A Preliminary Study On The Relationship Between Physico-chemical Properties And Biological Functions Of Calcium Phosphate Coatings Deposited By Electrochemical Method

Natural bone tissue is a composite consisted mainly of calcium phosphate(CaP),collagen and some trace elements with ordered micro-nano multi-level structure.From the perspective of bionics,different calcium phosphates(CaPs)are utilized to coat on the surface of metallic implants to enhance their biological activities,and to form facilitate bone integration at the implantation sites.The incorporation of trace elements into CaPs also helps to construct multifunctional CaP coatings.Among all the preparation methods,the electrochemical deposition method is widely used because of its high controllability.CaP coatings with highly ordered micron-nano multi-level structures can be prepared by a mild electrochemical deposition method,and the coatings have been proven to exhibit high biological activities.Despite of some clinically revenant achievements,the detailed mechanism for the high biological activities of CaPs are not yet fully understood.Therefore,it is of great significance to elucidate the correlations between the physico-chemical properties and the biological properties of CaPs coatings.The main research work of this thesis includes:to prepar of CaP coatings with gradually changing physico-chemical properties titanium substrate by electrochemical deposition method,and to investigate the correlations between the structure and composition properties and biological properties of the CaP coatings;to construc Sr ion-doped CaP coatings using electrochemical deposition method and to investigate the dependence of coating properties on doping,and to develop in situ Raman spectroscopy technique to monitor the interaction of the CaP coating/bioenvironment interphase.The main results are as follows:(1)The results of SEM,XRD,FTIR and Raman show that the CaP coatings prepared at different temperature(denoted as 40-CaP,55-CaP,70-CaP and OCP)exhibited gradually changing physico-chemical properties including surface morphology,Ca/P molar ratios,crystal structure,crystallinity and chemical composition.The simulated body fluid immersion experiment showed that the coating could induce the formation of B-type substituted bone-like apatite on the coating surface during the soaking process.The cell culture experiment showed that the topological structure of CaP coatings was the main factor affecting the morphology and proliferation of MC3T3-E1 cells.Under similar proliferation conditions,high crystallinity seemed to be more favorable for the MC3T3-E1 cell differentiation.The coatings also have regulation effect on the proliferation of MG63 cells and MEF cells.The proliferation activity of cells on the CaP coatings show a tendency of 40-CaP>55-CaP>70-CaP>OCP,which is directly related to the coating topography.(2)The CaP coating and the Sr ions were simultaneously deposited on the surface of titanium substrate by an electrochemical deposition method.The physico-chemical properties and biological properties of the doped OCPcoating with different Sr ion concentrations were systematically investigated.The successful controlled incorporation of Sr ions into the OCP lattice was determined by XRD,FTIR and Raman results.Simulated body fluid immersion experiments show that the incorporation of Sr ions is conducive to the conversion of OCP to apatite.In vitro cell experiments indicated that Sr/(Sr+Ca)=1%is an adequate Sr amount,to promote MC3T3-E1 cell differention on the surface.(3)The bone-like apatite formation process on 40-CaP,55-CaP and 70-CaP coatings in the simulated body fluids was in-situ monitored by micro-Raman spectroscopy.The spectroscopic test conditions for the in-situ monitoring of the interfacial interaction between the CaP coatings and the MC3T3-E1 cells including the lens used in the experiment and the liquid environment were initially determined.Raman spectroscopy was used to monitor the change of the CaP coatings in the cell culture medium environment.It was found that the presence of FBS reduced the dissolution rate of the coatings in the medium and reduced the incorporation amount of carbonate into the CaP coatings.