Study On N-Hap As A Model Of Targeted Drug Delivery System

In this paper, nano hydroxyapatite (n-Hap) crystals were synthesized by precipitation method using Ca(NO3)2 and NH4)2HPO4 as raw materials. The effects of reaction temperature, reactants concentration, acidity of the aqueous solution, and washing method of resulting products on the size and shape of Hap crystals were studied. Results show that, when the reactants concentration is 0.5mol/L at room temperature, the morphology of the as-prepared Hap precipitation is rod-shaped with the size of 10-20 X30~50nm, while after sintered at 700'C, the crystallinity increases with the particle size of 80~90 120~150nm, and the particle diameter becomes larger, and the ratio of length and width decreases. The particle size apparently reduces with the decrease of the reactants concentration. When the reactants concentration is 0.01mol/L at room temperature, the short-rod nano-hydroxyapatite crystals are obtained and the particle size is 10-20nm long, 5~10nm in diameter. At different reaction temperature, different size particles are obtained, for example, at 25 C, the average particle diameter of the hydroxyapatite powders is around 20nm, while at 80 C, the particles obviously grow up and the particle diameter is 100nm.Laser light scattering technique and zeta potential analysis were used to study the highly-dispersed nano-hydroxyapatite. Results show that, by adjusting the pH of the aqueous solution, adding the polyelectrolyte dispersants and surfactants, the hydroxyapatite powders' surface potential changes, and highly-dispersed nano- hydroxyapatite particles are obtained. The aggregates of nano-hydroxyapatite are 680nm and the zeta potential is -10.47mV; while after dispersed, the particle size of nano-hydroxyapatite is 45.7nm and the zeta potential is -50mV. Among these methods, the polyelectrolyte dispersants have best effect on dispersivity of the n-Hap. The fibroblast and lymphocyte were used to investigate the cytotoxicity of the stably dispersed nano-hydroxyapatite particles. Results demonstrate that the stably dispersed system has no cytotoxicity on cell's growth and their morphology.Using collagen as a model compound, through the nano-hydroxyapatite reacting with the collagen in different condition, the highly-dispersed collagen-wrapped hydroxyapatite compound was obtained, which is promising to be used as a model system for targeting drug or drug delivery system.