A Quartz Crystal Microbalance Method for Rapid Detection and Differentiation of Shiga Toxins by Applying a Monoalkyl Globobioside as the Toxin Ligand

A simple globobiosyl (Gb2) ceramide mimic carrying a monoalkyl chain (C18) was applied for a monolayer Langmuir−Blodgett (L−B) technique to detect Shiga toxins (Stxs) by a quartz crystal microbalance (QCM) method. The artificial glycolipid, synthesized from penta-O-acetyl-d-galactopyranose via a conventional glycosidation pathway, was developed at the air−water surface for the formation of the monolayer film. Then, the film was transferred onto a QCM cell surface modified with alkanethiols. Upon the addition of each of Stx-1 and Stx-2, the decrease of frequency reached saturation within 45 min at a few nanogram order per quartz cell. Binding constants (Ka) estimated for each of Stx-1 and Stx-2 showed little difference between the two toxins. On the other hand, in the presence of an artificial acrylamido Gb2 copolymer as a competitive inhibitor, the two toxins showed a large difference in the binding behavior to the L−B monolayer.