Synthesis Of Nano Hydroxyapatite In SDS-PVP Aqueous Solution

As the main inorganic components of skeleton and teeth of human, hydroxyapatite (Ca10(PO4)6(OH)2, HAP) has the characteristics of non-toxic, no side effect, good biocompatibility, biological activity and bone conductivity, so the preparation of HAP has become one of the focuses in biomedical field. However, the single method of preparation is difficult to achieve satisfactory results in the morphology and structure of HAP. In this dissertation, CaCl2and Na2HPO4·12H2O were used as the starting materials, sodium dodecyl sulfate (SDS)-polyvinylpyrrolidone (PVP) soft clusters were employed as synthetic templates, the HAP nano-particles were obtained by precipitation-hydrothermal method. The synthetic template has good biosecurity and the products have good crystallinities and regular morphology.Firstly, surface tensions of SDS-PVP-CaCl2aqueous systems were measured by volume method in this paper.The influences of the concentration of SDS, PVP and CaCl2on the surface tension were also discussed. The results show that, the addition of CaCl2contributes to the formation of soft cluster and increases the interaction range of SDS and PVP, the value of c1reduces, the value of c’ and c2increases with the increasing of CaCl2; Fixing the concentration of CaCl2, the value of c1keeps solid, the value of c’and c2increase with the increasing of PVP, this shows that increasing the concentration of PVP at the suitable range is favor to increase the boundaries of soft cluster.Secondly, in SDS-PVP system, the nano HAP particles were obtained by precipitation-hydrothermal method. The effects of SDS concentration, pH, hydrothermal reaction time and reaction temperature on morphology and size of nano HAP were preliminary studied, the ideal experimental conditions of synthetic nano HAP were obtained:in the system of SDS (2.3mmol·L-1)-PVP (2g·L-1)-CaCl2(10mmol·L-1), pH=9.5, first at60℃water bath for24h, then the precipitation was transferred into reaction vessel for10h at150℃.The morphology of obtained nano HAP at the ideal condition presented short rod-like particle and oval-shaped particle, with it’s size uniformly distributed with well-defined crystal. Comparing the nano HAP obtained at different conditions, in the presence of the template, the nano HAP obtained by hydrothermal has higher crystalline degree and more regular morphology, the hydrothermal reaction can promote the nano HAP grain growth well, comparing with the products synthesized in water bath; In the condition of hydrothermal, the morphology of nano HAP obtained in SDS-PVP system changes from irregular ribbon into short rod-like and oval-shaped, compared with the products synthesized without SDS-PVP. The probable mechanism of SDS-PVP may be as following:the growth behavior of HAP crystals could be influenced by the selective attaching of SDS-PVP soft clusters onto crystal surfaces and the spatial structures of PVP. The polar groups of SO42-with negative charged in SDS could interact with Ca2+on the (100) plane of nano HAP by electrostatic interactions. Then, the SDS-Ca2+complexes might act as nucleation sites and promote the stacking of Ca2+, PO43-, OH" ions on the (100) plane and induce reystallization; The amide groug in PVP polymer chains might adsorb on the surfaces of HAP through coordination. This could promote the adsorbtion on the surfaces of SDS-PVP soft clusters on the (100) plane, PVP molecules with certain configuration might also influence the morphologies of HAP. In summary, SDS-PVP clusters could induce the cryatal growth of nano HAP along a-axis, b-axis and relatively inhibit the growth along c-axis. and helped to obtain nano HAP with small length-diameter ratio.Finally, Dexamethasone with affect of promoting bone growth was chosen to test the medicine delayed-release performance of nano HAP. Results showed that so-obtained nano HAP had good drug loading capacity. In vitro drug delayed-release experiments showed that in simulated body fluid for7h the release percentage of dexamethasone only reached97.05%. This nano HAP-dexamethasone complex had obvious medicine delayed-release effect. The mechanism of drug release was also discussed. This method might have a good reference value in the further study of a novel bone-repairing material with biocompatibility.