Sensitive Detection and Differentiation of Biologically Active Ricin and Abrin in Complex Matrices via Specific Neutralizing Antibody-Based Cytotoxicity Assay

Ricin and abrin are highly potent plant-derived toxins, categorized as type II ribosome-inactivating proteins. High toxicity, accessibility, and the lack of effective countermeasures make them potential agents in bioterrorism and biowarfare, posing significant threats to public safety. Despite the existence of many effective analytical strategies for detecting these two lethal toxins, current methods are often hindered by limitations such as insufficient sensitivity, complex sample preparation, and most importantly, the inability to distinguish between biologically active and inactive toxin. In this study, a cytotoxicity assay was developed to detect active ricin and abrin based on their potent cell-killing capability. Among nine human cell lines derived from various organs, HeLa cells exhibited exceptional sensitivity, with limits of detection reaching 0.3 ng/mL and 0.03 ng/mL for ricin and abrin, respectively. Subsequently, toxin-specific neutralizing monoclonal antibodies MIL50 and 10D8 were used to facilitate the precise identification and differentiation of ricin and abrin. The method provides straightforward and sensitive detection in complex matrices including milk, plasma, coffee, orange juice, and tea via a simple serial-dilution procedure without any complex purification and enrichment steps. Furthermore, this assay was successfully applied in the unambiguous identification of active ricin and abrin in samples from OPCW biotoxin exercises.

A Proof-of-Concept, Two-Tiered Approach for Ricin Detection Using Ambient Mass Spectrometry

Ricin is a naturally occurring, highly potent toxin native to castor bean plants that has recently been used as a biological weapon in cases of bioterrorism and suicide attempts. Difficulties with direct detection arise from large heterogeneities in ricin glycosylation, which leads to markedly different bioactivity, and the fact that carefully developed and laborious sample preparation steps are required to maintain the activity of the protein during analysis. Herein, we present an alternative, two-tiered approach to identify the presence of ricin by detecting ricinoleic acid and ricinine, which are co-extracted with the protein. This direct mass spectrometric-based technique takes as little as 2 minutes, and we determined its sensitivity to be in the parts-per-trillion range. Our method is applicable to paper substrates from suspected contaminated envelopes and biofluids from at-risk patients. The fact that prior sample preparations are not needed in this procedure means that analysis can be performed in the field for emergency cases.

Ricin is a naturally occurring, highly potent toxin native to castor bean plants that has recently been used as a biological weapon in cases of bioterrorism and suicide attempts.

Ultrasensitive On-Site Detection of Biological Active Ricin in Complex Food Matrices Based on Immunomagnetic Enrichment and Fluorescence Switch-On Nanoprobe

Ricin is a highly toxic protein largely existing in castor beans, which could be used as a warfare agent due to its unique properties. As a deadenylase, inactivation of ricin means a loss of its toxic threat. Therefore, developing simple, accurate, and sensitive on-site detection of biologically active ricin in wide types of complex matrices is most valuable. Here, antifouling polymer brush modified magnetic beads were prepared first and post modified with ricin monoclonal antibody (the MB@P(C-H)-mAb_ricin) to efficiently capture ricin from various foods and biological matrices. Active ricin obtained in this manner were sequentially determined by a new designed AuNP/QDs nanoassembly. In this double strand oligodeoxynucleotides (dsODN) linked core-satellite nanoprobe, the fluorescence of satellite QDs was extensively quenched by AuNPs due to the dipole-metal interaction. Active ricin can react with its specific depurination substrates which had been inserted in the dsODN linkers. This reaction would trigger the separation of QDs from Au cores by cutting multiple adenines, and then result in the restoration of QDs fluorescence. By coupling with the magnetic enrichment, this AuNP/QDs nanoprobe provided a qualitative result for active ricin in the range from 10.0 to 100.0 ng mL^-1 with the limit of detection as low as 7.46 ng mL^-1. Compared with previously proposed methods, this on-site detection strategy offered an easy to handle on-site test for trace amounts of active ricin in a wide range of complex matrices.

Fast on-Site Visual Detection of Active Ricin Using a Combination of Highly Efficient Dual-Recognition Affinity Magnetic Enrichment and a Specific Gold Nanoparticle Probe

Ricin, a highly toxic protein, is a controlled substance by both the Chemical Weapons Convention (CWC) and the Biological Weapons Convention (BWC). Therefore, fast precaution of potential ricin toxin plays an important role in national security and public safety. Herein, a simple, sensitive, and accurate visual detection of active ricin in complex samples is presented by combining magnetic affinity enrichment with a specific gold nanoparticle (AuNP) probe. In the first step, a dual-recognition magnetic absorbent was fabricated by simultaneously incorporating two different affinity ligands (concanavalin A and galactosamine) on low-foul polymer brushes grafted magnetic beads, which showed remarkable multivalent synergy binding capacity for ricin even under complex interfering environments. Subsequently, a homoadenine-constituted oligodeoxynucleotide named poly(21dA) was conjugated to AuNPs (the poly(21dA)-AuNPs), which served as a specific depurination substrate of active ricin. Coralyne can trigger the intact poly(21dA)-AuNPs aggregate by forming a non-Watson-Crick homoadenine/coralyne complex, but the poly(21dA)-AuNPs after reacting with active ricin failed to form this complex due to the loss of adenines. Based on these facts, active ricin can be detected as low as 12.5 ng mL^-1 with the naked eyes. This detection strategy could be well-applied in various ricin-spiked complex matrices. The features such as ready operation, facile readout, and easy accessibility make the assay a better choice for fast on-site active ricin detection.

A Cell-Based Fluorescent Assay to Detect the Activity of AB Toxins that Inhibit Protein Synthesis

Many AB toxins elicit a cytotoxic effect involving the inhibition of protein synthesis. In this chapter, we describe a simple cell-based fluorescent assay to detect and quantify the inhibition of protein synthesis. The assay can also identify and characterize toxin inhibitors.

New Surface-Enhanced Raman Sensing Chip Designed for On-Site Detection of Active Ricin in Complex Matrices Based on Specific Depurination

Quick and accurate on-site detection of active ricin has very important realistic significance in view of national security and defense. In this paper, optimized single-stranded oligodeoxynucleotides named poly(21dA), which function as a depurination substrate of active ricin, were screened and chemically attached on gold nanoparticles (AuNPs, ∼100 nm) via the Au-S bond [poly(21dA)-AuNPs]. Subsequently, poly(21dA)-AuNPs were assembled on a dihydrogen lipoic-acid-modified Si wafer (SH-Si), thus forming the specific surface-enhanced Raman spectroscopy (SERS) chip [poly(21dA)-AuNPs@SH-Si] for depurination of active ricin. Under optimized conditions, active ricin could specifically hydrolyze multiple adenines from poly(21dA) on the chip. This depurination-induced composition change could be conveniently monitored by measuring the distinct attenuation of the SERS signature corresponding to adenine. To improve sensitivity of this method, a silver nanoshell was deposited on post-reacted poly(21dA)-AuNPs, which lowered the limit of detection to 8.9 ng mL(-1). The utility of this well-controlled SERS chip was successfully demonstrated in food and biological matrices spiked with different concentrations of active ricin, thus showing to be very promising assay for reliable and rapid on-site detection of active ricin.

Development of an ELISA microarray assay for the sensitive and simultaneous detection of ten biodefense toxins

Plant and microbial toxins are considered bioterrorism threat agents because of their extreme toxicity and/or ease of availability. Additionally, some of these toxins are increasingly responsible for accidental food poisonings. The current study utilized an ELISA-based protein antibody microarray for the multiplexed detection of ten biothreat toxins, botulinum neurotoxins (BoNT) A, B, C, D, E, F, ricin, shiga toxins 1 and 2 (Stx), and staphylococcus enterotoxin B (SEB), in buffer and complex biological matrices. The multiplexed assay displayed a sensitivity of 1.3 pg mL(-1) (BoNT/A, BoNT/B, SEB, Stx-1 and Stx-2), 3.3 pg mL(-1) (BoNT/C, BoNT/E, BoNT/F) and 8.2 pg mL(-1) (BoNT/D, ricin). All assays demonstrated high accuracy (75-120 percent recovery) and reproducibility (most coefficients of variation <20%). Quantification curves for the ten toxins were also evaluated in clinical samples (serum, plasma, nasal fluid, saliva, stool, and urine) and environmental samples (apple juice, milk and baby food) with overall minimal matrix effects. The multiplex assays were highly specific, with little cross-reactivity observed between the selected toxin antibodies. The results demonstrate a multiplex microarray that improves current immunoassay sensitivity for biological warfare agents in buffer, clinical, and environmental samples.

Review of the inhibition of biological activities of food-related selected toxins by natural compounds

There is a need to develop food-compatible conditions to alter the structures of fungal, bacterial, and plant toxins, thus transforming toxins to nontoxic molecules. The term 'chemical genetics' has been used to describe this approach. This overview attempts to survey and consolidate the widely scattered literature on the inhibition by natural compounds and plant extracts of the biological (toxicological) activity of the following food-related toxins: aflatoxin B1, fumonisins, and ochratoxin A produced by fungi; cholera toxin produced by Vibrio cholerae bacteria; Shiga toxins produced by E. coli bacteria; staphylococcal enterotoxins produced by Staphylococcus aureus bacteria; ricin produced by seeds of the castor plant Ricinus communis; and the glycoalkaloid α-chaconine synthesized in potato tubers and leaves. The reduction of biological activity has been achieved by one or more of the following approaches: inhibition of the release of the toxin into the environment, especially food; an alteration of the structural integrity of the toxin molecules; changes in the optimum microenvironment, especially pH, for toxin activity; and protection against adverse effects of the toxins in cells, animals, and humans (chemoprevention). The results show that food-compatible and safe compounds with anti-toxin properties can be used to reduce the toxic potential of these toxins. Practical applications and research needs are suggested that may further facilitate reducing the toxic burden of the diet. Researchers are challenged to (a) apply the available methods without adversely affecting the nutritional quality, safety, and sensory attributes of animal feed and human food and (b) educate food producers and processors and the public about available approaches to mitigating the undesirable effects of natural toxins that may present in the diet.