FREE-RADICAL ACTIVITY ASSOCIATED WITH THE SURFACE OF PARTICLES - A UNIFYING FACTOR IN DETERMINING BIOLOGICAL-ACTIVITY

Using a sensitive omega X174 RF plasmid DNA assay, free radical activi ty was detected at the surface of normal and ultrafine titanium dioxid e (TiO2), environmental particles (PM-10), asbestos and a range of man -made fibres. There were differences in the amount of free radical act ivity that was detected, with ultrafine TiO2 being much more active th an normal-sized TiO2; PM-10 also had substantial free radical activity . Amphibole asbestos samples were highly active, whilst man-made fibre s were much less active than asbestos. For all of the particles, the D NA damage could be ameliorated by mannitol, showing that hydroxyl radi cals were involved The ability of particles to generate free radicals at or near their surface, and thereby impose oxidant stress in key tar get cells, could be central to determining their pathogenicity.