Alkaline-earth metal tungstate AWO4 (A= Ca, Ba, Sr) nanoparticles are currently being used in a variety of applications, including use as components of medical equipment, optical fibers, and scintillator detectors. This versatility may lead to increases in manufacturing within the next 10 years and may subsequently result in more cases of occupational exposure. Therefore, it is important to assess the effects of tungstate nanoparticles on cellular systems. RAW 264.7 macrophage cells were used to assess tungstate nanoparticle toxicity and changes in reactivity based on shape (sphere vs. wire), size, and chemistry. Enhanced dark field microscopy and scanning electron microscopy were used to evaluate nanoparticle-cell association over multiple time points up to 7 hours. To assess uptake, transmission electron microscopy was implemented. Both wires and spheres showed cell surface interactions; however, only spheres were engulfed. To assess intracellular reactive oxygen species (ROS) production, a DCFH assay was performed. Results showed that nanowire-exposed cells had significantly increased levels of ROS over a 7 hour time-course, while nanosphere-treated cells did not. This may be a result of association versus engulfment. Based on ROS production and cell-particle interactions, overall cellular cytotoxicity was measured. A caspase activation assay was used to assess apoptosis, and an MTT assay was employed to determine cell viability. Minimal caspase activity was measured after 24 hours with both spheres and wires. Wire-cell interactions resulted in cell death after 24 hours and sphere treated cells had minimal changes in viability. This data shows that tungstate nanoparticles are not explicitly toxic; however, wires appear to be more reactive than spheres, and have an initial, but manageable toxic effect on cells.
The Toxicologist. Society of Toxicology 53rd Annual Meeting and ToxExpo, March 23-27, 2014, Phonex, Arizona