A549 cells are still the most commonly used cell line for cytotoxicity testing of nanoparticles (e.g., Akhtar et al., 2012, Lankoff et al., 2012 and Stoehr et al., 2011), although tightness of intercellular junctions is lower than that of other cell lines derived from the respiratory

system, such as H358, H596, H322 cells. The later cell lines, however, are used less often in pharmacological and toxicological testing because they are less well characterized. To test aerosol exposure, respiratory cells are often exposed in submersed culture, although this does not reflect their normal physiological situation. More advanced in vitro exposure models use culture in the air–liquid interface (ALI) where cells are cultured on semi permeable membranes of a transwell insert. Wortmannin Selleckchem Natural Product Library The insert is placed into a culture well, medium is supplied from the basal site only and cells are exposed to an aerosol at the apical part. Transwell cultures were first used for permeability

studies of gastrointestinal cells, like Caco-2 cells, and later adapted to other cell types (Hidalgo et al., 1989). Several systems are available to expose transwell cultures to aerosols: the Voisin chamber (Voisin et al., 1977 and Voisin and Wallaert, 1992), the Minucell system (Bitterle et al., 2006 and Tippe et al., 2002), the Cultex system (Aufderheide and Mohr, 2000 and Ritter et al., 2003) and the modified Cultex system, the VITROCELL system (Aufderheide and Mohr, 2004). These systems have been used for volatile organic compounds and carbon or cerium oxide nanoparticles in the atmosphere (Bakand et al., 2006, Bitterle et al., 2006, Gasser et al., 2009, Oxymatrine Paur et al., 2008 and Rothen-Rutishauser et al., 2009). For nanoparticle-containing aerosols the ALICE (air liquid interface exposure) system (Brandenberger et al., 2010a, Brandenberger et al., 2010b and Lenz et al.,

2009) and the MicroSprayer has been used (Blank et al., 2006). In this study, we evaluated a new test system based on the VITROCELL system by assessing the deposition rate of nanoparticle-containing aerosols in respiratory cells compared to a macromolecular reference substance. We were particularly interested in the suitability of this new system when using a nebulizer type also frequently used by patients. This VITROCELL based system was compared to a manual aerolizer, the MicroSprayer, which allows the direct application of aerosols to cells. Cellular effects observed by direct application of the aerosol to cells cultured in ALI were compared to those obtained by testing of nanoparticle suspension on cells cultured in submersed culture. These data can help to decide whether larger work and material efforts of aerosol exposure testing are justified. For the evaluation of the system two particle types were used.