Influência do nióbio nas propriedades química, estrutural, mecânica e biológica da hidroxiapatita natural tratada termicamente assistida por método sonoquímico

Abstract

This study aims to add value to the disposal of scales of the Arapaima gigas species based on these used as a precursor biogenic source for obtaining natural hydroxyapatite through heat treatments. In addition, Nb5+ ions are inserted into the ceramic phase through the sonochemical route, with the primary objective being to investigate, through chemical, morphological, structural, and biological characterizations, the influence of the metallic ion on the structure of hydroxyapatite. TG and DSC revealed that 700°C is ideal for thermal treatment because, in higher temperatures, there is no mass loss and, at the same time, the energy is necessary for the formation of the crystalline phase of HA. The SEM-FEG technique reveals that the thermally treated material presents hexagonal particles for all samples. However, for the doped samples, there is the appearance of small spheres around them arranged in clusters of particles, and it is a direct influence of the Sonochemistry application stage. The NIRS analysis showed that the wavelengths (2300- 2400 nm, 1800-2200 nm, 1390-1455 nm) characteristic of the vibrational mode of the phosphate group (PO4) have relative intensities affected as the molar concentration of Nb in the ceramic phase, it indicates that doping occurs at or near these sites. Analysis by XRD and refinement by the Rietveld method confirmed that the NbOPO phase presents isolated peaks in the region 23.84° and 24.50° (2Ɵ) in the HA samples – 5, 10, 15, and 20% Nb, in which the refinement converged for reliable parameter values of 𝜒2 close to 1. Furthermore, for all samples, it confirms that the predominant phase is the hexagonal HA with space group P63/m. The microbial analysis did not result in the inhibition of the growth of the Escherichia coli species. Therefore, it indicates the non-occurrence of the dihydroxylation process of the HA phase nor the influence of Nb for this to occur. This process englobes the loss of the structural hydroxyl group. This process is a link to the production of reactive oxygen species that cause the bactericidal effect of the ceramic phase. In addition, the nanoindentation test demonstrated that the HA samples – 10 and 15% Nb present a higher hardness than the samples with lower concentrations of Nb.