Toxic effects of alumino-silicates on nerve cells.

The recently reported presence of alumino-silicates in the core of Alzheimer's senile plaques raises a number of questions concerning the little studied area of interactions between solid particles and neuronal tissue. In this preliminary study we report that contact between crystalline alumino-silicates and cultured neuroblastoma cells selectively caused a rapid increase in membrane electrical conductance and loss of excitable activity. Severe morphological deterioration was subsequently evident within 30 min of exposure. Similar effects were induced by a magnesium silicate mineral but not by aluminum hydroxides or by silicon in the form of quartz. Homogeneously charged synthetic particles did not induce changes in electrical function of the cells. These results suggest that a layout incorporating both negative and positive charges, as can be found on the broken edges of platy clay metallo-silicates, and the non-isodiametrical geometry of the particles may be necessary for the acute neurotoxic interaction observed.