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Biomedical subjects

M Gazzano

Publications and source records attributed to M Gazzano.

8 recordsLinked to original sources
PubMed2004

Nanocrystalline hydroxyapatite-polyaspartate composites.

The direct synthesis of hydroxyapatite-poly-L-aspartic acid (HA-PASP) nanocrystals has been carried out in presence of increasing amounts of PASP in solution up to 56 mmol/l. WAXS, TEM, TGA, IR and chemical analyses were used to characterize the structure, morphology and composition of the products. PASP is quantitatively incorporated into HA crystals, provoking a reduction of the coherent length of the crystalline domains. Furthermore, composite crystals display a greater length/width ratio with respect to the control HA crystals, and show a remarkable trend towards aggregation. The broadening of the X-ray diffraction reflections indicate a reduction of the coherent length along the long dimension 002 and the cross section 310 of the apatite crystals. The comparison between the morphological and structural data allows to suggest a specific interaction between PASP and HA structure.

Biocompatible Materials↗
PubMed2003

Determination of low levels of free fibres of chrysotile in contaminated soils by X-ray diffraction and FTIR spectroscopy.

A new analytical method for the determination of low levels (0.01-1 wt%) of free fibres of chrysotile in contaminated clayey, sandy and sandy-organic soils is described. The detection limit of 0.01 wt% is reached with an enrichment of free fibres of chrysotile in the sample using a standard laboratory elutriator for sedimentation analysis. The chrysotile quantitative determination is performed both by X-ray powder diffraction, using the internal standard and reference intensity ratio methods, and by Fourier-transform infrared absorption spectroscopy. The procedure can be successfully applied to different soils after removal, by a thermal treatment, of the matrix components which can interfere. This straightforward method fulfils the request of public institutions and private companies for an appropriate quantitative determination of chrysotile-free fibres in contaminated soils.

Asbestos, Serpentine↗
PubMed2003

A new method for the detection of low levels of free fibres of chrysotile in contaminated soils by X-ray powder diffraction.

A new method for the determination of free fibres of chrysotile in contaminated soils is described. The detection limit of 0.5 wt per thousand is reached by an enrichment process of the asbestos fraction of the sample using a standard laboratory elutriator for sedimentation analysis. The analysis of the enriched fraction is performed by X-ray powder diffraction using a conventional instrument. The procedure can be successfully applied to several soils of different nature throughout thermal treatment and removal of possible interferences due to some matrix components. This method is straightforward, routinized and has been especially developed to fulfil the request of public and private institutions for an appropriate quantitative determination of chrysotile free fibres in contaminated soils.

Asbestos, Serpentine↗
PubMed2002

Electrocatalytic activity of cobalt phthalocyanine stabilized by different matrixes.

The behavior of cobalt phthalocyanine complexes incorporated inside an hydrotalcite-like clay (HT) or a sonogel-carbon composite has been investigated in order to develop chemically modified electrodes suitable for use as amperometric detectors. The electrocatalytic oxidation process of cysteine at this new electrode has been studied by cyclic voltammetry. For comparison, the oxidation of cysteine catalyzed by the cobalt phthalocyanine complex as a redox mediator, either dissolved in solution or entrapped inside the HT structure, has been followed by polarography. The sonogel-carbon composite electrode is stable and its response is repeatable. Cysteine oxidation is actually induced by the electrogenerated Co(III) complex, and the relevant anodic peak current varies linearly with cysteine concentration within the range 9.0x10(-4) to 1.0x10(-2) mol L(-1).

Calibration↗
PubMed2000

Bacterial poly(3-hydroxybutyrate): an optical microscopy and microfocus X-ray diffraction study.

Two-dimensional spatially resolved microfocus X-ray diffraction has been used to investigate spherulites of pure bacterial poly(3-hydroxybutyrate) (PHB) and of a blend of natural and synthetic atactic PHB (a-PHB) crystallized at a relatively high temperature (Tc = 140 degrees C). Both samples investigated contained practically two-dimensional spherulites, characterized by wide extinction bands (band spacing > 80 microns). The X-ray diffraction patterns confirmed that the unit cell alpha-axis is oriented along the spherulite radius in PHB and that the same is true for the a-PHB containing blend. Comparison of the matrix of diffraction patterns with the polarized optical micrograph of the scanned sample area indicated a very clear correlation between pattern changes and banding, yielding a straightforward picture of the structural variations within the spherulite.

Bacteria↗
PubMed1990

Thermal conversion of octacalcium phosphate into hydroxyapatite.

The thermal conversion of octacalcium phosphate into hydroxyapatite has been investigated by a crystallographic, thermogravimetric, and calorimetric study. The conversion of octacalcium phosphate takes place through the remotion of three of its five water molecules and yields a poor crystalline apatitic phase. The three water molecules are lost in two steps. The first one, which is reversible, corresponds to the remotion of one water molecule and induces a slight contraction of the unit cell of OCP. The successive remotion of two water molecules, which provokes the structural conversion of OCP into apatite, is in irreversible process. The mechanism of the water loss of OCP is explained in terms of its crystal structure.

Calcium Phosphates↗
PubMed1988

Structural and chemical characterization of inorganic deposits in calcified human mitral valve.

X-ray diffraction, i.r. absorption, and chemical analyses have been carried out on the mineral deposits of calcified human mitral valves and glutaraldehyde-preserved porcine aortic grafts. The mineral deposits isolated from highly calcified mitral valves and porcine aortic grafts are constituted of type B-carbonate apatite. Magnesium substituted beta-tricalcium phosphate is present, together with an apatitic phase similar to dahllite, in the ashes of poorly calcified mitral valves. The contraction of the unit cell of beta-tricalcium phosphate due to magnesium incorporation is compared with the variation of the lattice constants of synthetic beta-tricalcium phosphate at different degree of magnesium substitution for calcium. The results reveal the important role of magnesium on the calcification of human valves. In fact, the apatitic phase deposited at the beginning of the calcification process, when there is a high magnesium content, converts completely into beta-tricalcium phosphate by heat treatment at 1,000 degrees C. On the other hand, when the calcification becomes massive, magnesium content appears highly reduced, and the deposited apatitic phase is characterized by a high thermal stability.

Calcinosis↗