糖鎖を認識ツールに用いた生物毒素の高感度検出技術(誌上シンポジウム)  [in Japanese] Highly Sensitive Detection Technology for Biological Toxins Applying Sugar Epitopes(Symposium Review)  [in Japanese]

The Shiga toxin is a highly poisonous protein produced by enterohemorrhagic Escherichia coli O157. This bacterial toxin causes the hemolytic uremic syndrome. Another plant toxin from castor beans, ricin, is also highly toxic. The toxin was used for assassination in London. Recently, there were several cases of postal matter containing ricin. Both toxins are categorized as biological warfare agents by the Centers of Disease Control and Prevention. Conventional detection methods based on the antigen-antibody reaction, PCR and other cell-free assays have been proposed. However, those approaches have drawbacks in terms of sensitivity, analytical time, or stability of the detection reagents. Therefore, development of a facile and sensitive detection method is essential. Here we describe new detection methods applying carbohydrate epitopes as the toxin ligands, which is based on the fact that the toxins bind cell-surface oligosaccharides. Namely, the Shiga toxin has an affinity for globobiosyl (Gb_2) disaccharide, and ricin binds the β-D-galactose residue. For Shiga toxin detection, surface plasmon resonance (SPR) was applied. A polyanionic Gb_2-glycopolymer was designed for this purpose, and it was used for the assembly of Gb_2-chips using alternating layer-by-layer technology. The method allowed us to detect the toxin at a low concentration of LD_<50>. A synthetic carbohydrate ligand for ricin was designed and immobilized on the chips. SPR analysis with the chips allows us to detect ricin in a highly sensitive and facile manner (10pg/ml, 5min). Our present approaches provide a highly effective way to counter bioterrorism.