Structural and crystal-chemical characteristics of the apatite deposits from human aortic walls.

Thermal behavior of biological apatite is the object of several studies. Crystal size, carbonate content, phase composition, and other parameters change during annealing up to 900 °C in biological minerals with apatite structure. The way these parameters change reflects the specific properties of the initial bioapatite. This work presents data on thermal transformations of pathological bioapatite from the human cardiovascular system, namely aortic wall deposits. Some minor elements, foreign to calcium hydroxyapatite (e.g., Na and Mg), can be both incorporated in the apatite structure and localized in the surface layers of crystals, modifying functions of the mineral. A new approach was proposed to determine the predominant location of minor elements, such as Mg, Na, and K, in the mineral of pathological deposits. Mg and Na in pathological apatite can be in both structurally bound (substituting calcium in lattice) and labile (localized on the crystal surface) states, while K is not able to join the apatite structure in significant amount or be chemically bound to it. This approach, based on atomic spectrometry, can be used effectively in combination with a set of traditional techniques, such as like EDS, IRS, and XRD.

Morphological and crystal chemical characteristic of panсreatic lithiasis.

OBJECTIVE: Introduction: Information on chemical and phase composition of pancreoliths is limited and discrepant. There are reports, that pancreoliths are composed by calcium, phosphate, calcium carbonate or combination of calcium with fatty acids The aim of the work is studying of structural characteristics of pancreatoliths in 5 clinical cases. PATIENTS AND METHODS: Materials and methods: Morphological and crystal-chemical study of five cases of pathological biomineralization in the pancreas were conducted in the work. RESULTS: Results: Two stones were located in the pancreatic duct, in other cases - in the ductal system of pancreas. Concretion sizes ranged from 0.5 to 1.5 cm in diameter. Pancreatic lithiasis' form depended on the location: in the duct of Wirsung single concretions were found (they were relatively large, oval stones with smooth, regular edges); multiple, small concretions with irregular edges, coral-like stones dominated in the ductal system of pancreas. Histological study of pancreas showed the signs of chronic pancreatitis, tissue fibrosis, atrophy and edema of glandular component, system distension of ducts, nidal mix-cell inflammatory infiltrates, vessels' plethora. Structural phase and chemical analysis of pathological biominerals responded calcite in all studied cases. CONCLUSION: Conclusion: The presence of pancreatic lithiasis was found to be accompanied by significant morphological changes of the pancreas. The pancreatolith crystal phase was established to be calcium carbonate in the form of calcite.

Characterization and in vivo evaluation of chitosan-hydroxyapatite bone scaffolds made by one step coprecipitation method.

Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of auto- or allografts is impossible. The objective of the present work was to characterize and study in vivo biodegradation of simple chitosan/hydroxyapatite scaffolds. For this purpose, a series of chitosan/hydroxyapatite composites has been synthesized in aqueous medium from chitosan solution and soluble precursor salts by a one step coprecipitation method. A study of in vivo behavior of the materials was then performed using model linear rats. Cylindrical-shaped rods made of the chitosan/hydroxyapatite composite material were implanted into tibial bones of the rats. After 5, 10, 15, and 24 days of implantation, histological and histo-morphometric analyses of decalcified specimens were performed to evaluate the stages of biodegradation processes. Calcified specimens were examined by scanning electron microscopy with X-ray microanalysis to compare elemental composition and morphological characteristics of the implant and the bone during integration. Porous chitosan/hydroxyapatite scaffolds have shown osteoconductive properties and have been replaced in the in vivo experiments by newly formed bone tissue.