10 Validation of an Aerosol Exposure-Air Liquid Interface (AE-ALI) System to Facilitate Realistic Hazard Identification of Nano-Sized Aerosols

Abstract

Abstract To facilitate hazard characterisation for inhaled engineered nanomaterials we have established an aerosol exposure air-liquid-interface (AE-ALI) system, incorporating a Cultex RFSTM cell exposure system. While offering potential benefits in terms of more realistic aerosol exposure mode over traditional submerged in vitro models and being in-line with the principles of the 3Rs, (replace, reduce and refine animal use), detailed system characterisation is required to produce reliable and reproducible results. As such, this work looked to fully characterise our AE-ALI system with a view to optimising cell viability of system controls and deposition quantity, uniformity, and reproducibility for engineered nanomaterials. Using a nano-CeO2 aerosol, the effects of exposure conditions and system parameters (e.g. temperature, electrostatic precipitator voltage and airflow) on deposition efficiency, pattern and reproducibility were investigated using ICP-MS. While results showed that appropriate choice of operating parameters can produce broadly uniform deposition, reproducibility was low, and dose monitoring during exposures is recommended. After initial optimisation of the system for deposition, the effect of exposure duration, well size and flowrate on cellular responses (e.g. cytotoxicity (LDH) and selected gene expression (IL-8, CXCL1, HMOX1, SPP1) of system controls (H2O aerosol) was investigated using human lung alveolar (A549) and primary small airway epithelial cells. Results indicate that even after optimisation for cell health, the system itself is “toxic” to cells in comparison to incubator controls, with increasing effects observed with exposure duration meaning exposure durations must be minimised. Results from this study highlight the need for detailed characterisation of AE-ALI systems prior to use.