Key Engineering Materials Vols. 330-332

Abstract: Porous β-tricalcium phosphate (β-TCP)/ Poly L-lactic acid (PLLA) composites were prepared by thermally induced phase separation method. The results showed that the composite had an interconnected pore structure with ～200μm macropores. The inorganic particle content in the composites varied from 50% to 80% and these particles were homogeneously dispersed in PLLA matrix. The composites obtained in this study could act as a promising scaffold for bone tissue engineering because of the pore structure and the mechanical properties.

Abstract: Two starting collagens, sponge and floc collagen, were used to prepare collagen/tricalcium phosphate (TCP) composites. The resulting composites were porous and had 200μm pore size. However, there was a difference in the microstructure of the pore walls for the composites derived from the two collagens, the pore walls in sponge collagen/TCP composite were still porous and had 200 nm micropores size, TCP particles were trapped in collagen matrices. While floc collagen/TCP composite had smooth and dense walls in which TCP particles were embedded. The difference could be attributed to the starting collagen with different status. Sponge collagen has a soft structure, which easily becomes disassembled fibrils during alkali treatment, the disassembled fibrils are integrated again to form a dense morphology for pore walls after freeze-drying. While floc collagen has already a low disassembly degree, the alkali treatment could not be able to separate the fibrils, this remains as micropores in pore walls after freeze-drying. Both porous composites are significant in bone tissue engineering or regeneration. MTT test results showed the two composites had good cytocompatibility, and sponge collagen/TCP composite was somewhat better than floc collagen/TCP composite, which could result from that micropores derived roughness in pore walls of sponge collagen/TCP composite is suitable for cell growth.

Abstract: Strontium(Sr) containing CaSiO3 powders were synthesized using chemical precipitation. X-Ray Fluorescence (XRF) analysis confirmed the incorporation of Sr in CaSiO3. X-Ray diffraction (XRD) analysis revealed that the incorporation of Sr into the lattice structure of β-CaSiO3 powders, does not change its β-phase composition. The lattice dimension of β-CaSiO3 powders increased with the increase of Sr contents (0-10% Sr). Sr-CaSiO3 ceramic disk were prepared from the Sr-CaSiO3 poweders by uniaxial pressing at 150 MPa and sintering at 1100°C for 3h. XRD and Differential Thermal Anaysis (DTA) analysis indicated that there is a correlation betweem Sr concentration (0-10% Sr) and the phase transition from β-CaSiO3 to α-CaSiO3 with the increase of Sr contents. This transition was promoted by the decrease in temperature.

Abstract: A Bioglass® reinforced polyethylene (Bioglass®/polyethylene) composite has been prepared, which combines the high bioactivity of Bioglass® and the toughness of polyethylene. The spatial distribution of Bioglass® particles within the composite is important for the performance of composites in-vivo. Recent developments in X-ray microtomography (XμT) have made it possible to visualize internal and microstructural details with different X-ray absorbencies, nondestructively, and to acquire 3D information at high spatial resolution. In this study, the volume fraction and 3D spatial distribution of Bioglass® particles has been acquired quantitatively by XμT. The information obtained provides a foundation for understanding the mechanical and bioactive properties of the Bioglass®/polyethylene composites.

Abstract: Various reinforcements have been used to reinforce hydroxyapatite composites. Bioactivity of hydroxyapatite and excellent mechanical properties of titanium make titanium fiber reinforced hydroxyapatite composite a promising biomaterial. In this work, a titanium fiber was chosen as the reinforcement, and hydroxyapatite powders prepared by wet precipitation method were used as matrix material. The interface between titanium fiber and hydroxyapatite was investigated in terms of microstructure and chemical composition using a combination of scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy disperse spectroscopy (EDS). Experimental results showed that titanium/hydroxyapatite composite with controllable interface could be made by choosing proper preparation method.

Abstract: α-tricalcium phosphate (α-TCP) was prepared by a wet precipitation reaction between calcium hydroxide and orthophosphoric acid solutions. The as-synthesised powder was then characterised using a Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectroscope (EDS), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscope (FTIR). Analyses revealed that a phase-pure powder with a Ca/P ratio of 1.5 was produced. In addition, nanosized α-TCP particles of diameter ~ 70 nm were agglomerated to form larger particles of 10μm in diameter. It was found that by the combination of attritor milling and solution evaporation, the agglomerates of α-TCP nanoparticles could be broken down, and distributed evenly within the poly(D,L-lactic-co-glycolic acid) (PLGA) matrix. Thus, a α-TCP/PLGA nanocomposite was successfully produced by a modified solution evaporation method at room temperature followed by hot pressing at 150 °C. The achievable ceramic loading was approximately 38 wt.%, which was confirmed by thermal gravimetric analysis (TGA).

Abstract: GTR treatment alone has not led to predictable new periodontal tissue reconstruction. Recently, various types of tissue substitutes and alloplastic graft have been used in conjunction with the GTR technique. The aim of this study was to evaluate whether nano-hydroxyapatite/Polylactic acid (nHA/PLA) and bone-derived materials would be useful in the treatment of class II furcation, in order to provide an ideal bone replacement material for periodontal treatment. Mucoperiosteal flap was raised on the buccal aspects of the experimental teeth and class Ⅱ furcation defects were created surgically on premolars of each quadrant in 3 dogs. The defects were randomly repaired with nHA/PLA and collagenic membrane, partially deproteinized bone (PDPB) and collagenic membrane. Blank control group was stayed. Speciments obtained in 6 weeks were evaluated with general observation, histological microscopic analysis. The specimens of the implanted groups exhibited periodontal regeneration including newly formed cementum, periodontal ligament and new bone. The new-formed bone area in sites receiving nHA/PLA and PDPB combined with collagen membrane was greater than that in blank group.The new bone area in PDPB was smaller than that in nHA/PLA. nHA/PLA would be better alternative for periodontal regeneration.

Abstract: Crystalline hydroxyapatite thin coatings have been prepared using a novel opposing RF magnetron sputtering approach at room temperature. X-ray diffraction (XRD) analysis shows that all the principal peaks are attributable to HA, and the as-deposited HA coatings are made up of crystallites in the size range of 50-100nm. Fourier transform infrared spectroscopy (FTIR) studies reveal the existence of phosphate, carbonate and hydroxyl groups, suggesting that HA coatings are carbonated. Finally, in vitro cell culture experiments have demonstrated that murine osteoblast cells attach and grow well on the as-sputtered coatings. These results encourage further studies of hydroxyapatite thin coatings prepared by the opposing RF magnetron sputtering approach as a promising candidate for next-generation bioimplant materials.

Abstract: A network-like porous layer on titanium was prepared by acid-etching with a mixture of CaCl2 and HCl. The pores ranged from 1 to 10!m. The small pores distributed in big pores. In the simulated biological environment, porous octacalcium phosphate (OCP) coatings spontaneously formed on the porous- surfaced titanium. Pre-calcification after acid-etching accelerated OCP precipitation. The OCP coatings had big pores of about 25!m and small pores of 1~3!m, the latter distributed in the former at different depth.