Real-time non-invasive detection of inhalable particulates delivered into live mouse airways

Our plain-English summary of Real-time non-invasive detection of inhalable particulates delivered into live mouse airways, by M. Donnelley, K.S. Morgan, A. Fouras, et al (Journal of Synchrotron Radiation, 2009).

The study

• Authors: M. Donnelley, K.S. Morgan, A. Fouras, W. Skinner, K. Uesugi, N. Yagi, K.K. Siu, D.W. Parsons
• Journal: Journal of Synchrotron Radiation
• Published: 2009;16(Pt 4):553-61
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Fine non-biological particles small enough to be suspended in the air are continually inhaled as we breathe. These particles deposit on airway surfaces where they are either cleared by airway defences or can remain and affect lung health. Pollutant particles from vehicles, building processes and mineral and industrial dusts have the potential to cause both immediate and delayed health problems. Because of their small size, it has not been possible to non-invasively examine how individual particles deposit on live airways, or to consider how they behave on the airway surface after deposition. In this study, synchrotron phase-contrast X-ray imaging (PCXI) has been utilized to detect and monitor individual particle deposition. The in vitro detectability of a range of potentially respirable particulates was first determined. Of the particulates tested, only asbestos, quarry dust, fibreglass and galena (lead sulfate) were visible in vitro. These particulates were then examined after delivery into the nasal airway of live anaesthetized mice; all were detectable in vivo but each exhibited different surface appearances and behaviour along the airway surface. The two fibrous particulates appeared as agglomerations enveloped by fluid, while the non-fibrous particulates were present as individual particles. Synchrotron PCXI provides the unique ability to non-invasively detect and track deposition of individual particulates in live mouse airways. With further refinement of particulate sizing and delivery techniques, PCXI should provide a novel approach for live animal monitoring of airway particulates relevant to lung health.

In plain English

This laboratory and animal study tested whether synchrotron phase-contrast X-ray imaging could show individual inhalable particles in the airways of live mice. The authors first imaged several dusts sealed between layers of tape. Chrysotile (white asbestos), fibreglass, dolomite quarry dust and galena (a lead mineral) were visible. Diesel particles, roadside PM10 and laser printer toner were not visible enough to test in animals. The visible particles, plus hollow glass beads used as reference markers, were suspended in water and delivered into the noses of ten anaesthetized hairless mice. Motion-detection software picked up all five particle types. Asbestos did not appear as single fibres. It appeared as fluid-covered clumps of enmeshed fibres, which moved along the airway faster than the other particles. Fibreglass formed similar clumps that moved about one tenth as fast. Quarry dust appeared as single particles, and galena was hard to detect. The authors described this as, to their knowledge, the first such non-invasive detection. They noted that the doses were not yet optimal and that the particles were delivered in water rather than inhaled.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Imaging-method study: an in vitro test of which particles were visible, followed by an experiment in live anaesthetized mice
• Who was studied: Ten hairless mice (Crlj:CD1-Foxn1nu), imaged at the SPring-8 synchrotron facility in Hyogo, Japan
• Exposure: Chrysotile (white asbestos), fibreglass from pipe insulation, dolomite quarry dust and galena, plus silver-coated hollow glass beads as reference particles. In the mice, fibreglass and asbestos were given at 0.5% w/v and galena and quarry dust at 0.1%, suspended in water and delivered through a cannula into the nasal airway.
• Main results:
  • In vitro, the carbon-based particles (combusted diesel, PM10, laser printer toner) were not visible enough to be tested in mice.
  • In the live mice, all five particle types (asbestos, fibreglass, quarry dust, galena, glass beads) could be detected using motion-detection software.
  • In the mice, individual asbestos fibres were not detected. Asbestos appeared as clumps of enmeshed fibres trapped in liquid.
  • The asbestos clumps moved along the airway faster than all other particles studied.
  • In some animals, asbestos fibres took 4 to 5 minutes to appear at the imaging site.
  • Fibreglass formed similar fluid-enveloped shapes that moved at about one tenth the rate of the asbestos objects.
  • Quarry dust appeared only as individual particles, with no fluid envelope.
  • Galena was difficult to detect in the mice.
  • Fewer particles were detected than expected for the concentration and volume delivered.
  • The authors suggested that the fast movement of the fibre clumps raises the possibility that airways handle fibre-based particles by a different mechanism from non-fibrous particles.
• The authors' conclusion: The authors concluded that, to their knowledge, this was the first report of non-invasively detecting and monitoring the surface behaviour of these pollutant particles in live airways.
• Limitations the authors state:
  • The particle doses were not yet optimal or controllable, and normal exposure and uptake of these particles is quite different.
  • Delivering particles in a distilled water bolus is not how exposure occurs in life; inhalation would be more physiologically relevant.
  • Asbestos could not be ground into uniform size fractions.
  • Because individual asbestos fibres were never seen on the airway, the size of the delivered fibres could not be determined.
  • The ground galena is a different form of lead from lead fumes that people inhale.
  • Imaging was done in the nasal airway, while the lung airways are the relevant target organ.
  • Motion detection cannot detect particles that are not moving.
  • The radiation dose was too intense to allow animal recovery and repeated imaging.

Topics

Medical terms in this study, explained in our Lexicon: Deposition.

Related studies

• A new technique to examine individual pollutant particle and fibre deposition and transit behaviour in live mouse trachea — M. Donnelley, K.K. Siu, et al. (2010)
• Inhalation of rod-like carbon nanotubes causes unconventional allergic airway inflammation — E.M. Rydman, M. Ilves, et al. (2014)
• Real-time measurement of fibers using an HY-differential mobility analyzer with an optical particle counter (KOFAM) — S. Choi, K. Jang, et al. (2017)
• Cigarette smoke increases the penetration of asbestos fibers into airway walls — D. McFadden, J. Wright, et al. (1986)
• Inhalable particles and pulmonary host defense: in vivo and in vitro effects of ambient air and combustion particles — G.E. Hatch, E. Boykin, et al. (1985)
• Real-time detection of airborne asbestos by light scattering from magnetically re-aligned fibers — C. Stopford, P.H. Kaye, et al. (2013)

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