Critical-sized Bone Defects Research Articles

Extracellular vesicles: essential agents in critical bone defect repair and therapeutic enhancement.

Bone serves as a fundamental structural component in the body, playing pivotal roles in support, protection, mineral supply, and hormonal regulation. However, critical-sized bone injuries have become increasingly prevalent, necessitating extensive medical interventions due to limitations in the body's capacity for self-repair. Traditional approaches, such as autografts, allografts, and xenografts, have yielded unsatisfactory results. Stem cell therapy emerges as a promising avenue, but challenges like immune rejection and low cell survival rates hinder its widespread clinical implementation. Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have garnered attention for their regenerative capabilities, which surpass those of MSCs themselves. EVs offer advantages such as reduced immunogenicity, enhanced stability, and simplified storage, positioning them as a promising tool in stem cell-based therapies. This review explores the potential of EV-based therapy in bone tissue regeneration, delving into their biological characteristics, communication mechanisms, and preclinical applications across various physiological and pathological conditions. The mechanisms underlying EV-mediated bone regeneration, including angiogenesis, osteoblast proliferation, mineralization, and immunomodulation, are elucidated. Preclinical studies demonstrate the efficacy of EVs in promoting bone repair and neovascularization, even in pathological conditions like osteoporosis. EVs hold promise as a potential alternative for regenerating bone tissue, particularly in the context of critical-sized bone defects, offering new avenues for effective bone defect repair and management.

Biodegradable Janus sonozyme with continuous reactive oxygen species regulation for treating infected critical-sized bone defects

Critical-sized bone defects are usually accompanied by bacterial infection leading to inflammation and bone nonunion. However, existing biodegradable materials lack long-term therapeutical effect because of their gradual degradation. Here, a degradable material with continuous ROS modulation is proposed, defined as a sonozyme due to its functions as a sonosensitizer and a nanoenzyme. Before degradation, the sonozyme can exert an effective sonodynamic antimicrobial effect through the dual active sites of MnN4 and Cu2O8. Furthermore, it can promote anti-inflammation by superoxide dismutase- and catalase-like activities. Following degradation, quercetin-metal chelation exhibits a sustaining antioxidant effect through ligand-metal charge transfer, while the released ions and quercetin also have great self-antimicrobial, osteogenic, and angiogenic effects. A rat model of infected cranial defects demonstrates the sonozyme can rapidly eliminate bacteria and promote bone regeneration. This work presents a promising approach to engineer biodegradable materials with long-time effects for infectious bone defects.

Nanoparticle-Mediated Gene Delivery for Bone Tissue Engineering.

Critical-sized bone defects represent an urgent clinical problem, necessitating innovative treatment approaches. Gene-activated grafts for bone tissue engineering have emerged as a promising solution. However, traditional gene delivery methods are constrained by limited osteogenic efficacy and safety concerns. Recently, organic and inorganic nanoparticle (NP)vectors have attracted significant attention in bone tissue engineering for their safe, stable, and controllable gene delivery. Targeted gene delivery guided by insights into bone healing mechanisms, coupled with the multifunctional design of NPs, is crucial for enhancing therapeutic outcomes. Here, the theoretical foundations underlying NP-mediated gene therapy for enhancing bone healing across different histological stages are elucidated. Furthermore, the distinct attributes of functionalized NP vectors are discussed, and cutting-edge strategies aimed at optimizing gene delivery efficiency throughout the therapeutic process are highlighted. Additionally, the review addresses the unresolved challenges and prospects of this technology. This review may contribute to the continued development and clinical application of NP-mediated gene delivery for treating critical-sized bone defects.

An InVivo Assessment of Different Mesenchymal Stromal Cell Tissue Types and Their Differentiation State on a Shape Memory Polymer Scaffold for Bone Regeneration.

A combined biomaterial and cell-based solution to heal critical size bone defects in the craniomaxillofacial area is a promising alternative therapeutic option to improve upon autografting, the current gold standard. A shape memory polymer (SMP) scaffold, composed of biodegradable poly(ε-caprolactone) and coated with bioactive polydopamine, was evaluated with mesenchymal stromal cells (MSCs) derived from adipose (ADSC), bone marrow (BMSC), or umbilical cord (UCSC) tissue in their undifferentiated state or pre-differentiated toward osteoblasts for bone healing in a rat calvarial defect model. Pre-differentiating ADSCs and UCSCs resulted in higher new bone volume fraction (15.69% ± 1.64%) compared to empty (i.e., untreated) defects and scaffold-only (i.e., unseeded) groups (4.41% ± 1.11%). Notably, only differentiated UCSCs exhibited a significant increase in new bone volume, surpassing both undifferentiated UCSCs and unseeded scaffolds. Further, differentiated ADSCs and UCSCs had significantly higher trabecular numbers than their undifferentiated counterparts, unseeded scaffolds, and untreated defects. Although the mineral density regenerated within the unseeded scaffold surpassed that achieved with cell seeding, the connectivity of this bone was diminished, as the regenerated tissue confined itself to the spherical morphology of the scaffold pores. The SMP scaffold alone, with undifferentiated BMSCs, with undifferentiated and differentiated ADSCs, and differentiated UCSCs (29.72 ± 1.49 N) demonstrated significant osseointegration compared to empty defects (14.34 ± 2.21 N) after 12 weeks of healing when assessed by mechanical push-out testing. Based on these results and tissue availability to obtain the cells, pre-differentiated ADSCs and UCSCs emerge as particularly promising candidates when paired with the SMP scaffold for repairing critical size bone defects in the craniofacial skeleton.

Targeting Age-Related Impaired Bone Healing: ZnO Nanoparticle-Infused Composite Fibers Modulate Excessive NETosis and Prolonged Inflammation in Aging.

Bone defects present significant challenges in clinical contexts, particularly among the elderly, and are often linked to altered innate immune responses; however, underlying mechanisms remain to be understood. This study investigates immune changes in early bone healing in aged mice, emphasizing the effects of zinc in modulating inflammatory processes. By exploring the role of zinc and NETosis in this process, we seek to develop novel therapeutic strategies that could improve bone repair in aging populations. Critical-sized calvarial bone defects were induced in young (8-week-old) and aged (18-month-old) mice, with RNA sequencing analysis. Zinc oxide nanoparticle-infused polycaprolactone (ZnPCL) scaffolds were then fabricated using electrospinning, and their effects on intracellular zinc levels, NETosis, M2 polarization, and bone formation were assessed through in vitro and in vivo experiments. In aged mice, bone healing was delayed, inflammation was prolonged, and NETosis was excessive. RNA sequencing identified alterations in zinc ion transport genes, alongside excessive NETosis. Aged mouse neutrophils exhibited low intracellular zinc levels. ZnPCL fibers effectively reduced NETosis and inflammation, promoted M2 macrophage polarization, and enhanced new bone formation, thereby improving bone healing in aged mice. This study demonstrates that ZnO nanoparticle-infused biomaterials, ZnPCL, effectively deliver zinc to neutrophils, reduce NETosis, promote M2 polarization, and enhance bone healing in aged mice.

Scalable fabrication of freely shapable 3D hierarchical Cu-doped hydroxyapatite scaffolds via rapid gelation for enhanced bone repair

Critical-sized bone defects present a formidable challenge in tissue engineering, necessitating innovative approaches that integrate osteogenesis and angiogenesis for effective repair. Inspired by the hierarchical porous structure of natural bone, this study introduces a novel method for the scalable production of ultra-long, copper-doped hydroxyapatite (Cu-HAp) fibers, utilizing the rapid gelation properties of guar gum (GG) under controlled conditions. These fibers serve as foundational units to fabricate three-dimensional porous scaffolds with a biomimetic hierarchical architecture. The scaffolds exhibit a broad pore size distribution (1–500 μm) and abundant nanoporous features, mimicking the native bone extracellular matrix. Physicochemical characterization and in vitro assays demonstrated that the copper doping significantly enhanced osteogenic and angiogenic activities, with optimized concentrations (0.8 % and 1.2 % Cu) facilitating the upregulation of osteogenesis-related genes and proteins, as well as promoting endothelial cell proliferation. In vivo studies further confirmed the scaffolds' efficacy, with the 1.2Cu-HAp group showing a remarkable increase in bone regeneration (bone volume/total volume ratio: 35.7 ± 1.87 %) within the defect site. This research offers a promising strategy for the rapid fabrication of multifunctional scaffolds that not only support bone tissue repair but also actively accelerate the healing process through enhanced vascularization.

Bioinspired adhesive polydopamine-metal-organic framework functionalized 3D customized scaffolds with enhanced angiogenesis, immunomodulation, and osteogenesis for orbital bone reconstruction

Critical-sized orbital bone defects can lead to significant maxillofacial deformities and even eye movement disorders. The challenges associated with these defects, including their complicated structure, inadequate blood supply, and limited availability of progenitor cells that hinder successful repair. To overcome these issues, we developed a novel approach using computer numerical control (CNC) material reduction manufacturing technology to produce a customized polyetheretherketone (PEEK) scaffold that conforms to the specific shape of orbital bone defects. Deferoxamine (DFO) was in situ encapsulated into polydopamine-hybridized zeolitic imidazolate framework-8 (pZIF8-DFO) nanoparticles, which was subsequently adhered to the sulfonated PEEK (sPEEK) scaffold through polydopamine modification. This functionalization enhanced drug loading efficiency and imparted anti-inflammatory properties to the nanoparticle system. Our in vitro findings demonstrated that the sustained release of DFO from the sPEEK/pZIF8-DFO scaffolds extended over 14 days and significantly promoted angiogenesis and progenitor cell recruitment, as evidenced by increased expression of HIF-1α, VEGF, and SDF-1α expression in human umbilical vein endothelial cells (HUVECs). Moreover, sPEEK/pZIF8-DFO scaffolds exhibited superior immunomodulation and osteogenic differentiation capabilities on Raw 264.7 cells and rabbit bone marrow mesenchymal stem cells (rBMSCs), respectively. Most notably, our in vivo rabbit orbital bone defects revealed that sPEEK/pZIF8-DFO scaffolds resulted in a greater volume of new bone formation than on sPEEK and sPEEK/pZIF8 scaffolds, with partial bone connection to the sPEEK/pZIF8-DFO scaffolds. In summary, we develop a novel PEEK scaffold that combines enhanced angiogenesis, stem cell recruitment, immunomodulation, and osteogenic differentiation, showcasing its promising potential for orbital bone reconstruction.

Regenerative Therapy for Treatment of Critical-size Bone Defects

Regenerative Therapy for Treatment of Critical-size Bone Defects

Enhancing bone repair efficiency through synergistic modification of recombinant human collagen onto PLLA membranes

Given the exponential growth of the recombinant human collagen market, it is paramount to devise a robust and straightforward design strategy aimed at preserving the remarkable biological activity of recombinant human collagen while endowing it with tailored mechanical properties and stable morphologies. This innovative approach stands to broaden its applicability in hard tissue repair endeavors. Our study employed a synergistic approach of alkali hydrolysis and Schiff's base chemistry to graft Type I recombinant human collagen (rhCol-I) onto poly (L-lactic acid) (PLLA) membranes, yielding PLLA-rhCol composites. In vitro evaluations substantiated that this reengineered material not only retained the biological efficacy of rhCol-I but also imparted mechanical robustness and processability ideal for bone implant applications. Notably, it exhibited superior tissue engineering attributes, fostering proliferation, adhesion, osteogenic differentiation, mineralization of bone marrow mesenchymal stem cells (BMSCs), and encouraging vascularization. In a rat model of critical-sized bone defects, PLLA-rhCol exhibited markedly enhanced bone repair efficiency over conventional PLLA bone implants, achieving a bone volume fraction (BV/TV) of up to 32.57 ± 3.77 %, while promoting angiogenesis and effectively mitigating inflammatory cell infiltration. This pioneering method of modifying recombinant human collagen onto the side chains of polymeric macromolecules portends broad applicability in enhancing various biocompatible, yet mechanically robust and processable polymers, thereby expanding the horizons of recombinant human collagen utilization in tissue engineering and catering to the ever-evolving market demands.

3D-Printed Bifunctional Scaffold for Treatment of Critical Bone Defects Based on Osteoimmune Microenvironment Regulation and Osteogenetic Effects.

The critical-sized bone defect resulting from trauma, tumor resection, and congenital deformity fails to undergo spontaneous healing due to its substantial size, while the ensuing inflammatory process and hypoxic environment further impede the regenerative process. Therefore, it has consistently presented a significant clinical challenge. In the present study, we incorporate a glycyrrhizic acid (GA)-functionalized hydrogel onto the surface of a Hydroxyapatite (Hap)-modified Polycaprolactone (PCL) scaffold to fabricate a composite scaffold. The composed scaffold showed favorable anti-inflammatory and antioxidative capabilities by modulating macrophage polarization and scavenging reactive oxygen species (ROS); the modification of Hap enhanced its osteogenic ability. An in vivo rat skull defect model confirmed that the composed scaffold efficiently promotes bone regeneration. In general, the composed scaffold with the ability of osteoimmune microenvironment regulation can effectively repair critical-sized bone defects. This strategy provides a promising method for the reconstruction of large segmental bone defects.

Adipose-derived stem cell exosomal miR-21-5p enhances angiogenesis in endothelial progenitor cells to promote bone repair via the NOTCH1/DLL4/VEGFA signaling pathway

BackgroundAngiogenesis is essential for repairing critical-sized bone defects. Although adipose-derived stem cell (ADSC)-derived exosomes have been shown to enhance the angiogenesis of endothelial progenitor cells (EPCs), the underlying mechanisms remain unclear. This study aims to explore the effects and mechanisms of ADSC-derived exosomes in enhancing bone repair by promoting EPC angiogenesis.MethodsTransmission electron microscopy, nanoparticle tracking analysis, and Dil reagent kit were employed to identify ADSC-derived exosomes and their internalization by EPCs. Micro-CT analysis, H&E staining, and Masson staining were used to assess bone mineral density (BMD), bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and trabecular number (Tb.N), as well as the pathological changes and fibrosis at defect sites. Cell viability, migration, invasion, and tube formation of EPCs were evaluated using CCK-8, wound healing, Transwell, and tube formation assays. Immunohistochemical staining, RT-PCR, and Western blotting were utilized to measure the gene and protein expression of markers such as CD31, VEGFA, OCN, RUNX2, NOTCH1, and DLL4. Gene sequencing and bioinformatics analyses were conducted to identify the most highly expressed miRNA in exosomes, while miRDB and dual-luciferase reporter assays were used to explore the interaction between miR-21-5p and NOTCH1.ResultsThe ADSC-derived exosomes, averaging 126 nm in diameter, were internalized by EPCs. In vivo, these exosomes promoted new bone formation, increased BMD, BV/TV, Tb.Th, and Tb.N, reduced pathological damage to cranial defect tissues, enhanced vascular and bone tissue regeneration, and upregulated OCN and RUNX2 expression. In vitro, ADSC-derived exosomes enhanced EPC viability, migration, invasion, and tube formation. Both in vivo and in vitro experiments demonstrated that ADSC-derived exosomes upregulated CD31 and VEGFA expression. miR-21-5p, the most highly expressed miRNA in ADSC-derived exosomes, was found to target NOTCH1. Overexpression of miR-21-5p in these exosomes facilitated EPC migration, tube formation, and VEGFA expression while downregulating NOTCH1 and DLL4 expression. Inhibition of miR-21-5p produced opposite effects on EPCs.ConclusionsThese findings indicate that miR-21-5p in ADSC-derived exosomes promotes angiogenesis in EPCs to accelerate bone repair by targeting the NOTCH1/DLL4/VEGFA signaling pathway, offering a potential therapeutic strategy for bone defect treatment.Graphical

Multiphoton imaging for quantification of mesenchymal stem cell survival and distribution in PEG granular hydrogel scaffolds post-implantation into rat cranial bone defects

Mesenchymal stem cells (MSCs) are promising candidates for cellular therapies aimed at promoting bone regeneration due to their secretory properties and osteoblastic differentiation capacity. However, typically < 5% of delivered MSCs are retained at the healing site within days of delivery via injection. In this work, granular PEG hydrogel scaffolds were used to deliver MSCs, labeled with fluorescent Quantum Dots, into critical-sized rat calvarial bone defects. The presence, survival, and distribution of MSCs within the hydrogel scaffold were evaluated with multiphoton microscopy at 3- and 7-days post-implantation. Additionally, endogenous cell infiltration into scaffolds was quantified, and markers for M1 and M2 macrophages were identified with immunohistochemistry. This multiphoton microscopy technique provides a quantitative analysis of exogenous MSC presence and survival and allows for micron-level spatial resolution of cell distribution throughout the implanted scaffolds. When ∼750,000 MSCs were implanted in a calvarial bone defect via PEG granular hydrogel scaffolds, ∼27% and ∼8% survived 3- and 7-days post-implantation, respectively. At 3- and 7-days post-implantation, exogenous MSCs and infiltrating endogenous cells, including M1 and M2 macrophages, were well distributed throughout the scaffolds. This multiphoton microscopy technique could be used to assess biomaterial delivery systems that can improve exogenous MSC presence and survival, facilitate endogenous cell infiltration, and investigate exogenous-endogenous cell interactions for bone regeneration therapies.

Enhanced bone tissue regeneration via mesenchymal stem cells-laden Alginate/GelMa 3D-Bioprinted scaffold treated with Haplophyllum tuberculatum extract

Background and aimRegeneration of critical-sized bone defects is challenging due to avascular necrosis, inflammation, and disrupted osteogenesis. This study explores the synergistic effects of Haplophyllum tuberculatum (HT) extract and mesenchymal stem cells (MSCs) in an Alg/GelMa 3D-bioprinted scaffold to enhance bone regeneration. MethodsEthanolic extracts of stems (HTS), flowers (HTF), and a mixture (HTM) were obtained via Soxhlet extraction and subsequently characterized. Further investigations into their cytotoxicity, osteogenic and bone tissue regeneration potential were conducted, in vitro and in vivo. ResultsAlongside GC-MS analysis, vitamin and elemental analyses of HTS, HTF, and HTM revealed varying concentrations of key elements essential for bone regeneration. All extracts exhibited moderate antioxidant activity, with more potency in the HTF group. Cytotoxicity assays indicated the lack of cytotoxic effects from HTS and HTF on MSCs. The calcium secretion and deposition on MSCs revealed the osteogenic potential of HTF and HTM. Gene and protein expression analyses indicated significant upregulation of osteogenic markers in HTF-treated MSCs. The integration of MSCs into a Alg/GelMa 3D-bioprinted scaffold enhanced their viability and proliferation, validating its biocompatibility. Additionally, HTF promoted calcium deposition and ALP activity in the MSC-laden 3D-bioprinted scaffold. In vivo assessment in a rat calvarial defect model, demonstrated accelerated bone regeneration with HTF-treated scaffolds. The improved bone regeneration, vascularization, and collagen formation in HTF-treated defects were confirmed by histopathology results. ConclusionThis study underscores the significant role of the HTF in promoting osteogenesis, advocating for its incorporation into advanced tissue engineering strategies for bone regeneration.

Multifunctional Bone Regeneration Membrane with Flexibility, Electrical Stimulation Activity and Osteoinductive Activity.

The use of membrane-based guided bone regeneration techniques has great potential for single-stage reconstruction of critical-sized bone defects. Here, a multifunctional bone regeneration membrane combining flexible elasticity, electrical stimulation (ES) and osteoinductive activity is developed by in situ doping of MXene 2D nanomaterials with conductive functionality and β-TCP particles into a Poly(lactic acid-carbonate (PDT) composite nano-absorbable membrane (P/T/MXene) via electrostatic spinning technique. The composite membrane has good feasibility due to its temperature sensitivity, elastic memory capacity, coordinated degradation profile and easy preparation process. In vitro experiments showed the P/T/MXene membrane effectively promoted the recruitment and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) under ES and enhanced the angiogenic capacity of endothelial cells, which synergistically promoted bone regeneration through neovascularization. In addition, an in vivo rat model of cranial bone defects further confirmed the bone regeneration efficacy of the P/T/MXene membrane. In conclusion, the developed P/T/MXene membrane can effectively promote bone regeneration through their synergistic multifunctional effects, suggesting the membranes have great potential for guiding tissue regeneration and providing guidance for the biomaterials design.

Osteoinductively Functionalized 3D-Printed Scaffold for Vertical Bone Augmentation in Beagle Dogs.

To evaluate the efficacy of 3D-printed scaffolds that were osteoinductively functionalized with a bone morphogenetic protein 2 (BMP-2)-incorporated biomimetic calcium phosphate particles (BMP-2-inc. BpNcCaP)/hyaluronic acid (HA) composite gel in vertical bone augmentation in beagle dogs. Four Beagle dogs were used in this study. Three months after the extraction of 1st, 2nd, 3rd, and 4th premolars at both sides of the lower jaws of Beagle dogs, one or two critical-size vertical bone defects (4 mm vertical bone defect without buccal and lingual bone) on each sidewere surgically created. The defects were randomly subjected to the following groups: (1) Control (without bone-defect-filling materials); (2) 3D scaffold; (3) BMP2-inc. BpNcCaP/HA-functionalized 3D scaffold. Six weeks post-surgery, samples were harvested and subjected to micro-CT and histomorphometric analyses. The struts of the BMP2-inc. BpNcCaP/HA-func. 3D scaffold were covered by a thick layer of cemented irregular particles with an average pore size at 327 ± 27 μm. The BpNcCaP/HA-func. 3D scaffold group bore significantly higher bone volume, bone volume fraction, trabecular number, trabecular thickness, bone mineral density, connectivity density, and bone volumes in three directions (mesiodistal, buccolingual, and apicocoronal) when compared with the groups of Control and 3D scaffold. Moreover, the BMP2-inc. BpNcCaP/HA-func. 3D scaffold group bore significantly lower trabecular separation and exhibited significantly higher bone-to-scaffold contact percentage and newly formed bone area percentage within pores in comparison with 3D scaffold. BMP2-inc. BpNcCaP/HA-func. 3D scaffold dramatically enhanced vertical alveolar bone augmentation, which suggests a promising application potential of BMP2-inc. BpNcCaP/HA-func. 3D scaffold in dental clinic.

One-Step Gas Foaming Strategy for Constructing Strontium Nanoparticle Decorated 3D Scaffolds: a New Platform for Repairing Critical Bone Defects.

The management of critical-sized bone defects poses significant clinical challenges, particularly in the battlefield and trauma-related injuries. However, bone tissue engineering scaffolds that satisfy high porosity and good angiogenic and osteogenic functions are scarce. In this study, 3D nanofiber scaffolds decorated with strontium nanoparticles (3DS-Sr) were fabricated by combining electrospinning and gas foaming. Sodium borohydride (NaBH4) served a dual role as both a reducing and gas-foaming agent, enabling a one-step process for expansion and modification. In vitro experimental results demonstrated that 3DS-Sr possessed an integrated multilayered porous structure. It promoted angiogenesis by upregulating the expression of hypoxia-inducible factor-1α (HIF-1α) protein and phosphorylation of ERK through the sustained release of Sr2+ and created a favorable microenvironment for osteogenesis by activating the Wnt/β-catenin pathway. In vivo experiments indicated that 3DS-Sr promoted cranial bone regeneration by synergistically promoting the effects of vascularization and osteogenesis. In summary, this study proposed a bioactive bone scaffold in a "one stone, two birds" manner, providing a promising strategy for bone defect repair.

Osteogenic citric acid linked chitosan coating of 3D-printed PLA scaffolds for preventing implant-associated infections

>25 % of the patients who receive orthopedic implants have been reported with implant-associated osteomyelitis, which can result in inflammation, osteolysis, and aseptic loosening of implants. Current treatment methods doesn't ensure defect healing and prevention from reinfection. Thermoplastic-based 3D-printed scaffolds offer a bioresorbable, biocompatible, and mechanical strong implant system. However, the hydrophobicity and bio-inertness of these polymers prevent their use in clinics. In this study, we developed dual functionalized scaffolds with osteogenic and antibacterial properties by immobilizing citric acid-linked chitosan on oxygen plasma etched 3D-printed PLA scaffolds through an EDC-NHS coupling reaction. Acellular mineralization of these scaffolds in DMEM demonstrated the deposition of crystalline hydroxyapatite. In addition, the antibacterial properties of these surface-modified scaffolds have been determined against E. coli and S. aureus, where the citric-linked chitosan biofunctionalized 3D-printed PLA scaffolds showed significantly higher antibacterial activity in comparison to oxygen-etched PLA and PLA scaffolds due to the synergistic effect of citric acid and chitosan functionalities. MG-63 cells exhibited increased proliferation and osteogenic activity on the modified scaffolds compared to the PLA and OP-PLA. These 3D-printed scaffolds, coated with citric-linked chitosan, can be a potential solution to orthopedic complications such as critical-sized bone defects and implant-associated osteomyelitis.

Natural loofah sponge inspired 3D printed bionic scaffolds promote personalized bone defect regeneration

Critical-sized bone defects pose serious health concerns for patients. Clinically, the use of functionalized bone implants has emerged as an effective solution. However, the rapid advancement in drug and biomaterials has led to an increasing design cost, triggering discussions in the field about how to efficiently create customized functional bone implants. Inspired by the unique structure of natural loofah sponges that effectively deliver nutrients to seeds, we designed a functionalized bone implant emulating this structure. Drug-release gradients were achieved through the application of different concentrations of hydrogels within the composite scaffold. This approach allowed active substances to be released outwardly during the early stage of bone repair, sustaining a local drug micro-environment within the implant scaffold that promotes angiogenesis and osteogenic differentiation in damaged areas. In vivo experiments showed that our loofah sponge bionic scaffold outperformed traditional hydroxyapatite scaffolds by promoting both bone and vascular regeneration. We expect the design of loofah sponge bionic scaffold could potentially deliver an effective strategy in the development of functionalized bone implants.

Periosteum-bone inspired hierarchical scaffold with endogenous piezoelectricity for neuro-vascularized bone regeneration

The development of scaffolds for repairing critical-sized bone defects heavily relies on establishing a neuro-vascularized network for proper penetration of nerves and blood vessels. Despite significant advancements in using artificial bone-like scaffolds infused with various agents, challenges remain. Natural bone tissue consists of a porous bone matrix surrounded by a neuro-vascularized periosteum, with unique piezoelectric properties essential for bone growth. Drawing inspiration from this assembly, we developed a periosteum-bone-mimicking bilayer scaffold with piezoelectric properties for regeneration of critical-sized bone defects. The periosteum-like layer of this scaffold features a double network hydrogel composed of chelated alginate, gelatin methacrylate, and sintered whitlockite nanoparticles, emulating the viscoelastic and piezoelectric properties of the natural periosteum. The bone-like layer is composed of a porous structure of chitosan and bioactive hydroxyapatite created through a biomineralization process. Unlike conventional bone-like scaffolds, this bioinspired bilayer scaffold significantly enhances osteogenesis, angiogenesis, and neurogenesis combined with low-intensity pulsed ultrasound-assisted piezoelectric stimulation. Such a scheme enhances neuro-vascularized bone regeneration in vivo. The results suggest that the bilayer scaffold could serve as an effective self-powered electrical stimulator to expedite bone regeneration under dynamic physical stimulation.

Biomimetic non-collagenous proteins-calcium phosphate complex with superior osteogenesis via regulating macrophage IL-27 secretion

Traumatic defects or non-union fractures presents a substantial challenge in the fields of tissue engineering and regenerative medicine. Although synthetic calcium phosphate-based biomaterials (CaPs) such as dibasic calcium phosphate anhydrate (DCPA) are commonly employed for bone repair, their inadequate cellular immune responses significantly impede sustained degradation and optimal osteogenesis. In this study, drawing inspiration from the key structure of an acidic non-collagenous protein-CaP complex (ANCPs-CaP) essential for natural bone formation, we prepared biomimetic mineralized dibasic calcium phosphate (MDCPA). This preparation utilized plant-derived non-collagenous protein Zein as the organic template and acidic artificial saliva as the mineralization medium. Physicochemical property analysis revealed that MDCPA is a complex of Zein and DCPA, which mimics the composite of the natural ANCP-CaP. Moreover, MDCPA exhibited enhanced biodegradability and osteogenic potential. Mechanistic insight revealed that MDCPA can be phagocytized and degraded by macrophages via the FCγRIII receptor, leading to the release of interleukin 27 (IL-27), which promotes osteogenic differentiation by osteoimmunomodulation. The critical role of IL-27 in osteogenesis is further confirmed using IL-27 gene knockout mice. Additionally, MDCPA demonstrates effective healing of critical-sized defects in rat cranial bones within only 4 w, providing a promising basis and valuable insights for critical-sized bone defects regeneration.