(422b) Toxicity Effects Associated With Exposure of Lung Epithelial Cells to Polymer Nanocomposites and Nano-Platelets of Silicates

Montmorillonite, a layered silicate in the form of platelets having a thickness of about 1 nm, an aspect ratio exceeding 200 and a surface area of about 650 m²/g, is commercially compounded into polymers such as nylons and polyolefins. Even at low filler loading levels (about 5 wt%), the resulting polymer nanocomposites (PNCs) have improved properties, including reduced flammability when compared to the matrix polymer. Such enhanced property is observed when the nanofiller is deagglomerated and uniformly distributed throughout the plastic, with the nanofillers contributing to the formation of char that acts as a heat and mass transfer barrier. However, when such polymer nanocomposites are burnt, inhalation exposure to the nanoparticles contained within the PNCs can occur. Here we started to investigate the toxicological effects of associated with exposure of human epithelial cells to silicate nanoplatelets to determine the any harmful effects. For this, rectangular strips of PNCs were first ignited in air using a methane flame, and a Combustion™ DMS500 Differential Mobility Spectrometer was used to measure the number concentration of particles emanating from the burning sample. Measurements indicated the presence of nanoparticles in the 10 to 100 nm range and a concentration that was as much as 2.7 x 10⁹/cm³/s; these numbers are comparable to those encountered in the exhaust from heavy-duty diesel engines. Next, human lung epithelial cells were exposed to various concentrations of nanoplatelets and the effects of the nanoplatelets on the cells morphology, structure and functions were analyzed. Our studies allowed the characterization of the cytotoxicity associated with the combustion products of nanoplatelets and promises to help develop a tool for the prediction of large-scale burning behavior of polymer nanocomposites.