Background and study aims: An indocyanine green derivative (ICG-sulfo-OSu) that can be used as an infrared fluorescent labeling substance suitable for detecting microlesions with an infrared fluorescence endoscope has been developed. The aims of the present study were to develop an infrared fluorescence endoscope and to demonstrate its usefulness in detecting cancerous tissue using an antibody coupled with ICG-sulfo-OSu.
Materials and methods: ICG-sulfo-OSu-labeled mouse anti-human carcinoembryonic antigen (CEA) antibody and an infrared fluorescence endoscope were used in this study. Biopsy specimens of gastric cancer were stained with anti-CEA antibody using the avidin-biotinylated peroxidase complex method. The positive specimens used for the infrared imaging analysis were freshly resected stomachs from three patients.
Results: Treatment of freshly resected stomach specimens with ICG-sulfo-OSu-labeled-anti-CEA antibody complex resulted in positive staining of the tumor sites on infrared fluorescence endoscopy, and the infrared fluorescent images correlated well with the tumor sites.
Conclusions: An anti-CEA antibody with affinity for cancerous lesions and labeled with ICG-sulfo-OSu can therefore be imaged using this infrared fluorescence endoscope. Specific antibodies tagged with ICG-sulfo-OSu can label cancer cells and can generate a strong enough fluorescent signal to detect small cancers when examined with an infrared fluorescence endoscope.