Probing the silica surfaces by red blood cells

BACKGROUND: The polymorphic forms of silica (silicon dioxide; SiO(2)) interact with the cell membranes of many mammalian cells, including red blood cells (RBCs), causing hemolysis. The electrostatic factor, which is believed to be a major contributor to the silica-cell contact, might have potential interest for the study of cell surface properties. The surface properties of SiO(2) particles are also of interest. METHODS: Washed human RBCs interacted with the particles of highly dispersed fumed silica (Aerosil A-300) and silicas (nine samples) obtained from the initial A-300 by its dehydroxylation at various thermal conditions. Their light scatter (forward and side light scatter) in 0.01% silica solution was measured uninterruptedly within the first 5 min of the reaction by flow cytometry (flow erythrogram). The hemolytic effect of SiO(2) particles was evaluated by photometric measurement of hemoglobin in the supernatant 90 min after the reaction. RESULTS: Light scatter of affected RBCs and the degree of hemolysis revealed that the surface properties of SiO(2) particles had various effects on the RBCs. After thermal reduction of the surface hydroxyl groups, the membranotoxic effect of silica increased and then decreased. CONCLUSIONS: RBCs offer a convenient and informative model for examining the surface properties of silica.