Selective tumor imaging by a novel tumor specific aralin-infrared-to-visible phosphor conjugate

Aralin is a novel cytotoxic protein from Aralia elata and selectively induces apoptosis in transformed cells as compared to normal cells (1). Aralin is a lectin specific for sugar chain such as galactose and possesses RNA N-glycosidase activity. In this study, antitumor potency of aralin was analyzed using the poly(ethyleneglycol) (PEG)/streptavidin co-immobilized infrared-to-visible upconversion phosphors, Y2O3 nanoparticles (2). Cy3-conjugated aralin could clearly detect the surface of SV40-transformed VA13 and human cervical carcinoma HeLa cells, but to a lesser extent on the normal human fibroblast WI-38 cells. Conjugation of aralin with PEGylated Y2O3 nanophosphor was carried out via biotin-avidin binding. The Y2O3-conjugated aralin also clearly visualize by a fluorescence microscope measurements equipped with near-infrared excitation source scanning in HeLa cells. It is also important to note that no remarkable damage to the cells was observed during these observations. Thus, these data imply that the Y2O3-conjugated aralin would potentially be useful material for tumor detection in vivo.