RESUMO
This study focuses on the dissolution process and surface characterization of amosite fibres following interaction with a mimicked Gamble's solution at a pH of 4.5 and T = 37 °C, up to 720 h. To achieve this, a multi-analytical approach was adopted, and the results were compared to those previously obtained on a sample of asbestos tremolite and UICC crocidolite, which were investigated under the same experimental conditions. Combining surface chemical data obtained by XPS with cation release quantified by ICP-OES, an incongruent behaviour of the fibre dissolution was highlighted for amosite fibres, similarly to asbestos tremolite and UICC crocidolite. In particular, a preferential release of Mg and Ca from the amphibole structure was observed, in agreement with their Madelung site energies. Notably, no Fe release from amosite fibres was detected in our experimental conditions (pH of 4.5 and atmospheric pO2), despite the occurrence of Fe(II) at the M(4) site of the amphibole structure, where cations are expected to be rapidly leached out during mineral dissolution. Moreover, the oxidation of both the Fe centres initially present on the fibre surface and those promoted from the bulk, because of the erosion of the outmost layers, was observed. Since biodurability (i.e., the resistance to dissolution) is one of the most important toxicity parameters, the knowledge of the surface alteration of asbestos possibly occurring in vivo may help to understand the mechanisms at the basis of its long-term toxicity.
RESUMO
The unique property of phosphate-based glasses and fibres to be completely dissolved in aqueous media is largely dependent on the glass composition. This article focuses on investigating the effect of replacing Na2O with 3 and 5 mol% Fe2O3 on cytocompatibility, thermal and dissolution properties of P2O5-CaO-Na2O-MgO-B2O3 glass system, where P2O5 content was fixed at 45 mol%. The effect of increasing Fe2O3 from 3 to 5 mol% on P2O5-CaO-Na2O-MgO glasses was also evaluated. The glass transition temperature, onset of crystallisation temperature and liquidus temperature were found to decrease with increasing Fe2O3 content and the addition of B2O3, while the thermal expansion values were found to decrease. The density of the glasses decreased with increasing Fe2O3 content. However, an increase in the density was observed by the addition of 5 mol% B2O3. The dissolution properties and mode of bulk glass and fibres were also examined which were found to decrease with increasing B2O3 and Fe2O3. However, it was found that the dissolution properties of the glasses containing both B2O3 and Fe2O3 were lower than only Fe2O3 containing glasses. The in vitro cell culture studies using human osteoblast like (MG63) cell lines revealed that the glasses containing both B2O3 and Fe2O3 maintained and showed higher cell viability as compared to the only Fe2O3 containing glasses. Glasses containing both B2O3 and Fe2O3 showed a pronounced effect on the dissolution rate of the glasses, which eventually improved the cytocompatibility properties of the glasses investigated.
RESUMO
In this work, interactions between cellulose and ionic liquids were studied calorimetrically and by optical microscopy. Two novel ionic liquids (1,5-Diazabicyclo[4.3.0]non-5-enium propionate and N-methyl-1,5-diazabicyclo[4.3.0]non-5-enium dimethyl phosphate) and 1-ethyl-3-methylimidazolium acetate-water mixtures were used as solvents. Optical microscopy served in finding the extent of dissolution and identifying the dissolution pattern of the cellulose sample. Calorimetric studies identified a peak relating to dissolution of cellulose in solvent. The transition did, however, not indicate complete dissolution, but rather dissolution inside fibre or fibrils. This method was used to study differences between four cellulose samples with different pretreatment or origins.