Δημοσιεύσεις σε συνέδρια

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Browsing Δημοσιεύσεις σε συνέδρια by Subject "Apatite"

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    Open Access
    Effect of dilipidization and deproteination protocols of bone on biological apatite
    (2012-05-04) Kontoyannis, Christos; Orkoula, Malvina; Karampas, Ioannis; Κοντογιάννης, Χρήστος; Όρκουλα, Μαλβίνα; Καραμπάς, Ιωάννης
    Τμήμα Φαρμακευτικής (Δημοσ. Π.Π. σε συνέδρια)
    Delipidization and deproteination methods are essential for the isolation of the mineral phase of bone, the biological apatite. In the present work, the effect of the above methods on the crystal size and crystallinity of bone mineral was studied. Ten bovine bones were subjected to these protocols and their crystal size and crystallinity were determined by X-ray Diffraction. In all cases, the delipidization protocol was found not to affect these parameters. On the other hand, deproteination method induces noteworthy changes. All the results statistically tested for their significance.
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    Open Access
    New methodologies for the quantification of the consituens of bone by Raman spectroscopy
    (2012-04-27) Kontoyannis, Christos; Orkoula, Malvina; Karampas, Ioannis; Κοντογιάννης, Χρήστος; Όρκουλα, Μαλβίνα; Καραμπάς, Ιωάννης
    Τμήμα Φαρμακευτικής (Δημοσ. Π.Π. σε συνέδρια)
    Bone is a composite material consisting of inorganic material (biological apatite), embedded in an organic matrix (collagen type I). Both functionality and integrity of bone are related to those constituents. The mineral gives bone tissue mechanical strength while collagen is responsible for its elasticity. Pathological conditions like osteoporosis, osteopetrosis, osteomalacia are related chemical composition changes of the tissue. In the current study, an attempt was made to quantify both mineral and organic component simultaneously in a fast and accurate way, by employing Raman Spectroscopy. Two approaches were followed: one using peak ratios and a second implementing chemometric analysis. Results showed that calibration models based on ratios of the 961 cm-1 vibration for apatite to the 1667 cm-1 for collagen and the chemometric analysis of the obtained spectra exhibited similar ability of prediction but chemometric model was characterized by superior accuracy.
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    Open Access
    Raman spectroscopy of osteoporotic rat tibia
    (2012-03-08) Kontoyannis, Christos; Orkoula, Malvina; Vradaki, Martha; Κοντογιάννης, Χρήστος; Όρκουλα, Μαλβίνα; Βαρδάκη, Μάρθα
    Τμήμα Φαρμακευτικής (Δημοσ. Π.Π. σε συνέδρια)
    Fractures are the most frequent health problem associated with bone. Metabolic diseases, such as osteoporosis, affect skeletal integrity, reduce strength and toughness of bone and lead to increased risk of fragility. In the present work, changes in the amount and/or quality of bone were studied in osteoporotic tibiae from female wistar rats compared to healthy controls. Osteoporosis was induced through ovariectomy. Bone composition and quality was evaluated employing Raman Spectroscopy. Several spectra were recorded. The height of the primary phosphate band (PO43-, v1) for the mineral at 959 cm-1, the carbonate peak at 1070 cm-1 under the combined phosphate-carbonate envelope 1010-1100 cm-1 spectral range, the matrix bands at 855 cm-1 (hydroxyproline), 875 cm-1 and 920 cm-1 (proline), as well as the three major peaks under amide I envelope (1620-1710 cm-1) were measured after proper baselinining and deconvolution. The mineral to matrix ratio [959 cm-1 / (855 cm-1 + 875 cm-1 + 920 cm-1)] was reduced, suggesting decreased mineral quantity in the osteoporotic tibiae compared to controls. Carbonate levels remained stable which implies absence of new bone tissue formation, though bone is known to follow a constant renewal procedure. The mineral to amide I envelope ratio exhibited an increasing trend suggesting that amide I cannot be used as collagen metrics as it is subject to polarization effects. Further analysis of the amide I envelope shows that the band changes shape following bone disease, which is a result of the change in the ratio of the peaks lying under the amide I envelope. Therefore, changes in collagen cross-linking accompany reduction of mineral amount and lead to reduced strength and increased fragility in osteoporosis.