Advantages of ALI Exposure - expoCube

Traditional submerged cell culture techniques have well-known limitations for aerosol exposure studies; for instance, the impact of exposure dilution within the media and the poor solubility/sedimentation of some exposure particles1. Air liquid interface (ALI) cultures are a technique whereby cells are grown on a microporous membrane insert, immersed in a media-containing well. This arrangement allows cells to be fed and humidified from below, whist maintaining an air-liquid interface on the apical surface, which can be directly exposed to aerosolized exposures. This arrangement more closely models the airways, particularly the primary defense barrier of the pulmonary fluid-lined airways (mucus and surfactant) and avoids many of the limitations of submerged cultures.

The benefits of aerosol exposure with ALI cultures have previously been demonstrated across a range of scenarios, from infection models to the application of complex aerosol/vapor mixes, such as tobacco smoke, combustion by-products and pollutants. For instance, Creager et al. reported that cell cultures grown under ALI conditions have reduced efficiency of both initial viral infection and subsequent viral replication, speculating that mucus in ALI conditions may inhibit virus binding, thereby creating a more physiologically relevant model 2. Lenz et al. demonstrated significant differences in the proinflammatory and oxidative stress responses between submerged and ALI-cultured cells after application of zinc oxide nanoparticles 3. Similarly, Wang et al. directly compared submerged and ALI conditions using an A549 and macrophage co-culture system, observing that cultures exposed to PM2.5 had similar trends but with a blunted response under the co-culture ALI conditions, speculating that the more physiologically relevant ALI conditions (with a surfactant layer) were less likely to provide false-positive results than submerged cultures4.

expoCube with Tray
Figure 1: expoCube
The expoCube: efficient, reproducible and translational ALI exposure system

The expoCube allows scientists to precisely expose cells and tissue explants (e.g. Precision-Cut Lung Slices) to airborne particulates in a physiologically relevant ALI environment. The innovative design of the expoCube permits aerosol deposition profiles that are efficient, reproducible, and translational. The expoCube is engineered to create an efficient, uniform, and precise exposure of particulates onto target cells and tissues. Its flow paths were designed and optimized using advanced computational fluid dynamics (CFD) modelling. They allow a uniform deposition of airborne particles on the target cells, regardless of the particle size. The expoCube’s patented use of thermophoresis increases the deposition efficiency of small particles without imparting unnatural electrostatic charges onto the aerosols.

  1. Drug transport across pulmonary epithelial cell monolayers: effects of particle size, apical liquid volume, and deposition technique. Bur M, Huwer H, Muys L, Lehr CM. J Aerosol Med Pulm Drug Deliv. 2010;23(3):119-127. doi:10.1089/JAMP.2009.0757
  2. In vitro exposure system for study of aerosolized influenza virus. Creager HM, Zeng H, Pulit-Penaloza JA, Maines TR, Tumpey TM, Belser JA. Virology. 2017;500:62-70. doi:10.1016/J.VIROL.2016.10.007
  3. A dose-controlled system for air-liquid interface cell exposure and application to zinc oxide nanoparticles. Lenz AG, Karg E, Lentner B, et al. Part Fibre Toxicol. 2009;6(1):1-17. doi:10.1186/1743-8977-6-32/FIGURES/9
  4. Co-culture of human alveolar epithelial (A549) and macrophage (THP-1) cells to study the potential toxicity of ambient PM2.5: a comparison of growth under ALI and submerged conditions. Wang G, Zhang X, Liu X, Zheng J. Toxicol Res (Camb). 2020;9(5):636-651. doi:10.1093/TOXRES/TFAA072


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