| Mineralized materials in the nature,such as bone,teeth and shell,have superior strength,toughness,shock absorption capacities,and special biological properties.Research into the mechanisms and characteristics of the formation of these materials,or biominerlization,may provide insights into the development of hard tissues substitution materals.Biomineralization usually occurred in a confined environment containing various organic substances,an example being the formation of teeth.Therefore,studies on the mechanisms/characteristics of biomineralization should simulate the environment and the related conditions.This thesis studied the effect of(several model) organic compounds on the formation of bone-like apatite layer on calcium-phosphate-based biocomposites. The results showed that:the kinds of bone-like apatite formed on the surfaces of different composites were different types.The surface of hydroxyapatite/ polycaprolactone(HA/PCL) assisted the formation of the bone-like apatite (Ca10(PO4,CO3OH)6(OH)2) with OH-and CO32- substitution and the surfaces of HA/CS and HA/SF induced the formation of the bone-like apatite with CO32- substituted,their structure and composition is similar to that of the inorganic phase of natural bone.The biocomposites of HA/CS and HA/SF were well capable of inducing the formation of bone-like apatite on their surfaces,owing to many function groups in SF and CS,which may provide appropriate nucleation sites for crystal.Then the effect of bovine serum albumin(BSA) and chondroitin sulfate(ChS)on the formation of bone-like apatite in simulated body fluid(SBF) was investigated.The results showed that bone-like apatite with CO32- substitution formed on the surface of HA substrate after soaking in 2SBF modified with BSA or ChS for 3days.The presence of BSA in solution promoted the growth of bone-like apatite crystals with big crystals size.Moreover,it favored the oriented growth of crystals along(300) plane. In contrast,ChS had a strong negative influence on crystallinity of the biomineral and restrained the growth of crystal.When BSA and ChS coexisted in solution, BSA promoted crystal growth but ChS inhibited as they existed along.The diffraction peak intensity of bone-like apatite crystals increased with BSA concentration,and decreased with the increase of ChS concentration.In order to improve the growth rate of apatite coating on the surface of biomaterials,a new method to prepare biomimetic calcium phosphate coatings on Ti alloy was studied.The results showed that a uniform layer of calcium phosphate crystals surfaces formed on the surfaces of samples after treated 5 times with ACS solution,but the coating was thin.The surface of the sample pretreated 10 times was completely covered by thin flaky crystals,and the length of flaky crystals was about 2-3 microns.The calcium phosphate flakes aggregated densely after pretreated 10 times and then growth for 2h in ACS solution,and thickness of the coating was about 10μm.XRD analysis showed that calcium phosphate phase was Ca8(PO4)4(UPO4)2·5H2O.An "evaporation-induced" treatment is a convenient way for preparing coating and reduces the time of nucleation and growth of calcium phosphate,at the same time,there are no special requirements for the sizes and shapes of samples,and can be widely used in preparation calcium phosphate coating on the surface of variety of materials.
|
PDF Full Text Request