Evaluation of a B-Cell Biosensor Immunoassay for Rapid and Sensitive Detection of Ricin, a Harmful Plant Protein Toxin

Abstract

Ricin is a carbohydrate binding protein produced in the castor bean seeds and is very toxic to humans. Ricin is one of the most frequently used toxin as a biothreat agent in many individual incidents. PathSensors has licensed the Cellular Analysis and Notification of Antigen Risks and Yields (CANARY) technology from Massachusetts Institute of Technology and developed Zephyr biosensor sandwich immunoassay for rapid detection of Ricin. In this assay, CANARY technology utilizes engineered B Cells that express ricin specific monoclonal antibody on the surface as biosensors. Luminescence, emitted from the B cells upon binding of the toxin, is measured as photons in a Luminometer to detect ricin in a suspicious sample. In this study, a detailed performance evaluation of this rapid ricin detection test was done in multiple phases using well characterized materials. The dynamic range of this assay was determined by testing wide ranging concentrations (0 to 100 ng/test) of ricin and limit of detection (LOD) was calculated by PROBIT regression analysis. Further validation of assay was performed by testing inclusivity, informational, near neighbor, lectin, and white powder panels, and also environmental aerosol filter sample testing. LOD for ricin was found to be 1 ng/test. Repeatability testing showed more than 99% sensitivity and 100% specificity. There was no false positive detection of environmental background panel and other potentially interfering materials except Ricinus communis agglutinin also known as RCA120. The validation indicates that the ricin biosensor test is user-friendly laboratory detection method which has great potential for use in national and international public health and environmental test laboratories.