Study On Preparation And Performance Of PA12/HA Functionally Graded Scaffold Based On Selective Laser Sintering

Bone tissue engineering is the most popular bone tissue repair method in today’s society,and scaffolding as its core element is the top priority of research.As a carrier for cell growth,scaffolds have an important effect on cell behavior,but the difficulty in the research of bone tissue engineering scaffolds is the design of gradient structures.Selective laser sintering(SLS)is one of the latest development forms of additive manufacturing technology,which provides a new idea for the preparation of bone tissue scaffolds,which can precisely control the pore structure.In order to prepare bone tissue engineering porous scaffolds with excellent properties,the selection of materials is particularly important.Polydodecanolactam(PA12)has excellent mechanical properties,chemical stability and biocompatibility,and hydroxyapatite(HA)has excellent biological activity as a bone inducing factor.The purpose of this paper is to construct a PA12/HA gradient porous scaffold.First,the best SLS molding process parameters were obtained for PA12 powder.Then,the design method of gradient structure bone tissue engineering scaffold based on curve interference and minimal surface was studied,and SLS technology was successfully adopted.The scaffolds were prepared,and the mechanical properties and biological characteristics of PA12/HA composites under different mixing conditions were analyzed,which will provide a reference for the future research of scaffold grafts.The research content and achievements of this topic are as follows:(1)Process parameter optimization: Taking PA12 powder as the molding material optimized for the SLS parameters,the preheating temperature of the SLS technology was determined to be 170 °C and the thickness of the single layer was 0.1mm through single factor experiments.The laser energy density was used to study the interaction of laser power,scanning speed,and scanning pitch,and the optimal molding process parameters were determined to be laser power of 16 W,scanning speed of 2500mm/s,and scanning pitch of 0.12 mm.(2)Structure optimization of gradient support: Details The design ideas of designing square pore,cylindrical pore,regular hexagon pore scaffold and minimal curved surface method for designing Schwarz P,Diamond,Gyroid curved scaffold by curve interference method are introduced.And through mechanical experiments and finite element analysis,it is determined that the 75-60% radial gradient scaffold of the P-surface is the optimal gradient structure.(3)Characterization of PA12/HA composite materials: Characterization of PA12/HA composites: This paper studies the effects of composites on SLS process parameters by characterizing PA12/HA composites.The results show that there is no significant change in the preheating temperature of PA12/HA composites with different proportions,and there is no chemical reaction between PA12 and HA after sintering the composite.Therefore,the process parameters for forming PA12 powder are also applicable to PA12/HA composites.material.(4)Preparation and performance research of PA12/HA gradient scaffolds: This article uses SLS technology to prepare PA12/HA composite gradient scaffolds,and analyzes the effects of different proportions of composite materials on the micromorphology,hydrophilicity and mechanical properties of the scaffolds.External cell culture was performed to evaluate the biological activity of the scaffold.The results show that the addition of HA will increase the surface roughness of the scaffold.As the content of HA increases,the hydrophilicity of the scaffold increases.The degree of influence of HA content on the compression performance of the scaffold was 5% HA,PA12,10% HA,and 15% HA in descending order.The biological activity of PA12 scaffold was higher than that of 15% HA scaffold.