Study On The Longrange Ordered Lamellar Hydroxyapatite Via Templates And Composite Microspheres Based On Alginate

Materials with longrange ordered meso-structures were fabricated via templates technology based on molecular self-organization. In this process, hydrogen bond, Van der Waals bond and other noncovalent bonds cooperated as a whole, by which one or more units magnified themselves to form aggregates having steady structure, then these aggregates as structural units were multi-duplicated, which made the system's organization evolve to higher levels, finally the system with nanostructure was formed. Templates method is an effective and cheap way to build the nanostructure. Templates method were introduced into the synthesis of hydroxyapatite (HAP, Ca10(PO4)6(OH)2), which exhibits strong affinity to host tissue, to form hierarchy structure. Calcium hydroxyapatite with longrange ordered lamellar nanostructure and well-crystallized lattice, noted with Lα-HAP, was fabricated via sodium dodecyl sulfonate (SDS, C12H25SO3Na) as templates in ethanol-water solvent. The longrange ordered lamellar nanostructure was characterized by X-ray diffraction (XRD) in the small angles (2θ = 1~15°) and HAP phase in 9~60°. The longrange ordered lamellar nanostructure and the orientation of the growth of crystal were observed by High Resolution Transmission Electron Microscopy (HRTEM). Based on these, the model of this hierarchy structure was given. Followed, the hydroxyapatite was characterized by thermogravimetry (TGA), Fourier transform infrared spectroscopy (FTIR) and N2 adsorption and desorption isotherms. The result showed that the periodicity of the lamellar structure was about 3 nm. The crystal grew along the crystal faces (100) and (002) in the Lα phases, but the growth of perpendicular face was restricted by the templates. Template content, NaOH content, concentration of materials, phosphates resource, riping time and aging time have influence on the formation of longrange ordered lamellar nanostructure. The volume ratio of ethanol and water is 1:1 to 1:2.Calcium alginate/Lα-Hydroxyapatite composite microspheres were fabricated via inverse suspension (W/O) with chloroform and hexane as dispersed phase, ethyl cellulose as disperser, mixture of Lα-hydroxyapatite and sodium alginate solution as dispersing phase, finally, the microspheres were crosslinked with calcium chloride solution. The preparation conditions were optimized. The physical appearances of the microspheres were characterized. It was shown that content of ethyl cellulose should not less than 0.2 g in this experiment; the suitable adding speed of dispersed phase and the speed of stirring are about 25 mL/min and 120 r/min, respectively. The specific gravity of the microspheres containing 50% and 70% HAP is 1.06 and 1.15 g/cm3, respectively, evaluated by Archimedean method.