The Research Of Three-dimensional Printed Titanium Microporous Scaffold/Injectable Hydrogel Complex For Bone Defect Repairing

3D printing,also known as additive manufacturing,stirs up a hotspot in medical field for its great prospects for development.Metallic 3D printing is a kind of rapid prototyping technique based on digital file as its original model.During the manufacturing procedure,multiple solidification measures,e.g.electron beam melting & selective laser melting,cast paved metallic powder layer by layer as pre-designed and formed a three-dimensional shape.Contrast to traditional casting method,3D printing is characterized by its high customization and manufacturing process based on digital template.3D printing scaffolds with customized shape and fine internal structure provide the most matching degree implanted into the chamber and promote an optimal bone ingrowth effect to increase connect strength of bone-scaffold interface.Besides,porosity,pore size and pore shape can also be pre-designed which is much more advanced to scaffolds fabricated by conventional methods.Moreover,mechanical performance is affected by pore parameters.So,it is viable to manipulate mechanical property of scaffold via 3D printing technique to shrink the difference of modulus between natural bone and scaffold,which can avoid stress-shielding effect availably.Hydrogel constructed by natural macromolecules is characterized for high biocompatibility.Using hydrogel as a carrier,more growth space is provided owning to its 3D network construction after seeding the cells in.Besides,cells receive mechanical stimulations from hydrogel which process osteogenic potential.Our research aims to investigate the three-dimensional printed titanium microporous scaffold/ injectable hydrogel complex in repairing bone defect.The injectable capability of hydrogel benefits for the combination with 3D printing scaffold and fills the pores entirely.In in vitro test,favorable biocompatibility of 3D printing scaffold and injectable hydrogel was proved.After seeding BMSCs intocomplex,it was beneficial for the cell adhesion and proliferation.The mechanical stimulation of hydrogel on BMSCs can be observed by Calcein-AM staining;incorporated BMSCs lose its original spindle morphology and showed an approximate round shape.In in vivo test,complexes were implanted into distal femur of rabbits,and harvested the tissue after 3 months.Micro-CT was applied to assess the bone ingrowth volume and found that bone volume in experimental group(60.2mm3)was much higher than in contrast group(38.3mm3).Result of histological section was agreed to conclusion of Micro-CT assessment.In biomechanical push-out test,it verified that bone-scaffold interface strength in experimental group(0.177 k N)is significantly higher than in contrast group(0.015 k N).Based on the results of our research,we can conclude that: 1)three-dimensional printed titanium microporous scaffold/ injectable hydrogel complexis beneficial for the adhesion and proliferation of BMSCs seeded in it.Meanwhile,cell morphology can also be regulated after cooperated in the complex.2)Three-dimensional printed titanium microporous scaffold/ injectable hydrogel complexis good for bone ingrowth,the ingrowth bone volume and bone-scaffold connection strength are both highly improved.