Research On Synthesis Mechanism And Vitro Property Of The Hydroxyapatite Nanocomposite

The structure and the function of the nano-biomaterials are an important research topic and the development directions in the field of medicine and material recently. Nano-hydroxyapatite(HA)is the main constituent of hard tissues such as bone, dentin and enamel. It is an important inorganic biomedical material, which possesses finer degradability, better biocompatibility, higher absorbability for medicine. So it will create more value if mesoporous hydroxyapatite can be synthesized.In this investigation, the composite biological hydroxyapatite with mesoporous structure has been prepared successfully by using yeast cells as the biotemplate under room temperature and ordinary pressure. The orthogonal test was applied to optimize the synthetic parameters. Furthermore, synthesis mechanism and in vitro performance were researched systematically. The present technology has many advantages including the mild reaction condition, the simple process, and a good structure repetition. The composite biological hydroxyapatite has more merits than the blank hydroxyapatite synthesized by other methods. The structure and morphologies of resultant samples were characterized by X-ray diffractometry, Fourier transform infrared, transmission electron microscopy and so on. The results indicated that yeast cells can induce the nucleation and growth of crystal, which will control the size of nanoparticles. The size of nano-hydroxyapatite obtained at 80°C is approximately 10-30 nm. It has the unique multi-level porous and the distorting lattice structure. The synthetic mechanism was analyzed by fermentation of yeast cells, adsorption of metal ions, lewis acid-base theoryby, biomineralization, the nucleation and growth of crystal.In vitro degradation tests showed that the composite biological hydroxyapatite has a lower water sorption rate than the blank hydroxyapatite when immersing in simulated body fluid, which indicated that the former possessed better chemical stability. The exchange-depositon of Ca2+and PO43- are similar to the process of new bone formation. The composite biological hydroxyapatite also exhibited a unique fluorescence enhancement effect. It has the performance of transfection fluorescence to onion cells. Negatively charged composite nanoparticles are highly bioactive. Animal cells had well adherence and proliferation properties on the sample surface. The toxic degree of the nanocomposite was in zero grade standard and it had no hemolysis. The sample can induce the apoptosis of tumor cells which englobed superfluous Ca2+. The nanocompsite has no antibacterial activity, but the hydroxyapatite loading silver can kill gram-positive golden staphylococcus and gram-negative coli availably. The nanocomposite is suitable for the excellent antibacterial carrier.The composite nanoparticles of hydroxyapatite can be developed as bioactive materials for drug-controlled release carrier and bone regeneration. The mesoporous structure of nanocomposite is beneficial to drug controlled release. The hydroxyapatite has unique amphiphilic property for the hydrophilicity of hydroxyapatite and the hydrophobicity of some amino acid groups. It can improve drug bioavailability as hydrophobic/hydrophilic drug delivery.