New ricin detection test developed

As little as one-half milligram of ricin is lethal to humans, and no antidote is available. Ricin, a ribosomal inactivating protein found in castor beans, is one of the agents most likely to be used in acts of aerosol or food-related bioterrorism. Ricin can be obtained easily and quickly causes death when inhaled or eaten in small amounts.

U.S. scientists say they have developed a highly sensitive test that can accurately detect and quantify the presence of ricin. The test is so sensitive, one can detect one billionth of a gram of toxin in a single droplet of fluid in just five minutes, the scientists say. This is the most sensitive test to date for detecting ricin. UPI reports that researchers at Yeshiva University’s Albert Einstein College of Medicine, led by Professor Vern Schramm, said the protein — in the form of a powder, mist, pellet or solution — can be injected or inhaled.

The new assay can detect small amounts of ricin more accurately and faster than before. Users would place samples of potentially adulterated food or swabs used to wipe potentially contaminated surfaces into a few drops of a mixture of reagents. That mixture will emit light if ricin is present, with higher luminescence indicating greater concentrations of the toxin.

Schramm and colleague Matthew Sturm describe the test as detecting the presence of active ricin in any sample by measuring the release of adenine from specific ricin substrates. Ricin-catalyzed adenine release from ribosomes stops protein synthesis and is the mechanism of action of this deadly toxin. By coupling adenine release to light formation by firefly luciferase, scientists can visualize the presence of ricin by the simple detection of light. The test can detect nanogram (one-billionth of a gram) amounts of ricin in minutes, they note.

“In retrospect,” said Schramm, “like many scientific advances, it’s such a simple idea that I’m surprised it wasn’t thought of earlier.” Schramm said he believes the assay’s most immediate application is for discovering drugs that could serve as antidotes for ricin poisoning. The study is reported in the journal Analytical Chemistry.

In the other, John Barr and Suzanne Kalb describe development of a highly selective three-part test that involves capturing the ricin protein using special antibodies, evaluating the enzymatic activity of the ricin protein by mass spectrometry, and identifying the ricin protein by its amino acid sequence through mass spectrometry. In laboratory tests using small amounts of ricin spiked into food and body fluids, including milk, apple juice, serum, and saliva, the scientists found that the test was highly specific and accurate in comparison to current tests.

-read more in Matthew B. Sturm and Vern L. Schramm, “Detecting Ricin: Sensitive Luminescent Assay for Ricin A-Chain Ribosome Depurination Kinetics,” Analytical Chemistry (20 March 2009), (DOI: 10.1021/ac8026433); and Suzanne R. Kalb and John R. Barr, “Mass Spectrometric Detection of Ricin and its Activity in Food and Clinical Samples,” Analytical Chemistry 81, no. 6 (19 February 2009): 2037–42 (DOI: 10.1021/ac802769s)