Key Engineering Materials Vols. 361-363

Abstract: A composite of co-polymer of lactic and glycolic acids (PLGA) loaded with gatifloxacine (GFLX), an antibiotics, and a β-tricalcium phosphate (βTCP) porous ceramic body was prepared by a solvent-free process in which no toxic solvent was used. The GFLX-loaded PLGA released GFLX for 8 weeks in Hanks’ balanced solution. The inhibitory zone diameter (26.25±0.95 mm) for GFLX-containing PLGA disk against S. milleri was significantly larger than 18 mm, and comparable to that (24.88±1.6 mm) for the KB paper disk containing 5 μg of GFLX/disk. This means that the GFLX-containing PLGA has the clinical efficacy. The molten PLGA containing GFLX was successfully loaded in the pores and on the surface of the porous βTCP ceramic at 120 °C at a reduced pressure of 0.02 MPa. The composite of GFLX-loaded porous βTCP ceramic would be promising for treating osteomyelitis.

Abstract: Poly(lactic-co-glycolic)acid and silica gel fibers mixed non-woven fabric was made by electro-spinning method for the potential application as a bone grafting material. The silica gel, the source material for electro-spinning, was prepared by the hydrolysis of tetraethyl orthosilicate in the presence of calcium salt, water, hydrochloric acid and ethanol. Poly(lactic-co-glycolic)acid solution was prepared by dissolving it in the hexafluoroisopropanol. Then, they were transferred to two separate syringes which were connected to the high voltage supply generating a high electric field between the spinneret and the ground collecting drum. The silica gel containing calcium and poly(lactic-co-glycolic)acid solution were spun together under the electric field of 2 ㎸/㎝. The FE-SEM observations showed that the silica gel and poly(lactic-co-glycolic)acid fibers were mixed together completely and its handling property was much improved compared to that of the non-woven silica gel fabric. After soaking in the SBF for 1 week, low crystalline apatite crystals were also observed to occur on the silica fiber surfaces first and then they were also observed to occur on the poly(lactic-co-glycolic)acid fiber surfaces. From the results, it can be concluded that the poly(lactic-co-glycolic)acid and silica gel fibers mixed non-woven fabric made by electro-spinning method has a bioactivity. It means it has a potential to be used as a bone grafting material because of its apatite-forming ability, high surface area to volume ratio and high porosity.

Abstract: Composites of gelatin microspheres and injectable calcium phosphate cement were prepared to increase cement resorption and improve tissue ingrowth. To further enhance these properties, osteoinductive growth factors can be introduced into the microspheres. In this study, the in vitro release of preset gelatin microsphere/CaP composites was followed for 6 weeks by use of 125I-labelled rhBMP-2, rhTGF-β and rh-bFGF. Results for all gelatin microsphere composites showed a release curve that consisted of a small burst, followed by a sustained release. The magnitude of the sustained release was dependent on the growth factor used, and showed a slight dependency on the loading method and type of gelatin. Furthermore, no differences in release pattern or efficiency were found when growth factor concentration increased.

Abstract: Silanization of hydroxyapatite was employed to improve the bonding between hydroxyapatite and polycaprolactone. FTIR of HA after silanization showed that new peaks attributed to silane do exist. The increase of melting and crystallization temperatures of silaned composites shown from DSC implied that there exists much stronger bonding between PCL and silaned HA particles. Fracture surface of composites after tensile testing observed by using SEM showed that silaned HA particles dispersed much evenly and coalesced compactly in PCL matrix, suggesting that silaned HA particles had good compatibility with PCL. The tensile strength and modulus increased from 16.81 MPa and 239.21 MPa to 20.49 MPa and 539.57 MPa, respectively.

Abstract: Rigid hydroxyapatite (HAp)-alginate beads were prepared as drug delivery carriers for an anti-cancer drug, paclitaxel (Taxol). Paclitaxel was loaded into the HAp microparticle in process of a spray-drying technique. The HAp-alginate beads including paclitaxel were obtained by a droplet method into barium solution as ionic cross-linkage and dehydration. Cross-sectional analyses indicated the homogeneity of HAp microparticles and barium ions inside the bead. The ratio of alginate to HAp in the beads dominated both mechanical and swelling properties. Drug-release experiment demonstrated the sustained release of paclitaxel from the beads cross-linked with barium ion for 7 days.

Abstract: Many researchers have assumed that a combination of hydroxyl apatite (HAP) and collagen (COL) may be the best solution for bone replacement and have prepared their composites by several techniques [1]. However, such HAP/COL composite had no nanostructure similar to bone, and consequently indicated no bone-like mechanical properties. These results demonstrate that the chemical composition similar to bone only is insufficient for bone metabolism and mechanical properties. Mechanical and biological performance of this type of materials could be improved by adding TiO2 within the initial mixture of nanostructured composites [2]. Ternary nanostructured systems consisting of hydroxyl apatite, TiO2 aerogel and collagen were prepared for the first time by hydrothermal procedure in high pressure conditions. Among many advantages, the synthesis method proposed in this paper could lead to formation of chemically bonded compounds as a consequence of high pressure conditions. The resulted material could find applications in bone tissue regenerative medicine, either in powder form for bone defects treatment, or in matrix form as osteoconductive coating for metal implants. Further studies are necessary to evaluate the osteoconductive properties.

Abstract: The present work describes the development of biomimetic composites materials for bone tissue substitution and repair. At this purpose a biomimetic approach was used and apatitic phases were nucleated on macromolecular matrices like natural collagen, which act as template and induce peculiar physico-chemical features in the mineral phase.

Abstract: A novel foaming method of design and synthesis of porous Carbonate-apatite/gelatine composite scaffolds is proposed for biomedical applications. Two different suspensions, one constituted by a biomimetic inorganic phase (B-CHA) and the second by a protein (gelatine), are mixed, foamed, lyophilized and, in some cases, cross-linked to stabilize the organic phase. Chemical, morphological and mechanical features of the scaffolds are evaluated. The samples have chemical composition, compressive and flexural strengths and Young modulus values in the range of trabecular bone ones. A high interconnected porosity (about 90%) showing a micro- to macrosize distribution, that is needed for osteoconduction and vascolarization processes in vivo, is also detected.

Abstract: Silicone rubber substrates were irradiated at an acceleration voltage of 7 kV and a dose of 1×1015 ions/cm2 by the simultaneous use of oxygen cluster and monomer ion beams, and then soaked in CaCl2 solution. Apatite-forming ability of the substrates was examined using a metastable calcium phosphate solution that had 1.5 times the ion concentrations of a normal simulated body fluid (1.5SBF). After the irradiation, the silicon oxide clusters (SiOx) were formed at the silicone rubber surface. The hydrophilicity of the substrates was remarkably improved by the irradiation. The irradiated silicone rubber substrates formed apatite in 1.5SBF, whereas unirradiated ones did not form it. These results suggest that the functional groups such as Si–OH and/or COOH groups induced apatite nucleation in 1.5SBF.