RESUMEN
High-purity (SupT) and reagent-grade (ST), stoichiometric and silicate-containing α-tricalcium phosphate (α-TCP: ST0/SupT0 and Si-TCP x=0.10: ST10/SupT10) were prepared by solid-state reaction based on the substitution mechanism Ca3(PO4)(2-x)(SiO4)x. Samples were determined to be phase pure by X-ray diffraction (XRD), and Rietveld analysis performed on the XRD data confirmed inclusion of Si in the α-TCP structure as determined by increases in unit cell parameters; particularly marked increases in the b-axis and ß-angle were observed. X-ray fluorescence (XRF) confirmed the presence of expected levels of Si in Si-TCP compositions as well as significant levels of impurities (Mg, Al and Fe) present in all ST samples; SupT samples showed both expected levels of Si and a high degree of purity. Phosphorus ((31)P) magic-angle-spinning solid-state nuclear magnetic resonance (MAS NMR) measurements revealed that the high-purity reagents used in the synthesis of SupT0 can resolve the 12 expected peaks in the (31)P spectrum of α-TCP compared to the low-purity ST0 that showed significant spectral line broadening; line broadening was also observed with the inclusion of Si which is indicative of induced structural disorder. Silicon ((29)Si) MAS NMR was also performed on both Si-TCP samples which revealed Q(0) species of Si with additional Si Q(1)/Q(2) species that may indicate a potential charge-balancing mechanism involving the inclusion of disilicate groups; additional Q(4) Si species were also observed, but only for ST10. Heating and cooling rates were briefly investigated by (31)P MAS NMR which showed no significant line broadening other than that associated with the emergence of ß-TCP which was only realised with the reagent-grade sample ST0. This study provides an insight into the structural effects of Si-substitution in α-TCP and could provide a basis for understanding how substitution affects the physicochemical properties of the material.
Asunto(s)
Fosfatos de Calcio/química , Espectroscopía de Resonancia Magnética , Silicatos/química , Espectrometría por Rayos X , Difracción de Rayos X , Silicio/químicaRESUMEN
BACKGROUND: Cancellous bone from patients with osteoarthritis (OA) has been reported to be undermineralised and that from patients with osteoporosis (OP) is more liable to fracture. Changes in the mineral component might be implicated in these processes. OBJECTIVES: To investigate the thermal stability and the mineral structure of cancellous bone from femoral heads of patients with either OA or OP. METHODS: Powdered bone was prepared from femoral heads of patients with either OA or OP and a control group. Composition and thermal stability were determined using a thermogravimetric analyser coupled to a mass spectrometer. Unit cell dimensions and the crystallite size of the mineral were measured using x ray diffraction. RESULTS: Thermal stability of the bone matrix, or of the mineral phase alone, was little altered by disease, though OA bone contained less mineral than OP or control bone. In all three groups, x ray diffraction showed that the mineral unit cell dimensions and crystallite sizes were the same. The mean carbonate content in the mineral from all three groups was between 7.2 and 7.6% and is suggested to be located in both the A site (that is, substituting for hydroxyl groups), and the B site (that is, substituting for phosphate groups). CONCLUSIONS: These results confirm that there is a lower mass fraction of mineral in OA bone, and indicate that the nature of the mineral is not a factor in either disease process.
Asunto(s)
Cabeza Femoral/química , Minerales/análisis , Osteoartritis de la Cadera/metabolismo , Osteoporosis/metabolismo , Anciano , Anciano de 80 o más Años , Carbonatos/análisis , Femenino , Calor , Humanos , Masculino , Persona de Mediana Edad , Termogravimetría/métodos , Difracción de Rayos X/métodosRESUMEN
Thermogravimetric analysis linked to mass spectrometry (TGA-MS) shows changes in mass and identifies gases evolved when a material is heated. Heating to 600 degrees C enabled samples of bone to be classified as having a high (cod clythrum, deer antler, and whale periotic fin bone) or a low (porpoise ear bone, whale tympanic bulla, and whale ear bone) proportion of organic material. At higher temperatures, the mineral phase of the bone decomposed. High temperature X-ray diffraction (HTXRD) showed that the main solids produced by decomposition of mineral (in air or argon at 800 degrees C to 1000 degrees C) were beta-tricalcium phosphate (TCP) and hydroxyapatite (HAP), in deer antler, and CaO and HAP, in whale tympanic bulla. In carbon dioxide, the decomposition was retarded, indicating that the changes observed in air and argon were a result of the loss of carbonate ions from the mineral. Fourier transform infrared (FTIR) spectroscopy of bones heated to different temperatures, showed that loss of carbon dioxide (as a result of decomposition of carbonate ions) was accompanied by the appearance of hydroxide ions. These results can be explained if the structure of bone mineral is represented by [Formula: see text] where V(Ca) and V(OH) correspond to vacancies on the calcium and hydroxide sites, respectively, and 2-x-y = 0.4. This general formula is consistent in describing both mature bone mineral (i.e., whale bone), with a high Ca/P molar ratio, lower HPO4(2-) content, and higher CO3(2-) content, and immature bone mineral (i.e., deer antler), with a low Ca/P ratio, higher HPO4(2-), and lower CO3(2-) content.
Asunto(s)
Densidad Ósea , Huesos/química , Compuestos Orgánicos/análisis , Espectroscopía Infrarroja por Transformada de Fourier/métodos , Difracción de Rayos X/métodos , Animales , Ciervos , Gadiformes , Calor , Especificidad de la Especie , Termogravimetría , BallenasRESUMEN
OBJECTIVE: To determine the water content, collagen content and collagen orientation angle in different regions of sheep lumbar discs. DESIGN: A laboratory study of sheep discs obtained from an abattoir. METHODS: A total of 21 sheep lumbar discs were obtained from three lumbar spines. Water content was determined by oven drying (60 degrees C) to constant mass. Collagen content was determined by hydroxyproline analysis. Fibre orientation angles were determined by X-ray diffraction. RESULTS: Water content increased from 74% of total tissue mass in the outer annulus, to 82% in the inner annulus, to 86% in the nucleus. Collagen content decreased from 30% of total tissue mass in the outer region to 20% in the inner region of the anterior and lateral annulus; it was 16% in the posterior annulus. The orientation angle of the collagen fibres decreased from 59 degrees in the outer region to 56 degrees in the inner region of the anterior and lateral annulus; it was 51 degrees in the posterior annulus. CONCLUSIONS: Sheep lumbar intervertebral discs provide a reasonable model for human lumbar intervertebral discs. RELEVANCE: Sheep lumbar discs have been used to investigate the effects of removing and replacing the nucleus. These studies indicate that removal of nucleus may lead to further disc degeneration and indicate the material properties required for an implant material. The relevance of these previous studies is increased if human and sheep lumbar discs have a similar composition and structure.