Papers by Author: Li Zhang

Abstract: Acicular nano-hydroxyapatite (n-HA) was used to make a new biomaterial composite with polycarbonate by a novel technique. The physical and chemical characteristics of the composites were tested. It was found that the synthesized n-HA crystals were similar to bone apatite in size, phase composition and crystal structure. The TEM results indicated the biomimetic n-HA crystals were uniformly distributed in the polymer matrix. Chemical inter-action between inorganic n-HA and polycarbonate was investigated and discussed. These results indicate that the composite fulfills the basic requirement of bone substitute material, and has the potential for clinical applications.

Abstract: In the paper, ampicillin-loaded alginate(ALG) microspheres covered with chitosan (CS) were firstly prepared by emulsification/internal gelation method. These microspheres were mixed with n-HA/CS composite and then were fabricated into porous scaffold carrying micropheres by gas-foaming together with phase-separation. their properties were characterized by the methods of scanning electronic microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and inversed microscope. The drug releasing rate and entrapment efficiency were tested by spectrophotometry at 203 nm. The results show that the porous scaffold carrying microspheres has good property of slow drug releasing rate. The research will offer a new kind of degradable porous scaffold with good property of controlled drug release for bone or cartilage repairing.

Abstract: A novel nano-hydroxyapatite/chitosan (n-HA/CS) composite scaffold with high porosity was developed by a new method of emulsion-foaming/freeze-drying process and was characterized by means of infrared spectroscopy (IR), scanning electronic microscopy (SEM) and universal material testing machine. In addition, the porosity and density of the scaffold were also calculated. IR result shows that the characteristic absorption peaks belonging to both CS and HA are present in their composite, and the slight band-shifts and peak-decrease suggest that some interactions have taken place between the two phases of CS and n-HA in the composite. SEM photo displays that, with the dosage increase of Tween-80, the prepared scaffold shows highly porous and interconnected structure, in which macropores and micropores coexist. The calculated data demonstrate that the porosity of the scaffold is proportional to the content of the emulsifier, while the compressive strength is inversely. When 15wt% emulsifier used, the porosity of the scaffold can be up to 90% and the density is 0.453g/cm3, while the corresponding compressive strength is about 2.4MPa. The newly developed n-HA/CS composite scaffolds may serve as a good 3-D substrate for cell attachment and migration in bone tissue engineering.

Abstract: In this paper, using sodium phosphate and calcium nitrate as reagents, nano-hydroxyapatite (n-HA) was synthesised under 8 conditions. The morphology and crystallinity of these prepared HA were investigated by Transmission Electron Microscope (TEM) and X-ray diffraction pattern (XRD). The Ca/P molar ratio of n-HA was tested by chemical method. In order to find a better way to obtain purer nano-hydroxyapatite, the phases transition and purification of these 8 samples before and after sintering at 1000°C were compared. The results indicated that all these samples showed similar, poorly crystallized apatite structures before sintering. The adding order between calcium and phosphate would affect the crystallinity, structure and Ca/P molar ratio of hydoxyapatite significantly. XRD analysis showed that adding sodium phosphate into calcium nitrate could gain more HA phase after sintering at 1000°C. The pH of reaction system had obvious effects on the structure of hydroxyapatite. Besides the pH of reactants also affected the structure of hydoxyapatite.

Abstract: To compare with the human cortical bone, the biomimetic properties of nano-hydroxyapatite/polyamide 66 composite (n-HA/PA66) were preliminarily studied qualitatively and quantitatively with TEM, XRD in crystal morphology, phase composition and crystal structure. A series of structure parameters such as cell lattice parameters (a and c), mean crystallite size and micro-strain were calculated to characterize quantitatively the microstructure of n-HA/PA66 and human cortical bone at the atomic level. The results show that n-HA/PA66 is a good biomimetic biomaterial. But there still are some differences between n-HA/PA66 and human cortical bone. Compared to human cortical bone, the crystal microstructure of n-HA/PA66 is denser, the crystal lattice of n-HA is more perfect and the distortion of crystal lattice decreases.