RICIN DETERMINATION BY TEMPERATURE CONTROLLED PHASESEPARATION IMMUNOASSAY

A novel immunoassay of ricin in serum was developed. The antigen of ricin (Agricin)was labeled with isothiocyno-fluorecein (FITC). The antibody of Agricin (Abricin)was conjugated to poly-N-isopropylacrylamide (PNIP) to form Abricin bound thermally reversible hydrogel PNIP-Abricin. A competitive immunoassay method based on the competition of FITC-Agricin and free ricin with limited amount of PNIP-Abricin was established. The separation in the assay process was achieved by precipitation of the immuno-complex above its lower critical solution temperature (LCST). The fluorescence intensity was determined and the standard curve was obtained. The linear range was 30–200 ng/ml. The detection limit was 30 ng/ ml. The recoveries of ricin from serum were satisfactory.