Key Engineering Materials Vols. 309-311

Abstract: Calcium phosphate cement (CPC) has many advantages and is frequently used as a carrier of antibiotic and bone growth factors. Salmon calcitonin(S-CT) is effective in treating osteoporosis. Due to its potential of promoting bone cell proliferation, S-CT was combined with injectable CPC to accelerate the restoring of the bone defect induced by osteoporosis and the composite can be used in minimal invasive surgery. Uniform design was used to optimize the prescription, and the effects of pore-maker and S-CT on the characters of CPC were studied. The in vitro releasing of S-CT from the optimum CPC in deionized water, SBF and rabbit serum was studied with HPLC, respectively. The results showed that the contents of HA and citric acid-NaHCO3 affect the physical characters of CPC sharply, but S-CT has little effect on it. The releasing of S-CT in three different medium follow Hugichi equation, but the speed is slower in rabbit serum than in deionized water and SBF. S-CT carried porous injectable CPC composite possesses the basic performance for clinical needs, and it is promising to be used in osteoporosis induced bone defect and accelerate bone repair.

Abstract: In this study, biodegradable poly-lactic-acid (PLA) microspheres encapsulated with Salvia Miltiorrhiza Bunge (SMB), ranged from 100µm to 300µm, were prepared by a solvent evaporation method. Those PLA microspheres mixed with CPC powder, at a mass fraction of 0.2 to 0.8, to yield a self-emerged porous CPC. The surface morphology of PLA microspheres and CPC were observed by optical microscopy and scanning electron microscopy (SEM), respectively. The function groups of PLA microspheres and the phase composition of CPC were analyzed by Fourier transform infrared spectrometer (FTIR) and X-ray diffraction (XRD) , respectively. A preliminary study of drug release was performed by immersing PLA microspheres and CPC into simulated body fluid (SBF) for a various interval points. And the concentrations of SMB in SBF were measured by UV-VIS spectroscopy. The present results showed that the self-emerged porous CPC containing Chinese medicine could be prepared by adding biodegradable PLA microspheres. PLA microspheres can promote the CPC aqueous reaction to form final product, hydroxyapatite (HA).

Abstract: The purpose of this paper was to investigate the effect of various Chinese medicine adding methods on their contents in calcium phosphate (CaP) and the crystal structure of the CaP comparatively. In the present study, CaP was synthesized by the wet chemistry method, in which starting reagent grades calcium nitrate and diammonium phosphate were used as the molar ratio Ca/P=1.5. Chinese medicine parenteral solution, Salvia Miltirrhiza Bunge (SMB), was added into the Ca2+ and PO43- reactive solutions before, during or after synthesis process. CaP was synthesized without adding SMB as the control. UV-VIS spectrophotometer was used to measure the supernatant absorbency. Zeta potential was used to characterize the various CaP slurries. Thermogravimetry, X-ray diffraction and transmission electron microscope were used to characterize the various powders, respectively. The presented results showed that adding SMB during the reaction can obtain the maximal medicine content among the four different adding methods. There was a slight effect on the crystal structure of CaP by adding SMB.

Abstract: The bioactivity of a glass ionomer luting cement (Ketac®-cem, ESPE, Germany), which was modified by Bioglass® (PerioGlas® Synthetic Bone Graft Particulate, US Biomaterials) in different bioglass/powder weight ratios, and the biocompatibility of the produced mixtures were evaluated in this study using different cell lines. The incorporation of Bioglass® in the cement structure resulted in the formation of sparsely located biological apatite aggregations. However, although Bioglass® incorporation seemed to enhance cell proliferation, the materials became eventually brittle and highly soluble depending on Bioglass® amount.

Abstract: The mineral phase of bone and teeth is mainly hydroxyapatite. Currently there are numerous researches being conducted on the effect of the addition of hydroxyapatite to dental materials. Among them, several studied were published stating that the addition of hydroxyapatite to composite resin or glass ionomer cement resulted in an improvement in bonding strength and physical properties Therefore, this study will investigate the effect that the addition of hydroxyapatite to light curing glass ionomer cement has on bonding strength. Two different light curing glass ionomer cement products were selected (FujiⅡLC, GC Cor, Japan and Vitremer™ , 3M/ESPE, USA) and hydroxyapatite was mixed into the light curing glass ionomer cement at various concentrations to create hydroxyapatite-light curing glass ionomer cement mixture. In order to confirm that hydroxyapatite-light curing glass ionomer cement met the basic requirements of dental materials, sensitivity to ambient light, depth of cure, and flexural strength were tested. From the results of the above mentioned tests, the hydroxyapatite-light curing glass ionomer cement with the most superior physical properties for each product (15% HA-Fuji Ⅱ LC, 20% HA-Vitremer™)was bonded to the teeth and then immersed in artificial saliva(36.5°C) for four weeks. Finally the sectioned surface was observed under SEM after measuring the bonding strength. As the hydroxyapatite concentration increased, the depth of cure decreased. However flexural strength increased and there was not much change in the sensitivity to ambient light. Bonding strength, which was the main focus of this study, increased with the addition of hydroxyapatie and scanning electron microscope findings show a more cohesive type of fracture in the material with bone like apatite material formation along the tooth-material interface.

Abstract: Previous studies have shown that hydroxyapatite increases the bonding strength of dental luting cement with human teeth by forming bone-like apatite when it is added to cement. However, due to the low solubility of the hydroxyapatite, its ability to form bone-like apatite decreases in protein-free acellular simulated body fluid with ion concentrations nearly equal to those of the human blood plasma. The purpose of this experiment was to increase the formation of bone-like apatite by mixing hydroxyapatite with β-TCP of high solubility. RelyXTM glass ionomer cement(3M/ESPE, USA) was used as dental luting cement. Film thickness, setting time, and compressive strength was measured for each group of 15% hydroxyapatite, 15% β-TCP, and 15% mixed hydroxyapatite and β-TCP (85:15). Every specimen of each group was immersed in the simulated body fluid for four week before measuring bonding strength, and then their sectional surface was observed under SEM. The most noteworthy result was that the group containing β-TCP produced more amount of bone-like apatite compared with the group composed of only hydroxyapatite.

Abstract: To compare the chemical composition and mechanical properties of the bio-derived compact bone scaffold (BDCBS) with the normal compact bone in human. Human compact bone were harvested and divided into control and experimental group. For the latter, BDCBS was prepared with physical and chemical methods. The major components (calcium, phosphorus, collagen protein) and heavy metal contents of the two groups were determined with biochemical assay. Histological examinations were performed to investigate the structure. Cylindroids from the normal compact bone and the BDCBS (6 in each group) were tested under compression. There was no significant difference between the two groups for major components. In addition, there were a few amounts of heavy metal components in BDCBS and control. Histological examinations confirmed the acellular structure in the BDCBS. Results from mechanical testing showed the compressive strength, elastic modulus and ultimate strain (193MPa, 13.76GPa, and 2.3%) of the BDCBS were a bit lower than those (205MPa, 15.67GPa, and 2.5% respectively) of control, but the differences were not statistically significant. In conclusion, there are almost the same matrix structure and composition with similar biomechanical properties between the BDCBS and the control. These results may underscore the potential of the BDCBS in tissue engineering bone.

Abstract: Many scaffolds are candidates for use in tissue engineering approaches for the repair or replacement of bone defects. Among the scaffolds tested for tissue engineering of bone, bio-derived compact bone scaffold (BDCBS) containing mineralized collagen fibers, phosphorus and calcium, as natural bone does, is one of the most promising candidates for this purpose. To analyze how appropriate the BDCBS would be for tissue engineering purposes, we established an in vitro characterization system to describe the surface properties and cytocompaibility of the scaffold. Surface properties were determined by means of scanning electron microscope and scanning probe microscope. The surface phase was examined with the Fourier transform infrared spectroscopy and X-ray diffraction. Osteoblasts from human embryos were isolated from the periosteum. After in vitro expansion, cells were cultivated on the BDCBS. Real-time cell culture was used to monitor the growth process of cells seeded on the scaffold. Using this in vitro characterization, we were able to demonstrate effective growth of osteoblasts on this scaffold. In summary, BDCBS has the surface characterization similar to a natural bone and also has strong affinity for osteoblast attachment and proliferation, indicating the potential as an effective scaffold used in tissue engineering bone.

Abstract: Bisphosphonates (BPs) may play an important role in minimizing osteolysis. In this work two new bisphosphonates pertaining to second and third generations respectively, have been synthesized and incorporated onto a chemically enriched hydroxyapatite. BP synthesis has been performed by adding H3PO3, PCl3 and methanesulfonic acid over 4-aminophenyl acetic acid (APBP) and 1-H-indole-3-acetic acid (IBP) respectively at 65°C in a N2 atmosphere. These compounds bear a primary amine group bonded to an aromatic ring, and a secondary amine group within a heterocyclic ring respectively. A chemically enriched hydroxyapatite with a chemical content corresponding to a 50% fluorided hydroxyapatite has been synthesized. Ceramic bodies manufactured by uniaxial pressure followed by cold isostatic press have a 97% density and submicron grain size. The BP was adsorbed onto the surface by immersion in a stirred solution at 37°C for 48 hours. A 10-fold decrease of the surface energy was observed for bodies modified with the APBP whereas only a 25 % decrease is obtained for bodies loaded with the bisphosphonate loaded with the IBP.

Abstract: The ability of calcium titanium phosphate (CTP) and hydroxyapatite (HAp) microspheres to reversibly adsorb the enzyme glucocerebrosidase (GCR) while preserving its biological activity, and efficiently deliver it to Gaucher disease (GD) fibroblasts was investigated. CTP microspheres adsorbed ca. 3.6-fold more GCR than HAp microspheres. The activity of adsorbed GCR was higher than the free enzyme in the case of CTP microspheres and lower when HAp was used. GCR release from both types of microspheres was characterized by the initial elution of a large percentage of enzyme followed by a delayed release that extended for at least 30 days. Released GCR was internalized by GD fibroblasts increasing their intracellular enzymatic activity. In cells treated with the same amount of GCR-loaded CTP microspheres or free-GCR a higher intracellular activity was detected in the former case, suggesting an improved efficacy.