Selective detection of airborne asbestos fibers using protein-based fluorescent probes

Our plain-English summary of Selective detection of airborne asbestos fibers using protein-based fluorescent probes, by T. Ishida, M. Alexandrov, T. Nishimura, et al (Environmental Science & Technology, 2010).

The study

• Authors: T. Ishida, M. Alexandrov, T. Nishimura, K. Minakawa, R. Hirota, K. Sekiguchi, N. Kohyama, A. Kuroda
• Journal: Environmental Science & Technology
• Published: 2010;44(2):755-9
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Fluorescence microscopy (FM) is one of the most important analytical tools in modern life sciences, sufficiently sensitive to allow observation of single molecules. Here we describe the first application of the FM technique for the detection of inorganic environmental pollutants-airborne asbestos fibers that can cause asbestosis, mesothelioma, and lung cancer. In order to assess FM capabilities for detecting and counting asbestos fibers, we screened E. coli lysate for proteins that bind to amphibole asbestos. In combination with the previously discovered E. coli protein DksA (Kuroda et al., Biotechnol. Bioeng. 2008, 99, 285-289) that can specifically bind to chrysotile, the newly identified GatZ protein was used for selective and highly sensitive detection of two different asbestos types. Our novel FM-based method overcomes a number of limitations of the commonly used phase-contrast microscopy (PCM) method, offering a convenient alternative to PCM for airborne asbestos monitoring.

In plain English

This laboratory study tested whether fluorescence microscopy could detect and count asbestos fibers as an alternative to phase-contrast microscopy (PCM). No people were studied. The authors searched E. coli bacteria for proteins that bind amphibole asbestos and chose one, called GatZ. With a fluorescent label, GatZ bound to amosite, crocidolite, actinolite, anthophyllite and tremolite, but not to rockwool or glass wool. A protein the authors had identified earlier, DksA, bound to chrysotile but not to rockwool, glass wool or amphibole asbestos. On filters prepared in the laboratory from reference samples, fluorescence counts of chrysotile fibers were about 7 times the PCM counts (ratios of 7.03 and 6.92 on two filters). For amosite and crocidolite the two methods gave almost equal counts. Staining with both proteins told chrysotile apart from amosite in a mixed sample. The authors concluded that the method could be a viable alternative to PCM. They said it cannot replace more rigorous identification methods such as electron microscopy, and that it may not reliably separate the five amphibole types from one another.

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: Laboratory method-development study: screening of bacterial proteins that bind asbestos, building fluorescent probes from them, and comparing fluorescence microscopy (FM) fiber counts with phase-contrast microscopy (PCM) counts
• Who was studied: No human subjects. Reference samples of chrysotile, amosite and crocidolite from the Japan Association for Working Environment Measurement; actinolite, anthophyllite and tremolite from the US National Institute of Standards and Technology; rockwool and glass wool from the Japan Fibrous Material Research Association. Fibers were dispersed in liquid and collected on filters in the laboratory.
• Exposure: Not a human exposure study. Fiber types tested were chrysotile and five amphibole asbestos types (amosite, crocidolite, actinolite, anthophyllite, tremolite). Rockwool and glass wool were used as non-asbestos comparison fibers.
• Main results:
  • The chrysotile probe (DksA labeled with Cy3 dye) bound to chrysotile but not to rockwool, glass wool or amphibole asbestos
  • The amphibole probe (GatZ labeled with fluorescein) bound strongly to amosite and crocidolite, with dissociation constants of 22.1 and 13.9 nM respectively
  • After the binding buffer was optimized, GatZ-fluorescein bound to all kinds of amphibole asbestos tested (including actinolite, anthophyllite and tremolite) but not to rockwool or glass wool
  • For chrysotile samples, FM fiber counts were about 7 times higher than PCM counts. The authors attributed this, probably, to many thin fibers that PCM cannot see.
  • Table 1 gives FM-to-PCM relative fiber counts of 7.03 and 6.92 for the two chrysotile filters, 0.96 and 0.99 for the two amosite filters, and 0.99 and 1.05 for the two crocidolite filters
  • For amosite and crocidolite samples, FM and PCM counts were almost equal, showing no apparent gain in sensitivity for these fibers
  • Sequential staining with both probes distinguished chrysotile from amosite in a mixed laboratory sample
• The authors' conclusion: The authors concluded that FM cannot replace more rigorous identification methods such as TEM, but that its simplicity, sensitivity, low cost and fiber-identification capability should make it a viable alternative to PCM
• Limitations the authors state:
  • The method can distinguish fibers only by their surface characteristics
  • Reliably telling apart the five amphibole asbestos types may be beyond the reach of FM analysis
  • FM cannot replace more rigorous fiber identification methods such as TEM

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Lung Cancer, Amphibole Asbestos, Chrysotile.

Related studies

• Molecular engineering of a fluorescent bioprobe for sensitive and selective detection of amphibole asbestos — T. Ishida, M. Alexandrov, et al. (2013)
• Detection of chrysotile asbestos by using a chrysotile-binding protein — A. Kuroda, T. Nishimura, et al. (2008)
• Rapid on-site detection of airborne asbestos fibers and potentially hazardous nanomaterials using fluorescence microscopy-based biosensing — A. Kuroda, M. Alexandrov, et al. (2016)
• Evaluation of sensitivity of fluorescence-based asbestos detection by correlative microscopy — T. Ishida, M. Alexandrov, et al. (2012)
• Differential Counting of Asbestos Using Phase Contrast and Fluorescence Microscopy — T. Nishimura, M. Alexandrov, et al. (2016)
• Development of an automated asbestos counting software based on fluorescence microscopy — M. Alexandrov, E. Ichida, et al. (2015)

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