A thermal precipitator for the deposition of airborne nanoparticles onto living cells—Rationale and development

We have developed the Cyto-TP, a thermal precipitator capable of depositing airborne nanoparticles onto living cells directly from the gas. A temperature gradient is established between two parallel plates, therefore particles migrate toward the colder plate due to thermophoresis. The colder plate contains two transwells with attached cells forming a monolayer at the air–liquid interface. The front transwell is used for the cell exposure to particles transported into the device and deposited on the cells. Nanoparticles in the size range of 10–300 nm deposit homogeneously on the cell monolayer. All particles are deposited before the rear transwell hence its cells are exposed to the particle-free gas only, allowing for a differentiation between particle and gas effects. The modelling of the deposition of unit-density spherical nanoparticles in the flow channel led to the design and construction of this device. The Cyto-TP was initially tested by depositing fluorescent polystyrene-latex (PSL) nanoparticles on A549 alveolar epithelial cells, a common cell line for inhalation toxicology. The predicted deposition was verified, after the absence of particles on the rear transwell after exposure and in parallel the detection of PSL particles on the front transwell. Additionally, the experimental requirements for the Cyto-TP to function have at the most an insignificant effect on the cells as proven by assaying the living cell count of the transwells after exposure to particle-free air. Consequently, potential cell damages can unambiguously be related to particle and gas exposure.