Three Dimensional Printing Of Porous Composite Scaffolds And Their Properties

Bone tissue engineering has emerged as an innovative and promising technique to treat bone defects.Cells,scaffolds and signal factors are key points for bone tissue engineering,in which three dimensional?3D?porous scaffolds can be loaded with specific cells or tissue-inducing factors to launch a tissue replacement or regeneration in a natural way.In this thesis,pearl/calcium sulfate composite scaffolds?Pearl/CaSO₄?,mesoporous bioactive glass/silk fibroin scaffolds?MBG/SF?and mesoporous bioactive glass/sodium alginate-sodium alginate hierarchical scaffolds?MBG/SA-SA?were successfully fabricated using 3D printing technique.The physiochemical properties and biological properties of those three kinds of scaffolds were systematically investigated.?1?Pearl/CaSO₄ composite scaffolds were fabricated by 3D printing.Pearl/CaSO₄scaffolds showed uniform interconnected macropores??400?m?,high porosity??60%?and enhanced compressive strength??8MPa?.CaSO₄ scaffolds as a control,the biological properties of Pearl/CaSO₄ scaffolds were evaluated in vitro and in vivo.The results showed that Pearl/CaSO₄ scaffolds possessed good apatite-forming ability,stimulated the proliferation and differentiation of rat bone mesenchymal stem cells?rBMSCs?,as well as better expression of related osteogenic genes.Importantly,micro-computed tomography and histology of critical-sized rabbit femoral condyle defects implanted with the scaffolds illustrated the osteogenic capacity of Pearl/CaSO₄scaffolds.New bone was observed within 8 weeks.The bone-implant contact index was significantly higher for Pearl/CaSO₄ scaffolds than for CaSO₄ scaffolds.Hence,Pearl/CaSO₄ scaffolds would be promising scaffolds for bone regeneration.?2?Mesoporous bioactive glass?MBG?powders were synthesized by the approach of evaporation-induced self-assembly.A silk fibroin?SF?solution of 30 wt%was extracted from cocoons and combined with MBG to fabricate MBG/SF composite scaffolds by 3D printing.The results showed that MBG/SF had superior compressive strength??20Mpa?,good biocompatibility and stimulated bone formation ability compared to mesoporous bioactive glass/polycaprolactone scaffolds?MBG/PCL?.We subcutaneously injected hBMSCs-loaded MBG/SF scaffolds and MBG/PCL scaffolds into the back of nude mice for in vivo heterotopic bone formation assay,and qRT-PCR results of in vivo heterotopic bone formation experiments showed that the gene expression levels of the related biomarkers?BMP-2 and BSP?on MBG/SF scaffolds were significantly higher than MBG/PCL group.?3?Mesoporous bioactive glass?MBG?and alginate sodium?SA?were 3D printed into hierarchical scaffolds,named MBG/SA-SA.The hierarchical scaffold was integrated with two phases:SA hydrogel layer and MBG/SA composite layer.SA hydrogel layer can loaded with anti-inflammatory drugs and release drugs fast,and MBG/SA composite layer can loaded with antibacterial drugs and play the role of long-term and slow release.The alginate component in scaffolds served as adhesive among layers as well.The scaffold unity was crosslinked simultaneously through Ca²⁺salt solution immersion after 3D printing.In addition,the in vitro results showed that MBG/SA-SA scaffolds stimulated the adhesion,proliferation,alkaline phosphatase?ALP?activity and osteogenesis-related gene expression of hBMSCs.In conclusion,three kinds of porous scaffolds have been successfully fabricated by3D printing.Pearl/CaSO₄ scaffolds combined the cement chemistry with an excellent bioactivity of pearl together,resulting in good bone-forming bioactivity,enhanced mechanical strength and biological properties.MBG/SF scaffolds had superior mechanical strength??20 MPa?,and good biocompatibility and stimulated bone formation ability.MBG/SA-SA hierarchical scaffolds showed two different drug loading and release modes and could stimulate hBMSCs attachment,proliferation and differentiation.