Although alveolar macrophages are the primary defensive cells of the lung against invading bacteria and foreign particles, recent studies suggest that particle uptake and translocation is a role common to alveolar epithelium (reviewed by Churg). The purpose of this investigation is to define the phagocytic capabilities of human A549 cell line using 50 nm inert Titanium Dioxide, (TiO2), particles.

A549 cells at 0.5×l06cells/ml, in F12 Kaighn’s modification medium (F12K) with 10% heat-inactivated fetal bovine serum, l00U/ml penicillin and lOOng/ml streptomycin were cultured on alcar discs in 24-well plates, incubated at 37°C, 5% CO2 in a humidified incubator for 4 days. The cells were then exposed to TiO2 particles (final concentration 4Oμg/ml) in serum-free F12K media for 24 h. After 24h, the cells were fixed in 2.5% glutaraldehyde in 0.1 M potassium phosphate buffer overnight. The cells were post-fixed with 1% OSO4, dehydrated in series of ethanol and propylene oxide, infiltrated and embedded with araldite 502.