Preparation Of Nano-hydroxyapatite/chitosan Composites Via The In Situ Precipitation

The nano-composites of hydroxyapatite/chitosan (HA/CS) have been prepared via in situ growth of nano-hydroxyapatite in chitosan gel. The present thesis is aimed at exploring in situ precipitation method to synthesize nano-HA/CS (n-HA/CS) composites under room temperature and hydrothermal conditions. The formation mechanism of n-HA and the effect of reaction conditions was studied.Results indicate that the HA crystals were in nano size and the n-HA particles were dispersed homogeniously in the CS matrix. In-situ growth of n-HA crystals on surface layer and inside layer has obvious difference under room temperature condition due to the slow pervasion of sodium hydroxide solution. Under hydrothermal condition, in-situ growth of n-HA crystals on surface layer and inside layer has no obvious difference because of the rapid pervasion of sodium hydroxide solution.It was found that the in-situ growth of n-HA crystals could be affected by the temperature and pH easily. The in-situ growth of n-HA crystals has a high speed under high temperature and high pH conditions.The addition of HA can also reduce the ratio of water absorption of composite, which postponed the retention of mechanical properties of CS/HA composite under moisture condition.In this paper, porous n-HA/CS composite scaffolds have been prepared by particular leaching method. The scaffolds prepared have an open, uniform and interconnected porous structure with the porosity of 94.6%, average pore size of 500um and average window size of 200um, which benefits the cell adherence, proliferation and metabolization so as to be expected an extensive application in the tissue engineering.Simulated Body Fluid (SBF) system has been used to investigate the degradation process of n-HA/CS composite. Results indicate that the degradation of CS causes the decrease of pH, which could accelerate the degradation of CS.