Fabrication Of Three-dimensional TPU Porous Scaffold And Its Surface Modification

Bone graft substitute(bone tissue engineering)is a continuously developing field in orthopedics.Compared with polylactide(PLA)or poly(?-caprolactone)(PCL),the thermo polyurethane(TPU)have received increasing attention due to its high elasticity and flexibility,desirable physical properties.In additionally,it can establish an intimate contact with surrounding bones.This directly contact can provide a stable bone-material interface for cell proliferation and ingrowth.However,the lack of the cell recognition sites and poor hydrophilicity of TPU scaffold,which limit its application in practical applications.Therefore,preparing TPU scaffolds that can simultaneously fulfill all of the stringent requirements for potential clinical translation is still a challenge.These requirements usually include high porosity,suitable mechanical properties,excellent biocompatibility and bioactivity,etc.Therefore,this thesis work aimed to modify the surfaces of TPU scaffold.The following three projects showcase the major findings of this thesis work.1.The three-dimensional(3D)porous TPU scaffold was fabricated by VARTM,phase separation,solvent extraction,particle leaching approach.Two approaches have used for functionalization TPU/hydroxyapatite(HA)scaffold: ultrasonication-assisted(HA-decorated TPU)and physical blending method(HA-blended TPU).The results show that the TPU/HA composite scaffolds have a three-dimensional porous structure and good interconnectivity.It was found that HA had better dispersion in TPU matrix surface in HA-decorated TPU scaffold.The results showed that the water uptake,hydrophilicity and mechanical properties biocompatibility of HAdecorated TPU scaffold significantly improved compared with HA-blended TPU scaffold.2.In order to enhance the interfacial properties between TPU matrix and HA,the surface of HA-decorated TPU scaffold was modified by polydopamine(PDA)coating.We prepared a 3D PDA-HA@TPU composite scaffold with a uniformly PDA nanolayer.The result confirmed that PDA was successfully coated on the HA-decorated TPU scaffold.The PDA-HA@TPU scaffold exhibit superior hydrophilicity and mechanical properties.PDA-HA@TPU scaffold have high porosity,interconnected pore structure and superior comprehensive mechanical properties.Dynamic mechanical analysis(DMA)result showed that,for PDA-HA@TPU scaffold,the interfacial binding force between polymer matrix and organic filler increases,owing to the introduction of the PDA coating used as the glue transition layer.In vitro results indicated that the growth and proliferation of osteoblast-like cells on PDA-HA@TPU scaffold enhanced significantly.3.In order to solve the agglomerate proplems when HA nanoparticles blending with TPU matix.The HA nanoparticles were modified by PDA coating.Firstly,the p-HA nanoparticles were prepared by modifying HA nanoparticle using PDA coating.Secondly,the TPU/p-HA composite scaffold was fabricated by using blending method.Finally,the p-HA@TPU/p-HA was fabricated by using ultrasound-assisted technique to improve the comprehensive performance of scaffolds.The results showed that the hydrophilicity and thermal properties of p-HA@TPU/p-HA scaffold enhanced significantly.Meanwhile,the p-HA@TPU/p-HA scaffold demonstrated a superior compressibility property.Under 100 cycles at compressive strain over 60 %,the scaffold could recover to their original shape quickly after the release of the pressure.In vitro results indicated that the growth and proliferation of osteoblast-like cells on p-HA@TPU/p-HA scaffold enhanced significantly.