Alina Melinescu

Differentiation of mesenchymal stem cells onto highly adherent radio frequency-sputtered carbonated hydroxylapatite thin films.

In this work, an improved version of the radio frequency magnetron sputtering (RF-MS) technique was used to prepare highly adherent B-type carbonated hydroxylapatite (B-CHA) thin films. Fourier transform infrared spectroscopy (FTIR) and grazing incidence X-ray diffraction studies proved that the coatings maintained the composition and revealed the polycrystalline structure of HA. Scanning electron microscopy analysis showed that the CHA films are rough and exhibit a homogeneous microstructure. Energy-dispersive X-ray spectroscopy (EDX) mapping demonstrated a uniform distribution of the Ca and P cations while a Ca/P ratio of 1.8 was found. In addition, the FTIR experiments showed a remarkable reproducibility of the nanostructures. Human mesenchymal stem cells (hMSCs), in vitro differentiated osteoblasts, and explanted bone cells were grown over the surface of CHA coatings for periods between a few hours and 21 days. Osteoprogenitor cells maintained viability and characteristic morphology after adhesion on CHA coatings. Ki67-positive osteoblasts were the evidence of cell proliferation events. Cells showed positive staining for markers of osteoblast phenotype such as collagen type I, bone sialoprotein and osteonectin. Our data showed the formation of mineralized foci by differentiation of hMSCs to human primary osteoblasts after cultivation in osteogenic media on RF-sputtered films. The results demonstrate the capacity of B-type CHA coating to support MSCs adhesion and osteogenic differentiation ability.

Analysis of the Structure and Morphology of Hydroxyapatite Nanopowder Obtained by Sol-Gel and Pirosol Methods

Nano-size hydroxyapatite is the main inorganic component of bone. There is a critical particle size that each property starts to change. Each property can be modified under controlled conditions. Multifunctional materials for applications, one must consider several properties change. Bone properties, are those which dictate the properties of hydroxyapatite, properties to be followed the synthetic materials to be used successfully as implants. Of these mention those related to surface materials, solubility and biocompatibility and their mechanical strength. Depending on the location and functionality of the implant have met some of these properties. The purpose of this study is to develop a synthetic hydroxyapatite at nano scale, using sol-gel and pyrosol method, for its use in medicine

Sintered Hydroxyapatite with Additives

In present paper the sintering behaviour of HAP in the presence of 5 and 10wt% NC2P was studied. Relative density of 67-72% were obtained for samples sintered at temperatures ranged between 1000-1150°C. The shrinkage data revealed the formation of a liquid phase at 1100°C. This process was accompanied by the density increase and the porosity diminution respectively. The phase composition was investigated by X-ray diffraction. Even the major phase identified was 3CaO . P2O5, however small amounts of HAP were also detected until 1150°C. The IR spectra confirmed the presence of a HO ions in the HAP lattice at temperatures lower than 1150 0 C. Introduction Hydroxyapatite (HAP) is an inorganic compound of human bone, beside other phosphates, calcium carbonate, etc. It has two very important properties for the medical applications namely high bioactivity and good biocompatibility. The biocompatibility consists in the development of a strong chemical bond between the human bone and the HAP-based ceramics. Due to this characteristic HAP is especially used in reparatory orthopaedic and dental surgery. HAP can be obtained on synthetic way by various methods: chemical precipitation, sol-gel and hydrothermal route, etc. HAP contains one water molecule in its formulae, which can be released at temperatures between 600 and 850°C. However, due the reversibility of the reaction in the humid environment, HAP remains hydrated even at higher temperature [1]. Different additives are often used in order to improve the HAP properties. Santos and all [2] have studied the influence of glasses with compositions which belong to the P2O5-CaO-Na2O-SiO2 and P2O5-CaO-Na2O-Al2O3 systems, on the sintering behaviour of HAP fired at 1350 0 C with a soaking time of one hour. They have noticed an important increase of fracture toughness. The content of used glass was of 2 to 4% and the samples were fired in the range of 1200 to 1300°C for one hour at maximum temperature and cooled in the furnace. It was confirmed that there is only one crystalline phase, 3CaO . P2O5 at 1350°C there, the dissociation of HAP being total. Several substitutions of the host ions in the HAP lattice, such as CO3 2which can replace HO and PO4 3, F on the PO4 3sites, as well as Mg 2+ and Na + incorporated on the Ca 2+ sites were earlier reported [3]. The influence of other additives such as CaF2, Li2O, Na2O, NaPO3 and NaPO4 was also studied [4]. The calcium fluoride was found to be improper because it can react with HAP leading to the formation of free calcium oxide, which determines flaws appearance of products. Lithium oxide has a good influence on sintering of samples at high temperature when an eutectic melt is formed between 3CaO . P2O5 and Li3PO4. The NaPO3 and Na3PO4 compounds do not exhibit a significant effect concerning the density increase, because the lack of the liquid phase at the grains boundary. The aim of the work is to study the sintering behaviour of some HAP-based ceramics with sodium oxide used as additive. The compositions considered are located on the tie line HAPNa2O . 2CaO . P2O5 of the quathernary Na2O-CaO-P2O5-H2O system. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 2091-2094 doi:10.4028/www.scientific.net/KEM.264-268.2091

Feldspar Porcelain with High Mechanical Strength

There were studied three compositions, according to the masses vitrified between 1150° and 1250°C, placed in the leucite – mullite – silica subsystem. The reference sample (a mullite type one) was obtained from English kaolin and aplite (provided from “Philip’s Ravine”, Romania) and the other two (mullite – cristobalite type) were made from reference samples mixed with Romanian Uricani’s quartz (in proportions of 7.5% and 15%). It was used two different quartz grain size (a fine one and a coarse one). The samples were prepared through classical ceramic technology, by thermal treatment between 1150-1300°C with 2 hour soaking time. Through X rays diffraction analysis was confirmed the existence of theoretical mineralogical compounds: silica, mullite and orthose. The compressive strengths of samples thermally treated at 1250°C, 2h were between 98 and 183 MPa range. The highest value was observed for sample with 7.5% fine quartz (<100μm).

Synthesis and Characterisation of Cordierite - Mullite Composites

According to classic ceramic technology was prepared stoichiometric cordierite from illite, magnesium oxide and calcined alumina. The sinter was characterised granulometric, by DTA&TG analysis and textural by optical microscopy in the transmitted light. From cordierite sinter (1300 o C – 2h) and electromelted mullite were synthesised three composite compositions by thermal treatment at 1300-1350 o C2 h. Sintering characteristics, bending strength and texture were determined.