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Open AccessArticle

Molecular Binding Contributes to Concentration Dependent Acrolein Deposition in Rat Upper Airways: CFD and Molecular Dynamics Analyses

1
Department of Biomedical Engineering, California Baptist University, Riverside, CA 92504, USA
2
School of Engineering and Technology, Eastern Michigan University, Ypsilanti, MI 48197, USA
3
The Rutgers Center for Computational and Integrative Biology, Camden, NJ 08102, USA
4
Aerospace and Mechanical Engineering, California Baptist University, Riverside, CA 92504, USA
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2018, 19(4), 997; https://doi.org/10.3390/ijms19040997
Received: 30 December 2017 / Revised: 18 March 2018 / Accepted: 23 March 2018 / Published: 27 March 2018
Existing in vivo experiments show significantly decreased acrolein uptake in rats with increasing inhaled acrolein concentrations. Considering that high-polarity chemicals are prone to bond with each other, it is hypothesized that molecular binding between acrolein and water will contribute to the experimentally observed deposition decrease by decreasing the effective diffusivity. The objective of this study is to quantify the probability of molecular binding for acrolein, as well as its effects on acrolein deposition, using multiscale simulations. An image-based rat airway geometry was used to predict the transport and deposition of acrolein using the chemical species model. The low Reynolds number turbulence model was used to simulate the airflows. Molecular dynamic (MD) simulations were used to study the molecular binding of acrolein in different media and at different acrolein concentrations. MD results show that significant molecular binding can happen between acrolein and water molecules in human and rat airways. With 72 acrolein embedded in 800 water molecules, about 48% of acrolein compounds contain one hydrogen bond and 10% contain two hydrogen bonds, which agreed favorably with previous MD results. The percentage of hydrogen-bonded acrolein compounds is higher at higher acrolein concentrations or in a medium with higher polarity. Computational dosimetry results show that the size increase caused by the molecular binding reduces the effective diffusivity of acrolein and lowers the chemical deposition onto the airway surfaces. This result is consistent with the experimentally observed deposition decrease at higher concentrations. However, this size increase can only explain part of the concentration-dependent variation of the acrolein uptake and acts as a concurrent mechanism with the uptake-limiting tissue ration rate. Intermolecular interactions and associated variation in diffusivity should be considered in future dosimetry modeling of high-polarity chemicals such as acrolein. View Full-Text
Keywords: acrolein; molecular binding; molecular dynamics simulation; concentration-dependent; cigarette smoking acrolein; molecular binding; molecular dynamics simulation; concentration-dependent; cigarette smoking
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MDPI and ACS Style

Xi, J.; Hu, Q.; Zhao, L.; Si, X.A. Molecular Binding Contributes to Concentration Dependent Acrolein Deposition in Rat Upper Airways: CFD and Molecular Dynamics Analyses. Int. J. Mol. Sci. 2018, 19, 997.

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