A glyco-chip for the detection of ricin by an automated chemiluminescence read-out system

The plant toxin ricin is a lectin that binds to D-galactose or lactose moieties by multivalent interactions. In the present work, this avidity was used to develop a novel sandwich glyco-immunoassay using a carbohydrate microarray. For realization, 6-azidohexyl-lactose was immobilized on an alkyne silane surface by Cu(I) catalyzed click chemistry. This procedure is fast, and prevents any nonspecific binding on the microarray surface. Ricin binds via its B-chain to the lactose moieties, and is detected by the biotinylated anti-ricin A-chain. By adding a horseradish peroxidase-labeled streptavidin, a chemiluminescence signal can be generated. This method is described as a sandwich-type glyco-immunoassay. The signal on the glyco-chip can be regenerated for at least 10 measurements. The limit of detection was estimated to be 80 ng mL-1. The assay was carried out on the automated microarray readout platform MCR 3. In this way, it took 20 min for one measurement, including regeneration of the chip surface.