Hydroxyapatite Composite Scaffolds Research Articles

Nanomechanical mapping of PLA hydroxyapatite composite scaffolds links surface homogeneity to stem cell differentiation

Polymer composite scaffolds hold promise in bone tissue engineering due to their biocompatibility, mechanical properties, and reproducibility. Among these materials, polylactic acid (PLA), a biodegradable plastics has gained attention for its processability characteristics. However, a deeper understanding of how PLA scaffold surface properties influence cell behavior is enssential for advancing its applications. In this study, 3D-printed PLA scaffolds containing hydroxyapatite (HA) were analyzed using atomic force microscopy and nanomechanical mapping. The addition of HA significantly increased key surface properties compared to unmodified PLA scaffols. Notably, the HA-modified scaffold demonstrated Gaussian distribution of stiffness and adhesive forces, in contrast to the bimodal properties observed in the unmodified PLA scaffolds. Human adipose-derived mesenchymal stem cell (hADMSC) seeded on the 3D-printed PLA scaffolds blended with 10% HA (P10) exhibited strong attachment. After four weeks, osteogenic differentiation of hADMSCs was detected, with calcium deposition reaching 6.76% ± 0.12. These results suggest that specific ranges of stiffness and adhesive forces of the composite scaffold can support cell attachement, and mineralization. The study highlights that tailoring suface properties of composite scaffolds is crucial for modulating cellular interactions, thus advancing the development of effective bone replacement materials.

3D-Bioprinted Gelatin Methacryloyl-Strontium-Doped Hydroxyapatite Composite Hydrogels Scaffolds for Bone Tissue Regeneration.

New gelatin methacryloyl (GelMA)-strontium-doped nanosize hydroxyapatite (SrHA) composite hydrogel scaffolds were developed using UV photo-crosslinking and 3D printing for bone tissue regeneration, with the controlled delivery capacity of strontium (Sr). While Sr is an effective anti-osteoporotic agent with both anti-resorptive and anabolic properties, it has several important side effects when systemic administration is applied. Multi-layer composite scaffolds for bone tissue regeneration were developed based on the digital light processing (DLP) 3D printing technique through the photopolymerization of GelMA. The chemical, morphological, and biocompatibility properties of these scaffolds were investigated. The composite gels were shown to be suitable for 3D printing. In vitro cell culture showed that osteoblasts can adhere and proliferate on the surface of the hydrogel, indicating that the GelMA-SrHA hydrogel has good cell viability and biocompatibility. The GelMA-SrHA composites are promising 3D-printed scaffolds for bone repair.

Effect of Nanoceria Suspension Addition on the Physicochemical and Mechanical Properties of Hybrid Organic-Inorganic Hydroxyapatite Composite Scaffolds.

In the current study, the synthesis of hydroxyapatite-ceria (HAP-CeO2) scaffolds is attempted through a bioinspired chemical approach. The utilized colloidal CeO2 suspension presents antifungal activity against the Aspergillus flavus and Aspergillus fumigatus species at concentrations higher than 86.1 ppm. Three different series of the composite HAP-CeO2 suspensions are produced, which are differentiated based on the precursor suspension to which the CeO2 suspension is added and by whether this addition takes place before or after the formation of the hydroxyapatite phase. Each of the series consists of three suspensions, in which the pure ceria weight reaches 4, 5, and 10% (by mass) of the produced hydroxyapatite, respectively. The characterization showed that the 2S series's specimens present the greater alteration towards their viscoelastic properties. Furthermore, the 2S series's sample with 4% CeO2 presents the best mechanical response. This is due to the growth of needle-like HAP crystals during lyophilization, which-when oriented perpendicular to the direction of stress application-enhance the resistance of the sample to deformation. The 2S series's scaffolds had an average pore size equal to 100 μm and minimum open porosity 89.5% while simultaneously presented the lowest dissolution rate in phosphate buffered saline.

Development and Evaluation of 3D-Printed PLA/PHA/PHB/HA Composite Scaffolds for Enhanced Tissue-Engineering Applications

Recently, tissue engineering has been revolutionised by the development of 3D-printed scaffolds, which allow one to construct a precise architecture with tailored properties. In this study, three different composite materials were synthesised using a combination of polylactic acid (PLA), polyhydroxyalkanoates (PHA), poly(3-hydroxybutyrate) (PHB) and hydroxyapatite (HA) in varying weight percentages. Morphological properties were evaluated by scanning electron microscopy showing a uniform distribution of HA particles throughout the matrix, indicating good compatibility between the materials. Furthermore, the printed scaffolds were tested under pressure using a load cell to examine mechanical strength. Scanning electron microscopy (SEM) analysis showed favorable dispersion, biological compatibility together with enhanced bioactivity within the PHB/PHA/PLA/HA composite matrixes. Thus, this paper demonstrates the successful design and implementation of these composite structures for tissue-engineering applications and highlights the effective development of biocompatible scaffold designs with improved functionality.

3D-Printed Biomimetic Hydroxyapatite Composite Scaffold Loaded with Curculigoside for Rat Cranial Defect Repair.

The treatment of various large bone defects has remained a challenge for orthopedic surgeons for a long time. Recent research indicates that curculigoside (CUR) extracted from the curculigo plant exerts a positive influence on bone formation, contributing to fracture healing. In this study, we employed emulsification/solvent evaporation techniques to successfully fabricate poly(ε-caprolactone) nanoparticles loaded with curculigoside (CUR@PM). Subsequently, using three-dimensional (3D) printing technology, we successfully developed a bioinspired composite scaffold named HA/GEL/SA/CUR@PM (HGSC), chemically cross-linked with calcium chloride, to ensure scaffold stability. Further characterization of the scaffold's physical and chemical properties revealed uniform pore size, good hydrophilicity, and appropriate mechanical properties while achieving sustained drug release for up to 12 days. In vitro experiments demonstrated the nontoxicity, good biocompatibility, and cell proliferative properties of HGSC. Through alkaline phosphatase (ALP) staining, Alizarin Red S (ARS) staining, cell migration assays, tube formation assays, and detection of angiogenic and osteogenic gene proteins, we confirmed the HGSC composite scaffold's significant angiogenic and osteoinductive capabilities. Eight weeks postimplantation in rat cranial defects, Micro-computed tomography (CT) and histological observations revealed pronounced angiogenesis and new bone growth in areas treated with the HGSC composite scaffold. These findings underscore the scaffold's exceptional angiogenic and osteogenic properties, providing a solid theoretical basis for clinical bone repair and demonstrating its potential in promoting vascularization and bone regeneration.

A 3D-printed PLGA/HA composite scaffold modified with fusion peptides to enhance its antibacterial, osteogenic and angiogenic properties in bone defect repair

Scaffold materials, seed cells and growth factors are referred to as the three elements of bone tissue engineering (BTE). However, the physical properties and biocompatibility of these scaffolds and the safety and cost of their growth factors limit their clinical application. Therefore, it is critical to develop a novel scaffold modified with efficient growth factors that meets the requirements of BTE. Herein, 3D-printed poly (lactic-co-glycolic acid)/hydroxyapatite (PLGA/HA) composite scaffolds modified with new fusion peptides, which can effectively promote the regeneration and repair of bone defects, were developed. 3D-printed PLGA/HA composite scaffolds with appropriate HA contents were prepared and had appropriate mechanical properties. In addition, the surface of the 3D-printed PLGA/HA composite scaffold was modified with new fusion peptides to provide osteogenic, antimicrobial, and angiogenesis-promoting effects. In vitro experiments showed that the fusion peptide-modified scaffolds had good biocompatibility and a certain degree of antibacterial activity. Moreover, the fusion peptide-modified scaffolds significantly improved the migration ability of BMSCs and Ea.hy926 cells, promoted the expression of osteogenesis-related factors (BMP2, RUNX2, ALP, OPN) in BMSCs, and promoted the expression of angiogenesis-related factors (VEGF and HIF-1α) in Ea.hy926 cells. In vivo experiments showed that the fusion peptide-modified scaffolds had good osteogenic ability. This study reveals considerable application potential for bone defect repair and provides a new option of scaffold material for BTE.

A Gellan Gum, Polyethylene Glycol, Hydroxyapatite Composite Scaffold with the Addition of Ginseng Derived Compound K with Possible Applications in Bone Regeneration.

Engineered bone scaffolds should mimic the natural material to promote cell adhesion and regeneration. For this reason, natural biopolymers are becoming a gold standard in scaffold production. In this study, we proposed a hybrid scaffold produced using gellan gum, hydroxyapatite, and Poly (ethylene glycol) within the addition of the ginseng compound K (CK) as a candidate for bone regeneration. The fabricated scaffold was physiochemically characterized. The morphology studied by scanning electron microscopy (SEM) and image analysis revealed a pore distribution suitable for cells growth. The addition of CK further improved the biological activity of the hybrid scaffold as demonstrated by the MTT assay. The addition of CK influenced the scaffold morphology, decreasing the mean pore diameter. These findings can potentially help the development of a new generation of hybrid scaffolds to best mimic the natural tissue.

Influence of size and crystallinity of nanohydroxyapatite (nHA) particles on the properties of Polylactic Acid/nHA nanocomposite scaffolds produced by 3D printing

Polylactic acid (PLA) and hydroxyapatite (HA) composite scaffolds have been widely studied for applications in bone tissue engineering (BTE) due to their bioactive and biocompatible properties. However, there is a need for more knowledge about the influence of size and crystallinity of HA nanoparticles (nHA) on the properties of PLA/nHA nanocomposite scaffolds produced by 3D printing. In this study, 3D printing was used to produce PLA nanocomposite scaffolds incorporated with nHA filler with different particle sizes and crystallinities. Initially, the nanocomposites were prepared by casting for 3D printing of scaffolds, which were characterized by analysis of thermal, morphological, physical-chemical, mechanical, and biological properties in vitro. The results showed that the size and crystallinity of nHA particles mainly influenced the scaffolds' mechanical properties, degradation rate, and bioactivity. Incorporating nHA provided a gain in compressive strength compared to pure PLA, superior to natural cancellous bone, which varies between 2 and 12 MPa. The lower crystallinity, 39.46 %, promoted a higher rate of degradation and bioactivity in vitro due to its solubility in the simulated fluid. All nanocomposite scaffolds showed cell viability above 90 %. The scaffolds showed suitable properties for BTE applications.

In Vitro Studies on 3D-Printed PLA/HA/GNP Structures for Bone Tissue Regeneration.

The successful regeneration of large-size bone defects remains one of the most critical challenges faced in orthopaedics. Recently, 3D printing technology has been widely used to fabricate reliable, reproducible and economically affordable scaffolds with specifically designed shapes and porosity, capable of providing sufficient biomimetic cues for a desired cellular behaviour. Natural or synthetic polymers reinforced with active bioceramics and/or graphene derivatives have demonstrated adequate mechanical properties and a proper cellular response, attracting the attention of researchers in the bone regeneration field. In the present work, 3D-printed graphene nanoplatelet (GNP)-reinforced polylactic acid (PLA)/hydroxyapatite (HA) composite scaffolds were fabricated using the fused deposition modelling (FDM) technique. The in vitro response of the MC3T3-E1 pre-osteoblasts and RAW 264.7 macrophages revealed that these newly designed scaffolds exhibited various survival rates and a sustained proliferation. Moreover, as expected, the addition of HA into the PLA matrix contributed to mimicking a bone extracellular matrix, leading to positive effects on the pre-osteoblast osteogenic differentiation. In addition, a limited inflammatory response was also observed. Overall, the results suggest the great potential of the newly developed 3D-printed composite materials as suitable candidates for bone tissue engineering applications.

Fabrication and Characterization of a Polydopamine-Modified Bacterial Cellulose and Sugarcane Filter Cake-Derived Hydroxyapatite Composite Scaffold.

The search for environmentally friendly and sustainable sources of raw materials has been ongoing for quite a while, and currently, the utilization and applications of agro-industrial biomass residues in biomedicine are being researched. In this study, a polydopamine (PDA)-modified bacterial cellulose (BC) and hydroxyapatite (HA) composite scaffold was fabricated using the freeze-drying method. The as-prepared hydroxyapatite was synthesized via the chemical precipitation method using sugarcane filter cake as a calcium source, as reported in a previous study. X-ray diffraction analysis revealed a carbonated phase of the prepared hydroxyapatite, similar to that of the natural bone mineral. Wide-angle X-ray scattering analysis revealed the successful fabrication of BC/HA composite scaffolds, while X-ray photoelectron spectroscopy suggested that PDA was deposited on the surface of the BC/HA composite scaffolds. In vitro cell viability assays indicated that BC/HA and PDA-modified composite scaffolds did not induce cytotoxicity and were biocompatible with MC3T3-E1 preosteoblasts. PDA-modified composite scaffolds showed enhanced protein adsorption capacity in vitro compared to the unmodified scaffolds. On a concluding note, these results demonstrate that agro-industrial biomass residues have the potential to be used in biomedical applications and that PDA-modified BC/HA composite scaffolds are a promising biomaterial for bone tissue engineering.

Evaluation of human amnion denuded derived mesenchymal stem cell on 3D porous hydroxyapatite composite scaffolds for osteogenic differentiation: Prolonged in vitro study

Recent studies using composite porous scaffolds have globally demonstrated the biocompatibility of mesenchymal stem cell sources. It is especially important in hard tissue bioengineering due to its desirable features and stemness effectivity. This study has emphasized primarily the evaluation of the morphological aspects of human amnion-denuded derived mesenchymal stem cells (hAMMSC) in combination with the fabrication of three-dimensional (3D) porous hydroxyapatite (Hap) composite scaffolds for bone tissue engineering based on the principal component of bone mineralization. We presented a novel combination of hAMMSC and nano-crystalline powder hydroxyapatite/bioactive glass (Hap/BG) composite scaffolds fabricated through the hydrothermal method via a novel formulation method from a previous study of stem cell in vitro prolonged culture. The 3D porous scaffold, 6 mm in size, was fabricated from 70 nm nanocrystalline powder and interacted with hAMMSC cultured in osteo-inductive conditions for 30 days. The characterization of 3D porous scaffolds was analyzed via Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) to explore the particle structure, morphology, bioactivity, and porosity of the composite powder and scaffolds in contact with hAMMSCs culture. Furthermore, biocompatibility was assessed using the PrestoBlueTM viability assay and scanning electron microscopy observation (SEM), which revealed the attachment, morphology, and spreading of hAMMSCs on the 3D porous scaffolds of Hap/BG by showing spindle-like morphology and forming the spreading filopodia bridge-like structure within the scaffolds. Subsequently, the secondary objective is the characterization of human AMMSC differentiation capacity assessed by early osteoblast differentiation and mineralization behaviour investigated by early detected assay via alkaline phosphatase activity (ALP) activity marker and energy dispersive X-ray (EDX) analysis simultaneously of the mineralization within bone matrix elements. It was comparatively evaluated via ALP and EDX for calcium quantification elements. Immunomodulatory properties were analyzed via ELISA kits. In conclusion, our findings indicate that 3D porous scaffolds made of Hap/BG composites could be great candidates for future regenerative medicine applications due to their support towards stem cell growth and enhancement of bone cell capacity.

The compressive strength and static biodegradation rate of chitosan-gelatin limestone-based carbonate hydroxyapatite composite scaffold

Background: One of the main components in tissue engineering is the scaffold, which may serve as a medium to support cell and tissue growth. Scaffolds must have good compressive strength and controlled biodegradability to show biological activities while treating bone defects. This study uses Chitosan-gelatin (C–G) with good flexibility and elasticity and high-strength carbonate hydroxyapatite (CHA), which may be the ideal scaffold for tissue engineering. Purpose: To analyze the compressive strength and static biodegradation rate within various ratios of C–G and CHA (C–G:CHA) scaffold as a requirement for bone tissue engineering. Methods: The scaffold is synthesized from C–G:CHA with three ratio variations, which are 40:60, 30:70, and 20:80 (weight for weight [w/w]), made with a freeze-drying method. The compressive strengths are then tested. The biodegradation rate is tested by soaking the scaffold in simulated body fluid for 1, 3, 7, 14, and 21 days. Data are analyzed with a one-way ANOVA parametric test. Results: The compressive strength of each ratio of C–G:CHA scaffold 40:60 (w/w), 30:70 (w/w), and 20:80 (w/w), consecutively, are 4.2 Megapascals (MPa), 3.3 MPa, 2.2 MPa, and there are no significant differences with the p= 0.069 (p>0.05). The static biodegradation percentage after 21 days on each ratio variation of C–G:CHA scaffold 40:60 (w/w), 30:70 (w/w), and 20:80 (w/w) is 25.98%, 24.67%, and 20.64%. One-way ANOVA Welch test shows the result of the p-value as p<0.05. Conclusion: The compressive strength and static biodegradation of the C–G:CHA scaffold with ratio variations of 40:60 (w/w), 30:70 (w/w), and 20:80(w/w) fulfilled the requirements as a scaffold for bone tissue engineering.

A Novel Porous Butyryl Chitin-Animal Derived Hydroxyapatite Composite Scaffold for Cranial Bone Defect Repair.

Bone defects, a common orthopedic problem in clinical practice, are a serious threat to human health. As alternative materials to autologous bone grafts, synthetic cell-free functionalized scaffolds have been the focus of recent research in designing scaffolds for bone tissue engineering. Butyryl chitin (BC) is a derivative of chitin (CT) with improved solubility. It has good biocompatibility, but few studies have investigated its use in bone repair. In this study, BC was successfully synthesized with a degree of substitution of 2.1. BC films were prepared using the cast film method and showed strong tensile strength (47.8 ± 4.54 N) and hydrophobicity (86.4 ± 2.46°), which was favorable for mineral deposition. An in vitro cytological assay confirmed the excellent cell attachment and cytocompatibility of the BC film; meanwhile, in vivo degradation indicated the good biocompatibility of BC. Hydroxyapatite (HA), extracted from bovine cancellous bone, had good cytocompatibility and osteogenic induction activity for the mouse osteoblast cell line MC3T3-E1. With the aim of combining the advantages of BC and HA, a BC-HA composite scaffold, with a good pore structure and mechanical strength, was prepared by physical mixing. Administered into skull defects of rats, the scaffolds showed perfect bone-binding performance and effective structural support, and significantly promoted the regeneration of new bone. These results prove that the BC-HA porous scaffold is a successful bone tissue engineering scaffold and has strong potential to be further developed as a substitute for bone transplantation.

Biofabrication of Poly(aryletherketone)‐Hydroxyapatite Composite Scaffolds via Low‐Temperature Printing

AbstractInorganic nanoparticles doped into polymer can improve osteogenesis through structural and biological cues. However, the composite implants may be unsatisfactory partly due to the high surface energy of nanoparticles contributing to aggregation and inhomogeneity, resulting in impaired properties. Herein, poly(aryletherketone) bearing carboxyl groups (PAEK‐COOH) is synthesized, and fabricated to composites with nanohydroxyapatite (nHA) via chemical binding. The composites can be formulated to homogeneous and stable bioinks in solution, and the bioinks are fabricated to porous scaffolds via low‐temperature printing, avoiding high‐temperature damage to chemical integrations and bioactive factors. The composite scaffolds present uniform distribution of elements on the surface and mechanical properties are well‐matched with those of trabecular bone. The in vitro experiments show that the addition of nHA is conducive to promote cellular proliferation and induce osteogenic differentiation of cells. Therefore, this work develops a method to prepare uniform composites, and the composite scaffolds have the potential to be used in orthopedic applications.

Gentamicin-loaded polyvinyl alcohol/whey protein isolate/hydroxyapatite 3D composite scaffolds with drug delivery capability for bone tissue engineering applications

Bone defects caused by diseases such as bone diseases, tumours, and traumas negatively affect the lives of millions of people around the world. Bone tissue engineering offers a new approach to repairing bone defects. Here, a novel bioactive Polyvinyl alcohol (PVA)/ Whey protein isolate (WPI)/ Hydroxyapatite (HA) composite scaffolds with Gentamicin (GEN)-loaded at varying rates were successfully fabricated by 3D printing technology. The strong interaction between PVA, WPI, HA, and GEN were proved with Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). When the scanning electron microscopy (SEM) images of the produced 3D composite scaffolds were evaluated, it can be said that 3D composite scaffolds with the desired porosity and structure for bone tissue engineering applications were obtained. The 3D PVA/WPI/HA/12GEN composite scaffold was fabricated excellently with its 675 µm pore size. Compression tests revealed that the 3D composite scaffold had a compressive strength of 1.28–1.22 MPa and strain of % 12.89–8.70 and thus met the mechanical desirables of human trabecular bone. Moreover, the compressive strength and strain values of the scaffolds were decreased slightly due to adding the GEN drug. According to the Differential scanning calorimetry (DSC) analysis, it was determined that the highly crystalline structure of PVA was disrupted by adding GEN to the composite scaffolds. It was also observed that the addition of GEN to the scaffold did not significantly affect the swelling and degradation behaviour, and the scaffolds degraded by approximately 55% on the 10th day. The scaffolds exhibited a controlled release profile up to 240 and 264 h and were released with the Korsmeyer-Peppas kinetic model according to the highest correlation number. Cell analysis revealed that biocompatible structures were produced, and osteoblasts formed filopodia extensions, resulting in healthy cell attachment. According to these results, 3D GEN-loaded PVA/WPI/HA composite scaffolds may be a promising innovation for bone defect repair in bone tissue engineering applications.

The Characteristics, Swelling Ratio and Water Content Percentage of Chitosan-gelatin/limestone-based Carbonate Hydroxyapatite Composite Scaffold

The tissue engineering field has developed a scaffold that can be used to increase the bone regeneration process. Carbonate hydroxyapatite (CHA) is a well-known scaffold due to its human bones resembling components. The scaffold was synthesized from K, G, and limestone-based CHA using a freeze-drying method with K-G/CHA ratios (w/w) of 40:60, 30:70, 20:80, and 10:90. A Fourier transform infrared spectroscopy (FTIR), a scanning electron microscope-energy dispersive X-ray (SEM-EDX), and X-ray diffraction (XRD) were used to characterize the scaffold. The FTIR test showed some functional groups, such as hydroxyl, amide I, amide II, carbonate, and phosphate. The SEM-EDX test showed micropore (<50 um) and macropores (>50 um) structures as well as elements of C, N, O, Mg, Al, Si, P, and Ca. The XRD analysis obtained crystalline and amorphous particles. The water content percentage (WCP) values obtained were 61.29%, 64.30%, 67.71%, and 67.78%. The K-G/CHA composite scaffold with a ratio of 30:70 has ideal characteristics, a swelling ratio, and a water content percentage.

Preparation of gamma poly-glutamic acid/hydroxyapatite/collagen composite as the 3D-printing scaffold for bone tissue engineering

BackgroundAll types of movements involve the role of articular cartilage and bones. The presence of cartilage enables bones to move over one another smoothly. However, repetitive microtrauma and ischemia as well as genetic effects can cause an osteochondral lesion. Numerous treatment methods such as microfracture surgergy, autograft, and allograft, have been used, however, it possesses treatment challenges including prolonged recovery time after surgery and poses a financial burden on patients. Nowadays, various tissue engineering approaches have been developed to repair bone and osteochondral defects using biomaterial implants to induce the regeneration of stem cells. MethodsIn this study, a collagen (Col)/γ-polyglutamate acid (PGA)/hydroxyapatite (HA) composite scaffold was fabricated using a 3D printing technique. A Col/γ-PGA/HA 2D membrane was also fabricated for comparison. The scaffolds (four layers) were designed with the size of 8 mm in diameter and 1.2 mm in thickness. The first layer was HA/γ-PGA and the second to fourth layers were Col/γ-PGA. In addition, a 2D membrane was constructed from hydroxyapatite/γ-PGA and collagen/γ-PGA with a ratio of 1:3. The biocompatibility property and degradation activity were investigated for both scaffold and membrane samples. Rat bone marrow mesenchymal stem cells (rBMSCs) and human adipose-derived stem cells (hADSCs) were cultured on the samples and were tested in-vitro to evaluate cell attachment, proliferation, and differentiation. In-vivo experiments were performed in the rat and nude mice models.ResultsIn-vitro and in-vivo results show that the developed scaffold is of well biodegradation and biocompatible properties, and the Col-HA scaffold enhances the mechanical properties for osteochondrogenesis in both in-vitro and animal trials.ConclusionsThe composite would be a great biomaterial application for bone and osteochondral regeneration.

Anisotropic silk nanofiber layers as regulators of angiogenesis for optimized bone regeneration.

Osteogenesis-angiogenesis coupling processes play a crucial role in bone regeneration. Here, electric field induced aligned nanofiber layers with tunable thickness were coated on the surface of pore walls inside the deferoxamine (DFO)-laden silk fibroin (SF) and hydroxyapatite (HA) composite scaffolds to regulate the release of DFO to control vascularization dynamically. Longer electric field treatments resulted in gradually thickening layers to reduce the release rate of DFO where the released amount of DFO decreased gradually from 84% to 63% after 28 days. Besides the osteogenic capacity of HA, the changeable release of DFO brought different angiogenic behaviors in bone regeneration process, which provided a desirable niche with osteogenic and angiogenic cues. Anisotropic cues were introduced to facilitate cell migration inside the scaffolds. Changeable cytokine secretion from endothelial cells cultured in the different scaffolds revealed the regulation of cell responses related to vascularization in vitro. Peak expression of angiogenic factors appeared at days 7, 21 and 35 for endothelial cells cultured in the scaffolds with different silk nanofier layers, suggesting the dynamical regulation of angiogenesis. Although all of the scaffolds had the same silk and HA composition, in vitro cell studies indicated different osteogenic capacities for the scaffolds, suggesting that the regulation of DFO release also influenced osteogenesis outcomes in vitro. In vivo, the best bone regeneration occurred in defects treated with the composite scaffolds that exhibited the best osteogenic capacity in vitro. Using a rat bone defect model, healing was achieved within 12 weeks, superior to those treated with previous SF-HA composite matrices. Controlling angiogenic properties of bone biomaterials dynamically is an effective strategy to improve bone regeneration capacity.

A collagen(Col)/nano-hydroxyapatite (nHA) biological composite bone scaffold with double multi-level interface reinforcement

Bone scaffold is expected to possess excellent mechanical and biological properties similar to natural bone tissues. In this study, we aimed to prepare a biomineralized Col and hydroxyapatite composite scaffold consisting of biomimetic bone components and multi-level bionic bone structure to strengthen its mechanical properties. We prepared a Col/nano-hydroxyapatite biological composite scaffold with multi-level structure (from nanofibers to micron bionic bone motif to bionc bone scaffold) of biomimetic bone tissue, and biomineralized the scaffold in simulated body fluid (SBF) preheated to 37 °C. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Scanning electron microscope, were used to characterize the biomineralized products. Morphological study confirmed in situ deposition of nHA in the multi-scale hierarchical structure of the biomineralized scaffold. We explored the biomineralization nucleation mechanism of the scaffolds at the atomic level based on the first principles and the mechanisms for growth of mineralized nHA crystal array in its multi-scale structure, and how the double multiscales structure strengthened the mechanical properties of the material. This synthetic bone scaffold, with bionic bone composition and double multi-level interface reinforcement, provides a new strategy for synthesizing bioactive bone scaffolds with enhanced biomechanical properties.

3D printing of bioactive macro/microporous continuous carbon fibre reinforced hydroxyapatite composite scaffolds with synchronously enhanced strength and toughness

Continuous carbon fibre (CF) reinforced HA (CF/HA) composite scaffolds were prepared using a self-designed and manufactured 3D printer. The optimised design of nozzle structure and the tailored viscoelastic property of HA inks ensured compound extrusion of monofilament and multifilament CF with HA rod. The composite scaffolds designed using the CAD programme and sintered via a suitable process exhibited a hierarchical macro/microporous structure and contained approximately 50% HA and 50% β-TCP. The continuous CF synchronously enhanced the strength and toughness of the scaffolds. The compressive strengths of 1CF/HA and 5CF/HA were 11.4 ± 1.7 MPa and 16.3 ± 2.6 MPa, respectively, which were approximately double and triple compared with that of HA scaffolds. The fracture toughness of 1CF/HA was approximately double that of HA scaffolds and close to that of cortical bone. In vitro and in vivo studies demonstrated that 1CF/HA also had apatite formation capability and adequate bone regeneration capacity.