Development and validation of a system for the generation, characterization and subsequent air- liquid interface studies of aerosol particles
Abstract: Exposure to nano-sized and nanostructured aerosol particles with tailored properties are likely to increase in society. Occupational exposure to various kinds of nanostructured aerosol particles such as soot and metal aggregates already exists. To understand the adverse human health effects of these particles, there is a need for systems that can Generate a stable output of aerosol particles, Characterize their exposure and dose, and determine their toxicological and biological effects in an Air-liquid interface setting (GCA). The research presented in this thesis developed and validated a GCA that combines a high output of aerosol particles, online characterization, collection capabilities for a scanning electron microscope (SEM) and transmisson electron microscopy (TEM), as well as wet samples for protein interaction studies and particle toxicological effects. The GCA is composed of an air-liquid interface cellular exposure chamber – the Nano Aerosol Chamber for In Vitro Toxicity (NACIVT) – and an electrostatic precipitator. It also includes a high output aerosol particle generator with built-in capabilities for sintering and online mass mobility characterization, a scanning mobility particle sizer, and a tapered element oscillating microbalance (TEOM) for continuous characteristics and exposure measurements. The output characteristics of two spark discharge generators and a high temperature evaporation furnace were determined, including mass mobility relation. The results show that all three of these generators produced a stable output of nanostructured metal aerosol particles in the 30-300 nm size range; when sintered, these were near spherical in shape. In terms of dose, number, mass and surface area, the output was comparable to that of previous studies for all generators. The GCA with respect to toxicological studies was validated using primary human small airway epithelial cells (SAEC) and carcinoma cell line (A549). Aerosol particles of copper (Cu), palladium (Pd) and silver (Ag) were generated and administerd in the NACIVT during 1 hour exposures. For SAEC exposed to Cu, Pd or Ag, a significant (p<0.05) effect on both viability and cytokine expression was oberserved. Also a significant (p<0.05) dose response for SAEC exposed to Cu, Pd and Ag could be determined. For the A549, Cu and Pd exposure induced a significant reduction in cellular viability. The protein interactions of the near-spherical sintered and aggregted Au nanoparticles, that were generated using high temperature evaporation furnace, were investigated in serum and human lung fluid solutions. When administered to the air-liquid interface, the spherical Au particles formed a stable film with a pinkish hue; when agitated, <100 nm aggregates of particles and proteins were formed. This film formation is suggested as a protective property of the air-liquid interface itself.
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