Effect of Thermal Treatment of Refractory Ceramic Fibres on the Induction of Cytotoxicity and Cell Transformation

Abstract

Refractory ceramic fibres (RCFs) are amorphous fibres made up of various metal oxides (mainly Al2O3 and SiO2), used as high temperature insulation materials. We have examined the surface properties of three RCFs from the TIMA repository, RCF1, RCF3 and RCF4 (RCF1 heated at the expected working temperature), which showed different potentials for cytotoxicity and the induction of morphological transformation in Syrian hamster embryo cells, RCF4 being less active. The degree of surface hydrophilicity, evaluated by adsorption calorimetry, showed that RCF4 is less hydrophilic than RCF1, likely as a consequence of the prior thermal treatment. In order to investigate the effect of thermal treatment on the cellular response to RCFs we have heated (800°C for 24 h) the most active fibre (RCF3) in air until it was converted to a fully hydrophobic material. The cytotoxic (colony forming efficiency) and transforming potencies of heated and unheated RCF3, measured at concentrations between 1 and 16 µg/cm 2 of culture dish for 7 days, were then compared. Both cytotoxicity and potential to transform cells dramatically decreased when fibres were heated, indicating that hydrophobicity blunts the cellular response to RCF3. These results confirm that the state of the surface of RCFs modulates the biological response elicited and that a correlation exists between the degree of surface hydrophilicity and induction of cell damage and transformation. Thermal treatment, by lowering the surface affinity of RCFs for water, inhibits some cell–fibre interactions and decreases the extent of internalization of the fibres.