Fluorescent labeling of asbestos fiber for enhanced asbestos detection under fluorescence microscopy

Our plain-English summary of Fluorescent labeling of asbestos fiber for enhanced asbestos detection under fluorescence microscopy, by A. Kuroda (Frontiers in Public Health, 2025).

The study

• Author: A. Kuroda
• Journal: Frontiers in Public Health
• Published: 2025;13:1568581
• Type of article: Review
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The application of fluorescence microscopy (FM) for detecting micro- and nano-scale inorganic materials has historically been limited by the lack of specific fluorescent probes. However, recent research has demonstrated that asbestos-binding proteins can act as effective fluorescent probes, significantly enhancing the sensitivity and selectivity of FM for asbestos fiber detection. This advancement enables the identification of nano-scale fibers at lower magnifications, reducing the labor costs associated with asbestos contamination detection. Based on these advantages, two FM-based methods have been developed: (i) phase-contrast microscopy (PCM)-FM, a differential counting approach fully compatible with PCM-based epidemiological data, and (ii) portable FM, which shows strong potential for rapid on-site asbestos screening. Additionally, FM may enable multicolor labeling and live-cell fluorescent imaging of asbestos, opening new avenues for asbestos research. Despite these advancements, several challenges remain. Fluorescent probes alone cannot definitively identify asbestos, and issues such as cross-reactivity need to be addressed. This review highlights future perspectives and challenges for advancing FM methods in asbestos detection and research.

Copyright © 2025 Kuroda.

In plain English

This article was a review in which the author described research, mostly by the author's own team, on asbestos-binding proteins labeled with fluorescent dyes. These probes make asbestos fibers glow under a fluorescence microscope. One probe type bound chrysotile. A second type bound all five amphibole types: actinolite, amosite, anthophyllite, crocidolite and tremolite. In tests against 10 common non-asbestos fibers, the only one either probe bound was silicon carbide whiskers. Fluorescence counts of chrysotile were about seven times higher than phase-contrast microscopy counts. Counts for amosite and crocidolite were nearly identical between the two methods. The thinnest chrysotile fibers seen were about 30–35 nm wide. A portable fluorescence microscope was used at 20 demolition sites in Japan. Most sites were below 1 fiber/L, but at one site asbestos fibers (5.2 fibers/L) had leaked from containment, and laboratory analysis confirmed they were amosite. In earlier demolition-site samples, about 95% of stained fibers were correctly identified as asbestos. The author concluded that the probes improve sensitivity and selectivity. The author also noted that the probes alone cannot definitively identify asbestos and that cross-reactivity needs further study.

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 (narrative review of research on fluorescent probes for asbestos detection, largely the author's own team's earlier studies)
• Who was studied: No human subjects. The review covers laboratory tests on chrysotile, all amphibole asbestos types and 10 common non-asbestos fibrous materials, plus air samples taken with a portable microscope at 20 demolition sites across Japan.
• Exposure: Chrysotile and the five amphibole asbestos types (actinolite, amosite, anthophyllite, crocidolite, tremolite), detected with fluorescently labeled asbestos-binding proteins: type I for chrysotile and type II for amphiboles.
• Main results:
  • The type I probe bound chrysotile but not amphibole asbestos or any non-asbestos fiber, except silicon carbide whiskers.
  • The type II probe detected all five amphibole asbestos types and distinguished them from the 10 non-asbestos fibrous materials, except silicon carbide whiskers.
  • For chrysotile, fluorescence microscopy counts were about seven times higher than phase-contrast microscopy counts on the same filters (ratios of 7.03 and 6.92 for two samples).
  • For amosite and crocidolite, fluorescence and phase-contrast counts were nearly identical (ratios 0.96 to 1.05).
  • The thinnest fluorescent chrysotile fibers measured by scanning electron microscopy were about 30–35 nm in diameter.
  • In airborne dust samples from demolition sites in Japan, the combined phase-contrast/fluorescence (PCM-FM) counts correlated highly with phase-contrast counts adjusted by the electron-microscopy asbestos fraction.
  • Using the portable fluorescence microscope at 20 demolition sites across Japan, most sites were below 1 fiber/L. At one site, asbestos fibers (5.2 fibers/L) had leaked from containment, and SEM-EDX analysis confirmed them as amosite.
  • In a previous study by the author's team, about 95% of fluorescently stained fibers in demolition-site samples were correctly identified as asbestos. Some false positives occurred, including surface-coated mineral wool fibers.
• The authors' conclusion: The author concluded that asbestos-binding proteins work as fluorescent probes and enhance the sensitivity and selectivity of fluorescence microscopy for detecting asbestos fibers in air, liquids and materials.
• Limitations the authors state:
  • Asbestos cannot be definitively identified by fluorescent probes alone; detailed morphological analysis is needed.
  • More research is needed on the probes' cross-reactivity.
  • The probes cannot currently distinguish amphibole asbestos from cleavage fragments.
  • Fluorescence microscopy cannot accurately measure the diameters of nano-scale fibers, which appear thicker than under electron microscopy.
  • How the binding proteins selectively recognize chrysotile among other minerals and man-made fibers remains unclear.

Related studies

• Selective detection of airborne asbestos fibers using protein-based fluorescent probes — T. Ishida, M. Alexandrov, et al. (2010)
• Rapid on-site detection of airborne asbestos fibers and potentially hazardous nanomaterials using fluorescence microscopy-based biosensing — A. Kuroda, M. Alexandrov, et al. (2016)
• Multifluorescence labeling techniques and confocal laser scanning microscopy on lung tissue — M. Stern, D.J. Taatjes, et al. (2006)
• Live-cell imaging of macrophage phagocytosis of asbestos fibers under fluorescence microscopy — T. Ishida, N. Fujihara, et al. (2019)
• An Automated Fluorescence Microscopy-Based Sensing System for Continuous Detection of Airborne Asbestos Fibers on a PM2.5 Monitoring Platform — A. Kuroda, K. Kaga, et al. (2026)
• Evaluation of sensitivity of fluorescence-based asbestos detection by correlative microscopy — T. Ishida, M. Alexandrov, et al. (2012)

Browse more research in Frontiers in Public Health, or return to medical research.