Possible role of ascorbic acid in the oxidative damage induced by inhaled crystalline silica particles

The selective interaction of ascorbic acid with crystalline silica (quartz) has been studied by measuring the ascorbic acid consumption (by means of U V/vis and IR spectroscopy) and the release of silicon when quartz particles or amorphous silica (Aerosil 50) is incubated in ascorbic acid solution. A t a physiological ascorbic acid concentration, quartz, and not amorphous si lica, reacts, suggesting the formation of a 1:1 silicon-ascorbate complex, while at higher concentrations, the reacting amount of ascorbic acid exceed s the amount of silicon that is released. Silicon tetrahedra bearing free s ilanols at the quartz surface are selectively attached by ascorbic acid. Th e particle-derived hydroxyl radical yield in the presence of hydrogen perox ide is increased on ascorbic acid-treated quartz in comparison with the ori ginal sample. The results presented herein are relevant because the depleti on of ascorbic acid from the lung lining layer and the increased potential in particle-derived free radical generation may both contribute to the oxid ative damage following inhalation of crystalline silica.