In vitro effects of zirconia and alumina particles on human blood monocyte-derived macrophages: X-ray microanalysis and flow cytometric studies

The cytocompatibility of two particulate bioceramics, zirconia and alumina, was studied using human blood monocytes driven to differentiate into matur e macrophages with granulocyte macrophage-colony-stimulating factor. Change s in individual cell elemental composition, particularly sodium and potassi um content, were assessed by X-ray microanalysis of ultrathin freeze-dried sections. Phagocytosis and respiratory burst of macrophages exposed to biom aterial for 7 days were analyzed under flow cytometry using uptake of fluor escent latex beads and 2'7'-dichlorofluorescien diacetate oxidation, respec tively. Zirconia and alumina particles were found to decrease the intracell ular potassium/sodium ratio (an index of cell vitality) significantly (p <. 01) in 7-day-cultured macrophages compared to control cells cultured out of material. Phagocytosis of both ceramic particles by macrophages was follow ed by a decrease in cell phagocytic ability (27%) and a marked altered oxid ative metabolism (>2 times reduced by zirconia and >5 times reduced by alum ina). The present study clearly demonstrates that reduction of the phagocyt ic capacity of macrophages associated with altered oxidative metabolism cau sed by biomaterial particles is characterized by changes in intracellular e lemental content. Thus, investigation of cellular homeostasis by electron p robe microanalysis together with analysis of functional changes may improve estimation of biomaterial cytocompatibility. (C) 2000 John Wiley & Sons, I nc.