Complementary experimental techniques were applied to characterize bioapatite nanocrystals from pathological cardiovascular deposits. The investigated collection included the leaflets from aortic valve, leaflets from mitral valve, leaflets from tricuspid valve and calcified aorta's wall. XRD, EDX and FTIR data have shown that all studied samples consist of imperfect apatite with different crystallinity and variable chemical composition. In accordance with TEM data, the crystals of pathological calcified deposits frequently have oblong or rod‐like shape (length of 60‐90 nanometers, width of 20‐30 nanometers). At the same time, in the SEM and TEM experiments, the complex spheroid assemblies and planar sheet‐like shaped formations with crystal structure close to apatite were observed. Probably, the different shape and morphology of the particles are caused by different ways of crystal nucleation and growth, although the exact mechanisms remain an open question.

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.

The paper presents the results of study on morphology, structure, elemental and phase composition of the calcified fragments from pathological formations of the thyroid gland. The X-ray diffraction and infrared spectroscopy revealed that all investigated pathological calcifications are represented by a defective carbonate substituted calcium apatite Ca10(PO4)6(OH)2. The use of transmission electron microscopy in combination with electron microdiffraction is shown to reveal some structural and morphological features of crystals of thyroid apatite, which are not detectable by other methods. Therefore, the local morphological and structural analysis of a mineral component of the deposits can be implemented both in one clinical case and in a wide variety of cases, if a delicate preparation at anatomical studies and sample preparation procedure will be applied.

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