The Preparation Of Multifunctional Micro/Nano Coating On Substrates For Bone Induction Research

Biomedical metals/alloys play an important role in bone repair materials due to their excellent mechanical properties and biocompatibility.However,they are far from clinical requirements for bone induction.Therefore,surface modification by introducing multifunctional bioactive coating with micro/nano structure is a smart strategy to increase bone inductivity.In this study,we select two typical biomedical metals/alloys,Ti and biodegradable AZ31 magnesium alloy,as our base material.Then,HA and BMP-2,which has good bone conductibility and inductivity,respectively,were self-assembled on these base material surface.Such obtained multifunctional bioactive coatings with micro/nano structure have significantly improved the biocompatibility,corrosion resistanece and bone inductivity,and promote bone tissue repair with the synergetic effect of BMP-2 and HA.In Chapter 2 and Chapter 3,the PHA/PBSA(BMP-2)bioactive coating with micro/nano structure was introduced on the bioinert Ti substrate through layr-y-layer self-assembly approach.Firstly,HA nanoparticles were prepared by wet chemical precipitation,and the obtained HA nanoparticles were enrapped into super adhesive PDA.The BSA nanoparticles incorporated with BMP-2 was prepared through desolvation.By modifying the BSA nanoparticles by PDA,the PBSA(BMP-2)nanoparticles were obtained with super adhesive function.The various nanoparticles were characterized by XRD,SEM,TEM and laser particle size analyzer.The results show that the nanoparticles have regular shape,uniform particle size,and stable surface charge.TEM confirmed that the approach to modify nanoparticles by PDA is effective.The PHA/PBSA(BMP-2)were coated on the Ti surface after acid pre-treatment,alkali pre-treatment and PDA intermediate coating by layer-by-layer self-assembly method.The morphology and properties of the coating were characterized by SEM,water contact angle,mechanical tensile test,simulated body fluid immersion and growth factor release.The results show that the micro/nano structured coating was about 7.5?m in thick,improved wettability,good bonding strength with substrate,degradability,and play an active role in sustained release of BMP-2.BMSCs cell culture and in vivo implantation test in thigh bone marrow cavity of rats show that the PHA/PBSA(BMP-2)coating prepared by layer-by-layer self-assembly can promote cell adhesion,proliferation,the osteogenetic differentiation,and therefore improve the biocompatibility and bone inductivity of Ti.The synergetic effect of HA and BMP-2 can accelerate the bone tissue growth.In Chapter 4,to increase the corrosion resistance and improve the bone growth rate,PHA nanoparticles incorporated with BMP-2 weare assembled on the AZ31 magnesium alloy by the strong adhesion of PDA.Similarly,the morphology and properties of the coating were characterized by SEM,water contact angle and tensile test,the results show that the coating was about 1.1 ?m thick,excellent wettability and strong bonding with substrate.The corrosion behavior of AZ31 magnesium alloy with and without coating was studied by electrochemical potentiodynamic polarization test and in vitro hydrogen evolution experiment.The results show that PHA coating can obviously improve the corrosion resistance of AZ31 magnesium alloy and delay the degradation of the alloy.Finally,the biocompatibility and bone inductivity of the coating were studied by BMSCs cell culture and the in vivo implantation experiment in thigh bone marrow cavity of rabbit.The results show that the PHA coating can promote cell adhesion and poliferation,and thus improve the biocompatibility and bone inductivity of AZ31 magnesium alloy.This study provides a novel strategy to improve corrosion resistance,biocompatibility and bone inductivity of biomedical metals/alloys by surface modification,which will benefit the design of multifunctional coatings on metallic biomaterials for bone tissue repair and their clinical application.