Pure nano-crystalline hydroxyapatite (Hap) and Hap doped with magnesium, zinc and silicon, namely Hap-0.25wt%Mg: Hap01, Hap-0.25wt%Mg-0.47wt%Si: Hap02, Hap-1.50wt%Mg-0.47wt%Si: Hap03, Hap-0.67wt%Mg-0.2wt%Zn-0.13wt%Si: Hap04, were synthesized using aqueous precipitation method. The pure and doped Hap were calcined individually at 400, 650 and 850 �C for 2h, and investigated by Brunauer-Emmett-Teller (BET) specific surface area and porosity measurements, as well as by X-ray powder diffraction (XRD). The morphology and particle size of nano-crystalline powders were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal stability of the obtained nanoceramics from 30�C to 1000�C and the effect of calcination temperatures (400, 650 and 850 �C) on their composition and structure were also determined by using TG, DTG, TGA and DTA techniques coupled with SEM-EDX. Results analysis shows a high thermal stability (up to 1000 �C) of these nanomaterials, including the triple-substituted Hap with Mg, Zn and Si (Hap04). Simultaneous incorporation of Mg, Zn and Si into Hap lattice represents a novelty and promotes a new generation of synthetic porous nanoceramics with unique Hap structure, and high thermal stability. Due to their chemical composition and structure rather similar to those characteristic for the inorganic component of bone, these nanoceramics can have multiple applications in biomedicine, as bone substitutes, for metal coatings and in drug delivery systems.
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.
The thermal stability over time of the pure and multisubstituted hydroxyapatite (HAP) pastes, doped with magnesium, silicon, strontium and zinc, synthesized using aqueous precipitation method were investigated by thermal analyses (TG-DTA). Results show high thermal stability of pure and multidoped hydroxyapatite pastes, up to 1000 o C and even after ageing for 1 year, making these pastes promising nano materials for medical applications.
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