A new infrared fluorescent-labeling agent and labeled antibody for diagnosing microcancers.

PURPOSE: We have developed infrared fluorescent labeling agents and infrared-ray fluorescence endoscopes to establish a novel diagnostic technique. Since the fluorescence intensity of the initial labeled antibody (ICG-sulfo-OSu-labeled antibody) was not sufficient for practical use, we synthesized indocyanine green acylthiazolidinethione (ICG-ATT), which was expected to label various target molecules having amino groups efficiently.
MATERIALS AND METHODS: To confirm imaging of infrared fluorescence intensity of ICG-ATT- and ICG-sulfo-OSu-labeled anti-MUC1 antibodies, cotton thread was soaked in various concentrations of the antibody solution in 0.1M PBS, and observed under the epi-illumination infrared fluorescence microscope. Localization and the intensity of infrared fluorescence and DAB coloring was compared in paraffin sections of human gastric mucosa.
RESULTS: In the study of cotton threads, both labeled antibodies showed relatively clear infrared fluorescence, and significant difference was not observed between the two antibodies. ICG-ATT-labeled anti-MUC1 antibody produced stronger staining than that by ICG-sulfo-OSu-labeled antibody. Localization pattern of infrared fluorescent staining was in good agreement with that by the conventional method with oxidized DAB staining.
CONCLUSION: ICG-ATT is useful as a fluorescent-labeling agent for diagnosis of microcancers by infrared fluorescence endoscopes.