Estudo da dissolução de vidros niobofosfato em água e em solução simuladora de fluído fisiológico / Evaluation of the dissolution rate of niobium phosphate glasses in water and simulated body fluid solution

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

15/08/2008

RESUMO

The need to extend and improve the quality of life is leading to the search of new materials. Glasses containing phosphorous in their compositions are considered biomaterials and can be used as scaffolds because they have a structure close to the mineral component of bone tissues, and present relatively high solubility in water. The chemical composition, morphology, and mechanical properties of bioactive glasses can be properly fit to allow bonding with bones. Niobium phosphate glasses have been previously investigated. The addition of niobium oxide improves the chemical durability of phosphate glasses, and they are considered biocompatible. In the present work the dissolution rate of a wide range of niobium phosphate glass compositions were determined in water and Simulated Body Fluid (SBF). The glass compositions were in the range (32 - 37)P2O5 (2-15)Nb2O5 (6-7)Na2O (46-53)CaO mol%, and they were prepared by melting reagent grade chemical compounds in the temperature range 1300ºC - 1400ºC for 0.3h in an electrical furnace. Seven different glasses were prepared. The glasses were considered non-toxic after performing cytotoxicity tests. No evidence of crystalline phases was observed on X-rays diffraction patterns before and after the corrosion tests. The glass densities are in the range of 2.84 - 3.14 g/cm3. The density increases as the amount of niobium oxide increases. A mass loss was determined after immersing glass samples in water and in SBF at 37ºC during 21 days. The dissolution rate decreases as the amount of niobium oxide increases. The dissolution rate depends on the immersion medium and conditions. Cracks on the glass surfaces were observed by scanning electron microscopy after the corrosion tests which are related to the material release from the glass surface to the liquid. There is also evidence of formation of a layer on the surface of a specific glass composition. The glass compositions were determined before and after the corrosion tests by X-ray Fluorescence Spectrometry (EDS). Aluminum was detected in the glass composition. This element is related to the contamination of the glass by the crucible used in the glass melting. A significant variation of the amount of P2O5 compared to the nominal composition was also noticed, due to the volatilization of phosphorous during the glass melting. The surface glass composition changes during the leaching tests in water or SBF because of the preferential release of P, Na, and Al. EDS was also used to determine the concentration of P, Na, Nb, and Ca in the leaching solution by using the dry drop method.

ASSUNTO(S)

glasses hidroxiapatita hydroxyapatite sbf sbf vidros

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