Laser Additive Manufacturing And Performance Of Self-powered Electrical Stimulation Bone Scaffolds

Bone defects caused by fractures,bone tumors,trauma and infections,are still acommon refractory problem in the field of orthopedic.Artificial bone implants have attracted widely attention for its advantages of low immunogenicity,no secondary trauma and a wide variety source.After years of development,artificial bone implant has achieved a big breakthrough from short-term replacement filling to permanent replacement.However,there still exist some problems in the implants material such as a poor biological fusion,long and uncontrollable repair period and so on.To solve aforementioned problems,the increasing number of artificial bone implants material are required to mimic the growth microenvironment of cell and tissue,achieving the regulation of cell proliferation and differentiation,as well as the repair of tissue structure and function eventually.The electric microenvironment plays a vital role in maintaining physiological activity and metabolism of bone tissue.This thesis proposed fabricating porous piezoelectric scaffold by selective laser sintering（SLS）technology.On one hand,with the concept of additive manufacturing,the SLS technology can fabricate porous structure and complex shape of bone scaffold.One the other hand,with the force-electric conversion characteristics piezoelectric scaffold can in situ build electric microenvironment for tissue growth in response to external stress.The mainly innovations and contents of this thesis are as follows:1.The barium titanate（Ba Ti O₃）possesses excellent piezoelectric property and good biocompatibility,but its high brittleness,difficult-to-machine limited it to be used as a bone repair material alone.This thesis proposed that the Ba Ti O₃/nylon 12（PA12）piezoelectric bone scaffold was fabricated using SLS technology by introducing nano Ba Ti O₃into nylon12 which exhibit well good flexibility and process ability.The results show that under the action of external force,the oriented dipole within Ba Ti O₃will be deflected and polarized charges will be generated.The optimal content of BT was found to be 20 wt%,with which the electric output performance have increased 30%,enhancing the adhesion and proliferation of cells.Meanwhile,the nanoparticles can prevent the crack propagation,increasing the tensile strength and tensile module by 61%and 34.9%,respectively.2.In order to solve the problem that the Ba Ti O₃nanoparticle was prone to aggregate within polymer matrix because of the large specific surface area of nanoparticle weakened the mechanical electrical conversion property.This thesis proposed to functionalize Ba Ti O₃nanoparticle with polydopamine（PDA@BT）.It was found that the PDA@BT nanoparticles were uniformly distributed within PVDF matrix.Furthermore,the strong hydrogen bonding interaction between the functional group（amino and phenolic hydroxyl group）of polydopamine and C-F group of PVDF can produceβphase,and its content ofβphase increased from 46%to 59%.Because of the increased content ofβphase,the electric output performance was increased356%,which promoted cell adhesion,proliferation an differentiation.In addition,the polydopamine can be used as a coupling agent to improve interface compatibility between the polymer and ceramic,which promoted the mechanical strength and module.3.In order to overcome the difficulty in polarizing ceramic in polymer-based scaffold caused by the large dielectric differences between ceramic and polymer.The incomplete polarization of Ba Ti O₃leads the piezoelectric cannot be fully exerted.The strawberry-like Ag-Ba Ti O₃（Ag-p BT）structure nanoparticles that prepared by in suit growth technology were introduced into piezoelectric scaffold.The nano-silver can not only be used as a conductive phase to enhance the polarization electric field strength applied on of barium titanate,thereby improving the polarization efficient and electric active of the scaffold.More importantly,the Ag nanoparticles can release Ag⁺and produce reactive oxygen species to attack multiple targets in bacteria,which endowed scaffold antibacterial property.The results showed that the output current and voltage of the prepared scaffold were increased by 50%and 40%,respectively,which effectively promoted the proliferation and differentiation of cells.Meanwhile,the scaffold showed strong antibacterial effect with an antibacterial rate of 81%.