Bio-imaging and cancer targeting with glycoproteins and N-glycans.

Positron emission tomography (PET) is a non-invasive method that visualizes the locations and levels of radiotracer accumulation with high imaging contrast. A new labeling method using 6π-electrocyclization was developed for PET and fluorescence labeling. The high reactivity of the new method enabled the labeling of peptides and proteins at low concentration within a short period. PET or fluorescent imaging of the labeled glycoproteins and N-glycan glycoclusters successfully visualized their dynamics and bio-distribution depending on the glycan structures. The trafficking of the lymphocytes was also clearly visualized by the non-invasive fluorescence imaging. The present electrocyclization protocol was also applied to the cell-surface engineering by the oligosaccharides; the lymphocytes introduced with N-glycan successfully targeted the tumor tissue implanted in the nude mice.