Papers by Author: Hua De Zheng

Abstract: Porous HA/TCP bioceramics were immersed in pure bovine serum to observe the growth and formation of apatite. HRTEM, FTIR, and SEM coupled with EDS were used for the characterization of immersed samples. SEM results showed that some beamed crystals formed on the surface of ceramics granules, and with postponement of immersion time, crystals extended and became bigger, strap-like crystals became sheet-like crystals. HRTEM observations indicated that new-formed crystals developed along axes direction according to parallel layers. IR spectrum showed CO3 2- characteristic peaks existed besides O-P-O and OH- characteristic peaks. EDS results showed that calcium and phosphor ratio was 1.95 (mol ratio). The results indicated that bovine serums were advantaged to bone-like apatite formation.

Abstract: In this study, biomemitic hydroxyapatite was prepared as a nano-sized powder from calcium nitrate tetrahydrate and diammonium hydrogen phosphate salts, but using the different contents of PVP modified hydroxyapatite and synthetic body fluid (SBF) solutions as synthesis medium instead of pure water at 37.4C and pH of 7.4. SBF was prepared in accord with the chemical analysis of human body fluid, with ion concentrations nearly equal to those of the inorganic constituents of human blood plasma. Characterization and chemical analaysis of the synthesized biomemitic hydroxyapatite powders and pure hydroxyapatite were investigated by X-ray powder diffraction, scanning electron microscopy, and inductively coupled plasma atomic emission spectroscopy. Rheological properties of HAP sol which reflected the interaction of hydroxyapatite particles were measured by R/S rheometer. The results showed that PVP evidently affected the stability and rheological properties of HAP sol, and PVP were based on the different mechanism at different concentrations. PVP was operating as an interparticle bridging reagent at low concentrations(0.5%), while it acted as an dispersant at high concentrations(2.0%). The biomemitic hydroxyapatite with the sizes of 10~30nm was spherical and poor crystalline, which was synthesized in synthetic body fluid (SBF) by addition of 2.0% PVP.

Abstract: The spherical nano-sized bioactive particles in the system of CaO-P2O5-SiO2 were bio-mimetically synthesized using micro-emulsion method. The microstructures and properties of the bio- mimetic nano-materials were characterized using XRD, FTIR, SEM/EDAX and TEM techniques. It was indicated that the nano-particles possessed glassy structural characteristics. The porous composite for bone tissue reconstruction was prepared by compounding poly (hydroxybutyrate-2-co-2-hydroxyvalerate) (PHBV) and the nano-particles of bio-mimetic bioactive glasses (BMBG). Bone-like hydroxyl- carbonate-apatite (HCA) could formed on the surface of porous composite by immersing the composite in simulated body fluid (SBF) at 37°C for 8 hours. With increase of immersion time, the morphology of HCA changed from spherical into flake-like crystals. The study on cells attachment of the porous PHBV/BMBG composite proved that the material possessed satisfactory bioactivity, bio-mineralization function and cells biocompatibility.

Abstract: Porous HA/TCP bioceramics were immersed in pure dog serum to observe apatite formation. Deposited crystals were examined using SEM. Results showed that beamed sheet-like crystals formed on the surface of ceramics granules, and after postponement immersion time, crystals extended and became bigger. EDS and IR results suggested formed crystals were defect-calcium type carbonated hydroxyapatite. HRTEM photograph suggested formation process of new-formed crystals from non-crystal to crystal in serum. Directional organisms acted maybe as a template in process of crystals formation, so new crystals developed along certain direction.

Abstract: The PCL plates hydrolyzed by NaOH aqueous solutions and carboxylate groups were introduced onto the surfaces of specimen. Specimens were treated by CaCl2 and K2HPO4⋅3H2O under the normal-pressure condition and low-pressure of 103 Pa condition for 30min separately. Dense and uniform bone-like layers could be formed on the surface of specimens after mineralizing for less than 24h in simulated body fluids (SBF). The low-pressure condition could accelerate the formation of apatite layer.