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Magnesium (Mg) alloys that have both antibacterial and osteogenic properties are suitable candidates for orthopedic implants. However, the fabrication of ideal Mg implants suitable for bone repair remains challenging because it requires implants with interconnected pore structures and personalized geometric shapes. In this study, we fabricated a porous 3D-printed Mg-Nd-Zn-Zr (denoted as JDBM) implant with suitable mechanical properties using selective laser melting technology. The 3D-printed JDBM implant exhibited cytocompatibility in MC3T3-E1 and RAW267.4 cells and excellent osteoinductivity in vitro. Furthermore, the implant demonstrated excellent antibacterial ratios of 90.0% and 92.1% for methicillin-resistant S. aureus (MRSA) and Escherichia coli, respectively. The 3D-printed JDBM implant prevented MRSA-induced implant-related infection in a rabbit model and showed good in vivo biocompatibility based on the results of histological evaluation, blood tests, and Mg2+ deposition detection. In addition, enhanced inflammatory response and TNF-α secretion were observed at the bone-implant interface of the 3D-printed JDBM implants during the early implantation stage. The high Mg2+ environment produced by the degradation of 3D-printed JDBM implants could promote M1 phenotype of macrophages (Tnf, iNOS, Ccl3, Ccl4, Ccl5, Cxcl10, and Cxcl2), and enhance the phagocytic ability of macrophages. The enhanced immunoregulatory effect generated by relatively fast Mg2+ release and implant degradation during the early implantation stage is a potential antibacterial mechanism of Mg-based implant. Our findings indicate that 3D-printed porous JDBM implants, having both antibacterial property and osteoinductivity, hold potential for future orthopedic applications.

Due to their capability of fabricating geometrically complex structures, additive manufacturing (AM) techniques have provided unprecedented opportunities to produce biodegradable metallic implants—especially using Mg alloys, which exhibit appropriate mechanical properties and outstanding biocompatibility. However, many challenges hinder the fabrication of AM-processed biodegradable Mg-based implants, such as the difficulty of Mg powder preparation, powder splash, and crack formation during the AM process. In the present work, the challenges of AM-processed Mg components are analyzed and solutions to these challenges are proposed. A novel Mg-based alloy (Mg–Nd–Zn–Zr alloy, JDBM) powder with a smooth surface and good roundness was first synthesized successfully, and the AM parameters for Mg-based alloys were optimized. Based on the optimized parameters, porous JDBM scaffolds with three different architectures (biomimetic, diamond, and gyroid) were then fabricated by selective laser melting (SLM), and their mechanical properties and degradation behavior were evaluated. Finally, the gyroid scaffolds with the best performance were selected for dicalcium phosphate dihydrate (DCPD) coating treatment, which greatly suppressed the degradation rate and increased the cytocompatibility, indicating a promising prospect for clinical application as bone tissue engineering scaffolds.

BACKGROUND: Hypoxic-ischemic brain damage (HIBD) significantly affects neurodevelopment in infants and is a leading cause of severe neurological morbidity and mortality in neonates. Our previous study found that photobiomodulation therapy (PBMT) improves the impaired spatial learning and memory of HIBD rat models. However, the neuroprotective mechanism conferred by PBMT in HIBD is unclear. METHODS: In the present study, HIBD model rats were treated with PBMT at 5 mW/cm(2) per day in the dark for 14 days (10 min each day), and primary neural stem cells (NSCs) after oxygen-glucose deprivation (OGD) were treated with PBMT for 10 min at 1, 5, 10, and 20 mW/cm(2) in the dark. PBMT promoted hippocampal neural stem cell (NSC) proliferation in vivo and in vitro. RESULTS: Mechanistically, PBMT upregulated phosphatidylinositol 3 kinase (PI3K), phosphorylated protein kinase B (p-AKT), phosphorylated glycogen synthase kinase 3 beta (p-GSK-3β), β-catenin, and cyclin D1 expression in vivo and in vitro, promoting NSC proliferation. Furthermore, both LY294002 (a PI3K inhibitor) and IWR-1 (a Wnt/β-catenin inhibitor) inhibited the PBMT promotion of NSC proliferation after OGD and suppressed β-catenin and cyclin D1 expression in vitro. CONCLUSIONS: PBMT improved the spatial learning and memory of HIBD rats and promoted hippocampal NSC proliferation through the AKT/GSK-3β/β-catenin pathway.

Magnesium (Mg) alloys that have both antibacterial and osteogenic properties are suitable candidates for orthopedic implants. However, the fabrication of ideal Mg implants suitable for bone repair remains challenging because it requires implants with interconnected pore structures and personalized geometric shapes. In this study, we fabricated a porous 3D-printed Mg-Nd-Zn-Zr (denoted as JDBM) implant with suitable mechanical properties using selective laser melting technology. The 3D-printed JDBM implant exhibited cytocompatibility in MC3T3-E1 and RAW267.4 cells and excellent osteoinductivity in vitro. Furthermore, the implant demonstrated excellent antibacterial ratios of 90.0% and 92.1% for methicillin-resistant S. aureus (MRSA) and Escherichia coli, respectively. The 3D-printed JDBM implant prevented MRSA-induced implant-related infection in a rabbit model and showed good in vivo biocompatibility based on the results of histological evaluation, blood tests, and Mg2+ deposition detection. In addition, enhanced inflammatory response and TNF-α secretion were observed at the bone-implant interface of the 3D-printed JDBM implants during the early implantation stage. The high Mg2+ environment produced by the degradation of 3D-printed JDBM implants could promote M1 phenotype of macrophages (Tnf, iNOS, Ccl3, Ccl4, Ccl5, Cxcl10, and Cxcl2), and enhance the phagocytic ability of macrophages. The enhanced immunoregulatory effect generated by relatively fast Mg2+ release and implant degradation during the early implantation stage is a potential antibacterial mechanism of Mg-based implant. Our findings indicate that 3D-printed porous JDBM implants, having both antibacterial property and osteoinductivity, hold potential for future orthopedic applications., Graphical abstract Image 1, Highlights • Porous JDBM implants promising mechanical properties was fabricated by selective laser melting. • 3D-printed JDBM implant exhibited excellent antibacterial property, osteoinductivity, and biocompatibility. • Temporally enhanced immunoregulatory effect in early stage was a potential antibacterial mechanism of Mg-based implant.

In view of the low accuracy of existing fault location methods for traction networks with longer power supply lines, the equivalent model of the traction network for double-track electrified railways is calculated, and the power supply lines and contacts are introduced on the basis of traditional traction network fault location methods. The parameter of grid equivalent impedance ratio proposes a modified uplink and downlink current ratio ranging method, which effectively solves the problem of accurate fault location of the double-track electrified railway direct-supply traction network. The RT-plus smart grid real-time digital simulation instrument is used to establish the traction power supply dynamics. The simulation test system is simulated and tested, and the test results show that the proposed algorithm has good feasibility and accuracy, and fully meets the engineering requirements.