A computer model for the simulation of nanoparticle deposition in the alveolar structures of the human lungs

Abstract

Background: According to epidemiological and experimental studies, inhalation of nanoparticles is commonly believed as a main trigger for several pulmonary dysfunctions and lung diseases. Concerning the transport and deposition of such nano-scale particles in the different structures of the human lungs, some essential questions are still in need of a clarification. Therefore, main objective of the study was the simulation of nanoparticle deposition in the alveolar region of the human respiratory tract (HRT).

Methods: Respective factors describing the aerodynamic behavior of spherical and non-spherical particles in the inhaled air stream (i.e., Cunningham slip correction factors, dynamic shape factors, equivalent-volume diameters, aerodynamic diameters) were computed. Alveolar deposition of diverse nanomaterials according to several known mechanisms, among which Brownian diffusion and sedimentation play a superior role, was approximated by the use of empirical and analytical formulae. Deposition calculations were conducted with a currently developed program, termed NANODEP, which allows the variation of numerous input parameters with regard to particle geometry, lung morphometry, and aerosol inhalation.

Results: Generally, alveolar deposition of nanoparticles concerned for this study varies between 0.1% and 12.4% during sitting breathing and between 2.0% and 20.1% during heavy-exercise breathing. Prolate particles (e.g., nanotubes) exhibit a significant increase in deposition, when their aspect ratio is enhanced. In contrast, deposition of oblate particles (e.g., nanoplatelets) is remarkably declined with any reduction of the aspect ratio.

Conclusions: The study clearly demonstrates that alveolar deposition of nanoparticles represents a topic certainly being of superior interest for physicists and respiratory physicians in future.

Keywords: Nanoparticles; alveolar region; computer model; deposition; human respiratory tract (HRT); stochastic lung.

Figure 1

Entrance and input window of the computer program NANODEP, which was used for the theoretical calculations presented in this study. (A) Entrance window offering additional information on nanoparticles; (B) input of particle properties used for modeling; (C) input of specific lung parameters; (D) input of selected inhalation parameters.

Figure 2

Output generated by the computer program NANODEP. (A) Summary of the selected input data; (B) numerical and graphic presentation of regional deposition data, thereby distinguishing between extrathoracic, bronchial, ductal, and alveolar compartment; (C) numerical and graphic presentation of airway generation-specific deposition data, thereby distinguishing between bronchial and alveolar deposition.

Figure 3

Comparison between the stochastic model (ST) and a numerical model (NUM) of CNT deposition (3). (A) Generation specific deposition of CNT with a diameter of 10 nm and β =100 under assumption of light activity breathing conditions; (B) correlation of model data presented in graph (A); (C) deposition of CNT with a diameter of 10 nm and β =1,000 under assumption of light activity breathing conditions; (D) correlation of model data presented in graph (C).

Figure 4

Total alveolar deposition of variously shaped nanoparticles under the assumption of sitting breathing conditions. (A) Deposition data for 10-nm spheres and nanotubes with a cylindrical diameter of 10 nm and different aspect ratios; (B) deposition data for 10-nm spheres and nanodisks with a cylindrical diameter of 10 nm and different aspect ratios.

Figure 5

Total alveolar deposition of variously shaped nanoparticles under the assumption of heavy-exercise breathing conditions. (A) Deposition data for 10-nm spheres and nanotubes with a cylindrical diameter of 10 nm and different aspect ratios; (B) deposition data for 10-nm spheres and nanodisks with a cylindrical diameter of 10 nm and different aspect ratios.

Figure 6

Generation-specific alveolar deposition of variously shaped nanoparticles under the assumption of sitting breathing conditions. (A) Deposition data for 10-nm spheres and nanotubes with a diameter of 10 nm and aspect ratios of 10 and 1,000; (B) deposition data for 10-nm spheres and nanodisks with a diameter of 10 nm and aspect ratios of 0.1 and 0.001.

Figure 7

Generation-specific alveolar deposition of variously shaped nanoparticles under the assumption of heavy-exercise breathing conditions. (A) Deposition data for 10-nm spheres and nanotubes with a diameter of 10 nm and aspect ratios of 10 and 1,000; (B) deposition data for 10-nm spheres and nanodisks with a diameter of 10 nm and aspect ratios of 0.1 and 0.001.