Load-bearing Bone Defects Research Articles

Construction of multileveled and oriented micro/nano channels in Mg doped hydroxyapitite bioceramics and their effect on mimicking mechanical property of cortical bone and biological performance of cancellous bone

Drawing on the structure and components of natural bone, this study developed Mg-doped hydroxyapatite (Mg-HA) bioceramics, characterized by multileveled and oriented micro/nano channels. These channels play a critical role in ensuring both mechanical and biological properties, making bioceramics suitable for various bone defects, particularly those bearing loads. Bioceramics feature uniformly distributed nanogrooves along the microchannels. The compressive strength or fracture toughness of the Mg-HA bioceramics with micro/nano channels formed by single carbon nanotube/carbon fiber (CNT/CF) (Mg-HA(05-CNT/CF)) are comparable to those of cortical bone, attributed to a combination of strengthened compact walls and microchannels, along with a toughening mechanism involving crack pinning and deflection at nanogroove intersections. The introduction of uniform nanogrooves also enhanced the porosity by 35.4 %, while maintaining high permeability owing to the capillary action in the oriented channels. This leads to superior degradation properties, protein adsorption, and in vivo osteogenesis compared with bioceramics with only microchannels. Mg-HA(05-CNT/CF) exhibited not only high strength and toughness comparable to cortical bone, but also permeability similar to cancellous bone, enhanced cell activity, and excellent osteogenic properties. This study presents a novel approach to address the global challenge of applying HA-based bioceramics to load-bearing bone defects, potentially revolutionizing their application in tissue engineering.

A novel porous titanium with engineered surface for bone defect repair in load-bearing position.

Porous titanium exhibits low elastic modulus and porous structure is thought to be a promising implant in bone defect repair. However, the bioinert and low mechanical strength of porous titanium have limited its clinical application, especially in load-bearing bone defect repair. Our previous study has reported an infiltration casting and acid corrosion (IC-AC) method to fabricate a novel porous titanium (pTi) with 40% porosity and 0.4 mm pore diameter, which exerts mechanical property matching with cortical bone and interconnected channels. In this study, we introduced a nanoporous coating and incorporated an osteogenic element strontium (Sr) on the surface of porous titanium (named as Sr-micro arch oxidation [MAO]) to improve the osteogenic ability of the pTi by MAO. Better biocompatibility of Sr-MAO was verified by cell adhesion experiment and cell counting kit-8 (CCK-8) test. The in vitro osteogenic-related tests such as immunofluorescence staining, alkaline phosphatase staining and real-time polymerase chain reaction (RT-PCR) demonstrated better osteogenic ability of Sr-MAO. Femoral bone defect repair model was employed to evaluate the osseointegration of samples in vivo. Results of micro-CT scanning, sequential fluorochrome labeling and Van Gieson staining suggested that Sr-MAO showed better in vivo osteogenic ability than other groups. Taking results of both in vitro and in vivo experiment together, this study indicated the Sr-MAO porous titanium could be a promising implant load-bearing bone defect.

Strontium-loaded 3D intramedullary nail titanium implant for critical-sized femoral defect in rabbits.

The treatment of critical-sized bone defects has long been a major problem for surgeons. In this study, an intramedullary nail shaped three-dimensional (3D)-printed porous titanium implant that is capable of releasing strontium ions was developed through a simple and cost-effective surface modification technique. The feasibility of this implant as a stand-alone solution was evaluated using a rabbit's segmental diaphyseal as a defect model. The strontium-loaded implant exhibited a favorable environment for cell adhesion, and mechanical properties that were commensurate with those of a rabbit's cortical bone. Radiographic, biomechanical, and histological analyses revealed a significantly higher amount of bone ingrowth and superior bone-bonding strength in the strontium-loaded implant when compared to an untreated porous titanium implant. Furthermore, one-year histological observations revealed that the strontium-loaded implant preserved the native-like diaphyseal bone structure without failure. These findings suggest that strontium-releasing 3D-printed titanium implants have the clinical potential to induce the early and efficient repair of critical-sized, load-bearing bone defects.

3D-Printed Personalized Lattice Implant as an Innovative Strategy to Reconstruct Geographic Defects in Load-Bearing Bones.

Geographic defect reconstruction in load-bearing bones presents formidable challenges for orthopaedic surgeon. The use of 3D-printed personalized implants presents a compelling opportunity to address this issue. This study aims to design, manufacture, and evaluate 3D-printed personalized implants with irregular lattice porous structures for geographic defect reconstruction in load-bearing bones, focusing on feasibility, osseointegration, and patient outcomes. This retrospective study involved seven patients who received 3D-printed personalized lattice implants for the reconstruction of geographic defects in load-bearing bones. Personalized implants were customized for each patient. Randomized dodecahedron unit cells were incorporated within the implants to create the porous structure. The pore size and porosity were analyzed. Patient outcomes were assessed through a combination of clinical and radiological evaluations. Tomosynthesis-Shimadzu metal artifact reduction technology (T-SMART) was utilized to evaluate osseointegration. Functional outcomes were assessed according to the Musculoskeletal Tumor Society (MSTS) 93 score. Multiple pore sizes were observed in porous structures of the implant, with a wide distribution range (approximately 300-900 um). The porosity analysis results showed that the average porosity of irregular porous structures was around 75.03%. The average follow-up time was 38.4 months, ranging from 25 to 50 months. Postoperative X-rays showed that the implants matched the geographic bone defect well. Osseointegration assessments according to T-SMART images indicated a high degree of bone-to-implant contact, along with favorable bone density around the implants. Patient outcomes assessments revealed significant improvements in functional outcomes, with the average MSTS score of 27.3 (range, 26-29). There was no implant-related complication, such as aseptic loosening or structure failure. 3D-printed personalized lattice implants offer an innovative and promising strategy for geographic defect reconstruction in load-bearing bones. This approach has the potential to match the unique contours and geometry of the geographic bone defect and facilitate osteointegration.

Meticulously engineered three-dimensional-printed scaffold with microarchitecture and controlled peptide release for enhanced bone regeneration.

The repair of large load-bearing bone defects requires superior mechanical strength, a feat that a single hydrogel scaffold cannot achieve. The objective is to seamlessly integrate optimal microarchitecture, mechanical robustness, vascularisation, and osteoinductive biological responses to effectively address these critical load-bearing bone defects. To confront this challenge, three-dimensional (3D) printing technology was employed to prepare a polycaprolactone (PCL)-based integrated scaffold. Within the voids of 3D printed PCL scaffold, a methacrylate gelatin (GelMA)/methacrylated silk fibroin (SFMA) composite hydrogel incorporated with parathyroid hormone (PTH) peptide-loaded mesoporous silica nanoparticles (PTH@MSNs) was embedded, evolving into a porous PTH@MSNs/GelMA/SFMA/PCL (PM@GS/PCL) scaffold. The feasibility of fabricating this functional scaffold with a customised hierarchical structure was confirmed through meticulous chemical and physical characterisation. Compression testing unveiled an impressive strength of 17.81 ± 0.83 MPa for the composite scaffold. Additionally, in vitro angiogenesis potential of PM@GS/PCL scaffold was evaluated through Transwell and tube formation assays using human umbilical vein endothelium, revealing the superior cell migration and tube network formation. The alizarin red and alkaline phosphatase staining assays using bone marrow-derived mesenchymal stem cells clearly illustrated robust osteogenic differentiation properties within this scaffold. Furthermore, the bone repair potential of the scaffold was investigated on a rat femoral defect model using micro-computed tomography and histological examination, demonstrating enhanced osteogenic and angiogenic performance. This study presents a promising strategy for fabricating a microenvironment-matched composite scaffold for bone tissue engineering, providing a potential solution for effective bone defect repair.

Design and development of 3D printed shape memory triphasic polymer-ceramic bioactive scaffolds for bone tissue engineering.

Scaffolds for bone tissue engineering require considerable mechanical strength to repair damaged bone defects. In this study, we designed and developed mechanically competent composite shape memory triphasic bone scaffolds using fused filament fabrication (FFF) three dimensional (3D) printing. Wollastonite particles (WP) were incorporated into the poly lactic acid (PLA)/polycaprolactone (PCL) matrix as a reinforcing agent (up to 40 wt%) to harness osteoconductive and load-bearing properties from the 3D printed scaffolds. PCL as a minor phase (20 wt%) was added to enhance the toughening effect and induce the shape memory effect in the triphasic composite scaffolds. The 3D-printed composite scaffolds were studied for morphological, thermal, and mechanical properties, in vitro degradation, biocompatibility, and shape memory behaviour. The composite scaffold had interconnected pores of 550 μm, porosity of more than 50%, and appreciable compressive strength (∼50 MPa), which was over 90% greater than that of the pristine PLA scaffolds. The flexural strength was improved by 140% for 40 wt% of WP loading. The inclusion of WP did not affect the thermal property of the scaffolds; however, the inclusion of PCL reduced the thermal stability. An accelerated in vitro degradation was observed for WP incorporated composite scaffolds compared to pristine PLA scaffolds. The inclusion of WP improved the hydrophilic property of the scaffolds, and the result was significant for 40 wt% WP incorporated composite scaffolds having a water contact angle of 49.61°. The triphasic scaffold exhibited excellent shape recovery properties with a shape recovery ratio of ∼84%. These scaffolds were studied for their protein adsorption, cell proliferation, and bone mineralization potential. The incorporation of WP reduced the protein adsorption capacity of the composite scaffolds. The scaffold did not leach any toxic substance and demonstrated good cell viability, indicating its biocompatibility and growth-promoting behavior. The osteogenic potential of the WP incorporated scaffolds was observed in MC3T3-E1 cells, revealing early mineralization in pre-osteoblast cells cultured in different WP incorporated composite scaffolds. These results suggest that 3D-printed WP reinforced PLA/PCL composite bioactive scaffolds are promising for load bearing bone defect repair.

Smart stimuli-responsive strategies for titanium implant functionalization in bone regeneration and therapeutics.

With the increasing and aging of global population, there is a dramatic rise in the demand for implants or substitutes to rehabilitate bone-related disorders which can considerably decrease quality of life and even endanger lives. Though titanium and its alloys have been applied as the mainstream material to fabricate implants for load-bearing bone defect restoration or temporary internal fixation devices for bone fractures, it is far from rare to encounter failed cases in clinical practice, particularly with pathological factors involved. In recent years, smart stimuli-responsive (SSR) strategies have been conducted to functionalize titanium implants to improve bone regeneration in pathological conditions, such as bacterial infection, chronic inflammation, tumor and diabetes mellitus, etc. SSR implants can exert on-demand therapeutic and/or pro-regenerative effects in response to externally applied stimuli (such as photostimulation, magnetic field, electrical and ultrasound stimulation) or internal pathology-related microenvironment changes (such as decreased pH value, specific enzyme secreted by bacterial and excessive production of reactive oxygen species). This review summarizes recent progress on the material design and fabrication, responsive mechanisms, and in vitro and in vivo evaluations for versatile clinical applications of SSR titanium implants. In addition, currently existing limitations and challenges and further prospective directions of these strategies are also discussed.

Enhanced antimicrobial properties and bioactivity of 3D-printed titanium scaffolds by multilayer bioceramic coating for large bone defects

The restoration of large bone defects caused by trauma, tumor resection, or infection is a major clinical problem in orthopedics and dentistry because postoperative infections, corrosion, and limited osteointegration of metal implants can lead to loosening of the implant. The aim of this study was to improve the surface properties of a 3D-printed (electron beam melting) Ti6Al4V-based macroporous scaffold by multilayer coating with bioactive silicate glasses (BAGs) and hydroxyapatite doped with a silver (AgHAP) or AgHAP additionally sonochemically modified with ZnO (ZnO-AgHAP). The coated scaffolds AgHAP_BAGs_Ti and ZnO-AgHAP_BAGs_Ti enhanced cytocompatibility in L929 and MRC5 cell lines and expressed bioactivity in simulated body fluid. A lower release of vanadium ions in coated samples compared to bare Ti scaffold indicates decreased dissolution of Ti alloy in coated samples. The coated samples reduced growth of Escherichia coli and Staphylococcus aureus for 4–6 orders of magnitude. Therefore, the 3D-printed Ti-based scaffolds coated with BAGs and (ZnO-)AgHAP have great potential for application as a multifunctional implant with antibacterial properties for the restoration of defects in load-bearing bones.

Mineralized Collagen/Polylactic Acid Composite Scaffolds for Load-Bearing Bone Regeneration in a Developmental Model.

Repairing load-bearing bone defects in children remains a big clinical challenge. Mineralized collagen (MC) can effectively simulate natural bone composition and hierarchical structure and has a good biocompatibility and bone conductivity. Polylactic acid (PLA) is regarded as a gold material because of its mechanical properties and degradability. In this study, we prepare MC/PLA composite scaffolds via in situ mineralization and freeze-drying. Cell, characterization, and animal experiments compare and evaluate the biomimetic properties and repair effects of the MC/PLA scaffolds. Phalloidin and DAPI staining results show that the MC/PLA scaffolds are not cytotoxic. CCK-8 and scratch experiments prove that the scaffolds are superior to MC and hydroxyapatite (HA)/PLA scaffolds in promoting cell proliferation and migration. The surface and interior of the MC/PLA scaffolds exhibit rich interconnected pore structures with a porosity of ≥70%. The XRD patterns are typical HA waveforms. X-ray, micro-CT, and H&E staining reveal that the defect boundary disappears, new bone tissue grows into MC/PLA scaffolds in a large area, and the scaffolds are degraded after six months of implantation. The MC/PLA composite scaffold has a pore structure and composition similar to cancellous bone, with a good biocompatibility and bone regeneration ability.

Development and Characterization of Non-coated and PLGA-Coated S53P4 and S59 Bioactive Glass Scaffolds for Treatment of Load-Bearing Defects

Abstract We studied how in vitro reactions affect long-term biochemical and mechanical properties of porous tissue engineering scaffolds based on two bioactive glasses and accordingly their potential suitability for treating critical-size load-bearing bone defects. Granules of bioactive glass S53P4 and S59 were used to sinter the porous scaffolds. The sintering variables for mechanically durable scaffolds were initially selected according to the thermal behaviour of the glasses during heating. The S53P4 and S59 scaffolds were further divided into the following three groups: uncoated scaffolds, poly(dl-lactide-co-glycolide) (PLGA) coated scaffolds, and scaffolds coated with a mixture of PLGA and powdered S53P4. The purpose of the coating is to enhance mechanical abilities and to induce a membrane rich in growth factors surrounding the BAG implant. Characterization of the scaffolds included water absorption, pH, ion release, reaction layer formation, and compressive strength. Polymer coatings with powdered S53P4 absorbed more water than pure polymer coatings. The pH of the immersion solution increased more upon immersion of the uncoated scaffolds. No marked differences were seen between the coated scaffolds. During the 28-day in vitro immersion, the Ca-ion concentration initially increased for non-coated S53P4 scaffolds, followed by a slight increase starting at 14 days for all S53P4-based scaffolds and S59-PLGA scaffolds. The lowest P species concentration was observed for uncoated S53P4 scaffolds. The polymer coatings hindered the dissolution of Si-species from the scaffolds. Thicker calcium phosphate layers were identified at the uncoated scaffolds, suggesting a higher bioactivity. In contrast, the polymer coatings enhanced the compressive strength of the scaffolds. The results reflect the impact of glass composition and polymer coating on the chemical and physical properties of scaffolds, emphasizing the requirements in clinical applications for critical load-bearing bone defects. Graphical Abstract

Discovering an unknown territory using atom probe tomography: Elemental exchange at the bioceramic scaffold/bone tissue interface.

Here we report the first atom probe study to reveal the atomic-scale composition of in vivo bone formed in a bioceramic scaffold (strontium-hardystonite-gahnite) after 12-month implantation in a large bone defect in sheep tibia. The composition of the newly formed bone tissue differs to that of mature cortical bone tissue, and elements from the degrading bioceramic implant, particularly aluminium (Al), are present in both the newly formed bone and in the original mature cortical bone tissue at the perimeter of the bioceramic implant. Atom probe tomography confirmed that the trace elements are released from the bioceramic and are actively transported into the newly formed bone. NanoSIMS mapping, as a complementary technique, confirmed the distribution of the released ions from the bioceramic into the newly formed bone tissue within the scaffold. This study demonstrated the combined benefits of atom probe and nanoSIMS in assessing nanoscopic chemical composition changes at precise locations within the tissue/biomaterial interface. Such information can assist in understanding the interaction of scaffolds with surrounding tissue, hence permitting further iterative improvements to the design and performance of biomedical implants, and ultimately reducing the risk of complications or failure while increasing the rate of tissue formation. STATEMENT OF SIGNIFICANCE: The repair of critical-sized load-bearing bone defects is a challenge, and precisely engineered bioceramic scaffold implants is an emerging potential treatment strategy. However, we still do not understand the effect of the bioceramic scaffold implants on the composition of newly formed bone in vivo and surrounding existing mature bone. This article reports an innovative route to solve this problem, the combined power of atom probe tomography and nanoSIMS is used to spatially define elemental distributions across bioceramic implant sites. We determine the nanoscopic chemical composition changes at the Sr-HT Gahnite bioceramic/bone tissue interface, and importantly, provide the first report of in vivo bone tissue chemical composition formed in a bioceramic scaffold.

Reconstruction of Load-Bearing Segmental Bone Defects Using Carbonate Apatite Honeycomb Blocks

In a globally aging society, synthetic bone blocks are in increasing demand. An ideal synthetic bone block fuses early with bone and is replaced with new bone at a suitable speed while withstanding the weight load. Herein, we report carbonate apatite honeycomb (HC) blocks with superior mechanical strength, osteoconductivity, and bioresorbability compared to a clinically used synthetic porous block (control block). Three types of HC blocks were fabricated via the debinding of HC green bodies at 600, 650, and 700 °C and subsequent phosphatization, designated as HC-600, HC-650, and HC-700, respectively. The macropores in these HC blocks uniaxially penetrated the blocks, whereas those in the control block were not interconnected. Consequently, the HC blocks exhibited higher open macroporosities (18%–20%) than the control block (2.3%). In contrast, the microporosity of the control block (46.4%) was higher than those of the HC blocks (19%–30%). The compressive strengths of the HC-600, HC-650, HC-700, and control blocks were 24.7, 43.7, 103.8, and 38.9 MPa, respectively. The HC and control blocks were implanted into load-bearing segmental bone defects of rabbit ulnae. Uniaxial HC macropores enabled faster bone ingrowth than the poorly interconnected macropores in the control block. Microporosity in the HC blocks affected bone formation and osteoclastic resorption over a period of 24 weeks. The resorption of HC-650 corresponded to new bone formation; therefore, new bone with strength equal to that of the original bone bridged the separated bones. Thus, the HC blocks achieved the reconstruction of segmental bone defects while withstanding the weight load. The findings of this study contribute to the design and development of synthetic bone blocks for reconstructing segmental defects.

Multi-leveled Nanosilicate Implants Can Facilitate Near-Perfect Bone Healing.

Several studies have shown that nanosilicate-reinforced scaffolds are suitable for bone regeneration. However, hydrogels are inherently too soft for load-bearing bone defects of critical sizes, and hard scaffolds typically do not provide a suitable three-dimensional (3D) microenvironment for cells to thrive, grow, and differentiate naturally. In this study, we bypass these long-standing challenges by fabricating a cell-free multi-level implant consisting of a porous and hard bone-like framework capable of providing load-bearing support and a softer native-like phase that has been reinforced with nanosilicates. The system was tested with rat bone marrow mesenchymal stem cells in vitro and as a cell-free system in a critical-sized rat bone defect. Overall, our combinatorial and multi-level implant design displayed remarkable osteoconductivity in vitro without differentiation factors, expressing significant levels of osteogenic markers compared to unmodified groups. Moreover, after 8 weeks of implantation, histological and immunohistochemical assays indicated that the cell-free scaffolds enhanced bone repair up to approximately 84% following a near-complete defect healing. Overall, our results suggest that the proposed nanosilicate bioceramic implant could herald a new age in the field of orthopedics.

Functionalized 3D-printed porous titanium scaffold induces in situ vascularized bone regeneration by orchestrating bone microenvironment

Titanium (Ti) and its alloys have been extensively explored for treating load-bearing bone defects. However, high-stress shielding, weak osteogenic activity, and insufficient vascularization remain key challenges for the long-term clinical outcomes of Ti-based implants. Herein, inspired by structural and functional cues of bone regeneration, a silicon-doped nano-hydroxyapatite (nSiHA)/titanium dioxide (TiO2) composite coating with a hierarchical micro/nano-network structure is constructed on the surface of a 3D-printed porous Ti scaffold via a combined strategy of acid-alkali (AA) treatment and electrochemical deposition technique, which not only endows the scaffold with excellent osteoinduction ability but can also effectively immobilize and release vascular endothelial growth factor (VEGF). The results of the in vitro cell experiments show that the functionalized Ti scaffold significantly promotes osteogenesis in bone marrow mesenchymal stem cells (BMSCs) and angiogenesis in human umbilical vein endothelial cells (HUVECs) by activating the extracellular signal-regulated protein kinase (ERK) and HIF-1α signaling pathways. After being implanted into a rat femoral condyle defect model, the functionalized Ti scaffold can induce in situ vascularized bone regeneration by orchestrating the two coupled processes of angiogenesis and osteogenesis. These findings indicate that the functionalized Ti scaffold has great potential in bone tissue regeneration and is a promising candidate for load-bearing bone defect repair.

BE A SOFTY: ENHANCED BONE FORMATION IN OPTIMIZED, LOW-STIFFNESS 3D-PRINTED TITANIUM IMPLANTS. AN IN VIVO TIBIAL OSTEOTOMY STUDY

Introduction: The mechanobiology and response of bone formation to strain under physiological loading is well established, however investigation into exceedingly soft scaffolds relative to cancellous bone is limited. In this study we designed and 3D printed mechanically-optimised low-stiffness implants, targeting specific strain ranges inducing bone formation and assessed their biological performance in a pre-clinical in vivo load-bearing tibial tuberosity advancement (TTA) model. The TTA model provides an attractive pre-clinical framework to investigate implant osseointegration within an uneven loading environment due to the dominating patellar tendon force.A knee finite element model from ovine CT data was developed to determine physiological target strains from simulated TTA surgery. We 3D printed low-stiffness Ti wedge osteotomy implants with homogeneous stiffness of 0.8 GPa (Ti1), 0.6 GPa (Ti2) and a locally-optimised design with a 0.3 GPa cortex and soft 0.1 GPa core (Ti3), for implantation in a 12-week ovine tibial advancement osteotomy (9mm). We quantitatively assessed bone fusion, bone area, mineral apposition rate and bone formation rate.Optimised Ti3 implants exhibited evenly high strains throughout, despite uneven wedge osteotomy loading. We demonstrated that higher strains above 3.75%, led to greater bone formation. Histomorphometry showed uniform bone ingrowthin optimised Ti3 compared to homogeneous designs (Ti1 and Ti2), and greater bone-implant contact. The greatest bone formation scores were seen in Ti3, followed by Ti2 and Ti1.Results from our study indicate lower stiffness and higher strain ranges than normally achieved in Ti scaffolds stimulate early bone formation. By accounting for loading environments through rational design, implants can be optimised to improve uniform osseointegration. Design and 3D printing of exceedingly soft titanium orthopaedic implants enhance strain induced bone formation and have significant importance in future implant design for knee, hip arthroplasty and treatment of large load-bearing bone defects.

Strategies of strengthening mechanical properties in the osteoinductive calcium phosphate bioceramics.

Calcium phosphate (CaP) bioceramics are widely applied in the bone repairing field attributing to their excellent biological properties, especially osteoinductivity. However, their applications in load-bearing or segmental bone defects are severely restricted by the poor mechanical properties. It is generally considered that it is challenging to improve mechanical and biological properties of CaP bioceramics simultaneously. Up to now, various strategies have been developed to enhance mechanical strengths of CaP ceramics, the achievements in recent researches need to be urgently summarized. In this review, the effective and current means of enhancing mechanical properties of CaP ceramics were comprehensively summarized from the perspectives of fine-grain strengthening, second phase strengthening, and sintering process optimization. What's more, the further improvement of mechanical properties for CaP ceramics was prospectively proposed including heat treatment and biomimetic. Therefore, this review put forward the direction about how to compatibly improve mechanical properties of CaP ceramics, which can provide data and ideas for expanding the range of their clinical applications.

In vitro biological evaluation of epigallocatechin gallate (EGCG) release from three-dimensional printed (3DP) calcium phosphate bone scaffolds.

Three-dimensional printed (3DP) tricalcium phosphate (TCP) scaffolds can guide bone regeneration, especially for patient-specific defect repair applications in low-load bearing sites. Epigallocatechin gallate (EGCG), a green tea compound, has gained attention as a safer alternative treatment for bone disorders. The 3DP TCP scaffold is designed for localized EGCG delivery, which can enhance in vitro osteogenic ability, anti-osteoclastogenic activity, vascularization formation, and chemoprevention. In the cocultures of human bone marrow-derived mesenchymal stem cells (hMSCs) and monocytes (THP-1), EGCG release enhances osteogenic differentiation of hMSCs at day 16 compared to the control; this is indicated by a 2.8- and 4.0-fold upregulation of Runt-related transcription factor 2 (Runx2) and bone gamma-carboxyglutamic acid-containing protein (BGLAP), the early and late osteoblast differentiation marker expressions. However, EGCG significantly downregulates the receptor activator of nuclear factor-κB ligand (RANKL) expression by 7.0-fold, indicating that EGCG suppresses RANKL-induced osteoclast maturation. EGCG also stimulates endothelial tube formation at as early as 3 hours when human umbilical vein endothelial cells (HUVECs) grow on Matrigel. It reduces human osteosarcoma MG-63 cell viability by 66% compared to the control at day 11. An in vitro release kinetics study demonstrates that EGCG shows a ∼64% release within a day followed by a sustained release in the physiological environment (pH 7.4) because its phenolic hydroxyl groups are easily deprotonated at physiological pH. These findings contribute to developing a multifunctional scaffold for the treatment of low load-bearing patient-specific bone defects after trauma and tumor excision.

Corrosion fatigue behavior and anti-fatigue mechanisms of an additively manufactured biodegradable zinc-magnesium gyroid scaffold

Additively manufactured biodegradable zinc (Zn) alloy scaffolds constitute an important branch in orthopedic implants because of their moderate degradation behavior and bone-mimicking mechanical properties. This work investigated the corrosion fatigue response of a zinc-magnesium (Zn-Mg) alloy gyroid scaffold fabricated via laser-powder-bed-fusion additive manufacturing at the first time. The high-cycle compression-compression fatigue testing of the printed Zn-Mg scaffold was conducted in simulated body fluid, showing its favorable fatigue strength, structural reliability, and anti-fatigue capability. The printed Zn-Mg scaffold obtained a 227% higher fatigue strength than that of the printed Zn scaffold but 17% lower strain accumulation at 106 cycles. The accumulative strain of the Zn-Mg scaffold at its fatigue strength was dominant by fatigue ratcheting, since the fatigue damage strain of the scaffold was approximately zero. The corrosion products (ZnO and Zn(OH)2) were conducive to the inhibition of fatigue ratcheting and fatigue damage. Dislocation pile-up and solid solution phases at the grain boundaries of the Zn-Mg scaffold could retard the spreading of the crack tip and impede excessive grain coarsening, improving its fatigue endurance limit. Notably, the printed Zn-Mg scaffold could dissipate the fatigue energy through moderate grain boundary migration, thus reducing its plastic deformation. These findings illuminated the anti-fatigue mechanisms related to microstructural features and corrosive environments and highlighted the promising prospects of additively manufactured Zn-Mg scaffolds in orthopedic applications. Statement of significanceAdditive manufacturing (AM) of biodegradable metals shows unprecedented prospects for bone tissue regeneration medicine. The corrosion fatigue property is one of the key determinants in the performance of AM biodegradable scaffolds. In this study, a Zn-Mg gyroid scaffold was additively manufactured with admirable fatigue endurance limit and anti-fatigue capability. We reported that the corrosion fatigue performance was highly relevant to the microstructural features, validating that the grain boundary engineering strategy improved fatigue strength and inhibited crack penetration. Notably, moderate grain boundary migration could dissipate fatigue energy and reduce plastic deformation. Furthermore, corrosion products were conducive to impeding fatigue ratcheting and fatigue damage, indicating the promising potential of AM Zn-Mg scaffolds in treating load-bearing bone defects.

Customized Design 3D Printed PLGA/Calcium Sulfate Scaffold Enhances Mechanical and Biological Properties for Bone Regeneration

Polylactic glycolic acid copolymer (PLGA) has been widely used in tissue engineering due to its good biocompatibility and degradation properties. However, the mismatched mechanical and unsatisfactory biological properties of PLGA limit further application in bone tissue engineering. Calcium sulfate (CaSO4) is one of the most promising bone repair materials due to its non-immunogenicity, well biocompatibility, and excellent bone conductivity. In this study, aiming at the shortcomings of activity-lack and low mechanical of PLGA in bone tissue engineering, customized-designed 3D porous PLGA/CaSO4 scaffolds were prepared by 3D printing. We first studied the physical properties of PLGA/CaSO4 scaffolds and the results showed that CaSO4 improved the mechanical properties of PLGA scaffolds. In vitro experiments showed that PLGA/CaSO4 scaffold exhibited good biocompatibility. Moreover, the addition of CaSO4 could significantly improve the migration and osteogenic differentiation of MC3T3-E1 cells in the PLGA/CaSO4 scaffolds, and the PLGA/CaSO4 scaffolds made with 20 wt.% CaSO4 exhibited the best osteogenesis properties. Therefore, calcium sulfate was added to PLGA could lead to customized 3D printed scaffolds for enhanced mechanical properties and biological properties. The customized 3D-printed PLGA/CaSO4 scaffold shows great potential for precisely repairing irregular load-bearing bone defects.

Modified graphene oxide nanoplates reinforced 3D printed multifunctional scaffold for bone tissue engineering

Successful regeneration of load-bearing bone defects remains a major challenge in clinical orthopaedics. Designing biologically active 3-dimensional scaffolds possessing physiological responsiveness can potentially overcome current limitations. Here, we have described a novel approach to fabricate scaffolds with modified nanosheets reinforced on mechanically customized thermoplastic polymer-based 3D printed constructs. In this article, we have developed polydopamine-reduced graphene oxide (PD-RGO) reinforced 3D printed PLA scaffold for bone tissue construction. RGO was synthesized by reduction of GO under alkaline conditions using dopamine. 3D printed polylactic acid (PLA) scaffold with defined porosity was doped with PD-RGO. The designed scaffold was studied for its physiochemical properties and human umbilical cord-derived mesenchymal stem cell (hMSC) behaviour within the scaffold. In vitro hMSC studies revealed the influence of fibre direction and nanocoating on directional cell growth and proliferation. The fabricated scaffold showed antioxidant property along with pro-angiogenic and osteoinductive potential. The designed scaffold also successfully prevented the formation of biofilm. In vivo heterotopic implantation of the differentiated hMSC loaded scaffold confirmed the biocompatibility and bio functionality of the scaffold. In summary, the designed nanoplates doped 3D printed scaffold displays stem cell responsive, integrative and pro-regenerative multi functionalities, thereby, exhibiting potential application as bone tissue regeneration treatment alternative.