Characterization of the Vitrocell® Cloud SEQ 24 System and its Application in Exposure to Aerosolized Bortezomib and Ibuprofen

Introduction: The Vitrocell® Cloud is an in vitro aerosol exposure system specifically designed for exposing cell cultures to liquid aerosols. It consists of a cuboidal aerosol chamber below which a multi-well base module is located. The temperature-controlled base module provides reservoirs for cell culture medium and is designed to hold cell cultures grown on Transwell inserts at the air-liquid interface. Aerosols for exposures are generated from a defined volume, usually 200 µL, of a test solution by the action of a vibrating mesh nebulizer mounted on top of the aerosol chamber. The aerosol generated by the nebulizer forms a cloud within the aerosol chamber, distributes evenly above the surface of the base module and subsequently deposits on cell cultures present therein. By means of covers that can be moved over groups of four exposure chambers, the newly designed Vitrocell® Cloud SEQ 24 allows exposure of 24 cell cultures of the 24-well format to up to six different doses without opening the aerosol chamber and hence, is highly suitable for dose-response testing. In this work, we present a quantitative characterization of aerosol deposition in the Vitrocell® Cloud SEQ 24 system. We provide evidence that the Vitrocell® Cloud SEQ 24 is fit for purpose for cell culture exposures and describe biological responses of human bronchial organotypic cell cultures to Bortezomib and Ibuprofen exposure within the system. Conclusions: Our results demonstrate that the Vitrocell® Cloud SEQ 24 is fit for purpose for performing test exposures using aerosols generated from small volumes of liquids and suspensions; Test aerosols deposit uniformly across the 24 cell culture inserts, the inter-repetition variations in the deposited aerosol massed are low and the so far available results on the biological responses to Ibuprofen and Bortezomib exposures confirm that the system is a suitable tool for testing aerosolized solutions for their bioactivity. The results on proteasome activity and cytokine secretion will further substantiate this finding. The good system performance reported here, the system’s applicability for simple and efficient multiple dosing as well as the small volumes of test solution required (200 μL) render the Vitrocell® Cloud SEQ 24 particularly interesting for the initial activity screening of candidate drugs that have been synthesized in small amounts only.