Labeled anti-mucin antibody detectable by infrared-fluorescence endoscopy

The goal of our study was to develop a method for molecular imaging of the gastrointestinal tract using an infrared fluorescence endoscope (IRFE) and antibodies labeled with an indocyanine green (ICG) derivative to detect cancerous tissue. The IRFE comprised an infrared endoscope equipped with excitation (710-790 nm) and barrier (810-920 nm) filters. We developed ICG-N-hydroxysulfosuccinimide ester (ICG-sulfo-OSu) and 3-ICG-acyl-1,3-thiazolidine-2-thione (ICG-ATT) as infrared fluorescent-labeling reagents, and anti-human carcinoembryonic antigen (CEA) antibody and MUC1 antibody were labeled with the ICG-derivatives. Freshly resected specimens of gastric cancer were observed by IRFE after reaction with ICG-derivative-labeled antibodies. Positive fluorescence was observed at the tumor location by IRFE, and the immunofluorescent images correlated well with the tumor sites. The immunofluorescence studies suggested that the intensity of the infrared fluorescence of the ICG-ATT-labeled MUC1 antibody is stronger than the ICG-sulfo-OSu-labeled MUC1 antibody. We concluded that specific antibodies for gastrointestinal cancer labeled with an ICG-derivative accompanied by a reinforcing agent and an optimal electronic device can generate a strong enough fluorescent signal to visualize cancer proteins.