Method for detecting asbestos
In order to provide a method for more efficiently, easily, and accurately detecting asbestos without changing the asbestos detection criterion of the phase-contrast microscope/electron microscope method as compared with the phase-contrast microscope/electron microscope method, a phase-contrast microscope and a fluorescence microscope are used in combination to detect asbestos contained in a test sample after the test sample is made contact with an asbestos-binding protein having a fluorescent label.
1. A method for detecting asbestos, comprising the steps of:
a) contacting an asbestos-binding protein complex having a fluorescent label with a test substance;
b) detecting a fibrous substance contained in the test substance with use of a phase-contrast/fluorescence microscope in phase-contrast mode, the fibrous substance having a length of 5 μm or more, a width of less than 3 μm, and a length-width ratio of 3:1 or more; and
c) determining that the fibrous substance to which the asbestos-binding protein complex is bound is asbestos by detecting, with use of the phase-contrast/fluorescence microscope in fluorescence mode, the asbestos-binding protein complex bound to the fibrous substance detected in step b) based on the fluorescent label; and
wherein step b) and step c) are carried out without changing a visual field of the phase-contrast/fluorescence microscope, and
wherein the asbestos-binding protein complex comprises four biotin-modified H-NS 60-90 asbestos binding polypeptides and a fluorescently-labeled streptavidin, wherein each of the biotin-modified asbestos binding polypeptides has an amino acid sequence consisting of SEQ ID NO:8 and one biotin molecule at the C-terminus and wherein the biotin-modified asbestos polypeptides bind to the fluorescently-labeled streptavidin through a biotin-streptavidin interaction.
2. The method according to claim 1 , wherein:
the test substance is collected with use of a filter;
the contact between the asbestos-binding protein complex having a fluorescent label and the test substance in step a) occurs on the filter;
the method further comprises a transparency step of making the filter transparent by spraying an acetone vapor on the filter after the contacting step a); and wherein
step b) is carried out after the transparency step.
3. The method according to claim 1 , wherein steps b) and c) are repeated at least one time.
4. The method according to claim 2 , wherein:
the asbestos-binding protein complex binding with the fibrous substance is maintained after the transparency step; and
the fluorescent label is one whose fluorescence can be detected by the phase-contrast/fluorescence microscope in fluorescence mode after the transparency step.
5. The method according to claim 4 , wherein the fluorescent label is at least one fluorescent substance selected from the group consisting of Cy3, DyLight488, fluorescein, Alexa488, ATT0488, CF488A, DyLight550 and CF555.