Fosfatos de calcio aditivados com fosfato de niobio (V): analise por difração de raios X e de biocompatibilidade com eritrocitos humanos

Abstract

Hydroxyapatite (HAP) samples were prepared by the chemical precipitation method and were added niobium phosphate (NbOPO4) through wet grinding, up to 1%, 5% and 10% in mass of NbOPO4. The samples were thermally treated under 1100°C and 1300°C. Analysis through X-ray powder diffractometry using the Rietveld method identified the phases in each sample. In vitro tests were conducted with HAP powders activated and non activated with NbOPO4. Analysis by scanning electron microscopy (SEM) allowed the observation of erythrocyte cell’s morphology after incubation of the samples with HAP and spectrometry on the visible region was used to measure the hemolytic index (H.I.) in these cells as well as the functionality of the intra cellular hemoglobin after exposition to the samples. In the samples thermally treated under 1300°C, calcium phosphate phases (a-TCP and b-TCP) were observed and for the thermal treatment up to 1100°C, non stequiometric hydroxyapatite, tricalcium phosphate (b-TCP), CaNb2O6 and Ca2Nb2O7 phases were detected. Increasing the NbOPO4 percentage produced enhancement in the quantities of tricalcium phosphate phases as well as in the unit cell volume of these samples. That result was observed at both temperatures of thermal treatment. There were no observable isolated peaks referring to the phases with Nb in the samples thermally treated under 1300°C; at 1100°C, the increase in the cell volume of the phase b-TCP was followed by um decrease of the cell volume of the phase Ca2Nb2O7. These effects suggest that the deformation observed in the cell parameters of the mentioned phases were caused by the entrance of the Nb ion in to the unit cell of these phases, under substitutional or interstitial conditions. The photomicrographs revealed changes of the erythrocytes morphology of cells incubated with the HAP samples. The results show that these samples do not have a significant hemolytic index (H.I.<2), getting slightly hemolytic to the percentage of 10% of NbOPO4 (10>H.I.>20) in a 0.8% hematocrit. There were no alteration in the functionality of the intra cellular hemoglobin (O2 transport), according to the reoxigenation tests under a controlled atmosphere, for hematocrit 0.8% and 40%.