Preparation of radiolabeled bioactive asbestos fibers

We have developed an efficient procedure to radiolabel asbestos fibers while retaining the bioactivity of the fibers. The fibers are labeled with 68Ge. The 68Ge decays into 68Ga, which then can be detected by its characteristic positron emission. Both chrysotile and crocidolite asbestos, a serpentine and an amphibole, respectively, were radiolabeled successfully. Mild reaction conditions and short reaction times were found under which approximately 90% of the added 68Ge and 68Ga bound to the fibers. The radiolabel was retained even after washing the fibers extensively with physiologic buffers. The effects of the labeling on the bioactivity of the fibers were evaluated in an in vitro assay using guinea pig alveolar macrophages as a target cell. Labeled chrysotile fibers were found to retain greater than 95% of their ability to stimulate these cells. The labelling procedure described in this study should be useful in preparing labeled fibers to investigate both in vitro and in vivo phenomena.