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Mg-Nd-Zn-Zr (JDBM) alloy was studied as a candidate for biodegradable implant material because of its moderate mechanical properties, good biocompatibility, and favorable uniform degradation behavior. To verify whether JDBM alloy exhibits electroplasticity effect and then study the mechanism of electropulsing treatment on JDBM alloy, in this study, homogenized and pre-tensile deformed samples were treated by electropulsing. After the electropulsing treatment, the average grain size was refined due to recrystallization, micron-scale Mg12Nd secondary phases precipitated slightly, while the morphology of nanoscale Zr particles changed from rodlike to ellipsoidal shape. The elongation to failure (EL) increased obviously for the homogenized and pre-tensile deformed JDBM alloy samples after electropulsing treatment, accompanying with no obvious sacrifice of the yield strength (YS) for the former and an evident decrease of YS for the latter, mainly due to the reduction of the dislocation density. The YS decrement and EL increment (77.57%) for the latter are more apparent attributed to the higher density of dislocations introduced by pre-tensile deformation. Therefore, the electropulsing treatment can obviously improve the mechanical properties of JDBM alloy, especially for the plasticity. The present work opens a new window for the fabrication of JDBM alloy profiles with high mechanical properties, especially for the plasticity, such as the cold drawing wires and tubes for biomedical applications. It also could provide theoretical references for other magnesium alloy processing.

Effective management of malignant tumor-induced bone defects remains challenging due to severe systemic side effects, substantial tumor recurrence, and long-lasting bone reconstruction post tumor resection. Magnesium and its alloys have recently emerged in clinics as orthopedics implantable metals but mostly restricted to mechanical devices. Here, by deposition of calcium-based bilayer coating on the surface, a Mg-based composite implant platform is developed with tailored degradation characteristics, simultaneously integrated with chemotherapeutic (Taxol) loading capacity. The delicate modulation of Mg degradation occurring in aqueous environment is observed to play dual roles, not only in eliciting desirable osteoinductivity, but allows for modification of tumor microenvironment (TME) owing to the continuous release of degradation products. Specifically, the sustainable H2 evolution and Ca2+ from the implant is distinguished to cooperate with local Taxol delivery to achieve superior antineoplastic activity through activating Cyt-c pathway to induce mitochondrial dysfunction, which in turn leads to significant tumor-growth inhibition in vivo. In addition, the local chemotherapeutic delivery of the implant minimizes toxicity and side effects, but markedly fosters osteogenesis and bone repair with appropriate structure degradation in rat femoral defect model. Taken together, a promising intraosseous administration strategy with biodegradable Mg-based implants to facilitate tumor-associated bone defect is proposed.

In this study, the age-hardening response and microstructural evolution of an as-extruded biodegradable Zn-1.5Cu-1.5Ag (wt.%) alloy during ageing at 25 ℃, 100 ℃, 150 ℃ and 200 ℃ are studied. The age-hardening response is generally weak, and the largest hardness increment is observed after ageing at 150 ℃ for 24 hours. Discontinuous precipitation (DP) and continuous precipitation (CP) occur competitively during ageing at 150 ℃ or 200 ℃, while only DP is observed during ageing at 25 ℃ or 100 ℃. All the precipitates formed through DP and CP are identified as ε-(Ag, Cu)Zn4 that has a hexagonal structure. Analysis of possible strengthening mechanisms shows that grain boundary strengthening and precipitation hardening contribute to the major part of yield strength in the as-extruded condition. Ageing treatments generate a limited increment in yield strength due to the small difference between the hardness of ε-(Ag, Cu)Zn4 and the Zn matrix and the reduced solid solution strengthening effect. Artificial ageing at 150 ℃ for 48 hours effectively improves the stability of the mechanical properties of the as-extruded Zn-1.5Cu-1.5Ag alloy. This process fully depletes the excessive solutes in the supersaturated Zn matrix, ensuring that the alloy maintains consistent mechanical properties when stored at room temperature.

Osteoporotic fractures have become a common public health problem and are usually accompanied by chronic pain. Mg and Mg-based alloys are considered the next-generation orthopedic implants for their excellent osteogenic inductivity, biocompatibility, and biodegradability. However, Mg-based alloy can initiate aberrant activation of osteoclasts and modulate sensory innervation into bone callus resulting in postoperative pain at the sequential stage of osteoporotic fracture healing. Its mechanism is going to be investigated. Strontium hydrogen phosphate (SrHPO4) coating to delay the Mg-based alloy degradation, can reduce the osteoclast formation and inhibit the growth of sensory nerves into bone callus, dorsal root ganglion hyperexcitability, and pain hypersensitivity at the early stage. Liquid chromatography-mass spectrometry (LC-MS) metabolomics analysis of bone marrow-derived macrophages (BMMs) treated with SrHPO4-coated Mg alloy extracts shows the potential effect of increased metabolite levels of AICAR (an activator of the AMPK pathway). We demonstrate a possible modulated secretion of AICAR and osteoclast differentiation from BMMs, which inhibits sensory innervation and postoperative pain through the AMPK/mTORc1/S6K pathway. Importantly, supplementing with AICAR in Mg-activated osteoclasts attenuates postoperative pain. These results suggest that Mg-induced postoperative pain is related to the osteoclastogenesis and sensory innervation at the early stage in the osteoporotic fractures and the SrHPO4 coating on Mg-based alloys can reduce the pain by upregulating AICAR secretion from BMMs or preosteoclasts.

After reconstructing the anterior cruciate ligament (ACL), unsatisfactory bone tendon interface healing may often induce tunnel enlargement at the early healing stage. With good biological features and high formability, Magnesium-Zinc-Gadolinium (ZG21) wires are developed to bunch the tendon graft for matching the bone tunnel during transplantation. Microstructure, tensile strength, degradation, and cytotoxicity of ZG21 wire are evaluated. The rabbit model is used for assessing the biological effects of ZG21 wire by Micro-CT, histology, and mechanical test. The SEM/EDS, immunochemistry, and in vitro assessments are performed to investigate the underlying mechanism. Material tests demonstrate the high formability of ZG21 wire as surgical suture. Micro-CT shows ZG21 wire degradation accelerates tunnel bone formation, and histologically with earlier and more fibrocartilage regeneration at the healing interface. The mechanical test shows higher ultimate load in the ZG21 group. The SEM/EDS presents ZG21 wire degradation triggered calcium phosphate (Ca-P) deposition. IHC results demonstrate upregulation of Wnt3a, BMP2, and VEGF at the early phase and TGFβ3 and Type II collagen at the late phase of healing. In vitro tests also confirmed the Ca-P in the metal extract could elevate the expression of Wnt3a, β catenin, ocn and opn to stimulate osteogenesis. Ex vivo tests of clinical samples indicated suturing with ZG21 wire did not weaken the ultimate loading of human tendon tissue. In conclusion, the ZG21 wire is feasible for tendon graft bunching. Its degradation products accelerated intra-tunnel endochondral ossification at the early healing stage and therefore enhanced bone-tendon interface healing in ACL reconstruction.