A novel sugar-probe biosensor for the deadly plant proteinous toxin, ricin

Because of the illegal use of highly toxic ricin from the castor-oil plant, Ricinus communis, in bioterrorism and suspected white powder cases, anti-terrorism measures for the toxin are urgently required. Here we demonstrate a facile and sensitive detection method using synthetic analogues of beta-lactosyl- and beta-D-galactosyl ceramides as the ligands based on the fact that ricin binds cell-surface oligosaccharides. Sugar-probes having lipoic acids as anchor functions were synthesized via eithera chemical or chemo-enzymatic way and were immobilized on the sensor chips by a self-assembled monolayer technique. Surface plasmon resonance (SPR) analysis using these carbohydrate probes allowed us to detect the toxin in a highly sensitive and facile manner (10 pg/mL, 5 min), being the best benchmark as a method for detecting the toxin. In addition, a visual monitoring method was developed, in which sugar-coated Au nanoparticles were utilized for discriminating ricin from other proteins in a facile manner, taking 10-30 min for judgment. (C) 2008 Elsevier B.V. All rights reserved.