ARS | Publication request: Immunosorbent analysis of ricin contamination in milk using colorimetric, chemiluminescence, and electrochemiluminescence detection

Submitted to: Food and Agricultural Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 2012
Publication Date: January 9, 2013
Citation: Brandon, D.L., Korn, A.M., Yang, L. 2013. Immunosorbent analysis of ricin contamination in milk using colorimetric,chemiluminescence, and electrochemiluminescence detection. Food and Agricultural Immunology. doi:10.1080/09540105.2012.753515.

Interpretive Summary: Castor beans are an important agricultural crop, used to make castor oil, an industrial lubricant. Ricin is a highly toxic protein that remains in the solids after oil is extracted from castor beans. Ricin has been used for intentional poisoning, and there is a need for methods to detect ricin in food to ensure a safe food supply. In this paper we describe the use of an advanced technology to detect this binding in milk that was experimentally spiked with tiny amounts of ricin. The detection method, known as electrochemiluminescence, uses a weak electric current to produce a chemical reaction that leads to generation of light. The amount of light we measured was directly related to the amount of ricin in the sample. Our test was compared to other standard assay formats. It was able to detect very small amounts of the toxin – far less than the amount that would make a person sick if consumed in a serving of food. This means our test could be used to prevent intentional poisoning.

Technical Abstract: Analytical methodology to detect ricin in food matrices is important because of the potential use of foodborne ricin as a terrorist weapon. Monoclonal antibodies (mAbs) that bind ricin were used for both capture and detection in sandwich enzyme-linked immunosorbent assay (ELISA) and electrochemiluminescence (ECL) immunosorbent assays. In ELISA, two types of substrate were employed, for colorimetric or chemiluminescent detection. Although both fat content and protein content of samples influence the recovery of ricin, lower limit of detection (LOD) in ELISA and ECL systems permitted detection in of 0.1 ng/mL or less for milk samples containing 0 to 4% fat. The assay sensitivities permitted detection of less than 0.01% of an adult human lethal dose in a typical serving using standard 96-well assay plate technology. The assays are capable of detecting crude ricin in milk samples spiked with castor extract, and do not respond significantly to isolated ricin chains, heat-denatured ricin, or the related agglutinin, Ricinus communis agglutinin 1 (RCA-1).