FIRUTA GOGA, EDIT FORIZS, GEORGE BORODI, GHEORGHE TOMOAIA, ALEXANDRA AVRAM, REKA BALINT, AURORA MOCANU, OSSI HOROVITZ, MARIA TOMOAIA COTISEL BEHAVIOR OF DOPED HYDROXYAPATITES DURING THE HEAT TREATMENT The goal of this investigation is related to the development of nanostructured biomaterials based on hydroxyapatite (HAP) and multi-doped hydroxyapatites (HAPs), with essential physiological elements, like Mg, Zn, Sr, and Si, for bone repair and regeneration. Nano hydroxyapatites pastes and powders were obtained by wet chemical method using innovative nanotechnology and advanced processing of biomaterials at various temperatures to control the crystallite size and crystallinity degree. The prepared HAPs were analysed by various physical and chemical methods, like SEM, SEM-EDX, AFM, XRD, TG and DSC analysis. The results showed that these biomaterials both in pastes and in powders contained a unique phase, characterized by the HAP structure, which was substantially preserved even at 1000 oC, indicating a high thermal stability of these biomaterials. To enhance their usage, we have prepared HAP and multi-doped HAPs in the form of pastes with controlled humidity (moisture) and powders with controlled crystallinity, which were lyophilized or lyophilized calcined at 300 oC for 1 h. Preliminary biological tests showed that the adhesion and proliferation of human osteoblasts depended on the heat treatment of HAPs used for building the scaffolds. The findings suggest that these biomaterials based on HAPs may have a wide range of medical applications as bone substitute and coatings on metallic implants.