Key Engineering Materials Vols. 330-332

Abstract: Bioresorbable calcium metaphosphate (CMP) nanofibers were produced by an electrospinning technique. In order to produce the nanofibers, CMP sol was prepared by the mixing of two precursors, such as calcium nitrate tetrahydrate (Ca[NO3]⋅4H2O) and triethyl phosphate (TEP, [C2H5O]3PO), using methyl alcohol as a solvent. The Ca/P ratio of the mixture was set to be 0.50 to produce stoichiometric CMP sol. At least 5 hrs of pre-hydrolysis of phosphorus precursor were required to obtain β-CMP phase. Viscous solutions for the electrospinning were made by the mixing of CMP sol and high-molecular weight polymeric solution at various ratios. The ratio of CMP sol and polymer solution was controlled to obtain an appropriate viscosity for the electrospinning. As-electrospun CMP nanofibers were dried in a drying oven at 70°C for 24 hrs and then heat-treated at various temperatures at a ramp of 1°C/min in air for 1hr. The as-electrospun and heat-treated CMP nanofibers were characterized using X-ray analysis, FT-IR, TG-DTA and SEM techniques. The results showed that the preparation of CMP sol, mixed solution properties, and heat-treatment condition of as-electrospun nanofibers significantly affect the spinability and surface morphology of the CMP nanofibers.

Abstract: In our previous work the nano-sized hydroxyapatite (nano-HAP) with uniform morphology has been firstly synthesized by a wet chemical method based on dialysis, but the dialysis efficiency was not investigated in detail. In this paper, the removal efficiency of impurity ions such as NH4 + and NO3 - was respectively evaluated by calculating the concentration of the representative irons between the inner slurry and outer distilled water. Results showed that 99% NO3 - ions and 96.9% NH4 + - ions in the slurry has been eliminated. In the first dialysis time, the NH4 + ions diffuse faster than the NO3 - ions due to their smaller size. In the following dialysis times, the dialysis efficiency of NO3 - ions is higher than that of the NH4 + ions because of the presence of higher NO3 - ions concentration gradient. The final nano-HAP is also characterized by XRD, TEM, and FT-IR. It is revealed that the products are stick-like with a length of about 150nm and a diameter of about 20-50 nm. Current work suggests that dialysis is an efficient purified method for nano-HAP production and especially can be applied to industrial preparation of fine nano-sized HAP powders.

Abstract: Radix salvia miltiorrhiza is a commonly used herbal medicine in China, and tanshinone IIA is one of the major active ingredients. Nano Radix salvia miltiorrhiza particles were successfully prepared by high speed centrifugal sheering (HSCS) technology, and the prepared nanoparticles suspension was subsequently spray-dried. The different properties of nano particles and raw powder were systematically studied by laser light scattering granulometric analyzer, TEM, SEM and FTIR. The extractive quantity of tanshinone IIA was determined by high-performance liquid chromatography (HPLC). The results illustrate that raw Radix salvia miltiorrhiza powder can be ultrafinely ground to nanosize within 50min, and the molecular structure of active ingredients doesn’t change after being ground. Furthermore, the active ingredients can dissolve out directly and fully, and the extractive ratio of tanshinone IIA increases 28.6% by HSCS processing. It is valuable to combine nanotechnology and TCM to improve the bioavailability and rapid releasing.

Abstract: Nano-sized zinc-substituted hydroxyapatite (nano-ZnHA) has stimulatory effect on bone formation and inhibitory effect on osteoclastic bone resorption in vivo. Nano-ZnHA with serial zinc fractions (0, 2, 5, 10 mol%) were synthesized by an improved precipitation method based on dialysis process. Transmission electron microscopy observation indicated that the increase of Zn fraction led to smaller crystallite. X-ray diffraction of the products revealed that some typical characteristic peaks of HA displayed when the Zn fraction was below 10%. Fourier transform infrared spectroscopy showed that the bending peaks of the group-OH in HA became wider with the increase of Zn fraction and it disappeared at 10 mol%. The current work demonstrated that zinc could substitute for calcium into hydroxyapatite in the limited range of composition by using dialysis process.

Abstract: Stearic acid was utilized to modify biphasic alpha-tricalcium phosphate (α-TCP)/hydroxyapatite (HA) powders in the ethanol. The results showed that the dispersion of biphasic α-TCP/HA powders (BCPs) in non-polar matrix improved. And the released content of Ca2+ and PO4 3- of the BCPs soaked in the NaAc-HAc buffer solution (pH 5.0) was almost same as that before modification. Stearic acid could modify the suface properties of BCPs and would not obviously affect their biological characteristics, which affords a good groundwork of application of calcium phosphates powders.

Abstract: The aim of this study was to prepare dense hydroxyapatite (HA) by microwave sintering and to evaluate the dissolution behavior in distilled water. Commercially-obtained HA powders having Ca/P ratio of 1.67 were used as a starting material. The as-received powder of granular type consists of nano-sized particles. Microwave sintering was operated at 1200°C for 5 min with a heating rate of 50°C/min. Microwave sintering process reduced grain size of HA, compared with the case of conventional sintering. During the immersion in distilled water for 3-14 days, grain boundary dissolution occurred and the dissolution extended into the bulk following this path. As a result, particles were separated from the structure leaving micron-scale defects.

Abstract: Magnetic nano-particles of around 20nm synthesized by poly-ethylene glycol (PEG) and sodium oleate mediated approach show well stability without sediment during 6 months. Upon treated through the modification procedure, magnetic nano-particles have a weakly physical bond with PEG, meanwhile a strong bond with sodium oleate. Naked magnetic nano-particles present positive charges on the surface, while turn to be negative when modified with sodium oleate, which suggest that the hydrophilic carboxyl on the surface of the nano-particles is outward. Magnetic property of the nano-particles changes according to the concentrations of reactants and surfactant.

Abstract: The aim of this study is to prepare nano hydroxyapatite powder. Hydroxyapatite powder was prepared via co-precipitated method with the addition of citric acid at pH 9-11 in ambient environment. The precipitates were aged for 24hs, and then milled into powder after washed and dried. The particle morphology and particle size of as prepared HA powders were characterized. The results showed that hydroxyapatite powder with width of 10-30nm and length of 30-100nm was prepared by wet co-precipitation.

Abstract: Highly disgregated dicalcium phosphate anhydrate (DCP) nanoparticles 240-367 nm in diameter were synthesized by a reaction between calcium carbonate and phosphoric acid. When the DCP nanoparticles were immersed in a supersaturated calcium phosphate solution containing bovine serum albumin (BSA) and ethanol, BSA/DCP nano-composite particles were synthesized through the coprecipitation of BSA on the DCP nanoparticles. BSA was firmly immobilized on the BSA/DCP nano-composite particles. The results of this study suggest that DCP nanoparticles appear to be useful as a drug delivery vehicle.

Abstract: This study concerns the preparation and characterisation of microspheres associating alginate and two different types of hydroxyapatite (HA), which are intended to be used as drug delivery systems and bone regeneration matrices. Hydroxyapatite nanoparticles (HA-1 and HA-2) were prepared using a chemical precipitation synthesis based on H3PO4, Ca(OH)2 and a surfactant, SDS (sodium dodecylsulphate), as starting reagents. These two powders of nanoHA and alginate were used to prepare two different types of microspheres. Both powders and microspheres were characterised using FTIR, TEM, SEM, mercury porosimetry analysis and X-ray diffraction Results show that pure hydroxyapatite (HA) and mixtures of HA/β-TCP in the nanometre range were obtained from both HA syntheses. Microspheres with different characteristics were obtained from these two types of hydroxyapatite.