The widespread availability of ricin, a protein derived from the seeds of the castor bean plant (Ricinus communis) and its extreme toxicity make it an ideal agent for bioterrorism and self-poisoning.
A rapid, sensitive and reliable method for ricin identification in clinical samples is required for applying appropriate and timely medical intervention. However, this goal is challenging due to the low predicted toxin concentrations in bio-fluids, accompanied by significantly high matrix interferences.
In this study, researchers report the on a sensitive, rapid, antibody-independent assay for the identification of ricin in body fluids using mass spectrometry (MS). The assay involves lectin affinity capturing of ricin by easy-to-use commercial lactose–agarose (LA) beads, following by tryptic digestion and selected marker identification using targeted LC–MS/MS (Multiple Reaction Monitoring) analysis. This enables ricin identification down to 5 ng/mL in serum samples in 2.5 h.
A real-life test of the assay was successfully executed in a challenging clinical scenario, where the toxin was identified in an abdominal fluid sample taken 72 h post self-injection of castor beans extraction in an eventual suicide case.
This method developed for ricin identification in clinical samples has the potential to be applied to the identification of other lectin toxins. Being antibody independent, the assay can be extended to a multiplexed application for identifying the entire RIP II toxins family without skewing the result by a priori selection of target toxins by specific antibodies.
Rapid, Sensitive and Reliable Ricin Identification in Serum Samples Using LC–MS/MS. Toxins, 22 January 2021.