B. Dubini

Osteointegration of bioactive glass-coated zirconia in healthy bone: an in vivo evaluation

Osteointegration of yttria stabilised tetragonal zirconia (YSTZ), either coated with bioactive glass named RKKP bioglaze (RKKP) or uncoated, was evaluated in an animal model. RKKP-coated and uncoated (controls) YSTZ cylinders were implanted in the distal femoral epiphyses of 14 Sprague Dawley rats under general anaesthesia. At the experimental times of 30 and 60 days after sacrifice, histomorphometry and SEM microanalysis were performed on methylmethacrylate-embedded undecalcified sections to determine the osteointegration rate. At 30 days, a significantly higher affinity index was demonstrated in vivo by histomorphometric evaluation in RKKP-coated versus uncoated YSTZ implants p < 0.05); at 60 days, the coated implants behaved better than controls (affinity index of + 32%), but the difference observed lay within the statistical uncertainty. SEM analysis demonstrated better bone adhesion to the material in RKKP-coated YSTZ at both 30 and 60 days. These findings suggest that YSTZ coated with the bioactive glass named RKKP enhances osteointegration of ceramics.

Structural Modifications in the Liquid Crystalline Lα Phase of Distearoylphosphatidylcholine Induced by Variable Cholesterol Concentration

Abstract The melted chain liquid crystal phase of distearoyllecithin liposomes in water was investigated at various cholesterol content. X-ray diffraction and differential scanning calorimetry techniques were used. A fluidifying effect with respect to the chain melting temperature and a stiffening effect, deduced from the progressive increase of the lamellar repeat spacing in the melted chain phase, were deduced for low cholesterol concentrations, in agreement with the previous results in other phospholipids. An increase of the in plane lattice parameter and a decrease of the lamellar repeat spacing, corresponding to an overall non monotonic behaviour, were observed at higher concentrations, below the saturation value. The positional order inside the layers was considered for the first time in a phospholipid in a quantitative way by evaluating the correlation length ξ. That in plane correlation length remains constant for cholesterol concentrations lower than 35% and then decreases, indicating opposite ef...

Azelaic acid in model membranes: A thermodynamical and structural study

SummaryWe report a thermodynamical and structural investigation on the effect of a dicarboxylic acid, the azelaic acid, on a synthetic phosophatidylcholine in excess water condition. The results indicate that the drug interacts with the lipid headgroup region, near to the hydrocarbon chains: in particular, at higher concentrations investigated, an interdigitated «gel phase», with rigid chains, stiff and perpendicular to the lamellar planes, is induced. The experimental electron density profiles, obtained for samples containing low and high quantity of azelaic acid, support the proposed interaction. Moreover, step electron density models, used to confirm the selected sign combination of the observed structure factors, show the best agreement with the experimental data when the chain terminal methyl groups are frozen in fixed position.

Structural modifications in the distearoyl phosphatidyl choline liposomes induced by variable cholesterol concentration

SummaryLiposomes of distearoyl phosphatidyl choline (DSPC) in excess water and containing different quantities of cholesterol were studied by using X-ray diffraction and differential scanning calorimetry techniques. A phase diagram was obtained with phases not occurring in the absence of cholesterol. Coexistences of phases were also detected.

Study of Cholesteryl Oleate-Cholesteryl Linoleate Binary Mixtures

Abstract The phase transitions for several mixtures of cholesteryl oleate and cholesteryl linoleate have been investigated by X-ray diffraction, differential scanning calorimetry and optical microscopy. Several physical quantities, i.e. structural and thermodynamical data, have been obtained. The results are consistent with previous investigations on pure compounds. The phase diagrams on heating, involving the solid-isotropic liquid transition, and on cooling, involving the isotropic liquid-cholesteric and cholesteric-smectic A phase transitions, have been derived. A region of nonmiscibility, in which two saturated solid solutions coexist in equilibrium, together with the presence of a eutectic, have been observed in the first phase diagram.

Structural analysis of the Γ phase in cholesterol-distearoylphosphatidylcholine multilamellar vesicles

SummaryThe interaction of cholesterol with membranes is particularly interesting as the cholesterol concentration influences membrane stability and permeability by inducing changes in the structure and dynamics of the constituent lipid molecules. On the other hand, cholesterol is present in the atherosclerotic plaques and in some skin diseases, like xanthomas and xantelasmas. An investigation was performed on the Γ phase in a cholesterol-distearoyl phosphatidyl choline (DSPC) mixture by using X-ray diffraction and differential scanning calorimetry. The cholesterol/DSPC molar ratio was 35/65 and DSPC-to-water weight ratio was 1/3. The Γ phase appears at sufficiently high concentration of cholesterol and it is characterized by interchain positional order considerably lower than in theLβ′ andPβ′ phases but higher than in theL∝ liquid crystalline phase of pure lecithin in excess water. The results suggest that a lateral phase separation exists in the temperature range of existence of the Γ phase. The other phase Γ′ appears to be richer in cholesterol. The (Γ+Γ′) toL∝ phase transition was investigated and the temperature dependence of the in-plane correlation length in the Γ phase was determined. A very weak enthalpy peak was observed at the chain melting transition, confirming the highly disordered nature of phases Γ and Γ′.RiassuntoL’interazione fra colesterolo e membrana è particolarmente interessante poiché la concentrazione di colesterolo influenza la stabilità e la permeabilità della membrana, inducendo cambiamenti sulla struttura e dinamica dei lipidi che la costituiscono. D’altra parte il colesterolo è presente nelle placche aterosclerotiche e in malattie della pelle quali xantomi e xantelasmi. È presentato uno studio sulla fase Γ di una miscela acquosa di colesterolo e distearoilfosfatidilcolina (DSPC), mediante diffrazione di raggi X e microcalorimetria differenziale. Il rapporto molare colesterolo/DSPC vale 35/65 e il rapporto peso DSPC/acqua è 1/3. La fase Γ appare a concentrazioni di colesterolo abbastanza alte ed è caratterizzata da ordine posizionale fra le catene considerevolmente piú basso che nelle fasiLβ′ ePβ′ ma piú, alto che nella fase liquido-cristallinaL∝ della pura lecitina in eccesso d’acqua. I risultati suggeriscono che nell’intervallo di temperatura d’esistenza della fase Γ esiste una separazione laterale di fase. La seconda fase (Γ′) appare essere piú ricca di colesterolo. Si studia la transizione della fase (Γ+Γ′) alla faseL∝ e si determina la dipendenza dalla temperatura della lunghezza di correlazione sul piano (ξ) nella fase Γ. In corrispondenza della transizione di fusione delle catene è osservato un picco calorimetrico con entalpia molto bassa; ciò conferma la natura fortemente disordinata della fasi Γ e Γ′.РезюмеВзаимодействие холестерола с мембранами представляет особый интерес с точки зрения, как концентрация холестерола влияет на устойчивость и проницаемость мембраны, индуцируя изменения в структуре и динамике молекул, составляющих липид. С другой стороны холестерол присутсвует в атеросклеротических бляшках и в некоторых кожных заболеваниях. Проводится исследование Γ фазы в водной смеси холестерол-DSPC, используя дифракцию рентгеновских лучей и дифференциальную сканирующую калориметрию. Молекулярное отношение холестерол-DSPC составляет 35/36, а отношение весов DSPC-вода составляет 1/3. Γ фаза возникает при достаточной высокой концентрации холестерола и характеризуется позиционным порядком между цепочками более низким, чем в случае фазLβ иPβ но более высоким чем в случае фазы жидкого кристаллаL∝ для чистого лецитина при избытке воды. Полученные результаты показывают, что поперечное разделение фаз сущестует при температурах, когда существует Γ фаза. Возникает другая Γ′ фаза при более высоких концентрациях холестерола. Исследуется фазовый переход из (Γ+Γ′) фазы вL∝ фазу. Определяется температурная зависимость длины корреляции в Γ фазе. Обнаружен очень слабьй пик энтальпии при нереходе, связанном с плавлением цепочек, что подтверждает сильно разупорядоченную природу фаз Γ и Γ′.

Thermodynamical and Structural Effects of Diltiazem on Lecithin Liposomes

Abstract In the present work the structural and thermodynamical modifications induced by the calcium antagonist drug diltiazem, on DPPC liposomes, considered as model of the lipid matrix of the cell membrane, have been studied, by using differential scanning calorimetry, x-ray diffraction and optical microscopy techniques. Calorimetric scans and X-ray diffraction patterns show that, at higher concentration of diltiazem, the pretransition peak disappears, the main transition temperature decreases, the lamellar thickness increases and the chains, in the β conformation, are packed in a hexagonal undistorted lattice. Finally for higher concentrations of diltiazem the liquid crystalline phase with melted chains seems to become hexagonal.

Effects of cholesterol and azelaic acid in lecithin liposomes exposed to ELF fields: A thermodynamic and structural study

SummaryIn the present work some thermodynamic and structural aspects of electric-, magnetic- and electromagnetic-field interaction at 50 Hz with lecithin liposomes mixed with azelaic acid or cholesterol have been investigated by using differential scanning calorimetry and X-ray diffraction. Calorimetric scans and X-ray diffraction patterns show that no significant modifications of the two mixtures occur, except a little increase of the freezing temperature of the free water after exposure to electromagnetic field.

Study of Perturbations Induced by a Barbituric, the Phenobarbital, on DSPC Multilamellar Liposomes

Abstract Multilamellar liposomes of distearoyl phosphatidyl choline in excess water condition, doped by the barbituric drug Phenobarbital, in molar ratios between 0 and 0.5, were studied by using differential scanning calorimetry, X-ray diffraction and electron microscopy. The results suggest that the drug interacts with the lipid headgroup region: in particular, at the higher concentrations investigated, an interdigitated “gel phase,” with rigid chains, stiff and perpendicular to the lamellar planes, seems to be induced.

X-ray diffraction study of cholesterol-cholesteryl oleate binary mixtures

SummaryThe phase transitions for binary mixtures of cholesteryl oleate (CO) and cholesterol (CH) have been investigated by X-ray diffraction, differential scanning calorimetry and optical microscopy. The phase diagrams on heating, involving the solid-solid and solid-isotropic liquid transitions, and on cooling, involving the cholesteric and smectic mesophases, have been derived. In particular, a strong supercooling effect of liquid cholesterol and a progressive decrease of the isotropic liquid-cholesteric and cholesteric-smectic transition temperatures were observed. Moreover, some structural modifications induced in the smecticA and in the cholesteric phase by the presence of CH in CO were detected. Finally the dependence of intermolecular distance in the isotropic liquid phase was studied as a function of temperature and mixture composition.RiassuntoMediante diffrazione dei raggi X, calorimetria differenziale e microscopia ottica sono state studiate le transizioni di fase per miscele binarie di colesteril oleato (CO) e colesterolo (CH). Sono stati ricavati in riscaldamento il diagramma di fase per le transizioni solido-solido e solido-liquido isotropo ed in raffreddamento un diagramma di fase comprendente le mesofasi colesterica e smettica. In particolare sono stati osservati un marcato effetto di sovraraffreddamento del liquido del colesterolo ed una progressiva diminuzione delle temperature di transizione delle fasi liquido-isotropo colesterico e colestericosmettico. Inoltre sono state trovate alcune modificazioni strutturali indotte nella fase smetticaA ed in quella colesterica dalla presenza del CH nel CO. Infine è stata studiata la dipendenza della distanza intermolecolare nella fase liquido isotropo in funzione della temperatura e della composizione della miscela.РезюмеИсследуются фазовые переходы в бинарных смесях олеата холестерила (CO) и холестерола (CH) с помощью дифракции рентгеновских лучей, дифференциальной сканирующей калориметрии и оптической микроскопии. Получаются при нагревании фазовые диаграммы, вклюьающие переходы твердое тело-твердое тело и твердое тело-изотропная жидкость, а при охлаждении фазовая диаграмма, включающая холестерическую и смектическую мезофазы. В частности, наблюдается сильные эффект сверхохлаждения дия жидкого холестерола и постепенное уменьшение температур фазовых переходов изотропная жидкость-холестерик и холестерик-смектик. Кроме того, определяются структурные модификации, индуцированные в фазе смектикаА и в фазе холестерика наличием CH и CO. В эаключение, исследуется эависимость расстояния между молекулами в фазе изотропной жидкости, как функция температуры и состава смеси.