Browsing by Author "Jensen, Søren Lund"

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    Dissolution behaviour of biosoluble HT stone wool fibres
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Steenberg, Thomas; Kähler Hjenner, Helene; Jensen, Søren Lund; Guldberg, Marianne; Knudsen, Torben
    The dissolution behaviour of two types of fibres, the biosoluble HT and the traditional MMVF21 stone wool fibres, in synthetic simulated lung fluid (Gamble's solution) at pH 4.5 was investigated in order to clarify the mechanisms, and the effect of the various constituents in the liquid. The Gamble's solution contains various organic acids and salts. The study showed that organic acids which are able to form complexes with aluminium (e.g. citric and tartaric acid) caused both fibres to dissolve at a high rate at pH 4.5. Organic acids without the ability to form complexes with aluminium (e.g. acetic, maleic, lactic and pyruvatic acid) have no (or minor) impact on the dissolution rate at pH 4.5. The presence of sodium chloride lowers the dissolution rate, especially that of MMVF21. The silica that remains when the silica network has been depleted of aluminium ions (due to citric and tartaric acid) behaves differently in the two fibres. In HT fibres the silica dissolves at a high rate, probably as a diluted sol. Thus the HT fibre has a high dissolution rate in Gamble's solution at pH 4.5. For the MMVF21 fibre, condensation of the silica network as a gel results in a lower dissolution rate. It is assumed that the different Al/(Al+Si) ratios for HT and MMVF21 fibres explain why the fibres behave differently.
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    New type of stonewool (HT fibres) with a higli dissolution rate at pH = 4.5
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) Knudsen, Torben; Guldberg, Marianne; Christensen, Vermund R.; Jensen, Søren Lund
    A representative, the HT-3 fibre, of a new type of stonewool (HT fibres), characterized by a relatively high content of a lumina and a relatively low content of silica, has recently been tested in-vivo by Bellmann et al. to have a low biopersistence after intratracheal instilladon in rat lungs. Several advantages of this fibre were found: - a half-time T50 which is 2 respectively 4 times lower than that for the reference fibres glasswool and stonewool (after correcting to 1 µm median diameter), - a better ultimate clearance after 18 months, resulting in 3 % remaining for the HT-3 fibre compared to 32 % for normal stonewool, - an effective clearance of fibres with a diameter < 0.5 µm. Fibres with a diameter belonging to this class are generally thought to be those with the highest potency for tumour formadon. The HT fibres have a relatively low in-vitro dissolution rate at p H = 7.5, similar to that of normal stonewool fibres, but a high in-vitro dissolution rate at pH = 4.5. The explanation of the favourable in-vivo properties of t h e HT-3 fibre is based on the recent investigations of the ability of alveolar macrophages to dissolve certain fibres, coupled with the Observation of the high dissolution rate of the HT fibres at the pH value of 4.5 to 5 prevailing inside the macrophages. All HT fibres have been shown t o have comparable, high dissolution rates at pH = 4.5 to 5.