title: A single DNA aptamer functions as a biosensor for ricin.
abstract: The use of microorganisms or toxins as weapons of death and fear is not a novel concept; however, the modes by which these agents of bioterrorism are deployed are increasingly clever and insidious. One mechanism by which biothreats are readily disseminated is through a nation's food supply. Ricin, a toxin derived from the castor bean plant, displays a strong thermostability and remains active at acidic and alkaline pHs. Therefore, the CDC has assigned ricin as a category B reagent since it may be easily amendable as a deliberate food biocontaminate. Current tools for ricin detection utilize enzymatic activity, immunointeractions and presence of castor bean DNA. Many of these tools are confounded by complex food matrices, display a limited dynamic range of detection and/or lack specificity. Aptamers, short RNA and single stranded DNA sequences, have increased affinity to their selected receptors, experience little cross-reactivity to other homologous compounds and are currently being sought after as biosensors for bacterial contaminants in food. This paper describes the selection and characterization of a single, dominant aptamer, designated as SSRA1, against the B-chain of ricin. SSRA1 displays one folding conformation that is stable across 4-63 °C (ΔG = -5.05). SSRA1 is able to concentrate at least 30 ng mL(-1) of ricin B chain from several liquid food matrices and outcompetes a currently available ELISA kit and ricin aptamer. Furthermore, we show detection of 25 ng mL(-1) of intact ricin A-B complex using SSRA1 combined with surface enhanced Raman scattering technique. Thus, SSRA1 would serve well as pre-analytical tool for processing of ricin from liquid foods to aid current diagnostics as well as a sensor for direct ricin detection.
authors: Veterinary Population Medicine, University of Minnesota, Room 301E, 1971 Commonwealth Avenue, Saint Paul, Minnesota, USA.
authors: Elise A
authors: EA
authors: Lamont
authors: Lili
authors: L
authors: He
authors: Keith
authors: K
authors: Warriner
authors: Theodore P
authors: TP
authors: Labuza
authors: Srinand
authors: S
authors: Sreevatsan
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D012276:Ricin / Q000032:analysis*; D013059:Spectrum Analysis, Raman
chemical_list: D052157:Aptamers, Nucleotide; D012276:Ricin