Study On The Integration Of 3D Printed Porous Titannium Coated By Polydopamine Nanospheres And Bone

PART 1 PREPARATION AND CHARACTERIZATION OF POLYDOPAMINE NANOSPHERESObjective Polydopamine(PDA)has good adhesion and biocompatibility.In this part,PDA nanospheres were prepared and characterized to explore the best simple preparation method.Methods PDA was prepared by oxidative self polymerization in alkaline c ondition.A proper amount of Tris powder was dissolved in water,a nd dopamine hydrochloride(DA)was added to observe and stir at p H 7.5,8.0,8.5,9.0 and 9.5 respectively.The formation of PDA film and the formation of PDA nanospheres were observed.Optical micros cope,transmission electron microscope,laser particle size and surface potential were used to characterize PDA concentration and absorbanc e.Results After DA in the Tris-HCL(pH 7.5,8.0,8.5,9.0,9.5),the mixed s olution was light brown rapidly.After 36 hours,the film deepened w ith the increase of pH.At the same time,the increase of pH promot ed the formation and color of PDA film,which was dark brown.Th e particle size and surface potential of PDA nanospheres obtained at different pH values are respectively:pH 7.5:(236.30±93.56)nm,-(24.26±2.40)mV;pH 8.0:(198.40±62.30)nm,-(22.16±11.43)mV;pH 8.5:(253.62±30.15)nm,-(21.18±4.04)mV;pH 9.0:(230.70±145.70)nm,-(29.61±4.61)mV;pH 9.5:(244.70±116.5)nm,-(28.09±2.64)mV.At pH 8.5,PDA n anospheres were regular and uniform in size.PDA nanospheres with pH values of 7.5,8.0,9.0 and 9.5 were agglomerated and difficult to disperse.Conclusion In this part,we have successfully explored and established the best and simple preparation method of PDA nanospheres.The particle size and morphology of PDA nanospheres prepared at pH 8.5 were uniform,the particle size was about 253 nm,and the distribution was uniform.The successful preparation of PDA nanospheres provides the basis for the next experiment.PART 2 STUDY ON 3D PRINTED POROUS TITANNIUM COATED BY POLYDOPAMINE NANOSPHERES AND ITS MECHANICAL PROPERTIESObjective In this part,we set the pore size and porosity of porous titanium which was printed by 3D printing machine and coated by PDA nanospheres.The micro pore structure and the mechanical properties test,hydrophilicity test and adhesion of PDA nanospheres were investigated.Methods The 3D printed porous titanium(3DPPT)was fabricated by selective laser melting(SLM).The microstructure of the scaffold was observed by scanning electron microscope(SEM)and the biomechanical results was observed by compression test.At the same time,the 3D printed porous titanium mesh(PDA-3DPPT)was characterized by SEM and X-ray photoelectron spectroscopy(XPS).Results The measured porosity and pore diameter of 3DPPT and PDA-3DPPT were smaller than those of the designed porosity and pore diameter,but there was no significant difference between the two groups(P>0.05).The results of compression test of PDA-3DPPT was better than that of 3DPPT(P<0.05),but there was no difference in elastic modulus between them (P>0.05).The peak of Ti2 P,O(1s),C(1s),n(1s),Cl(2)and P(3)were detected on the surface of PDA-3DPPT by XPS.It was confirmed that there was PDA on the surface of 3DPPT and PDA successfully adhered to3 DPPT.The contact angles of 3DPPT and PDA-3DPPT were 83.40°±2.07°,23.80°±3.11°respectively,which indicated that the hydrophilicity of 3DPPT after PDA coating was significantly better than that of 3DPPT(P<0.05),suggesting that the surface hydrophilicity of 3DPPT was significantly improved by PDA nanospheres coating.Conclusion SLM technology can accurately produce porous scaffold with small error,and the model has good biomechanical properties.After the PDA nanosphere coating,the mechanical properties of 3DPPT were not affected,but also the hydrophilicity was improved.PART 3 STUDY ON THE INTEGRATION OF 3D PRINTED POROUS TITANNIUM COATED BY POLYDOPAMINE NANOSPHERES AND BONEObjective In this part,we studied the effect of PDA-3DPPT on promoting the osteogenesis and verified the ability of the integration between PDA-3DPPT and bone,and provided experimental basis for clinical application.Methods The materials were co cultured with C3H10T1/2 cells.The effect s of the coating on cell adhesion,expansion and proliferation were d etected by CCK8 and SEM.Western blot was analyzed by measuring alkaline phosphatase(ALP)activity,alizarin red staining and protein imprinting.The expression of osteogenic differentiation related protei ns was detected by WB to study the effect of PDA nanospheres coat ing on osteogenic differentiation.The New Zealand rabbits model of femoral condyle and material implantation were established.The effect of coating modification on bone interface osteogenesis was studied by micro computed tomography(micro-CT)and histological examination.Results In vitro biomimetic mineralization test showed that HA deposition was obvious on the surface of PDA nanospheres.The results of CCK8 the results show that the modification of PDA coating could improve to some extent cell adhesion,expansion and proliferation.The results of ALP activity test,alizarin red staining and WB detection showed that PDA nanospheres coating could promote the osteogenic differentiation of C3H10T1/2 cells.Micro-CT,histology and push out test showed that the nanosphere coating of PDA could promote the osteogenesis of the bone interface,and the new bone grew into the bone more obviously.(P<0.05)Conclusion In vitro study showed that PDA nanospheres modified 3DPPT c ould promote cell adhesion,proliferation and mineralization.In vivo experiments have proved that PDA nanospheres can promote the gro wth of new bone tissue and form close bone interface fusion,and pr omote bone integration with 3DPPT.Meanwhile,PDA-3DPPT showed good biocompatibility and safety.