Porous Mg-Zn-Ca scaffolds for bone repair: a study on microstructure, mechanical properties and in vitro degradation behavior.

Biodegradable porous Mg scaffolds are a promising approach to bone repair. In this work, 3D-spherical porous Mg-1.5Zn-0.2Ca (wt.%) scaffolds were prepared by vacuum infiltration casting technology, and MgF2 and fluorapatite coatings were designed to control the degradation behavior of Mg-based scaffolds. The results showed that the pores in Mg-based scaffolds were composed of the main spherical pores (450-600 µm) and interconnected pores (150-200 µm), and the porosity was up to 74.97%. Mg-based porous scaffolds exhibited sufficient mechanical properties with a compressive yield strength of about 4.04 MPa and elastic modulus of appropriately 0.23 GPa. Besides, both MgF2 coating and fluorapatite coating could effectively improve the corrosion resistance of porous Mg-based scaffolds. In conclusion, this research would provide data support and theoretical guidance for the application of biodegradable porous Mg-based scaffolds in bone tissue engineering.

3D printed Mg-incorporated polycaprolactone scaffolds for repairing rat skull defects / 口腔疾病防治

Objective@#To evaluate the bone repair effect of 3D-printed magnesium (Mg)-loaded polycaprolactone (PCL) scaffolds in a rat skull defect model.@*Methods@#PCL scaffolds mixed with Mg microparticles were prepared by using 3D printing technology, as were pure PCL scaffolds. The surface morphologies of the two scaffolds were observed by scanning electron microscopy (SEM), and the surface elemental composition was analyzed via energy dispersive spectroscopy (EDS). The physical properties of the scaffolds were characterized through contact angle measurements and an electronic universal testing machine. This study has been reviewed and approved by the Ethics Committee. A critical size defect model was established in the skull of 15 Sprague-Dawley (SD) rats, which were divided into the PCL group, PCL-Mg group, and untreated group, with 5 rats in each group. Micro-CT scanning was performed to detect and analyze skull defect healing at 4 and 8 weeks after surgery, and samples from the skull defect area and major organs of the rats were obtained for histological staining at 8 weeks after surgery.@*Results@#The scaffolds had a pore size of (480 ± 25) μm, a fiber diameter of (300 ± 25) μm, and a porosity of approximately 66%. The PCL-Mg scaffolds contained 1.0 At% Mg, indicating successful incorporation of Mg microparticles. The contact angle of the PCL-Mg scaffolds was 68.97° ± 1.39°, indicating improved wettability compared to that of pure PCL scaffolds. Additionally, compared with that of pure PCL scaffolds, the compressive modulus of the PCL-Mg scaffolds was (57.37 ± 8.33) MPa, demonstrating enhanced strength. The PCL-Mg group exhibited the best bone formation behavior in the skull defect area compared with the control group and PCL group at 4 and 8 weeks after surgery. Moreover, quantitative parameters, such as bone volume (BV), bone volume/total volume (BV/TV), bone surface (BS), bone surface/total volume (BS/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N) and bone mineral density (BMD), of skull defects were better than those in the other groups, indicating the best bone regeneration effect. H&E, Goldner, and VG staining revealed more mineralized new bone formation in the PCL-Mg group than in the other groups, and H&E staining of the major organs revealed good biosafety of the material.@*Conclusion@#PCL-Mg scaffolds can promote the repair of bone defects and have clinical potential as a new scaffold material for the repair of maxillofacial bone defects.

3D-printed Mg-incorporated PCL-based scaffolds: A promising approach for bone healing.

3D-printed scaffolds have been developed as potential therapeutic strategies in bone tissue engineering. Mg/PCL biomaterials have been attracted much attention owing to biocompatibility, biodegradability as well as tunable mechanical properties. In this work, we developed 3D-printed customized Mg/PCL composite scaffolds with enhanced osteogenesis and biomineralization. Mg microparticles embedded in PCL-based scaffolds took a positive role in the improvement of biocompatibility, biomineralization, and biodegradable abilities. When incorporated with 3 wt% Mg, PCL-based scaffolds exhibited the optimal bone repairing ability in vitro and in vivo. The in vitro experiments indicated that 3 Mg/PCL scaffolds had improved mechanical properties, good biocompatibility, enhanced osteogenic and angiogenic activities. Besides, the in vivo studies demonstrated that Mg/PCL scaffolds promoted tissue ingrowth and new bone formation. In sum, these findings indicated that 3D-printed cell-free Mg/PCL scaffolds are promising strategies for bone healing application.

Mechanical Properties and Degradation Behaviors of Zn-xMg Alloy Fine Wires for Biomedical Applications.

Zn and Zn-based alloys exhibit biosafety and biodegradation, considered as candidates for biomedical implants. Zn-0.02 wt.% Mg (Zn-0.02 Mg), Zn-0.05 wt.% Mg (Zn-0.05 Mg), and Zn-0.2 wt.% Mg (Zn-0.2 Mg) wires (Φ 0.3 mm) were prepared for precision biomedical devices in this work. With the addition of Mg in Zn-xMg alloys, the grain size decreased along with the occurrence of Mg2Zn11 at the grain boundaries. Hot extrusion, cold drawing, and annealing treatment were introduced to further refining the grain size. Besides, the hot extrusion and cold drawing improved the tensile strength of Zn-xMg alloys to 240-270 MPa while elongation also increased but remained under 10%. Annealing treatment could improve the elongation of Zn alloys to 12% -28%, but decrease the tensile strength. Furthermore, Zn-xMg wires displayed an increase in degradation rate with Mg addition. The findings might provide a potential possibility of Zn-xMg alloy wires for biomedical applications.

Insights into self-healing behavior and mechanism of dicalcium phosphate dihydrate coating on biomedical Mg.

Self-healing coatings have been developed as smart surface coatings for Mg and its alloys to retain local corrosion from the coating damages. In this study, we prepared dicalcium phosphate dihydrate (DCPD) coating on biomedical Mg, and found that the artificial scratches in DCPD coating can be efficiently sealed by anti-corrosive products in both Hank's and normal saline (NS) solutions. Besides, the in-depth study revealed that DCPD was served as not only a physical barrier but also a self-healing agent, demonstrating an autonomous self-healing coating without embedded extra corrosion inhibitors. Moreover, Hank's solution provided foreign-aid film-forming ions to promote self-healing behavior. The findings might offer new opportunities for further studies and applications of efficient self-healing coatings on biodegradable Mg implants.

Corrosion behavior and mechanical degradation of as-extruded Mg-Gd-Zn-Zr alloys for orthopedic application.

The microstructures, corrosion behavior, and mechanical degradation of the as-extruded Mg-6.0Gd-0.5Zn-0.4Zr (wt %, GZ60K) and Mg-6.0Gd-1.0Zn-0.4Zr (wt %, GZ61K) alloys were investigated. In both alloys, stacking faults and precipitates are formed in the recrystallized microstructures. The corrosion rate of GZ61K calculated by the hydrogen evolution in simulated body fluid is 0.34 ± 0.13 mm/year, which is lower than that of GZ60K (0.45 ± 0.09 mm/year); and the current density of GZ61K (5.23 ± 1.41 µA cm-2 ) is much lower than that of GZ60K (11.95 ± 3.37 µA cm-2 ). The corrosion results indicate GZ61K is more resistant to corrosion than GZ60K, but GZ60K presents more uniform corrosion mode as compared to GZ61K. After immersion in simulated body fluid for 7, 14, and 21 days, a slight decrease in the strength of both alloys is observed. The yield strength half-life is assessed for mechanical degradation and determined to be 125 and 85 days for GZ60K and GZ61K, respectively. The as-extruded GZ60K alloy with more uniform corrosion and longer mechanical integrity shows promising potential for orthopedic application.