Construction Of Black Phosphorus Nanocomposite Hydrogel For Bone Regeneration

Phosphorus is one of the main elements of bone composition,and it exists in bone tissue mainly in the form of hydroxyapatite.It is an essential mineral element in the process of bone regeneration and functional reconstruction.Black phosphorus as a new two-dimensional nanomaterial shares high homology with the inorganic components of natural bone.In the physiological environment,the phosphate produced by the degradation of black phosphorus nanosheets can participate in the regulation of the bone tissue microenvironment and mediate the deposition of calcium phosphate mineralized crystals.However,whether black phosphorus nanosheets can effectively exert its biological functions and be used in bone regeneration depends on the design of implanted carriers.The research of this thesis combined black phosphorus nanosheets with degradable biopolymers to construct black phosphorus-based hydrogels,and explored the effect of black phosphorus nanosheets on the physical and chemical properties of the polymer networks,as well as cell biology performance,especially the regulatory effect of black phosphorus nanosheets on the osteogenic differentiation of cells.The black phosphorus-based hydrogel was further functionalized by biomolecules,and the potential regulatory effect of black phosphorus nanosheets on bone regeneration in vivo was comprenhesively studied.It provides theoretical guidance for the development of new biopolymer materials for bone regeneration.(1)The interactions between black phosphorus nanosheets and polymers and the characterization of composite network and its osteoinductive propertiesTo reveal the regulation of black phosphorus nanosheets on the physical and osteoinductive properties of polymer materials,this study used methacrylate gelatin as a model polymer.Black phosphorus-based polymer composite networks were constructed using a chemical cross-linking strategy.The effect of black phosphorus nanosheets on the physical and chemical properties of hydrogel was characterized.The regulatory effect of black phosphorus nanosheets on cell behavior in vitro was discussed.The introduction of black phosphorus nanosheets can enhance the mechanical strength and biomineralization of crosslinking matrix and significantly up-regulate the expression of genes and proteins related to cell osteogenesis,effectively promoting the osteogenic differentiation of cells.(2)Construction of black phosphorus-based physical polymer network and study on its loaded VEGF of regulating angiogenic and osteogenic propertiesUsing black phosphorus nanosheets as a binding site of bioactive factor to realize the improvement of the bone repair performance of the hydrogels.In this study,vascular endothelial growth factor(VEGF)was selected as the bioactive factor,and the binding property between black phosphorus nanosheets and VEGF was studied.The influence of VEGF on the physical and chemical properties of black phosphorus nanosheets was analyzed by surface potential,particle size and other related parameters.Furthermore,the physical polymer network of deoxyribonucleic acid was used as the carrier matrix,and the black phosphorus-based hydrogel loaded with VEGF was constructed through the multiple hydrogen bonding.The introduction of black phosphorus nanosheets effectively improved the controlled release of VEGF from the hydrogel.The loading of VEGF effectively promoted the expression of angiogenesis genes and proteins of HUVECs,as well as the formation of reticular tubes.VEGF and black phosphorus nanosheets synergistically enhanced the osteogenic differentiation ability of stem cells and the regeneration of vascularized bone in vivo.(3)Construction of black phosphorus-based double-network porous hydrogel and its mechanism of regulating osteogenic differentiation of cellsIn order to realize the application of black phosphorus nanosheets in bone tissue engineering,it is necessary to construct a suitable three-dimensional porous structure in its composite hydrogel to promote cell migration and tissue ingrowth.In this study,the chemical network of methacrylate gelatin and the physical network of deoxyribonucleic acid were combined,and the high-porosity black phosphorus-based double-network porous hydrogels were successfully constructed through double cross-linking strategy and emulsion template method.The effect of black phosphorus nanosheets on cell behavior was discussed at a three-dimensional level,especially its regulatory effects and regulatory mechanisms on the osteogenic differentiation behavior of cells.The double-network porous hydrogels effectively promoted the proliferation and migration of stem cells,and the porous hydrogels containing black phosphorus nanosheets had an enhanced effect on the expression of cell osteogenic related genes,effectively promoting the formation of mineralized matrix.It was found from molecular mechanism studies that the black phosphorus-based double network porous hydrogel participated in promoting the osteogenic differentiation of cells by activating the Wnt/?-catenin signaling pathway.(4)Construction of aptamer functionalized black phosphorus-based double-network porous hydrogel and its bone repair performance in vivoIn the process of bone regeneration,different kinds of cells present around the bone defects.In order to selectively recruit endogenous stem cells to bone defect site for bone tissue regeneration,this study further anchored aptamer to black phosphorus-based double-network porous hydrogel.In vitro and in vivo experimental analysis was conducted to explore the recruitment effect of this system on stem cells and its bone repair performance.The modification of aptamer significantly improved the performance of the porous hydrogel to specifically capture stem cells,and mediated the homing of endogenous stem cells to bone defect site.The aptamer and black phosphorus nanosheets synergistically promoted the early repair of cranium defect.Overall,this study revealed the regulation of black phosphorus nanosheets on the physical and chemical properties and osteoinductive activity of the polymer networks.The synergy with aptamer proved the great potential of black phosphorus nanosheets in bone tissue engineering.It provides promsing strategy for the rational design and development of new biomaterials with bioadaptability for bone repair.