Rapid on-site detection of airborne asbestos fibers and potentially hazardous nanomaterials using fluorescence microscopy-based biosensing

Our plain-English summary of Rapid on-site detection of airborne asbestos fibers and potentially hazardous nanomaterials using fluorescence microscopy-based biosensing, by A. Kuroda, M. Alexandrov, T. Nishimura, et al (Biotechnology Journal, 2016).

The study

• Authors: A. Kuroda, M. Alexandrov, T. Nishimura, T. Ishida
• Journal: Biotechnology Journal
• Published: 2016;11(6):757-67
• Type of article: Review
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A large number of peptides with binding affinity to various inorganic materials have been identified and used as linkers, catalysts, and building blocks in nanotechnology and nanobiotechnology. However, there have been few applications of material-binding peptides in the fluorescence microscopy-based biosensing (FM method) of environmental pollutants. A notable exception is the application of the FM method for the detection of asbestos, a dangerous industrial toxin that is still widely used in many developing countries. This review details the selection and isolation of asbestos-binding proteins and peptides with sufficient specificity to distinguish asbestos from a large variety of safer fibrous materials used as asbestos substitutes. High sensitivity to nanoscale asbestos fibers (30-35 nm in diameter) invisible under conventional phase contrast microscopy can be achieved. The FM method is the basis for developing an automated system for asbestos biosensing that can be used for on-site testing with a portable fluorescence microscope. In the future, the FM method could also become a useful tool for detecting other potentially hazardous nanomaterials in the environment.

Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In plain English

This article is a review by researchers at Hiroshima University, Japan. It mostly describes their own earlier work on detecting airborne asbestos fibers with fluorescence microscopy. In this method, fibers collected on a filter are stained with fluorescent-labeled proteins or peptides that attach to asbestos. The review reported that a protein called DksA bound to chrysotile but not to amphibole asbestos or other non-asbestos fibers. A second probe detected all five amphibole types and distinguished them from ten common non-asbestos fibers, including wollastonite. The thinnest fibers seen under fluorescence microscopy were about 30 to 35 nm across, as measured by electron microscopy, and some stained fibers were invisible under conventional phase contrast microscopy. Automated counting software agreed well with manual counts at medium to high fiber concentrations but was less accurate at low concentrations. The authors described a portable microscope using an iPad camera and concluded it was sufficient for rapid on-site detection. They noted that fibers look thicker under this method than under electron microscopy, and that formal validation was still underway in Japan.

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: Review, focused mainly on the authors' own previously published work developing a fluorescence microscopy method for detecting asbestos
• Who was studied: No human subjects. Laboratory reference samples of chrysotile, the amphibole asbestos types and ten common non-asbestos fibrous materials, plus field air samples used in testing the counting software
• Exposure: Detection, not health effects, of airborne asbestos fibers: chrysotile (serpentine group) and the amphibole types amosite, crocidolite, tremolite, actinolite and anthophyllite, distinguished from non-asbestos substitute fibers such as wollastonite
• Main results:
  • In earlier work reviewed here, fluorescent-labeled DksA (dissociation constant about 3.5 nM for chrysotile) bound to chrysotile but not to amphibole asbestos or to non-asbestos fibers
  • An amosite-binding peptide displayed on a streptavidin tetramer had about 250-fold higher affinity than the single peptide (dissociation constant 1.0 nM for amosite). It detected all five amphibole types and distinguished them from ten non-asbestos fibers, including wollastonite
  • When very thin chrysotile fibers were viewed in the same field, some fibers seen under fluorescence microscopy were invisible under phase contrast microscopy
  • The thinnest fibers visible under fluorescence microscopy were approximately 30 to 35 nm in diameter as estimated by SEM, similar to single chrysotile fibrils
  • In the authors' experience, SEM above 4000x magnification is needed to reliably identify the thinnest chrysotile fibers, suggesting 100 SEM micrographs are needed to cover one fluorescence microscopy field of view
  • The authors' automated counting software agreed well with manual counts on field samples with medium to high fiber concentrations
  • The portable fluorescence microscope had a calculated spatial resolution of about 0.7 µm, and thin chrysotile fibers were clearly visible in initial tests
  • In unpublished data, the authors reported visualizing titanium dioxide nanoparticles and carbon nanotubes with binding peptides
• The authors' conclusion: The authors concluded that the portable fluorescence microscope performs well enough for rapid on-site asbestos detection. They also suggested the method could be applied to detecting environmental inorganic nanomaterials.
• Limitations the authors state:
  • Because fluorescence microscopy resolution is limited by optical diffraction, thin fibers appear thicker than under SEM
  • Automated counts were less accurate at low fiber concentrations, possibly because of autofluorescent dust particles
  • Like all current asbestos analysis methods, the fluorescence method is subject to variability from analyst skill and adherence to counting rules
  • Formal validation of the method, including comparison with existing methods and cross-testing between labs, was still underway
  • The specificity of binding peptides for other nanomaterials still needs improvement

Topics

Medical terms in this study, explained in our Lexicon: phase contrast microscopy (PCM).

Related studies

• Molecular engineering of a fluorescent bioprobe for sensitive and selective detection of amphibole asbestos — T. Ishida, M. Alexandrov, et al. (2013)
• Selective detection of airborne asbestos fibers using protein-based fluorescent probes — T. Ishida, M. Alexandrov, et al. (2010)
• 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)
• Asbestos Detection with Fluorescence Microscopy Images and Deep Learning — C. Cai, T. Nishimura, et al. (2021)

Browse return to medical research.