The calcium-deficient apatite (CDHA) powders were synthesized using a wet-chemical method. Based on HAP crystal model with space group P63/m with a=0.9432nm and b=0.6881nm, Rietveld structure refinement was performed on the X-ray diffraction (XRD) experimental data of CDHA powders. The Rwp of Rietveld refinement for all CDHA was about 8%, so the parameters of structure and microstructure obtained from the refinement for CDHA were credible. During synthesis in wet-chemical route, apatites with different Ca/P molar ratios were synthesized, except for ß-TCP. Then CDHA powders were sintered at 1100C for 2 and 4 hr to prove that CDHA was the precursor of bi-phase calcium phosphates (BCP) and able to transform to BCP. For CDHA with certain Ca/P molar ratio, BCP with different hydroxyapatite/tricalcium phosphate (HAP/TCP) ratio could be fabricated by adjusting the length of sintering periods. After 4 hr sintering, the transformation of CDHA was completed and CDHA were transformed to HAP, ß -TCP, or BCP with desired phase compositions. From the chemical analysis on CDHA and the XRD quantitative analysis on BCP, this method of synthesis was shown to produce CDHA with same apatite structure and HAP in BCP ceramics fabricated by incomplete sintering CDHA is also calcium-deficient apatite, which is more similar with bone than stoichiometric hydroxyaptite.
 

The present in vitro study investigated the effects of ion intensity and type of the immersion solution and the dissolution property of calcium phosphate (CaP) ceramics on the morphology and structure of bone-like apatite formed on CaP ceramics surface. In the experiments, ceramics plates of hydroxyapatite(HA) and α-tricalcium phosphate(α-TCP) were immersed into simulated body solution(SBF) and phosphate buffer solution(PBS) from 1 to 3 weeks. The structure characteristics and morphology of layers formed on the ceramics surface were characterized by thin-film X-ray diffraction (TF-XRD) and scanning electronic microscopy (SEM), respectively. The results demonstrated that the apatite formed on α-TCP and HA surface significantly differed in morphology and structure from each other in different immersion solutions. The plate-like crystal layer, octacalcium phosphate (OCP), was formed on the surface of α-TCP in PBS; but highly imperfect apatite particles, bone-like apatite, were formed on the surface of α-TCP in SBF. For HA, there were only a few small highly imperfect apatite particles formed on the surface in SBF, and almost nothing in PBS. XRD and SEM results also confirmed that those plate crystals of newly-formed OCP were able to be transferred to high-imperfect apatite particles during the immersion process in vitro.

Silk fibroin (SF) provides an important set of material options for biomaterials and scaffolds for tissue engineering. In the fields of biomimetic mineralization and bone tissue engineering, SF was also proved to play important roles. However, the correlation of the biomimetic mineralization with the parameters of apatite crystalline structure deposited on fibroin is not fully investigated. The aim of the present study was to investigate the biomineralization behavior of SB in vitro with the method of alternative calcium/phosphate soaking solutions (ACPS). The apatite formed on fibroin was characterized using X-ray diffraction (XRD), and its structure was refined with Rietveld method in order to understand its structure variation at atom level. The broadening effect of XRD reflections was separated to calculate the micro-strain/crystalline size, respectively. The results demonstrated that ACPS was an effective method of mineralization to fabricate fibroin/HAP composites. The process of precalcification significantly promoted the growth of hydroxyaptite crystal and influenced the structure of HAP. The apatite can deposit on SF surface by the 1st cycle (<24 hours) during the mineralization. The size of apatite crystallite gradually increased and the microstrain decreased along the process of biomineraliztion.

In this study, the effect of flax fiber surface modification by acetylation and ethylene plasma treatment on the interfacial and thermal properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biocomposites fabricated with woven flax fabrics was investigated in terms of interfacial shear strength (IFSS), interlaminar shear strength (ILSS), thermal stability, thermomechanical stability, dynamic mechanical properties and fracture surfaces of flax/PHBV biocomposites. Both acetylation and plasma treatment played an important role in improving the IFSS and the ILSS of unmodified flax/PHBV biocomposite, indicating that the ethylene plasma may impart more hydrophobic character to the flax fiber surfaces and consequently provide the stronger interfacial strength to the biocomposite than the acetylation. The incorporation of flax fabrics into the PHBV resin increased the thermal stability, the thermo-dimensional stability and the storage modulus of the PHBV. The improvement of the interfacial adhesion between the flax fibers and the PHBV resin also significantly contributed to increasing the thermal properties of unmodified flax fabric/PHBV biocomposite, especially with a marked reduction of the coefficient of thermal expansion. As a result, the plasma-treated flax fabric/PHBV biocomposite had the better thermal stability and the lower CTE than the acetylated counterpart.

Bone repair is one of the major concerns of reconstructive surgery and fractures. Healing of bone defects and fractures is often poor due to diminished availability of osteoprogenitor cells and growth factors. To aid the healing process it is often necessary to introduce a selective subpopulation of bone forming osteoprogenitor cells. Enhanced osteogenesis may be achieved by using a combination of the osteoinductive effect of growth factors and the conductivity of scaffolds. The aim of the present study was 1) to test the potential of a hydrogel scaffold loaded with growth factors to repair a defect in rat tibia; 2) to examine the ability of a hydrogel scaffold to act as a mesenchymal stem cell (MSC) carrier; 3) to test the biodegradability of the hydrogel. Hydrogel scaffolds containing either, TGF-β1, IGF-1, a combination of TGF-β1 and IGF-1, hydrogel alone or saline were inserted into the defect. CT images showed closure of the bone defect after six weeks of treatment with TGF-β1 or TGF β1 + IGF1. Less pronounced bone induction was observed in control specimens and IGF-1 treated defects. CT images revealed also that bone shape had been restored. Osteoprogenitor cells were isolated from rat bone marrow, cultured in DMEM supplemented with ascorbic acid, β-glycerophosphate and dexamethasone. The selected osteogenic subpopulation was identified by Alizarin Red S and seeded onto a hydrogel scaffold. Light and Scanning Elctron microscopy (SEM) demonstrated cell adhesion and osteogenic condensation. Partial biodegradability of the hydrogel was observed 14 days after in vivo transplantation. Future studies involve investigating the application of hydrogels containing combinations of growth factors together with MSCs for tissue engineering.