Electrochemiluminescence immunosorbent assay of ricin in ground beef: biotinylated capture antibodies and matrix effects

Ricin is a highly toxic protein present in the seeds of castor (Ricinus communis), grown principally as a source of high quality industrial lubricant. Because of the past use of ricin for intentional poisoning, there is a need for analytical methodology to detect ricin in food matrices. Ground beef and other fatty, solid matrices present challenges for extraction and detection of protein constituents. This study focused on the use of streptavidin-coated assay plates, with biotinylated monoclonal antibodies (mAbs) immobilised as capture reagents. It explored matrix effects on immunosorbent analyses of ricin in enzyme-linked and electrochemiluminescent detection systems. A variety of mAb pairs enabled assays with predetermined specificity for ricin vs. the related protein, Ricinus communis agglutinin-1 (RCA-1). Extraction of samples at low dilution (1:5) and inclusion of 100 mM galactose in the extraction medium produced excellent quantification of ricin in the 1–20 ng/g range in ground beef.