Abrin Toxin Research Articles

Ultrafast protein digestion using an immobilized enzyme reactor following high-resolution mass spectrometry analysis for rapid identification of abrin toxin.

Abrin toxin, highly dangerous with an estimated human lethal dose of 0.1-1 μg per kg body weight, has attracted much attention regarding criminal and terroristic misuse over the past decade. Therefore, developing a rapid detection method for abrin toxin is of great significance in the field of biosecurity. In this study, based on the specific dissociation method of an immobilized enzyme reactor, the trypsin immobilized reactor Fe3O4@CTS-GA-Try was prepared to replace free trypsin, and the immobilized enzyme digestion process was systematically investigated and optimized by using bovine serum albumin as the simulant of abrin. After 5 min one-step denaturation and reduction, a satisfactory peptide number and coverage were yielded with only 15 s assisted by an ultrasound probe to identify model proteins. Subsequently, abrin was rapidly digested using the established method, resulting in a stable and highly reproducible characteristic peptide number of 39, which can be analyzed by nanoelectrospray ionization coupled with high-resolution mass spectrometry. With the acquisition mode of full MS scan coupled with PRM, not only MS spectroscopy of total abrin peptides but also the corresponding MS/MS spectroscopy of specific abrin peptides can achieve the characteristic detection of abrin toxin and its different isoforms in less than 10 minutes, with high repeatability. This assay provides a universal platform and has great potential for the development of on-site detection and rapid mass spectrometric analysis techniques for macromolecular protein toxins and can further be applied to the integrated detection of chemical and biological agents.

Differential toxicity of abrin in human cell lines of different organ origin

Abrus precatorius is a highly toxic seed containing the poison abrin. Similar in properties to ricin, this toxin binds to ribosomes causing cessation of protein synthesis and cell death. With an estimated human lethal dose of 0.1–1 μg/kg, it has been the cause of fatalities due to accidental and intentional ingestion. In present study, we profiled seven human cell lines of different organ origin, for their sensitivity against abrin toxicity. These cell lines are, A549, COLO 205, HEK 293, HeLa, Hep G2, Jurkat, SH-SY5Y and derived from lung, intestine, kidney, cervix, liver, immune and nervous system respectively. MTT, NR, CVDE and LDH assays have been used to determine their response against abrin toxin. Among these cell lines A549 was the most sensitive cell line while Hep G2 was found least sensitive cell lines. Hep G2 cells are shown to have mitochondrial resistance and delayed generation of oxidative stress compared to A549 cells. Remarkable variation in sensitivity against abrin toxicity prompted the evaluation of Bcl2, Bax and downstream caspases in both cells. Difference in Bcl2 level has been shown to play important role in variable sensitivity. Findings of present study are helpful for selection of suitable cellular model for toxicity assessment and antidote screening.

Development and Evaluation of an Immuno-MALDI-TOF Mass Spectrometry Approach for Quantification of the Abrin Toxin in Complex Food Matrices.

The toxin abrin found in the seeds of Abrus precatorius has attracted much attention regarding criminal and terroristic misuse over the past decade. Progress in analytical methods for a rapid and unambiguous identification of low abrin concentrations in complex matrices is essential. Here, we report on the development and evaluation of a MALDI-TOF mass spectrometry approach for the fast, sensitive and robust abrin isolectin identification, differentiation and quantification in complex food matrices. The method combines immunoaffinity-enrichment with specific abrin antibodies, accelerated trypsin digestion and the subsequent MALDI-TOF analysis of abrin peptides using labeled peptides for quantification purposes. Following the optimization of the workflow, common and isoform-specific peptides were detected resulting in a ~38% sequence coverage of abrin when testing ng-amounts of the toxin. The lower limit of detection was established at 40 ng/mL in milk and apple juice. Isotope-labeled versions of abundant peptides with high ionization efficiency were added. The quantitative evaluation demonstrated an assay variability at or below 22% with a linear range up to 800 ng/mL. MALDI-TOF mass spectrometry allows for a simple and fast (<5 min) analysis of abrin peptides, without a time-consuming peptide chromatographic separation, thus constituting a relevant alternative to liquid chromatography-tandem mass spectrometry.

CCD Based Detector for Detection of Abrin Toxin Activity.

Abrin is a highly potent and naturally occurring toxin produced in the seeds of Abrus precatorius (Rosary Pea) and is of concern as a potential bioterrorism weapon. There are many rapid and specific assay methods to detect this toxic plant protein, but few are based on detection of toxin activity, critical to discern biologically active toxin that disables ribosomes and thereby inhibits protein synthesis, producing cytotoxic effects in multiple organ systems, from degraded or inactivated toxin which is not a threat. A simple and low-cost CCD detector system was evaluated with colorimetric and fluorometric cell-based assays for abrin activity; in the first instance measuring the abrin suppression of mitochondrial dehydrogenase in Vero cells by the MTT-formazan method and in the second instance measuring the abrin suppression of green fluorescent protein (GFP) expression in transduced Vero and HeLa cells. The limit of detection using the colorimetric assay was 10 pg/mL which was comparable to the fluorometric assay using HeLa cells. However, with GFP transduced Vero cells a hundred-fold improvement in sensitivity was achieved. Results were comparable to those using a more expensive commercial plate reader. Thermal inactivation of abrin was studied in PBS and in milk using the GFP-Vero cell assay. Inactivation at 100 °C for 5 min in both media was complete only at the lowest concentration studied (0.1 ng/mL) while treatment at 63 °C for 30 min was effective in PBS but not milk.

One step Purification and Characterisation of Abrin Toxin from Abrus Precatorius Seeds

Abrin is a plant toxin obtained from Abrus precatorius seeds. It belongs to the type II ribosomal inactivating proteins (RIPs) consisting of two chains namely, catalytically active A chain and sugar binding B chain linked by a single disulphide bond. Due to high toxicity of abrin, its exposure or consumption can lead to serious public health problems. In the present work, we have extracted and purified the abrin toxin from Abrus precatorius seeds. The toxin was purified using a single step anion exchange chromatography. The purified protein was characterized by SDS-PAGE and MALDI- TOF to confirm its purity. The toxicity of purified abrin toxin was also confirmed by injecting the toxin in mice. The purified protein was further used to raise antibodies in mice and characterized by indirect Enzyme Linked Immunosorbent Assay. The results of present study established the use of single step ion exchange chromatography to purify abrin toxin for further development of its detection system.

Neutrophil mediated inflammatory lung damage following single Sub lethal inhalation exposure to plant protein toxin abrin in mice

Abrin, a highly toxic plant protein found in the seeds of Abrus precatorius plant. To date, there is no antidote against abrin intoxication. Abrin is toxic by all routes of exposure, but inhalation exposure is the most toxic of all routes. Present study was conducted to evaluate the acute inhalation toxicity of aerosolized abrin in BALB/c mice. Animals were exposed to 0.2 and 0.8LC50 doses of aerosolized abrin and evaluated at 1 and 3 day post toxin exposure. Bronchoalveolar fluid from lungs was used for evaluation of markers for lung injury. Abrin inhalation exposure caused rise in LDH activity, protein content, increase in β-glucuronidase and myeloperoxidase activity. Increase in CRP activity, MMP-9 expression and recruitment of CD11b + inflammatory cells in lungs was also observed which was associated with severe inflammation and lung damage. Histopathological findings support the lung damage after abrin exposure. Our results indicate lung injury after single aerosol inhalation exposure, associated with excessive inflammation, oxidative stress, pulmonary edema followed by lung damage. These results could supplement treatment strategies and planning for therapeutic approaches against aerosolized abrin inhalation exposure.

Dose dependent acute toxicity of abrin in Balb/c mice after intraperitoneal administration

Abrin toxin is one of the most potent and deadly plant toxin obtained from the seeds of Abrus precatorious. It is more toxic than ricin which is classified as Schedule 1 agent by OPCW and Category B bioterrorism agent by Centre for Disease Control (CDC). Dose dependent acute toxicity of abrin is still a matter of investigation. The present study was carried out to assess the toxicity of abrin from sub lethal to supralethal doses (0.5X, 1X, 2X and 5XLD50) after intraperitoneal administration. After 8 and 24h of abrin exposure, hematological, biochemical, inflammatory and oxidative stress associated parameters were analyzed. Liver histology was also done to analyze the effect of abrin. Abrin exerts its toxicity in a dose and time dependent manner. Increases in neutrophil counts, lipid peroxidation with decreased lymphocyte counts, are the initiating factor irrespective of time and dose. At higher doses of abrin there was a decrease in hemoglobin level and RBC count which is reflected by increased levels of serum ammonia and bilirubin. Neutrophil infiltration in the liver and lipid peroxidation cause liver toxicity (increased production of ALT and ALP); oxidative stress (depletion of GSH and total antioxidant status); inflammation (increased production of TNF-α and IFN-γ). Further, at higher doses of abrin, intensity of oxidative stress, inflammation and liver toxicity are more pronounced which may have been maintained by the self-sustaining loop of toxicity leading to death of the animals.

Novel Phage Display-Derived Anti-Abrin Antibodies Confer Post-Exposure Protection against Abrin Intoxication.

Abrin toxin is a type 2 ribosome inactivating glycoprotein isolated from the seeds of Abrus precatorius (jequirity pea). Owing to its high toxicity, relative ease of purification and accessibility, it is considered a biological threat agent. To date, there is no effective post-exposure treatment for abrin poisoning and passive immunization remains the most effective therapy. However, the effectiveness of anti-abrin monoclonal antibodies for post-exposure therapy following abrin intoxication has not been demonstrated. The aim of this study was to isolate high affinity anti-abrin antibodies that possess potent toxin-neutralization capabilities. An immune scFv phage-display library was constructed from an abrin-immunized rabbit and a panel of antibodies (six directed against the A subunit of abrin and four against the B subunit) was isolated and expressed as scFv-Fc antibodies. By pair-wise analysis, we found that these antibodies target five distinct epitopes on the surface of abrin and that antibodies against all these sites can bind the toxin simultaneously. Several of these antibodies (namely, RB9, RB10, RB28 and RB30) conferred high protection against pulmonary intoxication of mice, when administered six hours post exposure to a lethal dose of abrin. The data presented in this study demonstrate for the first time the efficacy of monoclonal antibodies in treatment of mice after pulmonary intoxication with abrin and promote the use of these antibodies, one or several, for post-exposure treatment of abrin intoxication.

Rapid Detection of Abrin Toxin and Its Isoforms in Complex Matrices by Immuno-Extraction and Quantitative High Resolution Targeted Mass Spectrometry

Abrin expressed by the tropical plant Abrus precatorius is highly dangerous with an estimated human lethal dose of 0.1-1 μg/kg body weight. Due to the potential misuse as a biothreat agent, abrin is in the focus of surveillance. Fast and reliable methods are therefore of great importance for early identification. Here, we have developed an innovative and rapid multiepitope immuno-mass spectrometry workflow which is capable of unambiguously differentiating abrin and its isoforms in complex matrices. Toxin-containing samples were incubated with magnetic beads coated with multiple abrin-specific antibodies, thereby concentrating and extracting all the isoforms. Using an ultrasonic bath for digestion enhancement, on-bead trypsin digestion was optimized to obtain efficient and reproducible peptide recovery in only 30 min. Improvements made to the workflow reduced total analysis time to less than 3 h. A large panel of common and isoform-specific peptides was monitored by multiplex LC-MS/MS through the parallel reaction monitoring mode on a quadrupole-Orbitrap high resolution mass spectrometer. Additionally, absolute quantification was accomplished by isotope dilution with labeled AQUA peptides. The newly established method was demonstrated as being sensitive and reproducible with quantification limits in the low ng/mL range in various food and clinical matrices for the isoforms of abrin and also the closely related, less toxic Abrus precatorius agglutinin. This method allows for the first time the rapid detection, differentiation, and simultaneous quantification of abrin and its isoforms by mass spectrometry.

Evaluation of abrin induced nephrotoxicity by using novel renal injury markers

Abrin is a potent plant toxin analogous to ricin that is derived from the seeds of Abrus precatorius plant. It belongs to the family of type II ribosome-inactivating proteins and causes cell death by irreversibly inactivating ribosomes through site-specific depurination. In this study we examined the in vivo nephrotoxicity potential of abrin toxin in terms of oxidative stress, inflammation, histopathological changes and biomarkers of kidney injury. Animals were exposed to 0.5 and 1.0 LD50 dose of abrin by intraperitoneal route and observed for 1, 3, and 7 day post-toxin exposure. Depletion of reduced glutathione and increased lipid peroxidation levels were observed in abrin treated mice. In addition, abrin also induced inflammation in the kidneys as observed through expression of MMP-9 and MMP-9/NGAL complex in abrin treated groups by using zymography method. Nephrotoxicity was also evaluated by western blot analysis of kidney injury biomarkers including Clusterin, Cystatin C and NGAL, and their results indicate severity of kidney injury in abrin treated groups. Kidney histology confirmed inflammatory changes due to abrin. The data generated in the present study clearly prove the nephrotoxicity potential of abrin.

A novel recombinant vaccine protecting mice against abrin intoxication

Abrin toxin (AT) consisting of an A chain and a B chain is a potential agent for bioterrorism and an effective vaccine against AT poisoning is urgently required. In this study, AT B chain (ATB) was successfully expressed in the Escherichia coli (E. coli) and assessed the protection capacity against AT intoxication. The recombinant ATB (rATB) subunit induces a good immune response after 4 immunizations. All BALB/c mice immunized intraperitoneally (i.p.) with the purified rATB protein survived after challenged with 5 × LD50 of AT. Transfusion of sera from immunized mice provided passive protection in naive mice. Furthermore, histological findings showed that immunization with rATB decreased the severity of toxin-related tissue damage. This work indicates that the rATB protein may be a promising vaccine candidate against human exposure to AT.

Truncated abrin A chain expressed in Escherichia coli: A promising vaccine candidate

Abrin toxin (AT) is a highly potent toxin, and is classified as one of the most important biological warfare and bioterrorism agents. There is currently no approved vaccine for AT. Therefore, the development of an effective vaccine is important in the prevention of intoxication by abrin. In this study, five vectors containing different gene of truncated abrin toxin A chain (tATA) fragments were constructed, and two of them (tATA11-126, tATA41-188) were successfully expressed as a soluble form in E.coli strain. Both of the two tATA retained most of their immunogenicity with either low or no toxic effects as determined by both in vitro and in vivo assays. They were used to immunize BALB/c mice three times at an interval of three weeks apart. As a result, the tATA1 can elicite 80% protective efficacy against i.p. challenge of 5 × LD50 of abrin, and the tATA4 provides a better protection, which can elicite 100% protective efficacy against intraperitoneal challenge of 40 × LD50 of abrin. The superior fragment (tATA41-188) should be considered as a promising vaccine candidate for further investigations.

Plant toxin abrin induced oxidative stress mediated neurodegenerative changes in mice

Abrin is a potent plant toxin. It is a heterodimeric protein toxin which is obtained from the seeds of Abrus precatorius plant. At cellular level abrin causes protein synthesis inhibition by removing the specific adenine residue (A4324) from the 28s rRNA of the 60S – ribosomal subunit. In the present study we investigated the role of oxidative stress in neurotoxic potential and demyelinating effects of abrin on brain. The mechanism by which abrin induces oxidative damage and toxicity in brain are relatively unknown. Animals were exposed to 0.4 and 1.0 LD50 abrin dose by intraperitoneal route and observed for 1 and 3 day post-toxin exposure. Oxidative stress occurred in brain due to abrin was confirmed in terms of increased reactive oxygen species (ROS), glutathione depletion and increased lipid peroxidation. Significant increase in blood and brain ROS was observed at day 3, 1 LD50. Abrin induced changes in the neurotransmitters (5-hydroxy tryptamine, norepinephrine, dopamine and monoamine oxidase) levels were evaluated by spectroflourometry. Increase in the levels of 5-HT and NE was observed after abrin exposure. MAO activity was found to be decreased in abrin exposed animals compared to control. Significant inhibition in the activity of acetylcholine esterase enzyme in brain and serum was reported for both the doses and time points. Western blot analysis of iNOS expression indicated that abrin treatment resulted in dose and time dependent increase. Furthermore, protein expression of myelin basic protein (MBP) was down regulated in a dose and time dependent manner. Brain histopathology was carried out and cortical brain region showed demyelination after abrin exposure. Results confirmed that abrin poisoning leads to neurodegeneration and neurotoxicity mediated through oxidative stress, AChE inhibition, lipid peroxidation and decrease in MBP levels.

A Case of Abrin Toxin Poisoning, Confirmed via Quantitation of l-Abrine (N-Methyl-l-Tryptophan) Biomarker

The seeds of Abrus precatorius contain the highly toxic plant protein abrin. There is no antidote for abrin poisoning. Management, largely supportive, may consist of administering intravenous fluids, anti-emetics, and activated charcoal depending on the time of exposure. We report the presentation of a single case of unintentional abrin poisoning confirmed by the quantitation of L-abrine biomarker. A previously healthy 22-month-old, 11.5-kg female presented to the hospital after ingesting approximately 20 rosary peas (A. precatorius) sold as a "peace bracelet". Her primary manifestations were episodes of forceful emesis that included food particles progressing to clear gastric fluid. The patient was tachycardic (HR = 134 bpm) but had brisk capillary refill and normal blood pressure (96/60 mmHg). Laboratory testing revealed elevated blood urea nitrogen (16 mg/dL) and serum creatinine (0.4 mg/dL). In the emergency department, the patient was resuscitated with 40 mL/kg normal saline via peripheral IV and received ondansetron (0.15 mg/kg IV) to control retching. The patient was discharged well 24 h after the ingestion. This is the first case of human abrin toxin poisoning confirmed by the quantitation of L-abrine as a biomarker. Quantifying the levels of abrin toxin in the body after exposure can help clinicians make informed decisions when managing patients with symptomatic exposures to seeds of A. precatorius.

A recombinant chimeric protein containing B chains of ricin and abrin is an effective vaccine candidate

Both ricin toxin (RT) and abrin toxin (AT) are 2 important toxin agents as potantial bioweapons. A dual subunit vaccine against RT and AT exposure is a promising option for developing prophylactic vaccination. In this study, we constructed a dual vaccine with RT B chain and AT B chain named RTB-ATB. The RTB-ATB chimeric protein was expressed in Escherichia coli (E. coli), and the purified protein was used to evaluate the immune response by a 2 × 2 × 2 × 2 factorial design. The main effects included dose of RTB-ATB, route of immunization injection, immunization time interval, and dose of native toxins challenge. For 2 × LD50 challenge of RT or AT, 100% of the RTB-ATB immunized mice survived and regained or exceeded their initial weights within 10 days. For 4 × LD50 challenge, different routes of immunization injection caused significant difference (P < 0.05), intraperitoneal (i.p.) administration of immunogen protected mice better than the subcutaneous (s.c.) administration. In conclusion, when administered i.p. to mice with 25 μg per mouse and immunization time interval Π in the absence of adjuvant, the chimeric protein elicited a stronger immune response and protected the animals from a dose of native toxins which was 4 times higher than their LD50 in unvaccinated mice. Besides, the RTB-ATB chimeric protein could induce specific neutralizing antibodies against these 2 toxins. We anticipate that this study will open new possibilities in the preparation of RTB-ATB dual subunit vaccine against the exposure to deadly RT and AT.

Abrin Immunotoxin: Targeted Cytotoxicity and Intracellular Trafficking Pathway

BackgroundImmunotherapy is fast emerging as one of the leading modes of treatment of cancer, in combination with chemotherapy and radiation. Use of immunotoxins, proteins bearing a cell-surface receptor-specific antibody conjugated to a toxin, enhances the efficacy of cancer treatment. The toxin Abrin, isolated from the Abrus precatorius plant, is a type II ribosome inactivating protein, has a catalytic efficiency higher than any other toxin belonging to this class of proteins but has not been exploited much for use in targeted therapy.MethodsProtein synthesis assay using 3[H] L-leucine incorporation; construction and purification of immunotoxin; study of cell death using flow cytometry; confocal scanning microscopy and sub-cellular fractionation with immunoblot analysis of localization of proteins.ResultsWe used the recombinant A chain of abrin to conjugate to antibodies raised against the human gonadotropin releasing hormone receptor. The conjugate inhibited protein synthesis and also induced cell death specifically in cells expressing the receptor. The conjugate exhibited differences in the kinetics of inhibition of protein synthesis, in comparison to abrin, and this was attributed to differences in internalization and trafficking of the conjugate within the cells. Moreover, observations of sequestration of the A chain into the nucleus of cells treated with abrin but not in cells treated with the conjugate reveal a novel pathway for the movement of the conjugate in the cells.ConclusionsThis is one of the first reports on nuclear localization of abrin, a type II RIP. The immunotoxin mAb F1G4-rABRa-A, generated in our laboratory, inhibits protein synthesis specifically on cells expressing the gonadotropin releasing hormone receptor and the pathway of internalization of the protein is distinct from that seen for abrin.

Assessing Mutagenicity of Methanolic Exteract of Abrus precatorius Seeds using Ames Bioassay

Abrus precatorius seeds contain toxin abrin which inhibits protein synthesis and leading to cell death. This plant has Cytotoxic and pro-apoptotic effects. So, in this study, mutagnicity of methanolic seed extract of this plant was investigated using Ames test. The seeds were powdered and then maceration extracted with methanol for 48 h. Extract was analyzed for aflatoxin B1 and histidine contamination with TLC and MIC determined by broth dilution method. The test was performed using strain TA100). The genotypes was confirmed by presence of hisG46 Mutation, R factor plasmid and crystal violet sensitivity test. TA100 carries mutations in genes involved in histidine synthesis, so that it requires histidine for growth. Tests were performed with 4 concentrations 0.2, 0.3, 0.4 and 0.5 mg mL-1 (concentrations less than 0.1 MIC), negative control (methanol), positive control (NaN3), in the absence and presence of a rat liver metabolizing system. No increase in bacteria growth in the histidine-free medium was observed. In conclusion, Abrus precatorius was not genotoxic in Ames test. However, it is likely that the Abrus precatorius maybe inducing gonotoxicity at high concentrations. Thus, it is necessary to pay close attention while utilizing its products.

Transcriptomic profile of host response in mouse brain after exposure to plant toxin abrin

Abrin toxin is a plant glycoprotein, which is similar in structure and properties to ricin and is obtained from the seeds of Abrus precatorius (jequirity bean). Abrin is highly toxic, with an estimated human fatal dose of 0.1–1μg/kg, and has caused death after accidental and intentional poisoning. Abrin is a potent biological toxin warfare agent. There are no chemical antidotes available against the toxin. Neurological symptoms like delirium, hallucinations, reduced consciousness and generalized seizures were reported in human poisoning cases. Death of a patient with symptoms of acute demyelinating encephalopathy with gastrointestinal bleeding due to ingestion of abrin seeds was reported in India. The aim of this study was to examine both dose and time-dependent transcriptional responses induced by abrin in the adult mouse brain. Mice (n=6) were exposed to 1 and 2 LD50 (2.83 and 5.66μg/kg respectively) dose of abrin by intraperitoneal route and observed over 3 days. A subset of animals (n=3) were sacrificed at 1 and 2 day intervals for microarray and histopathology analysis. None of the 2 LD50 exposed animals survived till 3 days. The histopathological analysis showed the severe damage in brain and the infiltration of inflammatory cells in a dose and time dependent manner. The abrin exposure resulted in the induction of rapid immune and inflammatory response in brain. Clinical biochemistry parameters like lactate dehydrogenase, aspartate aminotransferase, urea and creatinine showed significant increase at 2-day 2 LD50 exposure. The whole genome microarray data revealed the significant regulation of various pathways like MAPK pathway, cytokine-cytokine receptor interaction, calcium signaling pathway, Jak-STAT signaling pathway and natural killer cell mediated toxicity. The comparison of differential gene expression at both the doses showed dose dependent effects of abrin toxicity. The real-time qRT-PCR analysis of selected genes supported the microarray data. This is the first report on host-gene response using whole genome microarray in an animal model after abrin exposure. The data generated provides leads for developing suitable medical counter measures against abrin poisoning.

Development of colloidal gold-based immunochromatographic assay for the rapid detection of ricin toxin in food samples

A rapid, sensitive immunochromatographic (IC) assay was developed to detect ricin toxin in assay buffer and food samples. The assay was based on the sandwich format using a monoclonal antibody (mAb) and a polyclonal antibody (pAb) of two distinct specificities. The ricin-containing sample was added to the membrane and allowed to react with pAb-coated particles. The mixture was then passed along the porous membrane by capillary action past the mAb in the detection zone, which would bind the particles that had ricin bound to their surfaces, giving a red colour within the detection zone with an intensity proportional to the ricin concentration. In the absence of ricin, no immunogold was bound to the solid-phase antibody. With this method, 30 ng/ml of ricin toxin was detected in less than 10 min, and the assay also showed no cross-reactivity with abrin toxin.

Two kinds of anti-ricin antibody and ricin interaction evaluated by biosensor based on imaging ellipsometry

In order to meet the requirements of antibody comparison and evaluation, the optimization for the surface modification, ligand immobilization, unspecific blocking and ligand–receptor interaction condition is introduced to the biosensor based on imaging ellipsometry (BIE), so that it may serve as an antibody screening platform to evaluate antibody–antigen interactions. Two kinds of anti-ricin antibody named pVHHS1 and 5S1R are immobilized in a patterned array format on the silicon surface modified with succinic anhydride, respectively, to form a sensing surface. Ricin and its similar toxin abrin as the reference in solution are delivered, respectively, on the patterned sensing surface for anti-ricin antibody and ricin interaction. The limit of detection value of ricin detected by pVHHS1 and 5S1R is obtained as 1μg/ml and 5ng/ml, respectively. Results show that pVHHS1 and 5S1R specifically bind with ricin but not with abrin, which is in accordance with ELISA's result.