancing research in bone repair.

Structure driven bio-responsive ability of injectable nanocomposite hydrogels for efficient bone regeneration

Injectable hydrogels are promising for treatment of bone defects in clinic owing to their minimally invasive procedure. Currently, there is limited emphasis on how to utilize injectable hydrogels to mobilize body's regenerative potential for enhancing bone regeneration. Herein, an injectable bone-mimicking hydrogel (BMH) scaffold assembled from nanocomposite microgel building blocks was developed, in which a highly interconnected microporous structure and an inorganic/organic (methacrylated hydroxyapatite and methacrylated gelatin) interweaved nano structure were well-designed. Compared with hydrogels lacking micro-nano structures or only showing microporous structure, the BMH scaffold enhanced the ingrowth of vessels and promoted the formation of dense cellular networks (including stem cells and M2 macrophages), across the entire scaffold at early stage after subcutaneous implantation. Moreover, the BMH scaffold could not only directly trigger osteogenic differentiation of the infiltrated stem cells, but also provided an instructive osteo-immune microenvironment by inducing macrophages into M2 phenotype. Mechanistically, our results reveal that the nano-rough structure of the BMH plays an essential role in inducing macrophage M2 polarization through activating mechanotransduction related RhoA/ROCK2 pathway. Overall, this work offers an injectable hydrogel with micro-nano structure driven bio-responsive abilities, highlighting harnessing body's inherent regenerative potential to realize bone regeneration.

Self-assembled peptide hydrogel loaded with functional peptide Dentonin accelerates vascularized bone tissue regeneration in critical-size bone defects

Regeneration of oral craniofacial bone defects is a complex process, and reconstruction of large bone defects without the use of exogenous cells or bioactive substances remains a major challenge. Hydrogels are highly hydrophilic polymer networks with the potential to promote bone tissue regeneration. In this study, functional peptide Dentonin was loaded onto self-assembled peptide hydrogels (RAD) to constitute functionally self-assembling peptide RAD/Dentonin hydrogel scaffolds with a view that RAD/Dentonin hydrogel could facilitate vascularized bone regeneration in critical-size calvarial defects. The functionalized peptide RAD/Dentonin forms highly ordered β-sheet supramolecular structures via non-covalent interactions like hydrogen bonding, ultimately assembling into nano-fiber network. RAD/Dentonin hydrogels exhibited desirable porosity and swelling properties, and appropriate biodegradability. RAD/Dentonin hydrogel supported the adhesion, proliferation and three-dimensional migration of bone marrow mesenchymal stem cells (BMSCs) and has the potential to induce differentiation of BMSCs towards osteogenesis through activation of the Wnt/β-catenin pathway. Moreover, RAD/Dentonin hydrogel modulated paracrine secretion of BMSCs and increased the migration, tube formation and angiogenic gene expression of human umbilical vein endothelial cells (HUVECs), which boosted the angiogenic capacity of HUVECs. In vivo, RAD/Dentonin hydrogel significantly strengthened vascularized bone formation in rat calvarial defect. Taken together, these results indicated that the functionalized self-assembling peptide RAD/Dentonin hydrogel effectively enhance osteogenic differentiation of BMSCs, indirectly induce angiogenic effects in HUVECs, and facilitate vascularized bone regeneration in vivo. Thus, it is a promising bioactive material for oral and maxillofacial regeneration.

Research Progress on Injectable Microspheres as New Strategies for the Treatment of Osteoarthritis Through Promotion of Cartilage Repair

Osteoarthritis (OA) is a degenerative disease caused by a variety of factors with joint pain as the main symptom, including fibrosis, chapping, ulcers, and loss of cartilage. Traditional treatment can only delay the progression of OA, and classical delivery system have many side effects. In recent years, microspheres have shown great application prospects in the field of OA treatment. Microspheres can support cells, reproduce the natural tissue microenvironment in vitro and in vivo, and are an efficient delivery system for the release of drugs or biological agents, which can promote cell proliferation, migration, and differentiation. Thus, they have been widely used in cartilage repair and regeneration. In this review, preparation processes, basic materials, and functional characteristics of various microspheres commonly used in OA treatment are systematically reviewed. Then it is introduced surface modification strategies that can improve the biological properties of microspheres and discussed a series of applications of microsphere functionalized scaffolds in OA treatment. Finally, based on bibliometrics research, the research development, future potential, and possible research hotspots of microspheres in the field of OA therapy is systematically and dynamically evaluated. The comprehensive and systematic review will bring new understanding to the field of microsphere treatment of OA.

A facile Immunoregulatory Constructional Design by Proanthocyanidin Optimizing Directional Chitosan Microchannel

Improving the interconnected structure and bioregulatory function of natural chitosan is beneficial for optimizing its performance in bone regeneration. Here, a facile immunoregulatory constructional design is proposed for developing instructive chitosan by directional freezing and alkaline salting out. The molecular dynamics simulation confirmed the assembly kinetics and structural features of various polyphenols and chitosan molecules. Along with the in vitro anti-inflammatory, antioxidative, promoting bone mesenchymal stem cell (BMSC) adhesion and proliferation performance, proanthocyanidin optimizing chitosan (ChiO) scaffold presented an optimal immunoregulatory structure with the directional microchannel. Transcriptome analysis in vitro further revealed the cytoskeleton- and immune-regulation effect of ChiO are the key mechanism of action on BMSC. The rabbit cranial defect model (Φ = 10 mm) after 12 weeks of implantation confirmed the significantly enhanced bone reconstitution. This facile immunoregulatory directional microchannel design provides effective guidance for developing inducible chitosan scaffolds.

Synergistic large segmental bone repair by 3D printed bionic scaffolds and engineered ADSC nanovesicles: Towards an optimized regenerative microenvironment

Achieving sufficient bone regeneration in large segmental defects is challenging, with the structure of bone repair scaffolds and their loaded bioactive substances crucial for modulating the local osteogenic microenvironment. This study utilized digital laser processing (DLP)-based 3D printing technology to successfully fabricate high-precision methacryloylated polycaprolactone (PCLMA) bionic bone scaffold structures. Adipose-derived stem cell-engineered nanovesicles (ADSC-ENs) were uniformly and stably modified onto the bionic scaffold surface using a perfusion device, constructing a conducive microenvironment for tissue regeneration and long bone defect repair through the scaffold's structural design and the vesicles' biological functions. Scanning electron microscopy (SEM) examination of the scaffold surface confirmed the efficient loading of ADSC-ENs. The material group loaded with vesicles (PCLMA-BAS-ENs) demonstrated good cell compatibility and osteogenic potential when analyzed for the adhesion and osteogenesis of primary rabbit bone marrow mesenchymal stem cells (BMSCs) on the material surface. Tested in a 15 mm critical rabbit radial defect model, the PCLMA-BAS-ENs scaffold facilitated near-complete bone defect repair after 12 weeks. Immunofluorescence and proteomic results indicated that the PCLMA-BAS-ENs scaffold significantly improved the osteogenic microenvironment at the defect site in vivo, promoted angiogenesis, and enhanced the polarization of macrophages towards M2 phenotype, and facilitated the recruitment of BMSCs. Thus, the PCLMA-BAS-ENs scaffold was proven to significantly promote the repair of large segmental bone defects. Overall, this strategy of combining engineered vesicles with highly biomimetic scaffolds to promote large-segment bone tissue regeneration holds great potential in orthopedic and other regenerative medicine applications.

Bushen Huoxue recipe ameliorates ovarian function via promoting BMSCs proliferation and homing to ovaries in POI mice

BACKGROUND

Premature ovarian insufficiency (POI) is a tricky puzzle in the field of female reproductive medicine. Bushen Huoxue recipe (BHR), a traditional Chinese medicine compound based on the combination of kidney-tonifying and blood-activating functions, has shown excellent efficacy in improving female irregular menstruation, POI, and infertility. However, the potential mechanism of BHR in POI treatment has not yet been elucidated. Bone marrow mesenchymal stem cells (BMSCs), a type of pluripotent stem cells, have received increasing attention for their significant role in improving ovarian function and restoring fertility in women with POI.

PURPOSE

This study aimed to evaluate the therapeutic effect of BHR in POI mice and explore its potential mechanism.

METHODS

A POI mouse model was established with a single intraperitoneal injection of 120 mg/kg cyclophosphamide (CTX). Distilled water, BHR, or dehydroepiandrosterone was administered via gavage for 28 consecutive days. The effect of BHR on ovarian function in POI mice was evaluated by assessing the estrous cycle, ovarian morphology, follicular development, hormone levels, and angiogenesis. The proportion of BMSCs in bone marrow, peripheral blood, and ovary was analyzed via flow cytometry, and the level of molecules mediating migration and homing in ovary was measured. Cell viability assays, scratch healing assays and transwell migration assays were performed to explore the effect of BHR on BMSCs proliferation and migration in vitro, and its potential mechanism was explored.

RESULTS

BHR significantly ameliorated estrous cycle disorders, hormone disorders, ovarian morphology, ovarian microvascular formation, and ovarian reserve in POI mice. Meanwhile, the number of BMSCs number in the bone marrow, peripheral blood, and ovary was apparently increased. Of note, BHR increased the level of hepatocyte growth factor (HGF)/cellular mesenchymal epithelial transition factor (cMET) and stromal cell-derived factor-1(SDF-1)/CXC chemokine receptor 4 (CXCR4) in the ovaries of POI mice. Moreover, BHR treatment promoted BMSCs proliferation and migration in vitro, with a significant increase in the level of proliferating cell nuclear antigen, cMET, and CXCR4.

CONCLUSIONS

BHR effectively restored ovarian reserve, ovarian function, and ovarian angiogenesis in CTX-induced POI mice. In addition, BHR promoted BMSCs proliferation, migration, and homing to the ovary, which was mediated by the SDF-1/CXCR4 and HGF/cMET signaling axis. Finally, the amelioration of ovarian reserve and ovarian function in CTX-induced POI mice by BHR may be related to its promotion of endogenous BMSCs proliferation and homing.

Bioinspired soft-hard combined system with mild photothermal therapeutic activity promotes diabetic bone defect healing via synergetic effects of immune activation and angiogenesis

Background: The comprehensive management of diabetic bone defects remains a substantial clinical challenge due to the hostile regenerative microenvironment characterized by aggravated inflammation, excessive reactive oxygen species (ROS), bacterial infection, impaired angiogenesis, and unbalanced bone homeostasis. Thus, an advanced multifunctional therapeutic platform capable of simultaneously achieving immune regulation, bacterial elimination, and tissue regeneration is urgently designed for augmented bone regeneration under diabetic pathological milieu. Methods and Results: Herein, a photoactivated soft-hard combined scaffold system (PGCZ) was engineered by introducing polydopamine-modified zeolitic imidazolate framework-8-loaded double-network hydrogel (soft matrix component) into 3D-printed poly(ε-caprolactone) (PCL) scaffold (hard matrix component). The versatile PGCZ scaffold based on double-network hydrogel and 3D-printed PCL was thus prepared and features highly extracellular matrix-mimicking microstructure, suitable biodegradability and mechanical properties, and excellent photothermal performance, allowing long-term structural stability and mechanical support for bone regeneration. Under periodic near-infrared (NIR) irradiation, the localized photothermal effect of PGCZ triggers the on-demand release of Zn2+, which, together with repeated mild hyperthermia, collectively accelerates the proliferation and osteogenic differentiation of preosteoblasts and potently inhibits bacterial growth and biofilm formation. Additionally, the photoactivated PGCZ system also presents outstanding immunomodulatory and ROS scavenging capacities, which regulate M2 polarization of macrophages and drive functional cytokine secretion, thus leading to a pro-regenerative microenvironment in situ with enhanced vascularization. In vivo experiments further demonstrated that the PGCZ platform in conjunction with mild photothermal therapeutic activity remarkably attenuated the local inflammatory cascade, initiated endogenous stem cell recruitment and neovascularization, and orchestrated the osteoblast/osteoclast balance, ultimately accelerating diabetic bone regeneration. Conclusions: This work highlights the potential application of a photoactivated soft-hard combined system that provides long-term biophysical (mild photothermal stimulation) and biochemical (on-demand ion delivery) cues for accelerated healing of diabetic bone defects.