Construction,Modification And Biological Evaluations Of Microspheres Based Topological Structures

Surface modification of metal implants for enhancing osseointegration is one of the most important issues in bone repair field.To establish microenvironment suitable for cell growth with topological and construction and composition modification on the surface of implant,is an effective approach to improve growth of bone tissue on the interface between implant and host bone and enchance osseointegration.However,how to design and construct appropriate surface to meet the best physiological effects of osteoblasts is still an open question.In this thesis,microsphere was used as the basic unit of topology construction,adopted different methods to construct surface topology with different scales,different density and different surface composition.Moreover,cell adhesion,proliferation and differentiation were adopted to evaluate the biological effects of the topological structured surface.In addition,the mechanism of the topological structure surface with microspheres on cell regulation was discussed.The research achievements of the following 3 aspects are mainly obtained:1.Construction,modification and evaluation of the topological structure of SiO2 microsphere.SiO2 microsphere of subcell scale(140 nm?500 nm)was used as the basic unit of structure constructing by spin-coating method.The topological structure of SiO2 microspheres with uniform dispersion and varied density can be formed by changing the parameters such as dispersion system and rotational speed.The topological structure with the best biocompatibility was selected and the components of TiO2,Al2O3 and Au were modified on the surface.Modification of the different components in different growth stages of the osteoblasts represented different promotion.TiO2 modification could effectively promote cell adhesion;Al2O3 modification played an impotant role in promoting cell proliferation;and Au modification palyed a significant role in promoting both the adhesion and proliferation of osteoblasts.It was likely that the stimulative effect of this different stage was related to the protein adsorption capacity and orientation of the topological surface.2.Construction,modification and evaluation of the topological structure of Ti microsphere.Ti microsphere or nanostructured Ti microsphere of supercell scale(10 ?m-53?m)was used as the basic unit of structure constructing by spin-coating method.By changing the parameters such as dispersion system,solid content and rotational speed,constructed topological structures with low density(120 per mm2),middle density(720 per mm)and high density(2400 per mm),respectively.And their biological properties were evaluated.Although the nanostructured Ti microspheres could significantly promote the absorption of the protein,and had obvious promotion effect on the adhesion and spread behavior of a single cell,while the middle density structure showed the most obvious promotion ability for cell adhesion,proliferation and differentiation.The possible mechanism was proposed for this anomaly,and it was verified by changing the inoculation density of cells:The middle density topological structure of supercell scale plays a space constraints role in cell distribution behavior,and promotes the formation of cell aggregates.Cell aggregates could significantly promote cell adhesion,proliferation and osteogenic differentiation by promoting the effective transmission of biological signal molecules between cells and cells.Topologic surface with nanostructured Ti microspheres though had better promoting of single cell adhesion,but also destroyed the space constraints;as a result,cell aggregates could not form,and its biological effects was inferior to middle density topologic structure.3.Construction,modification and evaluation of the topological structure of TC4 microsphere.TC4(Ti6Al4V)microsphere of supercell scale(10 ?m?53 ?m)was used as the basic unit of structure constructed by 3D printing.Three typical topological structured surfaces were obtained by changing the relative orientation of the sample forming process and the laser:3D-S with only the striated structure,3D-D with only dispersed microspheres,and 3D-SD with both striated structure and dispersed microspheres.The width and depth of the stripe structure could be adjusted by changing the 3D printing process parameters,but the dispersed microsphere structure had not been significantly affected in the range of process parameters.On the surface of 3 different topological structures,nano-structured modification was carried out,and each biocompatibility of above topological structures was evaluated.As the results of cell culturing,in the stage of cell adhesion and proliferation,the dispersed microsphere topological structure played a major role in regulating and promoting cell behavior,which may be related to the space constraints effect of the dispersed microspheres promoting the formation of cell aggregates.In cell differentiation stage,3D-SD with both striated structure structure and dispersed microspheres showed the best contribute to bone differentiation ability.In addition,the width and depth of the stripe structure also had certain regulation effect on osteogenetic differentiation.However,the 3D-S group with only the striped structure showed no obvious effect on differentiation,witch means that the stripe structure had certain regulation ability to promote differentiation,but it needed to be based on the dispersed microsphere structure which may promote cell aggregates formation,and the striped structure made the cell aggregates have certain orientation and promote cell differentiation.Moreover,nanostructure modifications also need to rely on the proper topological structure to show better cellular responsiveness.The nano-structure modified 3D-S did not have a significant effect on cell response behavior,while the cellular response of 3D-SD was significantly improved after the modification of the nano-structure.On the one hand,the nanostructure promotes protein absorption and provides more cell recognition sites;on the other hand,the nano-structure of 3D-SD does not inhibit the formation of cell aggregates,as a result,the nanostructure modification can play a positive role in promoting cell response.In this thesis,the topological structure and biological effects of microspheres as the basic structural units were studied,and the mechanism of good biological effect is analyzed and verified,which provides new ideas for the topological structure design and forming process selection of the surface modification of metal implants in the future,which is of great significance for the acquisition of implants with high surface osteosynthesis response.