Construction,Characterization And Evaluation Of Hydroxyapatite Nanocrystals As Calcium Supplement

ObjectiveCalcium is the most abundant mineral elements and important metal elements in human body.It almost participates all of body's life course.About 1200 g calcium is in human being and 99% of it presents in bones and teeth as Hydroxyapatite(HAP)[Ca10(PO4)6(OH)2] form.In this study,calcium chloride and disodium hydrogen phosphate were used to prepare hydroxyapatite nanocrystals by chemical precipitation and microemulsion method,respectively.The pharmaceutical properties of the nanocrystals were characterized and the calcium supplement effects were evaluated.MethodsHydroxyapatite nanocrystal A(n HAP-A)was prepared by chemical precipitation method.The stabilizer,temperature and stirring rate were preferred according to the index of particle size.Hydroxyapatite nanocrystal B(n HAP-B)was prepared by microemulsion method The three-phase diagram was drawn according to the maximum solubilization which was measured by the conductivity in this system.The organic phase,the proportion of emulsifier/co-emulsifier and the reaction concentration was confirmed.The calcium content of n HAP was determined by atomic absorption spectrophotometry.The structure,crystal form,particle size,zeta potential,crystal structure and morphology of HAP nanocrystals were characterized by Fourier infrared spectrum(FTIR),X-ray diffraction(XRD),dynamic light scattering(DLS)and scanning electron microscopy(SEM),respectively.The dynamic dialysis method was used to investigate the release of n HAP in vitro.The calcium supplement efficiency of n HAP-A/B was investigated.The mice were intragastric administration,the serum and bone calcium content were measured by atomic absorption spectrophotometry.the bone mineral density(BMD)was measured by the bone mineral density analyzer and the concentration of bone alkaline phosphatase(BALP)in mice was detected by enzyme-linked immunosorbent assay(ELISA).Resultsn HAP-A was prepared by chemical precipitation method.The temperature was 90?.The stirring rate was 500 r/min.Polyacrylic acid(PAA)was determined as stabilizer.n HAP-B was prepared by microemulsion method.n-hexane was determined as organic phase.The ratio of emulsifier to co-emulsifier(Km)was 0.5.The concentration of calcium chloride and sodium hydrogen phosphate were 0.2 and 0.12 mol/L,respectively.The n HAP-A and n HAP-B particle size were 144.1±1.65 nm and 35.51±1.32 nm.The Zeta potential were-23.2±0.45 m V and-25.13±1.27 m V,The shapes were needle-like and spherical.Compared with HAP,the release rate and release amount of n HAP-A were higher than those of HAP.The release amount of n HAP-B was higher than n HAP-A.The serum calcium concentration,bone calcium contents and bone mineral density of n HAP-A/B were higher than those of HAP.The BALP concentration was lower than those of HAP.Compared with n HAP-A,n HAP-B had better effect of calcium supplement.Conclusionsn HAP-A was prepareted by chemical precipitation method.It solved the problem of particle agglomeration.The products was relatively pure and the process was simple.Chemical precipitation method was easy to realize industrialization.n HAP-B was prepared by microemulsion method.The preparation of nanoparticles by microemulsion method,which had the advantages of narrow particle size distribution,good dispersibility,simple preparation process and industrialization.Compared with n HAP-A,the blood calcium concentration,and bone calcium contents of n HAP-B were higher.The femur density and decrease the concentration of BALP.It was promoted the calcium in bone deposition.It was inhibited the bone resorption and increased bone mineral density.It ensured the growth of bone calcified.Therefore,hydroxyapatite nanocrystal is expected to become a new generation of calcium supplement products.