3D Printing Of Mxene Composite Scaffolds Combined With Photothermal Therapy For Osteogenesis And Angiogenesis In Bone Defect Repair

Background and Objective:Bone defect caused by trauma,infection,or tumor has always been a challenge in clinical treatment.Over the years,various methods have been developed to address bone defects.Traditional approaches,such as bone grafting and the use of biologics,have limitations in efficacy and availability.Tissue engineering has emerged as a promising alternative to bone regeneration,with the potential to tailor bone tissue to integrate well with host tissue.In addition,3D printing technology can support cell growth and differentiation by constructing complex structures with precise size and porosity,which brings more possibilities to bone tissue engineering.The use of 3D printing technology can mimic the natural structure of bone tissue to build personalized scaffolds and implants for bone regeneration.Methods:1.Niobium carbide（Nb₂C）MXene was loaded into the scaffold by low-temperature 3D printing,to prepare MXene composite scaffold polylactic acid-glycolicacidcopolymer/tricalciumβ-phosphate/Nb₂CMXene（PLGA/β-TCP/MXene,PTM）,and characterize and test the physical and chemical properties of the scaffold.2.Evaluation of biological and osteogenic properties of PTM scaffolds.Rat bone marrow mesenchymal stem cells were seeded on PTM scaffolds,and the scaffolds were periodically irradiated with 808nm near-infrared（NIR）light.CCK-8,live-dead staining,q RT-PCR,quantitative detection of alkaline phosphatase activity,immunofluorescence staining,and Western Blot were used to study the biocompatibility of the scaffolds and the ability to promote the proliferation and osteogenic differentiation of BMSCs and the mechanism.3.Evaluation of the angiogenic performance of PTM scaffolds.The angiogenic performance and mechanism of PTM scaffolds under NIR irradiation were studied by transwell,tube formation assay,q RT-PCR,immunofluorescence staining,and Western Blot.4.Evaluation of the therapeutic effect of PTM scaffolds in bone defects in vivo.The cranial defect model of the rat was established.The PTM scaffolds were implanted into the defect and irradiated with NIR irradiation periodically.Micro-CT and immunohistochemistry were used to evaluate osteogenesis and vascularization in vivo.Results:1.The composite scaffold loaded with MXene was successfully prepared by 3D printing technology.The scaffold had suitable porosity,biodegradability,good mechanical strength,and excellent photothermal conversion performance.2.PTM scaffold had good biocompatibility and showed good osteogenic potential in vitro under NIR irradiation,which could promote the proliferation of bone marrow mesenchymal stem cells and the expression of genes（ALP,RUNX2,COL-1,OCN）and proteins（RUNX2,OCN）related to osteogenic differentiation.The mechanism was closely related to the high expression of Hsp90.3.PTM scaffolds could promote endothelial cell migration,in vitro tubular formation,and expression of angiogenesis-related genes（HIF-1α,VEGFA,PDGFA,α-SMA）and protein（HIF-1α）,showing well in vitro angiogenesis performance.The up-regulation of Hsp90 expression induced by hyperthermia played an important role.4.In vivo experiments proved that PTM scaffolds could effectively treat bone defects under NIR irradiation.Conclusion:In this study,a customized bone tissue engineering composite scaffold PTM with top-of-the-line mechanical properties,distinct pore structure,bone conduction,and bone-induced balance was prepared using cryogenic 3D printing technology.After periodic NIR irradiation,the mild thermal stimulation generated by PTM scaffolds can effectively promote the expression of Hsp90 in bone marrow mesenchymal stem cells and endothelial cells,and then up-regulate the expression of osteogenic and angiogenic factors.The coupling of osteogenesis and angiogenesis greatly accelerates the formation of new bone,showing great potential in the treatment of bone defects.