Environ. Sci. Technol. 2010, 44, 755–759
Selective Detection of Airborne Asbestos Fibers Using Protein-Based Fluorescent Probes TAKENORI ISHIDA,† MAXYM ALEXANDROV,† TOMOKI NISHIMURA,‡ KENJI MINAKAWA,‡ RYUICHI HIROTA,† KIYOSHI SEKIGUCHI,‡ NORIHIKO KOHYAMA,§ AND A K I O K U R O D A * ,†,‡ Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8530, Japan, Siliconbio Inc., Higashi-Hiroshima, Hiroshima 739-0046, Japan, and Department of Economics, Toyo University, Bunkyo-Ku, Tokyo 112-8606, Japan
Received August 06, 2009. Revised manuscript received November 10, 2009. Accepted November 10, 2009.
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 pollutantssairborne asbestos fibers that can cause asbestosis, mesothelioma, and lung cancer. In order to assess FM capabilities for detecting and counting asbestos fibers,wescreenedE. coli lysateforproteinsthatbindtoamphibole 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 FMbased 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.
Introduction Asbestos is a group of six fibrous silicate minerals that has been widely used in various construction materials because of its chemical and thermal stability (1, 2). Asbestos minerals are made up of microscopic bundles of silicate fibers that can easily become airborne. Asbestos minerals differ in their chemical composition, fiber shape, and toxicity. Chrysotile, a member of serpentine mineral group, accounts for more than 90% of industrial use of asbestos (3). Amosite and crocidolite, which are members of amphibole mineral group, have been linked to much higher risks of pleural mesothelioma as compared to chrysotile (4). Actinolite, anthophyllite, and tremolite are other members of the amphibole group and have been less commonly used in industry. Although the use of asbestos is now prohibited in most developed countries, asbestos contamination remains a common * Corresponding author phone: +81-82-424-7758; fax: +81-82424-7047; e-mail:
[email protected]. † Hiroshima University. ‡ Siliconbio Inc. § Toyo University. 10.1021/es902395h
2010 American Chemical Society
Published on Web 12/14/2009
problem, contributing to the increasing incidence of asbestoslinked pleural mesothelioma and lung cancer (5, 6). A number of analytical methods are available for asbestos detection and identification. The most commonly used method for air samples relies on phase contrast microscopy (PCM) to identify and count all fibers that are longer than 5 µm, thinner than 3 µm, and have aspect ratios larger than 3:1 (7). While simple and cheap, PCM has a number of limitations. It cannot detect asbestos fibers thinner than about 0.25 µm and is not able to distinguish asbestos fibers from other natural or man-made fibers of similar dimensions (8). However, some epidemiological studies suggested that both lung cancer and asbestosis were most strongly associated with exposure to thin fibers (
