Rabbit Cranial Defect Research Articles

Fluorinated Porcine Bone-Derived Hydroxyapatite Promotes Vascularized Osteogenesis by Coordinating Human Bone Marrow Mesenchymal Stem Cell/Human Umbilical Vein Endothelial Cell Complexes

Biogenic hydroxyapatite is known for its osteoinductive potential due to its similarity to human bone and biocompatibility, but insufficient vascularization compared to autogenous bone during early implantation limits bone integration and osteogenesis. Fluorine has been shown to improve hydroxyapatite’s mechanical properties and the coupling of osteogenic and angiogenic cells. In this study, fluorine-modified biogenic hydroxyapatite (FPHA) with varying fluorine concentrations was prepared and tested for its ability to promote vascularized osteogenesis. FPHA prepared in this study retained the natural porous structure of biological cancellous bone and released F− ions when immersed in cell culture medium. The extraction solutions of FPHA0.25 and FPHA0.50 promoted the formation of capillary-like tubes by human umbilical vein endothelial cells (HUVECs), with FPHA0.25 significantly upregulating vegf mRNA and VEGF protein levels in co-cultured human bone marrow mesenchymal stem cells (HBMSCs). Additionally, FPHA0.25 and FPHA0.50 upregulated pdgf-bb mRNA and PDGF-BB protein levels in HUVECs. In vivo experiments using a rabbit cranial defect model demonstrated that FPHA0.25 promoted early bone formation and angiogenesis in the defect area, enhanced VEGF secretion, and increased PDGFR-β expression in endothelial and mesenchymal cells. These findings suggest that fluorine-modified biogenic hydroxyapatite with an optimal fluorine concentration (FPHA0.25) may offer a promising strategy to enhance the body’s innate bone-healing potential by accelerating vascularization.

Bone regeneration in rabbit cranial defects: 3D printed polylactic acid scaffolds gradually enriched with marine bioderived calcium phosphate

ObjectiveThis study aimed to evaluate the in vivo biocompatibility, mechanical performance and osteoconductive potential of 3D-printed polylactic acid (PLA) scaffolds enriched with marine bioderived calcium phosphate (bioCaP) for bone tissue engineering. Materials and MethodsPLA-bioCaP composite scaffolds were specifically designed for the rabbit cranial defect model by 3D printing, with a uniform distribution of open square-shaped pores and contributions in bioCaP. Physicochemical and mechanical characterization and the evaluation of biological response are presented. ResultsThe scaffolds demonstrated mechanical properties comparable to human bones, integration with the host bone, and osteoconductive behavior promoting cell ingrowth from the defect edge. Strong mineralized tissue ingrowth through the scaffolds’ pores was observed, providing notable support to the host bone. In quantitative terms, micro-CT and histomorphometry analysis post-implantation revealed no significant differences in bone regeneration across all groups. ConclusionThe 3D-printed scaffolds with perpendicular patterning, open porosity, and proposed composition displayed satisfactory mechanical properties, biocompatibility, and osteoconductive response. The scaffolds promoted bone regeneration at similar levels as the PLA. The highest contribution of bioCaP promoted a positive influence in certain histomorphometric parameters; however, it did not significantly improve their osteogenic capability. Further research is required to optimize scaffold composition and enhance their osteogenic potential. Clinical RelevanceThis study presents a significant advancement in bone tissue engineering through the development of personalized composite scaffolds for bone-related applications. The clinical implications of this research are profound, especially considering the increasing demand for functional bone regeneration technologies capable of producing cost-effective producing cost-effective customized scaffolds.

Injectable dual drug-loaded thermosensitive liposome-hydrogel composite scaffold for vascularised and innervated bone regeneration

Adequate blood supply and thorough innervation are essential to the survival of tissue-engineered bones. Though great progress has been created in the application of bone tissue engineering technology to bone defect repair, many challenges remain, such as insufficient vascularisation and deficient innervation in newly regenerated bone. In the present study, we addressed these challenges by manipulating the bone regeneration microenvironment in terms of vascularisation and innervation. We used a novel injectable thermosensitive liposome-hydrogel composite scaffold as a sustained-release carrier for basic fibroblast growth factor (bFGF, which promotes angiogenesis and neurogenic differentiation) and dexamethasone (Dex, which promotes osteogenic differentiation). In vitro biological assessment demonstrated that the composite scaffold had sufficient cell compatibility; it enhanced the capacity for angiogenesis in human umbilical vein endothelial cells, and the capacity for neurogenic/osteogenic differentiation in human bone marrow mesenchymal stem cells. Moreover, the introduction of bFGF/Dex liposome-hydrogel composite scaffold to bone defect sites significantly improved vascularisation and innervated bone regeneration properties in a rabbit cranial defect model. Based on our findings, the regeneration of sufficiently vascularised and innervated bone tissue through a sustained-release scaffold with excellent injectability and body temperature sensitivity represents a promising tactic towards bone defect repair.

Biomimetic peroxidase MOF-Fe promotes bone defect repair by inhibiting TfR2 and activating the BMP2 pathway

BackgroundLarge bone defects pose a clinical treatment challenge; inhibiting transferrin receptor 2 (TfR2), which is involved in iron metabolism, can promote osteogenesis. Iron-based metal-organic frameworks (MOF-Fe) particles not only inhibit TfR2 but also serve as biomimetic catalysts to remove hydrogen peroxide in reactive oxygen species (ROS); excess ROS can disrupt the normal functions of osteoblasts, thereby hindering bone regeneration. This study explored the potential effects of MOF-Fe in increasing osteogenic activity and clearing ROS.MethodsIn vitro experiments were performed to investigate the osteogenic effects of MOF-Fe particles and assess their impact on cellular ROS levels. To further validate the role of MOF-Fe in promoting bone defect repair, we injected MOF-Fe suspensions into the femoral defects of SD rats and implanted MOF-Fe-containing hydrogel scaffolds in rabbit cranial defect models and observed their effects on bone healing.ResultsIn vitro, the presence of MOF-Fe significantly increased the expression levels of osteogenesis-related genes and proteins compared to those in the control group. Additionally, compared to those in the untreated control group, the cells treated with MOF-Fe exhibited a significantly increased ability to remove hydrogen peroxide from ROS and generate oxygen and water within the physiological pH range. In vivo experiments further confirmed the positive effect of MOF-Fe in promoting bone defect repair.ConclusionThis study supports the application of MOF-Fe as an agent for bone regeneration, particularly for mitigating ROS and activating the bone morphogenetic protein (BMP) pathway, demonstrating its potential value.

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 = 10mm) 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.

3D-printed near-infrared-light-responsive on-demand drug-delivery scaffold for bone regeneration

Although several bioactive 3D-printed bone scaffolds loaded with multiple kinds of biomolecules for enhanced bone regeneration have been recently developed, the manipulation of on-demand release profiles of different biomolecules during bone regeneration remains challenging. Herein, a 3D-printed dual-drug-loaded biomimetic scaffold to regulate the host stem cell recruitment and osteogenic differentiation in a two-stage process for bone regeneration was successfully fabricated. First, a chemotactic small-molecule drug, namely, simvastatin (SIM) was directly incorporated into the hydroxyapatite/collagen bioink for printing and could be rapidly released during the early stage of bone regeneration. Further, near-infrared (NIR)-light-responsive polydopamine-coated hydroxyapatite nanoparticles were designed to deliver the osteogenic drug, i.e., pargyline (PGL) in a controllable manner. Together, our scaffold displayed an on-demand sequential release of those two drugs and could optimize their therapeutic effects to align with the stem cell recruitment and osteoblastic differentiation, thereby promoting bone regeneration. The results confirmed the suitable mechanical strength, high photothermal conversion efficiency, good biocompatibility of our scaffold. The scaffold loaded with SIM could efficiently accelerate the migration of stem cells. In addition, the scaffold with on-demand sequential release promoted alkaline phosphatase (ALP) activity, significantly upregulated gene expression levels of osteogenesis-related markers, and enhanced new-bone-formation capabilities in rabbit cranial defect models. Altogether, this scaffold not only offers a promising strategy to control the behavior of stem cells during bone regeneration but also provides an efficient strategy for controllable sequential release of different biomolecule in bone tissue engineering.

Hierarchical Scaffold with Directional Microchannels Promotes Cell Ingrowth for Bone Regeneration.

Bone regenerative scaffolds with a bionic natural bone hierarchical porous structure provide a suitable microenvironment for cell migration and proliferation. Here, a bionic scaffold (DP-PLGA/HAp) with directional microchannels is prepared by combining 3D printing and directional freezing technology. The 3D printed framework provides structural support for new bone tissue growth, while the directional pore embedded in the scaffolds provides an express lane for cell migration and nutrition transport, facilitating cell growth and differentiation. The hierarchical porous scaffolds achieve rapid infiltration and adhesion of bone marrow mesenchymal stem cells (BMSCs) and improve the expression of osteogenesis-related genes. The rabbit cranial defect experiment presents significant new bone formation, demonstrating that DP-PLGA/HAp offers an effective means to guide cranial bone regeneration. The combination of 3D printing and directional freezing technology might be a promising strategy for developing bone regenerative biomaterials.

Polysaccharide-Based Composite Hydrogel with Hierarchical Microstructure for Enhanced Vascularization and Skull Regeneration.

Critical-size skull defects caused by trauma, infection, and tumor resection raise great demands for efficient bone substitutes. Herein, a hybrid cross-linked hierarchical microporous hydrogel scaffold (PHCLS) was successfully assembled by a multistep procedure, which involved (i) the preparation of poly(lactic-co-glycolic)/nanohydroxyapatite (PLGA-HAP) porous microspheres, (ii) embedding the spheres in a solution of dopamine-modified hyaluronic acid and collagen I (Col I) and cross-linking via dopamine polyphenols binding to (i) Col I amino groups (via Michael addition) and (ii) PLGA-HAP (via calcium ion chelation). The introduction of PLGA-HAP not only improved the diversity of pore size and pore communication inside the matrix but also greatly enhanced the compressive strength (5.24-fold, 77.5 kPa) and degradation properties to construct a more stable mechanical structure. In particular, the PHCLS (200 mg, nHAP) promoted the proliferation, infiltration, and angiogenic differentiation of bone marrow mesenchymal stem cells in vitro, as well as significant ectopic angiogenesis and mineralization with a storage modulus enhancement of 2.5-fold after 30 days. Meanwhile, the appropriate matrix microenvironment initiated angiogenesis and early osteogenesis by accelerating endogenous stem cell recruitment in situ. Together, the PHCLS allowed substantial skull reconstruction in the rabbit cranial defect model, achieving 85.2% breaking load strength and 84.5% bone volume fractions in comparison to the natural cranium, 12 weeks after implantation. Overall, this study reveals that the hierarchical microporous hydrogel scaffold provides a promising strategy for skull defect treatment.

Highly Malleable Personalized Prostheses with Hierarchical Microstructure Boost the Long‐Term Osteointegration in Irregular Craniofacial Reconstruction

AbstractThe desired clinical bone prostheses should achieve satisfactory interface integration and osteoinduction, as well as good surgical convenience. Here, a highly malleable 3D printed prosthesis with compressive strength at 13 MPa is constructed by dopamine, polyvinyl alcohol, and micro‐sized hydroxyapatite (86 wt%) as composite bioinks, which is endowed with good plasticity and can quickly match irregular defects by easily trimming. Spatially decorated collagen and hyaluronan greatly enriched the hierarchical microstructure and biological activity of malleable prosthesis. This prosthesis accelerates the proliferation and osteogenic differentiation of stem cells, regulates M2 polarization of macrophage, and promotes endogenous stem cell recruitment and early angiogenesis. Meanwhile, it significantly reinforces biomineralized deposition and vascularization, reaches full coverage of new bone in the rabbit cranial defect after 15 weeks (Φ = 10 mm), and achieves well osseointegration capacity with interfacial binding strength at 71.2% of the natural skull. This osteoinductive prosthesis provides a new design idea for bone filling.

Nanostructured 3D-Printed Hybrid Scaffold Accelerates Bone Regeneration by Photointegrating Nanohydroxyapatite.

Nanostructured biomaterials that replicate natural bone architecture are expected to facilitate bone regeneration. Here, nanohydroxyapatite (nHAp) with vinyl surface modification is acquired by silicon-based coupling agent and photointegrated with methacrylic anhydride-modified gelatin to manufacture a chemically integrated 3D-printed hybrid bone scaffold (75.6wt% solid content). This nanostructured procedure significantly increases its storage modulus by 19.43-fold (79.2kPa) to construct a more stable mechanical structure. Furthermore, biofunctional hydrogel with biomimetic extracellular matrix is anchored onto the filament of 3D-printed hybrid scaffold (HGel-g-nHAp) by polyphenol-mediated multiple chemical reactions, which contributes to initiate early osteogenesis and angiogenesis by recruiting endogenous stem cells in situ. Significant ectopic mineral deposition is also observed in subcutaneously implanted nude mice with storage modulus enhancement of 25.3-fold after 30 days. Meanwhile, HGel-g-nHAp realizes substantial bone reconstruction in the rabbit cranial defect model, achieving 61.3% breaking load strength and 73.1% bone volume fractions in comparison to natural cranium 15 weeks after implantation. This optical integration strategy of vinyl modified nHAp provides a prospective structural design for regenerative 3D-printed bone scaffold.

Covalently Grafted Biomimetic Matrix Reconstructs the Regenerative Microenvironment of the Porous Gradient Polycaprolactone Scaffold to Accelerate Bone Remodeling.

Integrating a biomimetic extracellular matrix to improve the microenvironment of 3D printing scaffolds is an emerging strategy for bone substitute design. Here, a "soft-hard" bone implant (BM-g-DPCL) consisting of a bioactive matrix chemically integrated on a polydopamine (PDA)-coated porous gradient scaffold by polyphenol groups is constructed. The PDA-coated "hard" scaffolds promoted Ca2+ chelation and mineral deposition; the "soft" bioactive matrix is beneficial to the migration, proliferation, and osteogenic differentiation of stem cells in vitro, accelerated endogenous stem cell recruitment, and initiated rapid angiogenesis in vivo. The results of the rabbit cranial defect model (Φ= 10mm) confirmed that BM-g-DPCL promoted the integration between bone tissue and implant and induced the deposition of bone matrix. Proteomics confirmed that cytokine adhesion, biomineralization, rapid vascularization, and extracellular matrix formation are major factors that accelerate bone defect healing. This strategy of highly chemically bonded soft-hard components guided the construction of the bioactive regenerative scaffold.

Dopamine‐Integrated Nanointerface between Fibrillar Matrix and Hydrophilic Nanohydroxyapatite Regulates Immune Microenvironment to Boost Endogenous Bone Regeneration

AbstractDriving endogenous bone regeneration by cell‐ and factor‐free biomaterials is the most ideal repair strategy. Herein, hybrid interleaved scaffold (HDSH) with nanosized interfacial integration is assembled by organic/inorganic interactive bonding at the nanoscale. With the help of transcriptome and proteome analysis, the regenerative mechanism of this scaffold is elaborated at the molecular level, which confirms that this strategy recreates a suitable immune microenvironment (anti‐inflammatory and M2‐polarizing) and drives functional cell and cytokine adhesion, as well as inchoate vascularization. It greatly enhances endogenous stem cell recruitment, and subsequently initiates robust vasculogenesis and osteogenesis. Significant bony reconstitution in the rabbit cranial defect model (Φ = 10 mm) is observed after 12 weeks, which realizes completely new bone coverage and 79% breaking load strength relative to the natural cranium. By enhancing nano‐sized functional interfacial integration, this strategy can provide effective guidance for developing highly bioactive bone‐regenerative implants.

3D-Printed Flat-Bone-Mimetic Bioceramic Scaffolds for Cranial Restoration.

The limitations of autologous bone grafts necessitate the development of advanced biomimetic biomaterials for efficient cranial defect restoration. The cranial bones are typical flat bones with sandwich structures, consisting of a diploe in the middle region and 2 outer compact tables. In this study, we originally developed 2 types of flat-bone-mimetic β-tricalcium phosphate bioceramic scaffolds (Gyr-Comp and Gyr-Tub) by high-precision vat-photopolymerization-based 3-dimensional printing. Both scaffolds had 2 outer layers and an inner layer with gyroid pores mimicking the diploe structure. The outer layers of Gyr-Comp scaffolds simulated the low porosity of outer tables, while those of Gyr-Tub scaffolds mimicked the tubular pore structure in the tables of flat bones. The Gyr-Comp and Gyr-Tub scaffolds possessed higher compressive strength and noticeably promoted invitro cell proliferation, osteogenic differentiation, and angiogenic activities compared with conventional scaffolds with cross-hatch structures. After implantation into rabbit cranial defects for 12 weeks, Gyr-Tub achieved the best repairing effects by accelerating the generation of bone tissues and blood vessels. This work provides an advanced strategy to prepare biomimetic biomaterials that fit the structural and functional needs of efficacious bone regeneration.

Repair of Cranial Defects in Rabbits with 3D-Printed Hydroxyapatite/Polylactic Acid Composites.

The safety and efficacy of three-dimensional- (3D-) printed hydroxyapatite/polylactic acid (HA-PLA) composites in repairing cranial defects were evaluated in a rabbit experimental model. Twelve New Zealand rabbits were selected as experimental subjects. Two holes (A and B), each with a diameter of approximately 1 cm, were made in the cranium of each rabbit. Hole A served as the experimental manipulation, and hole B served as the control manipulation. A 3D-printed HA-PLA composite was used for placement onto hole A, whereas autologous bone powder was used for placement onto hole B. Samples from the experimental holes and the control holes were collected at 30 and 90 days after surgery. The obtained materials were examined in terms of their morphologies and histopathologies and were also subjected to simultaneous hardness tests. Both the 3D-printed HA-PLA composite and autologous bone powder were able to repair and fill the cranial defects at 30 days and 90 days after surgery. At 30 days after surgery, the microhardness of the area repaired by the HA-PLA composite was lower than that of the area repaired by autogenous bone powder (p < 0.01), but neither of these treatments reached the hardness of normal bone at this time (p < 0.01). At 90 days after surgery, there was no statistically significant difference in the microhardness of the repaired area from the 3D-printed HA-PLA composite compared with that of the repaired area from autologous bone powder (p > 0.05), and there was no statistically significant difference in the hardness of the two repaired areas compared with that of the normal bone (p > 0.05). Hematoxylin-eosin staining showed that bone cells in the HA-PLA material in the experimental group grew and were arranged in an orderly manner. Bone trabeculae and marrow cavities were formed on the pore surface and inside of the HA-PLA scaffold, and the arrangement of bone trabeculae was regular. 3D-printed HA-PLA composites can induce bone regeneration, are biocompatible, have the same strength as autologous bone powder, are able to degrade, and are ultimately safe and effective for repairing cranial defects in rabbits. However, further research is needed to determine the feasibility of 3D-printed HA-PLA composites in human cranioplasty.

Development of a Novel Perfusion Rotating Wall Vessel Bioreactor with Ultrasound Stimulation for Mass-Production of Mineralized Tissue Constructs.

As stem cells are considered a promising cell source for tissue engineering, many culture strategies have been extensively studied to generate in vitro stem cell-based tissue constructs. However, most approaches using conventional tissue culture plates are limited by the lack of biological relevance in stem cell microenvironments required for neotissue formation. In this study, a novel perfusion rotating wall vessel (RWV) bioreactor was developed for mass-production of stem cell-based 3D tissue constructs. An automated RWV bioreactor was fabricated, which is capable of controlling continuous medium perfusion, highly efficient gas exchange with surrounding air, as well as low-intensity pulsed ultrasound (LIPUS) stimulation. Embryonic stem cells encapsulated in alginate/gelatin hydrogel were cultured in the osteogenic medium by using our bioreactor system. Cellular viability, growth kinetics, and osteogenesis/mineralization were thoroughly evaluated, and culture media were profiled at real time. The in vivo efficacy was examined by a rabbit cranial defect model. Our bioreactor successfully maintained the optimal culture environments for stem cell proliferation, osteogenic differentiation, and mineralized tissue formation during the culture period. The mineralized tissue constructs produced by our bioreactor demonstrated higher void filling efficacy in the large bone defects compared to the group implanted with hydrogel beads only. In addition, the LIPUS modules mounted on our bioreactor successfully reached higher mineralization of the tissue constructs compared to the groups without LIPUS stimulation. This study suggests an effective biomanufacturing strategy for mass-production of implantable mineralized tissue constructs from stem cells that could be applicable to future clinical practice.

Rabbit's cranial defect regeneration using a fine-grained ZrO2- (15 wt%)HAp ceramic implant fabricated by SPS-RS technique

ZrO2-hydroxyapatite composite bioceramics is considered to be a promising material for bone defects recovery, at the same time there are virtually no “in vivo” biotests reported for this system combining modern imaging techniques, histological studies, and blood biochemical analysis. Here we have thoroughly researched biocompatibility of high quality bioceramics based on ZrO2-(15 wt%)-hydroxyapatite composite fabricated by spark plasma sintering-reactive sintering technique. Implant's osteointegration mechanism was studied for the case of regeneration of the rabbit's cranial bone involving a complex of histological, morphometric, X-ray, and hematological techniques. Bioceramics osteointegration was shown to be efficient, proceeding through ossification of the newly formed cartilaginous tissue and bioceramics-driven bone matrix remodeling in the region of trepanation defect. Obtained results clearly show bright prospects of implementing spark plasma sintered zirconia-hydroxyapatite composite ceramics as a potential implant material for regenerative and bone-reconstructive surgery.

In vivo efficacy of low-level laser therapy on bone regeneration

In clinical use of low-level laser therapy for bone regeneration (LLLT), application protocol (dose, duration, and repetitions) has not been established. This study aimed to depict a reliable dosage of LLLT by evaluating the efficacy of different dosing of LLLT (diode) on the healing of rabbit cranial defects. Critical size defects were prepared in calvarias of 26 New Zealand White Rabbits in such each animal containing both test and control groups. Test groups were irradiated with 4Joule/cm2 (j/cm2), 6 j/cm2, and 8 j/cm2. The rabbits were subjected to six times of laser treatments in 10days. At the end of the second week, 5 rabbits were sacrificed for histopathological and immunohistochemical analyses. At the 4th and 8th weeks, 20 rabbits (10 each) were sacrificed for micro-CT and histopathological analyses. Micro-CT evaluation revealed improved new bone formation in all test groups compared to the control group. 6 j/cm2 group demonstrated the highest bone formation. The highest bone morphogenic protein -2 levels were found in the 4 j/cm2 group. Osteocalcin expression was significantly higher in 4 j/cm2 group. Our findings indicate that LLLT have a positive effect on new bone formation. The high efficacy of doses of 4 j/cm2 and 6 j/cm2 is promising to promote early bone healing.

Biomimetic reduced graphene oxide coated collagen scaffold for in situ bone regeneration

A variety of bone-related diseases and injures and limitations of traditional regeneration methods require new tissue substitutes. Tissue engineering and regeneration combined with nanomedicine can provide different natural or synthetic and combined scaffolds with bone mimicking properties for implantation in the injured area. In this study, we synthesized collagen (Col) and reduced graphene oxide coated collagen (Col-rGO) scaffolds, and we evaluated their in vitro and in vivo effects on bone tissue repair. Col and Col-rGO scaffolds were synthesized by chemical crosslinking and freeze-drying methods. The surface topography, and the mechanical and chemical properties of scaffolds were characterized, showing three-dimensional (3D) porous scaffolds and successful coating of rGO on Col. The rGO coating enhanced the mechanical strength of Col-rGO scaffolds to a greater extent than Col scaffolds by 2.8 times. Furthermore, Col-rGO scaffolds confirmed that graphene addition induced no cytotoxic effects and enhanced the viability and proliferation of human bone marrow-derived mesenchymal stem cells (hBMSCs) with 3D adherence and expansion. Finally, scaffold implantation into rabbit cranial bone defects for 12 weeks showed increased bone formation, confirmed by Hematoxylin–Eosin (H&E) and alizarin red staining. Overall, the study showed that rGO coating improves Col scaffold properties and could be a promising implant for bone injuries.

Shapable bulk agarose–gelatine–hydroxyapatite–minocycline nanocomposite fabricated using a mineralizing system aided with electrophoresis for bone tissue regeneration

To develop a shapable bulk antibacterial nanocomposite biomaterial for bone regeneration. A bulk agarose–gelatine hydrogel was mineralized using a hydrogel mineralizing system aided with electrophoresis, and the mineralized hydrogel was loaded with minocycline to obtain the agarose–gelatine–hydroxyapatite–minocycline nanocomposite. The nanocomposite had a large Brunauer–Emmett–Teller surface area of 44.4518 m2 g−1 and a high porosity of 76.9%. Hydroxyapatite crystals were well developed in the hydrogel matrix and exhibited a hybrid structure of microscale and nanoscale motifs. The addition of minocycline resulted in a continuous antibiotic release, inhibiting the growth of Staphylococcus aureus over 2 weeks in vitro. Exposed to rabbit bone marrow mesenchymal stem cells, the nanocomposite revealed good cytocompatibility in vitro. Furthermore, the biomaterial could effectively enhance the bone regeneration in a critical-size rabbit cranial defect model in vivo. These findings depicted that the nanocomposite, with good biocompatibility and good antibacterial property, is a promising candidate for future clinical application in bone tissue engineering or as a prospective bone replacement biomaterial.

Enhancement of osteoblast cells osteogenic differentiation and bone regeneration by hydroxyapatite/phosphoester modified poly(amino acid).

Hydroxyapatite/poly(amino acid) (HA/PAA) has been used to treat a variety of long bone and vertebral bony defects, and a further biocompatibility improvement is a key for better application. Phosphoester (PE) contained materials are highly biocompatible but could hardly treat massive bone defects due to its fast-degradation-derived mechanical instability. To address the problems of the two materials, we have incorporated PE molecule into the main chain of PAA by chemical bonding. As a result, the compressive strength of HA/PAA with 1wt% and 2.5wt% PE maintained in the range of 80-150MPa after soaking in PBS for 12weeks, which could be attributed to the amplified hydrogen-bonding inside composites. Besides, the PE-containing HA/PAAs with increased hydrophilic function groups (O=P-O bonds and O=P-N), created a more favourable surface for cell adhesion. Meanwhile, compared with HA/PAA, the PE-containing HA/PAAs had a fast minerlization speed and promoted cell osteogenic differentiation. Furthermore, the in vivo study indicated that PE-containing HA/PAAs could facilitate bone formation (4weeks), and form a complete bone bridging (12weeks) in a rabbit cranial bone defect. In summary, the HA/PE-m-PAAs possessed good mechanical stability, improved cytocompatibility and osteoconductivity, so the composites have a great potential for massive bone defect treatment.