Preparations Of Biomimetic Carbonate Hydroxyapatite And Study Of Cartilage Mineralization

Hydroxyapatite(HA)is a natural mineral compound of calcium apatite that can be represented by the formula Ca10(PO4)6(OH)2 to highlight that it is composed of two parts.HA is a new common biological material with excellent biocompatibility and bioactivity,owing to its non-toxic and non-corrosive characteristics,it has been widely applied in the field of biomedicine.Since hydroxyapatite play an important role of mechanical modification in polymer materials and the cartilage surface,the main contents of the paper are as follows:1.Different doping amount of carbonate hydroxyapatite(CHA)by classical natural precipitation method were successfully prepared.Carbonated hydroxyapatite(CHA)with different carbonate contents was synthesized by a simple precipitation method in Ca(NO3)2-(NH4)2HPO4-NH4HCO3-SBF reaction system.The effects on synthesized crystal structure were investigated with different hydrothermal parameters including temperature,time and pH values.The composition,particle size and carbonate contents were analyzed by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),Transmission electron microscopy(TEM),Thermo-gravimetry and differential thermal analysis(TG-DTA)and X-ray photoelectron spectroscopy(XPS),respectively.The CHAs synthesized at pH value of 10 and 95 ℃ show the following characteristics,the substitution of carbonate in CHA lattice is mainly B type,and the crystallinity of CHAs decreases and the average particle size with the length of-35nm reduces to 10-20 nm when the carbonate content increases.2.Strengthening nano-hydroxyapatite with carbon content of 8%/polylactic acid nano-composite sheet materials were prepared by blending method in SBF to study the microscopic morphology and mechanical properties of the sheet.Scanning electron microscopy(SEM)showed the apparent morphology of hydroxyapatite blend on polylactic acid sheet.Infrared and Raman analysis in a sheet having PO43-reflects that hydroxyapatite and polylactic acid were blended evenly.A high-resolution multi-parameter atomic force microscope(AFM)was used to study the mechanical properties of nano-sheet,with the increase of doping amount,the Young’s modulus,roughness and surface area increased.3.In this study,Atomic force microscopy(AFM)was used to characterize the differences in morphology and nanomechanical properties of the poly(lactic acid)fibers in the mineralization process.Nanofibers of poly(lactic acid)were soaked in 5 times SBF(5 SBF)for different periods(0,1,3,5,7 and 21 days)to perform the biomineralization.Hydroxyapatite distribution was inconspicuous in the samples without mineralization but more obvious in mineralized one.AFM was used to examine the difference of nano-scale structure on the surface of the poly(lactic acid)fibers.It has been shown in the AFM images that with the increasing days of mineralization,the surface roughness of the poly(lactic acid)nanofiber increased.Here,High-resolution multi-parametric Atomic force microscopy(AFM)was used to make a research that how the structure and nano-mechanical properties of fiber changed when poly(lactic acid)nanofiber were mineralized in 5 times simulated body fluid(5 SBF).In the period of mineralization,change of Young’s Modulus was especially obvious along with time.4.In this study,Atomic force microscopy(AFM)was used to characterize apparent morphology and biomechanical properties of bovine articular cartilage in mineralization.Morphological differences of mineralized cartilage collagen bundle were more conspicuous than unmineralized samples.Owing to bovine articular cartilage after guanidine gydrochloride treatment,this results in accelerated cartilage mineralization.AFM was used to examine the nano-scale structure difference in the superficial and intermediate layer of cartilage.AFM images showed that the cartilage in the mineralized condition is much rougher than that in the unmineralized condition.Proteoglycans embedded in type Ⅱ collagen bundles can affect the biomechanical properties of articular cartilage.Despite its crucial role,its architecture remains largely unknown.Here using high-resolution multi-parametric atomic force microscopy(AFM),we studied how the structure and biomechanical properties of collagen bundle change when cartilage was mineralized in simulated body fluid(SBF).Mineralization can directly result in a rougher structure both on the surface and bulk of articular cartilage.The morphology change of mineralization processes in cartilage extracellular matrix(ECM)is irreversible.The nanostructure of cartilage is measured by length and thickness.With the increase of the mineralization time,the length decreases but the thickness increases.Mechanical properties such as Young’s modulus,adhesion also change correspondingly.