Key Engineering Materials Vols. 368-372

Abstract: In this work, porous titania-based coatings containing Ca and P ions were prepared on titanium alloy by micro-plasma oxidation (MPO) in an electrolyte containing nano-HA, calcium salts and phosphate under various applied voltages (200~450 V). The results showed that the MPO coatings formed at 250-450 V were composed of anatase and amorphous phase. With increasing applied voltage, the micropore size and thickness of the MPO coatings increase, while the micropore number decreases. Furthermore, the Ca and P concentrations, as well as atomic ratio of Ca/P are highly dependent on the applied voltage. In addition, the cross-sectional view results showed good adhesion between the MPO coatings and titanium alloy substrate at various applied voltages. In vitro experiments indicated that the MPO coating can induce apatite formation.

Abstract: The bioactivity of porous titanium is poor. Alkali treatment and heat treatment were used in porous titanium to induce apatite biocoatings on the surface of porous titanium and improve the bioactivity of porous titanium. The results indicate that grass-blade fibre Na2TiO3 and amorphous rutile form on alkali and heat treatment samples and (102) plane Ti disappeared. Octacalcium phosphate (OCP) and Hydroxyapatite (HA) were found on the surface of samples in simulation body fluid (SBF) for 2w. The intensity of OCP and HA increased with time of samples in vivo increased. Ti-OH formed on the surface of the gel was explained by the point of view of negative and positive ion exchange. The mechanism of formation of OCP and HA induced by Na2TiO3 and TiO2 gel was studied.

Abstract: Bioglass (BG) particles were treated by 3-aminopropyltriethoxysilane (APTES) in order to improve the interface compatibility with polymer materials. The surface structures of modified BG were characterized through Fourier transformed infrared spectroscopy with attenuated total reflectance accessory, thermogravimetric analysis, differential scanning calorimetry analysis and X-ray photoelectron spectroscopy. The results showed that APTES was successfully grafted on the surface of BG. The biomineralization properties of APTES modified bioglass were also studied through FTIR, XRD and SEM. Results showed that hydroxylcarbonateapatite (HCA) was formed on the surface of modified BG after soaked into SBF solution. It was shown that the APTES modified BG could possess good mineralization properties and could be intended as a composition of scaffolds for bone tissue engineering applications.

Abstract: In order to form the firm active fixation with the adjacent bone, a new kind of bioactive composite hydrogel was prepared as calcic layer of cartilage with polyvinyl alcohol (PVA) and bioglass (BG). The biomineralization properties of the PVA/BG biocomposite hydrogel were studied through Fourier transformed infrared spectroscopy, XRD and SEM with EDX. Results showed that hydroxylcarbonateapatite was formed on the surface of the PVA/BG biocomposite hydrogel after the biocomposite hydrogel soaked into SBF solution. The composite possesses good mineralization properties and could form good firm active fixation with the adjacent bone.

Abstract: Yttria stabled zirconia fiber reinforced polymethyl methacrylate-polymethyl acrylate (PMMAPMA) composites (ZrO2(f)/PMMA-PMA) were prepared by a suspension polymerization method. The effects of MMA/MA volume ratio, initiator and fiber mass ratio on the mechanical properties of the composites were investigated. Results showed that the flexural strength of the composites reaches the optimum value when the volume ratio of methyl methacrylate /methyl acrylate (MMA/MA) = 9/1. With the increase of benzoyl peroxide (BPO) mass ratio, the flexural strength of ZrO2(f)/PMMA-PMA composites increases to maximum and then decreases. With the increase of ZrO2 fiber mass ratio, the microstructure of the fractured surfaces changes from smooth to crapy, implying that the toughness of the composites is improved.

Abstract: The microstructure of scaffold was one of key factors for tissue engineering. Porous polycaprolactone (PCL) scaffolds were fabricated by combination of porogen-leaching and freeze-drying process. Ice particulates were used as porogen material, and PCL solutions in chloroform were mixed with ice particulates for 5minuture at zero temperature. Then the mixture was freezed in liquid nitrogen, and porous scaffold was prepared by freeze - drying finally. The microstructure and properties of the scaffolds were investigated. Porous structure of the scaffolds showed that good 3D microstructure and no porogen remained in the scaffold; pore size and porosity were determined by the size and mass fraction of ice particulates. The results demonstrated that the Scaffolds possessed open and interconnected pores with sizes ranging from several μm to more than 300μm and porosities of 50~80%.

Abstract: A novel calcium phosphate cement (CPC) was prepared by mixing partially crystallized calcium phosphate (PCCP) containing carbonate and dicalcium phosphate anhydrous (DCPA) in this work. The effects of the carbonate content on the phase composition, strength, prosity, and degradation of the set bodies were studied. The results showed that the cement formed into hydroxyapatite (HAp) after setting, in which carbonate doped into the HAp crystal lattice. With the increase of the carbonate to phosphate ratio in PCCP, the compressive strength of the cement declined and the setting of the cement accelerated. Furthermore, the calcium phosphate cement formed a more porous structure with the increase of the carbonate to phosphate ratio in PCCP. The results also indicated that the degradation of CPC may be speeded up by introducing carbonate to the cement.

Abstract: Hemocompatibility of a biomaterial is determined by the interactions between its surface and blood. Due to the complicated action mechanism, various effective ways and the multiple affective factors of the hemocompatibility, a comprehensive evaluation needs to be built instead of single index. Therefore, the platelet consumption ratio of 10 kinds of biomaterials including Ti6Al4V-TiC-DLC gradient coat material was studied based on image analysis method. Combined with the kinetic clotting time and the hemolysis ratio, the comprehensive hemocompatibility evaluation of the material is carried out based on the improved principal component analysis. First, linear transformation of negative index is carried out. Second, index is under a dimensionless using the logarithmic treatment, then to acquire all variants’ principal component and their characteristic vectors. Finally, comprehensive evaluation index of hemocompatibility is constructed. The improved principal component analysis avoids the effect of correlativity among indexes during anaphase evaluation, and can more correctly maintain the original information of indexes. Thus, the research provides a new idea to the comprehensive evaluation of Hemocompatibility.

Abstract: Hydroxyapatite-tricalcium phosphate (HA-TCP) is a new kind of material which shows good biocompatibility, biological degradability, and porosity. This study aimed to determine the effectiveness of HA-TCP as a bone tissue engineering scaffold. In this study, critical size cranial defects were reconstructed with compounds of autogenous bone marrow stromal cells (BMSCs) and HA-TCP. The resulting grafts were examined by X-ray, histological examination, semi-quantitative analysis of osteogenesis, immunochemical examination (collagen type I and III), scanning electron microscopy and transmission electron microscopy. The results showed that HA-TCP is a good bone tissue engineering scaffold and BMSCs/HA-TCP is a promising technique for reconstruction of bone defects.

Abstract: Hydroxyapatite (HAp) coatings were prepared by a hydrothermal electrodeposition method on Carbon/carbon (C/C) composites. The as-prepared HAp coatings were characterized by XRD and SEM analyses. The influence of hydrothermal temperature on the phase and surface microstructures of HAp coatings and the corresponding deposition kinetics were particularly investigated. Results show that with the increase of hydrothermal temperature, the crystallinity, density and homogenous of the prepared HAp coatings are improved. The deposition rate also increases with the increase of hydrothermal temperature. The deposition activation energy of HAp coatings by the hydrothermal electrodeposition process is calculated to be 25.89 kJ/mol.