Evaluation of Sensitivity of Fluorescence-Based Asbestos Detection by Correlative Microscopy
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Fluorescence microscopy (FM) has recently been applied to the detection of airborne asbestos fibers that can cause asbestosis, mesothelioma and lung cancer. In our previous studies, we discovered that the E. coli protein DksA specifically binds to the most commonly used type of asbestos, chrysotile. We also demonstrated that fluorescent-labeled DksA enabled far more specific and sensitive detection of airborne asbestos fibers than conventional phase contrast microscopy (PCM). However, the actual diameter of the thinnest asbestos fibers visualized under the FM platform was unclear, as their dimensions were below the resolution of optical microscopy. Here, we used correlative microscopy (scanning electron microscopy [SEM] in combination with FM) to measure the actual diameters of asbestos fibers visualized under the FM platform with fluorescent-labeled DksA as a probe. Our analysis revealed that FM offers sufficient sensitivity to detect chrysotile fibrils as thin as 30–35 nm. We therefore conclude that as an analytical method, FM has the potential to detect all countable asbestos fibers in air samples, thus approaching the sensitivity of SEM. By visualizing thin asbestos fibers at approximately tenfold lower magnifications, FM enables markedly more rapid counting of fibers than SEM. Thus, fluorescence microscopy represents an advanced analytical tool for asbestos detection and monitoring.
KeywordsAsbestos detection Fluorescence Asbestos-binding protein Chrysotile Correlative microscopy DksA
This work was supported by the Environment Research and Technology Development Fund (C-1101) of the Ministry of the Environment, Japan, and the Development of Systems and Technology for Advanced Measurement and Analysis Program of the Japan Science and Technology Agency. We thank Mr. Shigeaki Tachibana (SII Nanotechnology Inc.) and Mr. Kazunori Sugai and Mr. Shinji Iguchi (Carl Zeiss MicroImaging Co., Ltd) for technical assistance with correlative microscopic imaging.
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