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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.

The samples of hydroxyapatite and carbonate substituted hydroxyapatite (CHA) were obtained under the influence of physical factors, namely ultrasound (US) and microwave (MW) radiations. The results of Fourier transform infrared spectroscopy and X-ray diffraction analysis have proved the formation of the calcium deficient hydroxyapatite and B-type CHA with the Ca/P ratio in the ranges 1.62-1.87. In vitro studies have showed the increased bioactivity of the samples, synthesized under the influence of physical factors as compared to the standard ones. The samples of both groups, synthesized under the influence of 600 W MW, have shown the greatest stability in biological environment. In vivo tests confirm that obtained under US and MW radiations hydroxyapatite-based biomaterials are biocompatible, non-toxic and exhibit osteoconductive properties. The usage of US and MW radiations can significantly shorten the time (up to 5-20 min) of obtaining of calcium deficient hydroxyapatite and B-type CHA in nanopowder form, close in structure and composition to the biological hydroxyapatite.

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h i g h l i g h t s Hydroxyapatite-gelatine composites with addition of Ag þ and ZrO 2 were obtained. Composites were synthesized in two ways: simple mixing and co-precipitation. Co-precipitation synthesis combined ultrasonic treatment and low concentration of gelatine. Obtained composites have different weight ratios of organic/inorganic components. Some composites are osteoconductive and all of them have high level of porosity (75e85%).

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