Detection of ochratoxin A in porcine kidneys by a monoclonal antibody-based radioimmunoassay

Functionalized Parylene Films for Enhancement of Antibody Production by Hybridoma Cells

In this study, the influence of microenvironments on antibody production of hybridoma cells was analyzed using six types of functionalized parylene films, parylene-N and parylene-C (before and after UV radiation), parylene-AM, and parylene-H, and using polystyrene as a negative control. Hybridoma cells were cultured on modified parylene films that produced a monoclonal antibody against the well-known fungal toxin ochratoxin-A. Surface properties were analyzed for each parylene film, such as roughness, chemical functional groups, and hydrophilicity. The proliferation rate of the hybridoma cells was observed for each parylene film by counting the number of adherent cells, and the total amount of produced antibodies from different parylene films was estimated using indirect ELISA. In comparison with the polystyrene, the antibody-production by parylene-H and parylene-AM was estimated to be observed to be as high as 210-244% after the culture of 24 h. These results indicate that the chemical functional groups of the culture plate could influence antibody production. To analyze the influence of the microenvironments of the modified parylene films, we performed cell cycle analysis to estimate the ratio of the G0/G1, S, and G2/M phases of the hybridoma cells on each parylene film. From the normalized proportion of phases of the cell cycle, the difference in antibody production from different surfaces was considered to result from the difference in the proliferation rate of hybridoma cells, which occurred from the different physical and chemical properties of the parylene films. Finally, protein expression was analyzed using an mRNA array to determine the effect of parylene films on protein expression in hybridoma cells. The expression of three antibody production-related genes (CD40, Sox4, and RelB) was analyzed in hybridoma cells cultured on modified parylene films.

Recent Progress in Rapid Determination of Mycotoxins Based on Emerging Biorecognition Molecules: A Review

Mycotoxins are secondary metabolites produced by fungal species, which pose significant risk to humans and livestock. The mycotoxins which are produced from Aspergillus, Penicillium, and Fusarium are considered most important and therefore regulated in food- and feedstuffs. Analyses are predominantly performed by official laboratory methods in centralized labs by expert technicians. There is an urgent demand for new low-cost, easy-to-use, and portable analytical devices for rapid on-site determination. Most significant advances were realized in the field bioanalytical techniques based on molecular recognition. This review aims to discuss recent progress in the generation of native biomolecules and new bioinspired materials towards mycotoxins for the development of reliable bioreceptor-based analytical methods. After brief presentation of basic knowledge regarding characteristics of most important mycotoxins, the generation, benefits, and limitations of present and emerging biorecognition molecules, such as polyclonal (pAb), monoclonal (mAb), recombinant antibodies (rAb), aptamers, short peptides, and molecularly imprinted polymers (MIPs), are discussed. Hereinafter, the use of binders in different areas of application, including sample preparation, microplate- and tube-based assays, lateral flow devices, and biosensors, is highlighted. Special focus, on a global scale, is placed on commercial availability of single receptor molecules, test-kits, and biosensor platforms using multiplexed bead-based suspension assays and planar biochip arrays. Future outlook is given with special emphasis on new challenges, such as increasing use of rAb based on synthetic and naïve antibody libraries to renounce animal immunization, multiple-analyte test-kits and high-throughput multiplexing, and determination of masked mycotoxins, including stereoisomeric degradation products.

Ochratoxin a: general overview and actual molecular status

Ochratoxin A (OTA) is a mycotoxin produced by several species of Aspergillus and Penicillium fungi that structurally consists of a para-chlorophenolic group containing a dihydroisocoumarin moiety that is amide-linked to L-phenylalanine. OTA is detected worldwide in various food and feed sources. Studies show that this molecule can have several toxicological effects such as nephrotoxic, hepatotoxic, neurotoxic, teratogenic and immunotoxic. A role in the etiology of Balkan endemic nephropathy and its association to urinary tract tumors has been also proved. In this review, we will explore the general aspect of OTA: physico-chemical properties, toxicological profile, OTA producing fungi, contaminated food, regulation, legislation and analytical methods. Due to lack of sufficient information related to the molecular background, this paper will discuss in detail the recent advances in molecular biology of OTA biosynthesis, based on information and on new data about identification and characterization of ochratoxin biosynthetic genes in both Penicillium and Aspergillus species. This review will also cover the development of the molecular methods for the detection and quantification of OTA producing fungi in various foodstuffs.

Enzyme-linked immunosorbent assay and colloidal gold immunoassay for ochratoxin A: investigation of analytical conditions and sample matrix on assay performance

A polyclonal antibody against ochratoxin A (OTA) was produced from rabbits immunized with the OTA-BSA conjugate. A competitive direct enzyme-linked immunosorbent assay (cdELISA) and a membrane-base colloidal gold immunoassay in flow-through format were developed for the rapid detection of OTA in various food matrices. In the cdELISA, the concentration causing 50% inhibition was 0.07 ng mL(-1), and the effects of different chemical conditions (ionic strength, pH value, and organic solvent) were studied. The sensitivity of the assay was higher than those previously reported. A simple, rapid, and efficient extraction method was developed and 74-110% recoveries of spiked samples were obtained. Fifty percent methanol extracts of some food samples such as barley, wheat, oat, corn, rice, and raisins could be analyzed directly by immunoassay after dilution in PBS; grape juice and beer samples could be analyzed directly after dilution with PBS; for coffee samples, a more complex method was used to remove the matrix effect effectively. Membrane-based colloidal gold immunoassays had a visual detection limit of 1.0 ng mL(-1) for OTA with a detection time of less than 10 min. For the validation of the cdELISA and membrane-based colloidal gold immunoassay, samples were analyzed by high-performance liquid chromatography. The correlation between data obtained using the microwell assay and HPLC was good (R2 = 0.984). The developed immunoassay methods are suitable for the rapid quantitative or qualitative determination of OTA in food samples.

Production and characterization of monoclonal antibodies against ochratoxin B

Monoclonal antibodies against ochratoxin B (OTB) were generated by immunizing Balb/c mice with OTB conjugated to keyhole limpet hemocyanin (KLH) via carbodiimide reactions with CHMC and EDAC. A stable hybridoma cell line 2F1.E10 was produced by fusion of murine splenocytes and myeloma cells. The obtained antibodies were characterized using an indirect competitive ELISA. The detection limit was calculated (27+/-2 nM OTB) and 50% binding inhibition was reached at 500 nM free OTB. A low cross-reactivity to ochratoxin A (OTA) of 3.3% and no cross-reactivities to either coumarin or DL-phenylalanine were observed, suggesting a highly specific OTB antibody. The antibody type was identified as IgG class 1 with the light chain being of the kappa configuration. These antibodies can be used in an indirect competitive ELISA to detect OTB in the nanomolar to micromolar concentration range and may be useful for the analysis of contaminated food items.

Development of immunosensor based on OWLS technique for determining Aflatoxin B1 and Ochratoxin A

Mycotoxins are toxic secondary metabolites produced by a number of different fungi, and can be present in a wide range of food and feed commodities including cereal grains, oil seeds, dried fruits, apple juice, wine and meat products from animals fed contaminated meal. Many mycotoxins are highly resistant, and survive food processing, and therefore enter the food chain and provide a threat to human health. The optical waveguide lightmode spectroscopy (OWLS) technique has been applied to the detection of Aflatoxin and Ochratoxin in both competitive and in direct immunoassays. After immobilizing the antibody or antigen conjugate for the direct or indirect measurement, respectively, the sensor chip was used in flow-injection analyser (FIA) system. When using non-competitive method, sensor responses were obtained first only at analyte concentrations of 5-10 ng ml(-1). In both cases, the responses were very unstable. For competitive sensor investigation with the sensitized chip first the optimal dilution rate of monoclonal antibodies was determined, for the measurement of Ochratoxin A and Aflatoxin B1 the monoclonal antibody stock solution was diluted to 1 microg ml(-1) and to a 1:400 dilution, respectively. During the competitive measurement standard solutions were mixed with monoclonal antibodies at the appropriate concentration, the mixture was incubated for 1 min and injected into the OWLS system. The sensitive detection range of the competitive detection method was between 0.5 and 10 ng ml(-1) in both cases. After the establishment of the indirect method, barley and wheat flour samples were measured, and the results were in good correlation by those measured by enzyme linked immuno-sorbent assay (ELISA). Regression coefficient between the two methods for Ochratoxin and Aflatoxin was determined as 0.96 and 0.89, respectively.

Monoclonal antibody technology for mycotoxins

Specific monoclonal antibodies (MABs) against aflatoxins, ochratoxin A, zearalenone, diacetoxyscirpenol and T-2 toxin have been prepared in various laboratories by the application of hybridoma technology to mycotoxins. These antibodies can be selected for sensitivity, reduced cross-reactivity, reliability and ease of production. When a suitable antibody is chosen it can then be used in a rapid immunological method such as an enzyme-linked or radio-immunoassay or immunoaffinity chromatography system. These assays have a lower limit of mycotoxin detection in the ng/ml range and have been applied to the determination of mycotoxins in samples such as maize, peanuts, peanut butter, milk and porcine kidneys. Using these immunoassay techniques, sample preparation has generally been simplified to a matter of solvent extraction of mycotoxins from the sample followed by dilution; under these conditions, levels of 1-5ug of mycotoxins/kg of sample can be found. The application and advantages of MABs to mycotoxins and the use of these antibodies in various assay techniques is discussed.

Analysis of serum and seminal plasma after feeding ochratoxin A with breeding boars

The aim of the experiment was to investigate whether or not ochratoxin A (OA) can be detected in seminal plasma after feeding the toxin in five and 10 times of the human tolerable daily intake with breeding boars and how toxin profiles of serum and seminal plasma correspond to each other. In addition to that, the effect of the toxin challenge on motility and longevity of boar semen was also evaluated. OA from samples was analyzed by microplate ELISA. Percentage of progressive motility of spermatozoa was determined initially and after 24, 48, 96, 120 and 144 h of storage. OA appeared in serum and seminal plasma shortly after toxin application had started. Significant reduction of initial motility and impaired longevity was observed after toxin withdrawal. These findings suggest that OA might have the potential to affect sperm production and semen quality of boars, but further research is required to elucidate whether OA exerts direct effect on germinal epithelium or disturbs sperm cell maturation only.

Chromatographic methods for the determination of ochratoxin A in animal and human tissues and fluids

This paper gives a review of chromatographic methods used for the determination of ochratoxin A (OA) in animal and human tissues and fluids. These methods are needed for example for monitoring studies of OA occurrence in the food chain and for studies dealing with the OA carry-over. In this survey, emphasis was given to HPLC methods. The review includes sampling, sample storage, extraction, spiking procedures, clean-up, detection and determination, and confirmation procedures. Emphasis is laid on special problems associated with the analysis of animal tissues and fluids.

Immunochemical detection of ochratoxin A in black Aspergillus strains

One hundred and fifty-seven strains belonging to Aspergillus section Nigri were tested for ochratoxin A production using three different methods: a relatively new immunochemical method based on an enzyme-linked immunosorbent assay (ELISA), thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). The monoclonal antibody-based ELISA technique was successfully used to screen for low levels of ochratoxin A in the black Aspergilli without concentrating the culture filtrates. The results were confirmed by TLC and HPLC analysis and chemical derivatization. These latter methods required concentrated filtrates. Ochratoxin A was detected in the culture filtrates of five of the 12 A. carbonarius strains, none of the 45 A. japonicus strains and three of the 100 isolates in the A. niger aggregate (A. foetidus, A. awamori and A. niger.

A new monoclonal antibody detecting ochratoxin A at the picogram level

A monoclonal antibody against ochratoxin A was produced after immunization of Balb/c mice with ochratoxin A-BSA. This antibody was of the IgG1 heavy chain subclass with a kappa type light chain. The 50% inhibition value was 0.45 ng ml-1 in a direct competitive ELISA and the detection limit was 42 pg ml-1. This antibody is very specific, cross-reacting only with ochratoxin B (9.3%).

Use of monoclonal antibodies for the analysis of mycotoxins

Hybridomas producing monoclonal antibodies against aflatoxin M1, ochratoxin A, zearalenone, T-2 toxin, diacetoxyscirpenol, 3-acetyl-deoxynivalenol, fusarenon X, and roridin A were developed after immunization of BALB/c mice and fusion of the splenocytes with myeloma cells. The antibodies were characterized in terms of immunoglobulin subclass, sensitivity, and specificity. The use of these antibodies in competitive enzyme immunoassays, either as microtiter plate assays or membrane-based quick tests, as well as for the production of immunoaffinity columns is described. The advantages and disadvantages of monoclonal antibodies compared to polyclonal antisera for the improvement of mycotoxin analysis are discussed.

Determination of ochratoxin A in urine and faeces of swine by high-performance liquid chromatography

Sensitive methods for the determination of ochratoxin A in urine and faeces of swine are described. The samples were extracted with chloroform at pH < 2, and the extracts were cleaned up by a combination of solid-phase extraction and liquid-liquid partition. High-performance liquid chromatography with fluorescence detection was used for detection and determination. The detection limits were 0.3 ng/ml for urine and 1.5 ng/g for faeces. Recoveries of ochratoxin A from spiked samples of urine and faeces were 93% and 60%, respectively. Because of the low detection limit and the fast and relatively easy performance, the method for the determination of ochratoxin A in urine proved suitable for the estimation of possible contamination of live animals.

Plasma ochratoxin A levels in three Swedish populations surveyed using an ion-pair HPLC technique

A new HPLC method for the analysis of ochratoxin A in plasma samples is described. The analysis is performed at an alkaline pH using an ion-pair technique, fluorescence detection at an excitation wavelength 380 nm, and an emission wavelength 420 nm. The detection and quantification limits are 0.02 ng and 0.05 ng ochratoxin A/ml plasma, respectively. The method was used to determine the ochratoxin A content of human plasma samples, collected in three districts of Sweden. The Visby district had a significantly higher proportion of ochratoxin A positive samples and higher levels than the other two districts--Uppsala and Ostersund. The calculated daily intake of ochratoxin A in the Visby district (0.35 ng/kg body weight), exceeds the lower tolerable daily intake (TDI) value suggested by Kuiper-Goodman and Scott (1989). The calculated daily intake by the population on the mainland of Sweden (0.04 ng/kg body weight) is below the proposed TDIs.

Modern immunoassays in meat-product analysis

The increased regulation of foodstuffs in modern society requires analytical methods which are easy to perform, sensitive, specific and relatively inexpensive. The basic antigen-antibody reaction provides means for very specific analytical procedures. Immunoassays are powerful analytical tools that permit the specific and rapid detection or measurement of antigens and haptens to which antibodies can be produced. Sensitive recognition of the interaction is made possible by labelling the analyte or antibody, mainly with radioisotope (RIA) and enzyme (ELISA). Wide applications of these modern immunoassays to food analysis began about 1980. The paper reviews investigations, where various types of RIA and ELISA were developed for the use in meat product analysis. Detection and determination of various meat species, non-meat proteins, microorganisms and bacterial toxins, drugs, anabolic hormones, pesticides, mycotoxins, and other contaminants in meat and meat products by the means of immunoassays is described. Now, the commercial kits are available for most of these compounds. They make possible to perform analysis in different laboratories under standard conditions. The reason of an enthusiasmic acceptance of this technology is related to its inherent specificity, high sensitivity, and the facility of application. In fact, immunoassays compete with other analytical technics. They have the advantage of economy when screening large numbers of samples.

Application of immunoassay in the food industry

Immunoassay techniques using the highly specific and sensitive nature of immunological reactions have been developed and applied in the food industry for detecting the naturally occurring constituents, antibiotics, pesticide residues, microorganisms, and fragments of microbial constituents related to food analysis, food production, food processing, and food safety. Both polyclonal and monoclonal antibodies are employed for the development of the various immunoassay systems, including enzyme-linked immunoassay (ELISA) and radioimmunoassay (RIA). Immunoassay techniques provide complementary and/or alternate approaches in reducing the use of costly, sophisticated equipment and analysis time, but still maintaining reliability and improved sensitivity. Immunoassay techniques in their most simple forms provide excellent screening tools to detect adulteration and contaminations qualitatively. The application of immunoassay techniques contributes tremendously to the quality control and safety of our food supply.

A sensitive enzyme-linked immunosorbent assay of ochratoxin A based on monoclonal antibodies

We prepared seven monoclonal antibodies (mAbs, OTA.1, 2, 3, 4, 5, 6 and 7) which were reacted with ochratoxin A (OTA), and have developed a specific and highly sensitive enzyme-linked immunosorbent assay (ELISA) for detection of OTA. The mAbs, OTA.1, 3, 4, 5 and 7, specifically reacted with OTA but much less with its analogs, ochratoxin B (OTB, about 1% of OTA) and ochratoxin alpha (OT alpha, less than 0.1% of OTA). One of the mAbs, OTA.2, equally reacted with OTA and OTB but hardly at all with (4R)-4-hydroxyochratoxin A or OT alpha (less than 0.1% of OTA). All of the mAbs reacted with ochratoxin C. None of the mAbs reacted with coumarin, 4-hydroxycoumarin or L-beta-phenylalanine. In the competitive ELISA with OTA.1 and OTA.7, the lowest detectable amount of standard OTA in solution was 50 pg/ml (2.5 pg per assay). This assay was applied for the quantitation of OTA added to chicken meat, wheat flour, porcine plasma and bovine serum. With minimal sample preparation, reliable and reproducible determinations were possible when concentrations of OTA were higher than 0.1-1 ng/g.