Peer-Reviewed Publications

      Characterization and modeling of aerosol deposition in Vitrocell® exposure systems - exposure well chamber deposition efficiency

      Lucci, F.; Castro, N. D.; Rostami, A. A.; Oldham, M. J.; Hoeng, J.; Pithawalla, Y. B.; Kuczaj, A. K.
      Published
      Jun 30, 2018
      DOI
      10.1016/j.jaerosci.2018.06.015
      Link to publication
      Topic
      Summary

      Multi-well aerosol exposure systems are used in modern toxicology assessment studies to deliver aerosol to a large number of tissue/cell culture samples simultaneously. These systems are designed to control the experimental conditions of a delivered aerosol. In these systems (e.g., those developed by Vitrocell GmbH), the aerosol mixture is delivered perpendicularly to the tissue culture through a trumpet-shaped (flared) pipe. In the well chamber where the tissue/cell culture is exposed, the flow is smooth and laminar, which limits shear forces and potential moisture loss that may damage the tissue/cells. These operating flow conditions also determine the aerosol dynamics and deposition mechanisms within the system. The utility of these systems to evaluate biological responses depends on the quantity of tissue culture. With limited experimental data, evaluating the aerosol deposition via computational means is necessary to predict the deposition efficiency. For our investigations, we employed a recently developed Eulerian Computational Fluid Dynamics solver (available at www.aerosolved.com) for simulations of polydisperse multi-species aerosol transport and deposition. We investigated deposition efficiency using various exposure distances to the tissue culture, aerosol properties, and operating conditions. Terms associated with drag, gravitation, and Brownian diffusion were included in the aerosol equations to predict the deposition of the polydisperse aerosol. Results were verified by comparisons with the available experimental data, and predictions were obtained from the Lagrangian simulations using commercially available software. Within the recommended operating conditions, inertial impaction was found not to affect aerosol deposition, which is driven mainly by the size-dependent sedimentation and diffusion mechanisms. An important implication is that for a wide range of droplet sizes, the delivered dose to the tissue is independent of sampled flow rate. Taking this into account, a simple and robust size-dependent theoretical model of the aerosol deposition efficiency was developed. This theoretical model is based on aerosol characteristics, flow, and geometry inputs without the use of any fitting parameter. It can be applied to various exposure system geometries under different operating conditions, as verified in comparisons with published deposition efficiency data obtained from experiments and computations.

      PMIScience.com is operated by Philip Morris International for the purpose of publishing and disseminating scientific information about Philip Morris International’s efforts in support of its smoke-free product portfolio. This site is a global site for use by scientists, the public health and regulatory communities, and other stakeholders with an interest in tobacco policy. The purpose of this site is not advertising or marketing, nor is it directed at any specific market. It is not intended for use by consumers. New tobacco products sold in the United States are subject to FDA regulation; therefore the content of this site is not intended to make, and nor should it be construed as making, any product related claims in the United States without proper FDA authorization. ​
      ​
      Reduced Risk Products ("RRPs”) is the term we use to refer to products that present, are likely to present, or have the potential to present less risk of harm to smokers who switch to these products versus continuing smoking. PMI has a range of RRPs in various stages of development, scientific assessment and commercialization. All of our RRPs are smoke-free products that deliver nicotine with far lower quantities of harmful and potentially harmful constituents than found in cigarette smoke.