RICIN DETERMINATION BY TEMPERATURE CONTROLLED PHASE-SEPARATION IMMUNOASSAY

Abstract

A novel immunoassay of ricin in serum was developed. The antigen of ricin (Ag_ricin)was labeled with isothiocyno-fluorecein (FITC). The antibody of Ag_ricin (Ab_ricin)was conjugated to poly-N-isopropylacrylamide (PNIP) to form Ab_ricin bound thermally reversible hydrogel PNIP-Ab_ricin. A competitive immunoassay method based on the competition of FITC-Ag_ricin and free ricin with limited amount of PNIP-Ab_ricin 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.

Keywords:

• Ricin
• Phase-separation immunoassay
• Thermally reversible hydrogel
• FITC

ACKNOWLEDGMENTS

This work is supported by National Natural Science Foundation of P.R. China (29775002).