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Biology

Whole-Body Nanoparticle Aerosol Inhalation Exposures

Published: May 7th, 2013

DOI:

10.3791/50263

1Department of Physiology and Pharmacology, School of Medicine, West Virginia University , 2Center for Cardiovascular and Respiratory Sciences, West Virginia University , 3National Institute for Occupational Safety and Health

A whole-body nanoparticle aerosol inhalation exposure facility was constructed for nano-sized titanium dioxide (TiO2) inhalation toxicology studies. This system provides nano-TiO2 aerosol test atmospheres that have: 1) a steady mass concentration; 2) a homogenous composition free of contaminants; and 3) a stable particle size distribution during aerosol generation.

Inhalation is the most likely exposure route for individuals working with aerosolizable engineered nano-materials (ENM). To properly perform nanoparticle inhalation toxicology studies, the aerosols in a chamber housing the experimental animals must have: 1) a steady concentration maintained at a desired level for the entire exposure period; 2) a homogenous composition free of contaminants; and 3) a stable size distribution with a geometric mean diameter < 200 nm and a geometric standard deviation σg < 2.5 5. The generation of aerosols containing nanoparticles is quite challenging because nanoparticles easily agglomerate. This is largely due to very strong inter-particle forces and the formation of large fractal structures in tens or hundreds of microns in size 6, which are difficult to be broken up. Several common aerosol generators, including nebulizers, fluidized beds, Venturi aspirators and the Wright dust feed, were tested; however, none were able to produce nanoparticle aerosols which satisfy all criteria 5.

A whole-body nanoparticle aerosol inhalation exposure system was fabricated, validated and utilized for nano-TiO2 inhalation toxicology studies. Critical components: 1) novel nano-TiO2 aerosol generator; 2) 0.5 m3 whole-body inhalation exposure chamber; and 3) monitor and control system. Nano-TiO2 aerosols generated from bulk dry nano-TiO2 powders (primary diameter of 21 nm, bulk density of 3.8 g/cm3) were delivered into the exposure chamber at a flow rate of 90 LPM (10.8 air changes/hr). Particle size distribution and mass concentration profiles were measured continuously with a scanning mobility particle sizer (SMPS), and an electric low pressure impactor (ELPI). The aerosol mass concentration (C) was verified gravimetrically (mg/m3). The mass (M) of the collected particles was determined as M = (Mpost-Mpre), where Mpre and Mpost are masses of the filter before and after sampling (mg). The mass concentration was calculated as C = M/(Q*t), where Q is sampling flowrate (m3/min), and t is the sampling time (minute). The chamber pressure, temperature, relative humidity (RH), O2 and CO2 concentrations were monitored and controlled continuously. Nano-TiO2 aerosols collected on Nuclepore filters were analyzed with a scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis.

In summary, we report that the nano-particle aerosols generated and delivered to our exposure chamber have: 1) steady mass concentration; 2) homogenous composition free of contaminants; 3) stable particle size distributions with a count-median aerodynamic diameter of 157 nm during aerosol generation. This system reliably and repeatedly creates test atmospheres that simulate occupational, environmental or domestic ENM aerosol exposures.

The whole-body nanoparticle inhalation exposure step-by-step operating procedures are described as follows.

Note: 1) steps 1 and 3 should be performed in a fume hood; 2) operators must wear appropriate personal protective equipment (respirators, goggles and rubber gloves).

1. Conditioning TiO2 Nanoparticle Dry Powders

  1. Place nano-TiO2 powders in a nontransparent container.
  2. Leave the container lid open.
  3. .......

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An inhalation exposure study typically involves maintaining an experimental animal in a known and constant test environment while exposing the experimental animal to a defined concentration of a test material 8,9. The whole-body nanoparticle inhalation exposure system is shown in Figure 1. The whole-body chamber was operated on a dynamic flow basis where there was a 90 LPM continuous flow of air through the chamber. This air flow provided 10.8 air changes/hr which exceeds the minimum number of.......

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We have assembled and described here in a whole-body nanoparticle aerosol inhalation exposure system. The system functionality was validated with state-of-the-art nanoparticle aerosol characterization techniques. With a novel nanoparticle aerosol generation system, this inhalation exposure system can provide a well characterized, controlled and uniform nanoparticle aerosol test atmosphere with relatively consistent temperature, humidity, air flow, and oxygen content for experimental animals. The exposure system is most e.......

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List acknowledgements and funding sources.

NIH-ES015022 and ES018274 (TRN)

NSF-Cooperative Agreement 1003907 (VCM)

....

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Name Company Catalog Number Comments
Name of Reagent/Material Company Catalog Number Comments
Inhalation exposure system TSE Systems GmbH, Bad Homburg, Germany
Air monitoring system TSE Systems GmbH, Bad Homburg, Germany
Titanium dioxide Aeroxide P25 Evonik, Germany
Scanning mobility particle sizer-3936L75 TSI Inc., Shoreview, MN
Electric low pressure impactor, Standard 10 LPM Dekati, Tampere, Finland
Ultra Micro Balance, XP2U METTLER TOLEDO, Switzerland
Field Emission Scanning Electron Microscope-S-4800 Hitachi, Japan
Energy dispersive X-ray analysis Princeton Gamma-Tech, Rocky Hill, N.J.
Nuclepore polycarbonate filters Whatman, Clinton, PA
PTFE membrane filters Pall corporation, Ann Arbor, Michigan

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