Promising Bone Repair Material Research Articles

Investigation of zinc-silver alloys as biodegradable metals for orthopedic applications

Biodegradable zinc (Zn) alloys are promising implant materials to restore bone defects in orthopedics. Adding silver (Ag) to Zn not only enhances its mechanical properties but also improves its antibacterial properties. However, the regular pattern of Ag composition on the properties of Zn-xAg alloys remains unclear. In this paper, Zn-Ag alloys with different Ag contents ranging from 0.5 to 6.0% were prepared by casting process and were systematically investigated both in vitro and in vivo. Mechanical tests suggest that the increase of Ag content enhanced the yield strength (YS), ultimate tensile strength (UTS), Vickers hardness, and elongation. Compared with pure Zn, the maximum YS, UTS, Vickers hardness, and elongation were achieved at Zn-6Ag, which were increased by 267%, 295%, 115%, and 172%, respectively. The degradation rate increased and the antibacterial properties were enhanced accordingly. All 25% and most 50% extracts of Zn-Ag alloys significantly promoted the proliferation of MC3T3-E1 cells, except for 50% Zn-6Ag extracts showing cytotoxicity. In the rat femoral condyle model, Zn-2Ag and Zn-4Ag alloys exhibited enhanced osteogenic performance at the early stage of implantation compared with pure Zn. Zn-Ag alloys (especially Zn-2Ag and Zn-4Ag) are identified as promising bone repair materials.

Enhanced bone regeneration via local low-dose delivery of PTH1-34 in a composite hydrogel.

Introducing bone regeneration-promoting factors into scaffold materials to improve the bone induction property is crucial in the fields of bone tissue engineering and regenerative medicine. This study aimed to develop a Sr-HA/PTH1-34-loaded composite hydrogel system with high biocompatibility. Teriparatide (PTH1-34) capable of promoting bone regeneration was selected as the bioactive factor. Strontium-substituted hydroxyapatite (Sr-HA) was introduced into the system to absorb PTH1-34 to promote the bioactivity and delay the release cycle. PTH1-34-loaded Sr-HA was then mixed with the precursor solution of the hydrogel to prepare the composite hydrogel as bone-repairing material with good biocompatibility and high mechanical strength. The experiments showed that Sr-HA absorbed PTH1-34 and achieved the slow and effective release of PTH1-34. In vitro biological experiments showed that the Sr-HA/PTH1-34-loaded hydrogel system had high biocompatibility, allowing the good growth of cells on the surface. The measurement of alkaline phosphatase activity and osteogenesis gene expression demonstrated that this composite system could promote the differentiation of MC3T3-E1 cells into osteoblasts. In addition, the in vivo cranial bone defect repair experiment confirmed that this composite hydrogel could promote the regeneration of new bones. In summary, Sr-HA/PTH1-34 composite hydrogel is a highly promising bone repair material.

Ti–Mo–Zr alloys for bone repair: mechanical properties, corrosion resistance, and biological performance

Titanium (Ti) alloys have been widely used as bone implants, but challenges such as the stress shielding effect still compromise long-term clinical successes. To improve the mechanical properties of Ti, non-toxic alloying elements zirconium (Zr) and molybdenum (Mo) were added either alone or in combination to produce Ti–Mo–Zr alloys. The influence of Zr or Mo addition on the alloy properties, such as the microstructure and the corrosion resistance, were investigated. The cytocompatibility and osteointegration of prepared alloys were evaluated to determine the potential for bone repair. The results showed that Ti–10Zr displayed an acicular α′ phase, while Ti–12Mo and Ti–12Mo–10Zr comprised a metastable β phase. Due to the solid solution and phase precipitation strengthening effect of Zr and Mo elements, the prepared alloys showed higher microhardness and compressive yield strength when compared with commercially pure Ti (CP–Ti). Ti–12Mo–10Zr possessed the lowest Young's modulus, while CP-Ti and Ti–10Zr showed a comparable Young's modulus. The corrosion resistance was in the order of Ti–12Mo–10Zr > Ti–12Mo > CP-Ti > Ti–10Zr. Notably, all alloys showed good cytocompatibility and osteointegration, which were similar to those of CP-Ti. Taken together, due to excellent material and biological performance, Ti–12Mo–10Zr presents a promising material for bone repair.

Microstructure, mechanical properties, in vitro degradation behavior and cytocompatibility of biodegradable Zn-3Fe-HAP composites prepared by vacuum heating-press sintering

Zinc (Zn) is a promising biodegradable material, and have attracted widespread attention due to its befitting degradation rate compared to magnesium (Mg) and iron (Fe). However, the inferior mechanical strength of pure Zn limits its application for bone repair. Therefore, there is an urgent need to improve its mechanical properties, regulate its degradation rate, and endow it with optimal biocompatibility. The alloying of metallic elements and preparation of Zn-based composites can be a promising approach for this purpose. In this study, the pure Zn and Zn-3 wt%Fe-xHAP (x = 0, 5, 10, 15, 20 wt%) samples were fabricated by vacuum heating-press sintering. The microstructure, compressive mechanical property, in vitro degradation behavior, antibacterial property and in vitro cytocompatibility of different samples were investigated. We confirmed that the secondary phase Zn13Fe significantly improved the mechanical property, and micro-galvanic between Zn and Fe accelerated degradation of the samples. Compressive yield strength of all samples ranges from 85.65 MPa to 301.99 MPa, compressive elastic modulus varies between 8.26 GPa and 15.03 GPa, and corrosion rates are significantly improved which are about 0.005–3.065 mm/y. Moreover, Zn-3Fe-xHAP samples exhibited better biocompatibility and antibacterial property than pure Zn, especially the sample of Zn-3Fe-5HAP. In summary, biodegradable Zn-based composites prepared by vacuum heating-press sintering could be promising material for bone repair.

Microstructures and mechanical properties of biphasic calcium phosphate bioceramics fabricated by SLA 3D printing

Porous biphasic calcium phosphate (BCP) bioceramics are considered to be the most promising bone repair materials in clinical medicine. Stereolithography (SLA) 3D printing can precisely fabricate bioceramic scaffolds with complex porous structure. During this process, how to obtain a suitable sintering procedure for BCP bioceramics by SLA 3D printing is the key to determine the microstructures and mechanical properties, but this is absent. In this present study, we prepared BCP bioceramics with superior densification and mechanical properties by SLA 3D printing, and mainly investigated the effects of sintering temperature and condition on the microstructures and mechanical properties of SLA 3D printed BCP bioceramics for the first time. At the optimized procedure of sintering temperature 1250 °C for 2 h, the 3D printed BCP bioceramics showed uniform shrinkage in all directions, and especially the mechanical properties were close to that of human cortical bone. Furthermore, complex porous BCP scaffolds with high porosity (51.49 %) and compressive strength (8.14 MPa) were successfully obtained. BCP bioceramics greatly promoted the proliferation of MC3T3-E1 cells by the release of Ca and P ion and presented excellent bioactivity. This work proves that SLA 3D printing technology can prepare BCP bioceramics with high mechanical and functional properties, and provides a new route for manufacturing high performance BCP bioceramic scaffolds with complex structure by SLA 3D printing for repairing bone defect in clinical.

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.

Beta-tricalcium phosphate enhanced mechanical and biological properties of 3D-printed polyhydroxyalkanoates scaffold for bone tissue engineering

Polyhydroxyalkanoates (PHA) is a naturally degradable polyester with good biocompatibility. However, several disadvantages including poor bioactivity and mechanical properties limit the biomedical application of PHA. To circumvent these drawbacks, PHA needs to be blended with other materials to improve performance. Beta-tricalcium phosphate (β-TCP) has emerged as one of the most promising bone repair materials due to its good biocompatibility, satisfactory mechanical properties, and excellent bone osteoconductivity. In this study, PHA filled with β-TCP in 0 wt%, 5 wt%, 10 wt%, 20 wt%, and 30 wt% of concentrations were produced using a twin-screw extruder. The extruded 3D filaments made with 20% β-TCP exhibited the maximum mechanical properties to manufacture 3D scaffolds for bone tissue engineering. We then prepared the 3D-printed PHA/β-TCP scaffolds by using the fused deposition modeling (FDM) technique. The compressive strength and the shore hardness of the PHA/20%β-TCP scaffold were 36.7 MPa and 81.1 HD. The produced scaffolds presented compressive strength compatible with natural bone. In addition, the scaffolds with a well-controlled design of pore shape and size provided sufficient space for cellular activity. In vitro studies demonstrated that the addition of β-TCP could significantly improve the proliferation, adhesion, and migration of MC3T3-E1 cells in the PHA/β-TCP scaffold. Moreover, the osteogenesis-related genes expression of the PHA/β-TCP scaffold was enhanced compared to the PHA scaffolds. Therefore, the 3D-printed PHA/β-TCP scaffold represents an effective strategy to promote mechanical and biological properties, showing huge potential for bone tissue engineering applications.

Effects of Mg-Nd-Gd-Sr alloy on bone marrow mesenchymal stem cell function derived from SD rats

Introduction The aim of this study was to determine the effect of a new type of Mg-3Nd-1Gd-0.3Sr-0.2Zn-0.4Zr (abbreviated to Mg-Nd-Gd-Sr) alloy on bone marrow mesenchymal stem cell (BMSCs) function derived from SD rats. Methods BMSCs were first isolated and cultured in vitro using the whole bone marrow adherence method, and identified by BMSC surface biomarkers and osteogenic induction. The in vitro biological safety of the Mg-Nd-Gd-Sr alloy was studied by cytotoxicity and apoptosis experiments, and the in vitro biological functions were studied by cell adhesion and cell proliferation experiments. Results The results showed that high-purity BMSCs were isolated using the whole bone marrow adherence method. Flow cytometry showed high expression of CD44 and CD90, and low expression of CD31 and CD45 in the BMSCs. Osteogenic induction showed that the BMSCs differentiated into osteoblasts, and mineralized nodules were observed. The cytotoxicity of the Mg-Nd-Gd-Sr alloy to SD rat BMSCs was 0–1 grade, suggesting that the Mg-Nd-Gd-Sr alloy had no significant cytotoxic effect on SD rat BMSCs; compared with the control group, there was no significant cell apoptosis in any of the experimental groups ( p > 0.05). Cell adhesion experiments showed that the number of adherent cells increased with the duration of culture with the exception of the 100% concentration group; compared with the control group, the 75% concentration group had the highest number of adherent cells at the 1st, 3rd, 5th, and 7th hours ( p < 0.05). Cell proliferation experiments showed that the number of cells in all experiment groups was higher than the control group ( p < 0.05) on the 1st, 3rd, 5th, and 7th days, with the highest number of cells in the 75% concentration group ( p < 0.05). Conclusion Our data indicate that the extracts of new type of Mg-Nd-Gd-Sr alloy has no apparent cytotoxicity to BMSCs, does not affect cell apoptosis, and has good biocompatibility. Different concentrations of Mg-Nd-Gd-Sr alloy extracts promoted the adhesion and proliferation of BMSCs. The alloy had good biological functions, and is thus a promising bone repair material.

Static Compressive Behavior and Material Failure Mechanism of Trabecular Tantalum Scaffolds Fabricated by Laser Powder Bed Fusion-based Additive Manufacturing.

Additively manufactured trabecular tantalum (Ta) scaffolds are promising bone repair materials for load-bearing applications due to their good pore interconnectivity. However, a thorough mechanical behavior evaluation is required before conducting animal studies and clinical research using these scaffolds. In this study, we revealed the compressive mechanical behavior and material failure mechanism of trabecular tantalum scaffolds by compression testing, finite element analysis (FEA), and scanning electron microscopy (SEM). Trabecular tantalum scaffolds with porosities of 65%, 75%, and 85% were fabricated by laser powder bed fusion-based additive manufacturing. Porosity has a significant effect on their compressive mechanical properties. As the porosity decreased from 85% to 65%, the compressive yield strength and elastic modulus increased from 11.9 MPa to 35.7 MPa and 1.1 GPa to 3.0 GPa, respectively. Compression testing results indicate that trabecular tantalum scaffolds demonstrate ductile deformation and excellent mechanical reliability. No macroscopic cracks were found when they were subjected to strain up to 50%. SEM observations showed that material failure results from tantalum strut deformation and fracture. Most microcracks occurred at conjunctions, whereas few of them appear on the struts. FEA-generated compressive stress distribution and material deformation were consistent with experimental results. Stress concentrates at strut conjunctions and vertical struts, where fractures occur during compression testing, indicating that the load-bearing capability of trabecular tantalum scaffolds can be enhanced by strengthening strut conjunctions and vertical struts. Therefore, additively manufactured trabecular tantalum scaffolds can be used in bone tissue reconstruction applications.

The personalized design and customization of bone cement can be realized by adjusting the carbonization process of modified tricalcium silicate

Tricalcium silicate (C3S) has been attested to be self-curable, bioactive and biodegradable, but its high alkalinity could inhibit cell proliferation and differentiation. By designing the preparation process, biomaterials could be adjusted to confer the desired properties. This study showed that the pH value of modified C3S by carbonization (signed as C–C3S) notably reduced from 11.2 to 8.15 with adjusting the carbonization process. Meanwhile, C–C3S displayed a suitable setting time (from 9.49 ± 0.19 to 11.20 ± 0.18 min). In addition, its compressive strength can reach about 10.61 MPa, which is comparable to that of cancellous bone. Carbonation time was confirmed to be a key factor in the formation of calcite by using carbon dioxide modified hydrolyzed tricalcium silicate. The results of cell activity and proliferation suggested that the C–C3S had improved osteogenic activity. Therefore, personalized design and customization of biomaterials can be realized by adjusting carbonization processes according to clinical requirements for bone cement. C–C3S may be a promising material for bone repair.

Effects of bovine cancellous bone powder/poly amino acid composites on cellular behaviors and osteogenic performances

Xenogeneic bone has good biological activity, but eliminating immunogenicity, while retaining osteogenic abilities, is a challenge. By combining xenogeneic bone with poly amino acid (PAA) that has an amide bond structure, a new type of composite conforming to bionics and low immunogenicity may be obtained. In this study, according to the principles of component bionics, three composites of delipidized cancellous bone powder (DCBP) and PAA were designed and obtained by an in situ polycondensation method, an extrusion molding (EM) method, and a solution-blend method. The three composites were all macroscopically uniform, non-cytotoxic, and demonstrated low immunogenicity by effective removal of residual antigens during preparation. Compared with PAA, mouse bone marrow mesenchymal stem cells (BMSCs) on the surfaces of three composites showed different cellular morphologies. The effects of different preparation methods and cellular morphology on cellular differentiation were confirmed by alkaline phosphatase activity, calcium nodule formation and the expression levels of osteogenic differentiation-related genes (bone morphogenetic protein 2, runt-related transcription factor 2, osteopontin and osteocalcin). Among these composites, DCBP/PAA EM showed best cell proliferation and osteogenic differentiation in vitro, and possessed greater bone formation than PAA in a rabbit femoral condyle study. This study may provide a new method for preparing bioactive bone repair materials with low immunogenicity and superior ability to stimulate differentiation of BMSCs in vitro and osteogenesis in vivo. DCBP/PAA EM might be a promising bone repair material for bone defect treatment.

Formulation and characterization of hydroxyapatite-based composite with enhanced compressive strength and controlled antibiotic release.

A composite based on hydroxyapatite (HA) and chitosan (CS) combined with ciprofloxacin (CIP) was formulated by the solid-liquid mixing method. The optimization of the solid to the liquid ratio and the use of chitosan in a small amount (≤5wt%) promoted the preparation of stable and rigid monoliths. A synergistic effect of CS and CIP contents on the compressive strength of the CIP-loaded composite was evidenced. The compressive strength of the fabricated biocomposite ranged in values from 1 to 6MPa, comparable to those reported for cancellous bone. The improvement of the mechanical properties with the increase of the rate of organic components was correlated with the diminution of the surface area and the reduction in the pore volume of the specimens. On the other hand, the in vitro release experiments of the antibiotic indicated a sustained and controlled release of CIP over 10 days. Moreover, in vitro antibacterial tests performed on the biocomposite HA-CS5-CIP showed significant inhibition of Staphylococcus aureus and Escherichia coli pathogens. According to the showed results, the formulated composite with three-phase components could be a promising material for bone repair and local antibiotic release for the treatment of bone infections.

A co-dispersed nanosystem of strontium-anchored reduced graphene oxide to enhance the bioactivity and mechanical property of polymer scaffolds

Poly(l-lactide) (PLLA) is a promising bone repair material owing to its good biocompatibility and natural degradability, but its lack of bioactivity and insufficient mechanical property restrict its further application.

Forming quality, mechanical properties, and anti-inflammatory activity of additive manufactured Zn-Nd alloy

Zinc (Zn) has recently been recognized as a promising bone repair material due to its inherent biodegradability and favorable biocompatibility. In this work, rare earth neodymium (Nd) was introduced into a Zn-based alloy fabricated using a laser powder bed fusion (LPBF) process. Results showed that addition of Nd significantly improved the melt fluidity and reduced the evaporation of Zn, thereby achieving parts with a high densification rate of 98.71%. Significantly, the Nd alloying treatment effectively refined the grain size from 25.3 to 6.2 µm. NdZn5 eutectics precipitated and contributed to a second-phase strengthening effect. As a result, the tensile strength increased to (119.3±5.1) MPa and the Vickers hardness to (76.2±4.1). Moreover, the Zn-Nd alloy exhibited good anti-inflammatory activity, as the Nd ions released during degradation had a strong affinity with cell membrane phospholipids and consequently inhibited the release of inflammatory cytokines. It also presented favorable cytocompatibility, showing great potential as a bone repair material.

Preparation and characteristics of a novel oxygen-releasing coating for improved cell responses in hypoxic environment.

Affected by environmental factors such as oxygen deficiency, the secretion of growth factor was abnormal in bone injury sites, resulting in the poor responses of osteoblasts and prolonging the healing process. Herein, in this study, we reported an in situ oxygen-releasing porous titanium coating that combines the dual degradability of poly(lactic-co-glycolic acid) with the self-releasing oxygen capacity of the CaO2 core. The resulting formulation exhibited stable oxygen-releasing capacity as well as the ability to promote proliferation and differentiation of the MC3T3 cell line under hypoxia conditions. According to these results, oxygen-releasing coatings based on improved cellular microenvironment may be a promising bone repair material that would reduce the incidence of difficult bone healing in the future.

Clinical Application of Concentrated Growth Factor Fibrin Combined With Bone Repair Materials in Jaw Defects

We investigated the promoting effect of concentrated growth factor (CGF) fibrin on the repair of jaw bone defects. We designed a clinical trial composed of patients with jaw defects. Forty patients were divided into the test and control groups. CGF fibrin combined with Bio-Oss bone powder (Giestlich Pharma, Wolhusen, Switzerland) was used in the test group. Bio-Oss bone powder alone was used in the control group. The concentration of vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-β in the red blood cell (RBC) layer and CGF gel was measured. At different time points before and after surgery, the serum bone alkaline phosphatase (BAP), osteocalcin, and bone mineral density levels were measured. Regular examinations and computed tomography scans were also performed in the follow-up period. The CGF fibrin available for clinical use was obtained by centrifugation. One day after preparation by centrifugation, the VEGF and TGF-β concentration in the CGF gel was 2.57-fold and 3.4-fold greater than the concentration in the RBC layer, respectively. The BAP and osteocalcin levels increased at 1and 12weeks postoperatively in both groups. Furthermore, the BAP and osteocalcin levels in the test group were significantly greater than those in the control group at 1 and 12weeks postoperatively (P<.05 for all). The bone mineral density in the bone defect area of the test group was also significantly greater than that of the control group at 6months postoperatively (P<.05). Evaluation of the regular radiographic scans revealed that the effects in the test group were better than those in the control group. CGF fibrin could promote new bone formation in jaw defects, with benefit to the healing of bone tissue and, thus, is a promising bone repair material.

High strength brushite bioceramics obtained by selective regulation of crystal growth with chiral biomolecules

Chirality seems to play a key role in mineralization. Indeed, in biominerals, the biomolecules that guide the formation and organization of inorganic crystals and help construct materials with exceptional mechanical properties, are homochiral. Here, we show that addition of homochiral l-(+)-tartaric acid improved the mechanical properties of brushite bioceramics by decreasing their crystal size, following the classic Hall-Petch strengthening effect; d-(-)-tartaric acid had the opposite effect. Adding l-(+)-Tar increased both the compressive strength (26 MPa) and the fracture toughness (0.3 MPa m1/2) of brushite bioceramics, by 33% and 62%, respectively, compared to brushite bioceramics without additives. In addition, l-(+)-tartaric acid enabled the fabrication of cements with high powder-to-liquid ratios, reaching a compressive strength and fracture toughness as high as 32.2 MPa and 0.6 MPa m1/2, respectively, approximately 62% and 268% higher than that of brushite bioceramics prepared without additives, respectively. Characterization of brushite crystals from the macro- to the atomic-level revealed that this regulation is attributable to a stereochemical matching between l-(+)-tartaric acid and the chiral steps of brushite crystals, which results in inhibition of brushite crystallization. These findings provide insight into understanding the role of chirality in mineralization, and how to control the crystallographic structure of bioceramics to achieve high-performance mechanical properties. Statement of SignificanceCalcium-phosphate cements are promising bone repair materials. However, their suboptimal mechanical properties limit their clinical use. Natural biominerals have remarkable mechanical properties that are the result of controlled size, shape and organization of their inorganic crystals. This is achieved by biomineralization proteins that are homochiral, composed of l- amino acids. Despite the importance of chiral l-biomolecules in biominerals, using homochiral molecules to fabricate bone cements has not been studied yet. In this study, we showed that homochiral l-(+)-tartaric acid can regulate the crystal structure and improve the mechanical properties of a calcium-phosphate cement. Hence, these findings open the door for a new way of designing strong bone cement and highlight the importance of chirality in bioceramics.

A promising material for bone repair: PMMA bone cement modified by dopamine-coated strontium-doped calcium polyphosphate particles.

Polymethyl methacrylate (PMMA) bone cement has been widely used in clinics as bone repair materials for its excellent mechanical properties and good injection properties. However, it also has defects such as poor biological performance, high temperature, and the monomer has certain toxicity. Our study tried to modify the PMMA bone cement by doping with various particle weight fractions (5, 10 and 15%) of SCPP particles and polydopamine-coated SCPP particles (D/SCPP) to overcome its clinical application disadvantages. Our study showed that all results of physical properties of samples are in accordance with ISO 5833. The 15% D/SCPP/PMMA composite bone cement had much better biocompatibility compared with pure PMMA bone cement and SCPP/PMMA composite bone cement due to the best cell growth-promoting mineralization deposition on the surface of 15% D/SCPP/PMMA composite bone cements and Sr2+ released from SCPP particles. Our research also revealed that the reaction temperature was found to be reduced with an increase in doped particles after incorporating the particles into composite bone cements. The novel PMMA bone cements modified by D/SCPP particles are promising materials for bone repair.

Laser additive manufacturing of Zn-2Al part for bone repair: Formability, microstructure and properties

Zinc (Zn) alloys are promising bone repair materials due to their inherent degradability, favorable mechanical property and biocompatibility. In this investigation, laser powder bed fusion (LPBF) known as a representative additive manufacturing technique was applied to fabricate Zn-2Al (wt.%) part for bone repair application. A low energy density (Ev) led to the formation of pores and resultant insufficient densification rate due to the high liquid viscosity within the molten pool. In contrast, a high Ev caused the evaporation of Zn powder and resultant failure of LPBF. With Ev increasing, the obtained grains and the precipitated lamellar eutectic structure contained η-Zn and α-Al phase became coarsened, which could be attributed to the enhanced heat accumulation and consequently decreased cooling rate. At optimized Ev of 114.28 J/mm3, fully dense Zn-2Al part with a densification rate of 98.3 ± 1.4% was achieved, which exhibited an optimal hardness of 64.5 ± 1.8 Hv, tensile strength of 192.2 ± 5.4 MPa and a moderate corrosion rate of 0.14 mm/year. In addition, in vitro cell tests confirmed its good biocompability. This study indicated that LPBF processed Zn-2Al part was a potential material for bone repair.

Rapid mineralization of hierarchical poly(l-lactic acid)/poly(ε-caprolactone) nanofibrous scaffolds by electrodeposition for bone regeneration.

Introduction: Hierarchical nanofibrous scaffolds are emerging as a promising bone repair material due to their high cell adhesion activity and nutrient permeability. However, the existing method for hierarchical nanofibrous scaffolds fabrication is complicated and not perfectly suitable for further biomedical application in view of both structure and function. In this study, we constructed a hierarchical nanofibrous poly (l-lactic acid)/poly(ε-caprolactone) (PLLA/PCL) scaffold and further evaluated its bone healing ability.Methods: The hierarchical PLLA/PCL nanofibrous scaffold (PLLA/PCL) was prepared by one-pot TIPS and then rapidly mineralized at room temperature by an electrochemical deposition technique. After electrode-positioning at 2 V for 2 hrs, a scaffold coated with hydroxyapatite (M-PLLA/PCL) could be obtained.Results: The pore size of the M-PLLA/PCL scaffold was hierarchically distributed so as to match the biophysical structure for osteoblast growth. The M-PLLA/PCL scaffold showed better cell proliferation and osteogenesis activity compared to the PLLA/PCL scaffold. Further in vivo bone repair studies indicated that the M-PLLA/PCL scaffold could accelerate defect healing in 12 weeks.Conclusion: The results of this study implied that the as-prepared hydroxyapatite coated hierarchical PLLA/PCL nanofibrous scaffolds could be developed as a promising material for efficient bone tissue repair after carefully tuning the TIPS and electrodeposition parameters.