Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Biocompatibility evaluation of medical grade and EPD-proven AL2O3 and ZrO2 powders and of FGM alumina wear debris

1. Cytotoxicity testing of the Al2O3 and ZrO2 starting powders was performed according to ISO 10993-5, in the framework of GLP, using two test systems : one established cell line (Balb 3T3) and primary human cell cultures (human osteogenic cells arising from bone marrow stroma) (HOBM). Three parameters were assessed at 24 h and 72 h: cell viability through cell counting, cell mitochondria activity trough MTT test, and necrosis versus apoptosis.This study pointed out the difficulties in interpreting the results : one has to take into account the specific surface area of the powders, toxic ion dissolution specially from additive, or dopants, using AAS when possible, the event of phagocytosis depending on the chemistry of the powder particles which might alter cell growth and phenotype expression. One has to focus on the difference between a cytostatic and a cytotoxic effect.

Moreover it pointed out the differences in sensitivity to cytotoxic or cytostatic elements between established cell lines (Balb 3T3), which are very useful for screening purpose and human primary cell cultures (Ex : HOBM) arising from the implantation site. Human cells were shown much more sensitive to powder particles than Balb 3T3.

2. Cytocompatibility testing (HOBM cell growth and phenotype expression) of Al2O3 and ZrO2 starting powders let us show that, although powder particles undergo phatocytosis, HOBM cell growth and differentiation (ALP acitivity, collagen synthesis) was not significantly altered except for high concentrations (100 µg/mL). At the contrary HOBM challenged with FGM aluminas wear debris generated by a hip stimulator phagocytosed partially wear debris and exhibit altered functions resulting in a partial loss of their capacity to proliferate and differentiate.

Moreover the mode of generation of wear debris seems to be a critical point. These different results obtained with starting powders and wear debris arising from the final component gives food for thought and needs to go deeper into: size, surface chemistry depending on generation mode. It could be very useful in risk analysis study of ceramics.

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Technopole Montesquieu
33650 Martillac