Detection and traceability of genetically modified organisms in the food production chain

Biosafety and toxicity assessment of transgenic cotton-harboring insecticide and herbicide tolerant genes on albino mice

Introduction

Genetic engineering has revolutionized agriculture by transforming biotic and abiotic stress-resistance genes in plants. The biosafety of GM crops is a major concern for consumers and regulatory authorities.

Methodology

A 14-week biosafety and toxicity analysis of transgenic cotton, containing 5 transgenes ((Cry1Ac, Cry2A, CP4 EPSPS, VIP3Aa, and ASAL)), was conducted on albino mice. Thirty mice were divided into three groups (Conventional, Non-transgenic, without Bt, and transgenic, containing targeted crop) according to the feed given, with 10 mice in each group, with 5 male and 5 female mice in each group.

Results

During the study, no biologically significant changes were observed in the non-transgenic and transgenic groups compared to the control group in any of the study's parameters i.e. increase in weight of mice, physiological, pathological, and molecular analysis, irrespective of the gender of the mice. However, a statistically significant change was observed in the hematological parameters of the male mice, while no such change was observed in the female study group mice. The expression analysis, however, of the TNF gene increases many folds in the transgenic group as compared to the non-transgenic and conventional groups.

Conclusion

Overall, no physiological, pathological, or molecular toxicity was observed in the mice fed with transgenic feed. Therefore, it can be speculated that the targeted transgenic crop is biologically safe. However, more study is required to confirm the biosafety of the product on the animal by expression profiling.

Checkmeat: A Review on the Applicability of Conventional Meat Authentication Techniques to Cultured Meat

The cultured meat industry is continuously evolving due to the collective efforts of cultured meat companies and academics worldwide. Though still technologically limited, recent reports of regulatory approvals for cultured meat companies have initiated the standards-based approach towards cultured meat production. Incidents of deception in the meat industry call for fool-proof authentication methods to ensure consumer safety, product quality, and traceability. The cultured meat industry is not exempt from the threats of food fraud. Meat authentication techniques based on DNA, protein, and metabolite fingerprints of animal meat species needs to be evaluated for their applicability to cultured meat. Technique-based categorization of cultured meat products could ease the identification of appropriate authentication methods. The combination of methods with high sensitivity and specificity is key to increasing the accuracy and precision of meat authentication. The identification of markers (both physical and biochemical) to differentiate conventional meat from cultured meat needs to be established to ensure overall product traceability. The current review briefly discusses some areas in the cultured meat industry that are vulnerable to food fraud. Specifically, it targets the current meat and meat product authentication tests to emphasize the need for ensuring the traceability of cultured meat.

A paired-end whole-genome sequencing approach enables comprehensive characterization of transgene integration in rice

Efficient, accurate molecular characterization of genetically modified (GM) organisms is challenging, especially for those transgenic events transferred with genes/elements of recipient species. Herein, we decipher the comprehensive molecular characterization of one novel GM rice event G281 which was transferred with native promoters and an RNA interference (RNAi) expression cassette using paired-end whole genome sequencing (PE-WGS) and modified TranSeq approach. Our results show that transgenes integrate at rice chromosome 3 locus 16,439,674 included a 36 bp deletion of rice genomic DNA, and the whole integration contains two copies of the complete transfer DNA (T-DNA) in a head-to-head arrangement. No unintended insertion or backbone sequence of the transformed plasmid is observed at the whole genome level. Molecular characterization of the G281 event will assist risk assessment and application for a commercial license. In addition, we speculate that our approach could be further used for identifying the transgene integration of cisgenesis/intragenesis crops since both ends of T-DNA in G281 rice were from native gene or elements which is similar with that of cisgenesis/intrasgenesis. Our results from the in silico mimicking cisgenesis event confirm that the mimic rice Gt1 gene insertion and its flanking sequences are successfully identified, demonstrating the applicability of PE-WGS for molecular characterization of cisgenesis/intragenesis crops.

Coupling paired-end whole-genome sequencing with droplet digital PCR enabled precise identification of a transgene insertion in the genetically modified rice event G281 on chromosome 3 and the potential for exploring the native gene integration.

Measuring the process and rate of exogenous DNA degradation during digestion in mice

This study aimed to perform qualitative and quantitative examination of DNA degradation during the digestion process in the mouse gut through PCR, qPCR and short tandem repeat (STR) analysis. Human blood leukocytes were gavaged into the digestive tract in mice. GAPDH, TH01, TPOX and D7S820 genes in the contents of the stomach and small intestine were analyzed with PCR and qPCR at various times pre- and post-gavage. Through STR analysis, 21 human genomic DNA loci were analyzed. The half-life of DNA degradation, and the relationship between the average peak area and digestion time were determined. The PCR results showed bands of amplified genes at pre-gavage (0 min) and post-gavage (40, 80 and 120 min) from the mouse stomach contents, whereas no DNA bands from small intestinal chyme were observed after gavage. The qPCR results revealed a significant decrease in DNA concentrations during 40–120 min in the mouse stomach after gavage. At 120 min, 85.62 ± 8.10% of the DNA was degraded, and the half-life of exogenous DNA degradation in the mouse stomach was 70.50 ± 5.46 min. At various digestion times, almost no target genes were detected in the mouse small intestinal chyme. STR analysis showed a decrease in allele numbers with bowel advancement in the small intestine in mice. The degradation of exogenous DNA was higher in the mouse stomach during the first 2 h, and almost complete degradation was observed within 40 min after entering the small intestine in mice.

Using Combined Methods of Genetic Mapping and Nanopore-Based Sequencing Technology to Analyze the Insertion Positions of G10evo-EPSPS and Cry1Ab/Cry2Aj Transgenes in Maize

The insertion position of the exogenous fragment sequence in a genetically modified organism (GMO) is important for the safety assessment and labeling of GMOs. SK12-5 is a newly developed transgenic maize line transformed with two trait genes [i.e., G10evo-5-enolpyrul-shikimate-3-phosphate synthase (EPSPS) and Cry1Ab/Cry2Aj] that was recently approved for commercial use in China. In this study, we tried to determine the insertion position of the exogenous fragment for SK12-5. The transgene-host left border and right border integration junctions were obtained from SK12-5 genomic DNA by using the thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR) and next-generation Illumina sequencing technology. However, a Basic Local Alignment Search Tool (BLAST) analysis revealed that the flanking sequences in the maize genome are unspecific and that the insertion position is located in a repetitive sequence area in the maize genome. To locate the fine-scale insertion position in SK12-5, we combined the methods of genetic mapping and nanopore-based sequencing technology. From a classical bulked-segregant analysis (BSA), the insertion position in SK12-5 was mapped onto Bin9.03 of chromosome 9 between the simple sequence repeat (SSR) markers umc2337 and umc1743 (26,822,048-100,724,531 bp). The nanopore sequencing results uncovered 10 reads for which one end was mapped onto the vector and the other end was mapped onto the maize genome. These observations indicated that the exogenous T-DNA fragments were putatively integrated at the position from 82,329,568 to 82,379,296 bp of chromosome 9 in the transgenic maize SK12-5. This study is helpful for the safety assessment of the novel transgenic maize SK12-5 and shows that the combined method of genetic mapping and the nanopore-based sequencing technology will be a useful approach for identifying the insertion positions of transgenic sequences in other GM plants with relatively large and complex genomes.

Willingness to Pay for Enhanced Mandatory Labelling of Genetically Modified Soybean Oil: Evidence from a Choice Experiment in China

This study investigates consumers’ preferences for mandatory labelling conveying the health and safety attributes of genetically modified soybean oil. The enhanced mandatory labelling includes allergen presence labelling, nutrient and compositional change labelling and traceability codes. The data were collected from a consumer survey in the eastern, central and western regions of China, with a total sample size of 804 respondents. We evaluated consumer willingness to pay (WTP) for enhanced mandatory labelling using a choice experiment approach. The results show that Chinese consumers are most favorable to traceability codes with a WTP of RMB 8.92, followed by allergen presences labelling, with RMB 6.57. Eastern consumers would like to pay a higher premium for the three types of enhanced mandatory labelling information, while central consumers only show a positive preference for traceability codes. The results imply that the efforts and policy strategies for enhanced mandatory labelling will benefit residents. Further studies can be expended to other genetically modified (GM) foods. This study provides information for the agency to improve mandatory GM food labelling management. This paper contributes to the growing body of the GM food literature by explicitly investigating consumer preference and WTP for mandatory labelling conveying the health and safety attributes of the GM foods.

Consumer perception, mandatory labeling, and traceability of GM soybean oil: evidence from Chinese urban consumers

Consumer preference for the mandatory labeling of genetically modified (GM) foods promotes public support for the implementation of GM food policies. This study analyzes consumers’ preference for the traceability of GM soybean oil. Survey data were collected through a self-administered survey covering 804 randomly sampled urban residents in the eastern, central and western regions of China. Using a logit model, this analysis examines the impacts of influential factors on consumers’ preference for traceability. The results show that about 56.5% of the respondents have a positive preference for the traceability of GM soybean oil. Factors increasing the preference for traceability include a better perception of the attributes of nutrition benefit and potential health risk, perceived inadequacy of simple mandatory labels, more attention paid to food labels, and distrust in the agencies overseeing GM food safety. Enhancing consumers’ perceptions of GM-related attributes and awareness of food labels will help improve the mandatory labeling management of GM foods.

Detection of genetically modified maize in Jordan

This study aimed to detect genetically modified maize (GMM) in seeds of eleven imported maize hybrids grown in Jordan. We used promoter 35 S and T-nos terminator for general screening of transgenic materials. Conventional PCR detected the specific events for the screening of Bt 11, MON810, and Bt176 events. Seeds of eleven maize hybrids samples showed a positive response to the 35 S promoter; nine out of eleven showed a positive response for T-nos terminator. Bt11 event was the most used in GMM seeds, where seven out of eleven samples showed positive results. Two out of eleven hybrids showed the presence of the Bt176 event; however, MON810 not detected in any of the tested hybrids. We studied the Bt11 event in imported GMM seeds in Jordan for the first time, reinforcing the need for a mandatory labeling system and a valid simple qualitative method in routine analysis of GMCs.

A simple and accurate PCR method for detection of genetically modified rice

BACKGROUND

Legislation regulating for labeling and use of genetically modified (GM) crops are increased considerably worldwide in order to health and safety assurance of consumers. For this purpose, a polymerase chain reaction (PCR) method has been developed for detection of GM rice in people's food diet.

METHODS

In this study, eighty-one non-labeled rice samples were collected randomly from different market sites of Tehran, Iran. In order to analysis, rice genomic DNA was extracted using MBST DNA extraction kit and subsequently, sucrose phosphate synthase (SPS) gene was used to confirm the quality of extracted DNA. Then, cauliflower mosaic virus (CaMV) 35S promoter and Agrobacterium nopaline synthase (NOS) terminator were selected as screening targets for detection of GM rice sequences by PCR.

RESULTS

According to our results, 2 out of 81 (2.4%) samples tested were positive for CaMV 35S promoter while no positive result was detected for NOS terminator.

CONCLUSION

The obtained data indicated that this method is capable to identify the GM rice varieties. Furthermore, it can demonstrate the possibility of the presence of GM rice in Tehran's market, thus putting emphasis on the requirement for developing a precise approach to evaluate this product.

Quick Test for Transgenic Components in Rice Using Terahertz Spectra

The terahertz (THz) spectrum of 0.2-1.6 THz (6.6-52.8 cm^-1) was used to identify the existence of transgenic rice Bt63 contents in non-GMO rice using a THz time-domain spectroscopy system. Principal component analysis (PCA) was used to extract the feature data based on the cumulative rate of information contribution ( > 90%); the top four principal components were selected and a radial basis function neural network (RBFNN) method was then trained and used. Three selection radial basis functions including a Gaussian function were used to identify the three types (strong positive, weak positive, and negative). The results show that the samples were identified with an accuracy of nearly 90%; additionally, the positive identification rate was > 87.5% and the negative identification rate reached 100% using the proposed method (PCA-RBF). The proposed approach was then compared with other methods, including back propagation (BP) neural networks and support vector machine (SVM). The results of the comparison show that the accuracy of PCA-RBF method reaches 92% in total and all the rest are < 90% using 100 samples. Obviously, the proposed approach outperforms the other methods and also indicates that the proposed method, in combination with THz spectroscopy, is efficient and practical for transgenic ingredient identification in rice.

Molecular Analysis for Characterizing Transgenic Events

To develop a commercial trait product, a large number of transgenic events are often produced to obtain the event with desired level of expression. It is crucial to develop efficient and sensitive molecular characterization methods to advance events with stable transgene expression, free of vector backbone sequences and without major changes to the native genome caused by transgene insertion. Here, we discuss a variety of analytical tools, including quantitative PCR (qPCR), Southern blot analysis, and various sequencing technologies, which have been widely used to determine the insert copy number, presence/absence of vector backbone sequences, integrity of the T-DNA, and genomic location of the T-DNA insertion. Moreover, since the discovery of RNA interference in 1998 (Fire et al., Nature 391:806-811, 1998), RNAi has emerged as another powerful tool in in the development of a new transgenic trait for insect control. RNAi creates a double-stranded RNA duplex as the active molecule which forms a strong secondary structure, resulting in challenges for detection. In addition to molecular analysis at the DNA level, this chapter describes detection methods of the active molecules (i.e., double-stranded RNA) for RNAi-based traits.

Development of an immunochromatographic assay for the specific detection of Bacillus thuringiensis (Bt) Cry1Ab toxin

Cry1Ab has been widely used in genetically modified (GM) crops and its amino acid sequence had high identity to Cry1Ac toxin. Existing nanogold immunochromatographic strips cannot distinguish Cry1Ab from Cry1Ac toxin. In this study, a rapid (5-6 min), qualitative nanogold immunochromatographic strip was successfully developed for the specific detection of Cry1Ab toxin. The assay was based on double antibody sandwich format with the visual detection limit (vLOD) of 0.1 μg mL^-1. The results of immunochromatographic assay were all positive validated against the DAS-ELISA (recoveries between 109.6 and 111.8%). In addition, 10%, 5% and 0% error probability results were found in 20 times repeated tests for Cry1Ab concentration of 0.1, 0.2, 0.5 and 1 μg mL^-1, respectively, demonstrating the reproducibility of the test strip. Furthermore, the test strip could be stored for 3 months under dry conditions without significant loss of sensitivity. Furthermore, the practical sample analysis results showed that the test strip was able to detect the presence of Cry1Ab in GM materials containing as low as 0.5% MON 810 Bt maize which indicated the practical value of the test strip. To our knowledge, this is the first report on the detection of Cry1Ab by immunochromatographic assay without interference from Cry1Ac toxin.

Panorama general de los organismos genéticamente modificados en Colombia y en el mundo: Capacidad nacional de detección

Los organismos genéticamente modificados (OGM) y en particular los cultivos genéticamente modificados (GM), son el resultado de la modificación de la información genética de una especie a partir del uso de la biotecnología moderna para proporcionar nuevas características que su contraparte no modificada no posee, tales como resistencia a insectos, tolerancia a herbicidas, contenido de nutrientes entre otros. La mayor parte de estos cultivos se concentran en cuatro productos: soya (Glycine max), maíz (Zea Mays), canola (Brassica napus) y algodón (Gossypium hirsutum); y los principales productores son Estados Unidos, Brasil, Argentina, India y Canadá. Por su parte, Colombia ocupa el puesto 18 con cultivos de maíz, algodón y claveles azules. La introducción de estas especies en cualquier mercado está limitada por la legislación propia del país destino, así como por los estudios que permiten establecer su efecto sobre el medio ambiente, la salud humana y animal; en este sentido, la precisión y confianza de las técnicas analíticas empleadas en la evaluación del contenido de OGM son un elemento importante para la toma de decisiones basadas en evidencias objetivas, especialmente frente al debate en torno a su uso. Este documento presenta una revisión de las tecnologías de análisis más importantes disponibles a nivel mundial, frente a las capacidades nacionales para su detección.

Gene Editing of Microalgae: Scientific Progress and Regulatory Challenges in Europe

It is abundantly clear that the development of gene editing technologies, represents a potentially powerful force for good with regard to human and animal health and addressing the challenges we continue to face in a growing global population. This now includes the development of approaches to modify microalgal strains for potential improvements in productivity, robustness, harvestability, processability, nutritional composition, and application. The rapid emergence and ongoing developments in this area demand a timely review and revision of the current definitions and regulations around genetically modified organisms (GMOs), particularly within Europe. Current practices within the EU provide exemptions from the GMO directives for organisms, including crop plants and micro-organisms that are produced through chemical or UV/radiation mutagenesis. However, organisms generated through gene editing, including microalgae, where only genetic changes in native genes are made, remain currently under the GMO umbrella; they are, as such, excluded from practical and commercial opportunities in the EU. In this review, we will review the advances that are being made in the area of gene editing in microalgae and the impact of regulation on commercial advances in this area with consideration to the current regulatory framework as it relates to GMOs including GM microalgae in Europe.

Phage-Mediated Competitive Chemiluminescent Immunoassay for Detecting Cry1Ab Toxin by Using an Anti-Idiotypic Camel Nanobody

Cry toxins have been widely used in genetically modified organisms for pest control, raising public concern regarding their effects on the natural environment and food safety. In this work, a phage-mediated competitive chemiluminescent immunoassay (c-CLIA) was developed for determination of Cry1Ab toxin using anti-idiotypic camel nanobodies. By extracting RNA from camels' peripheral blood lymphocytes, a naive phage-displayed nanobody library was established. Using anti-Cry1Ab toxin monoclonal antibodies (mAbs) against the library for anti-idiotypic antibody screening, four anti-idiotypic nanobodies were selected and confirmed to be specific for anti-Cry1Ab mAb binding. Thereafter, a c-CLIA was developed for detection of Cry1Ab toxin based on anti-idiotypic camel nanobodies and employed for sample testing. The results revealed a half-inhibition concentration of developed assay to be 42.68 ± 2.54 ng/mL, in the linear range of 10.49-307.1 ng/mL. The established method is highly specific for Cry1Ab recognition, with negligible cross-reactivity for other Cry toxins. For spiked cereal samples, the recoveries of Cry1Ab toxin ranged from 77.4% to 127%, with coefficient of variation of less than 9%. This study demonstrated that the competitive format based on phage-displayed anti-idiotypic nanobodies can provide an alternative strategy for Cry toxin detection.

An overview of genetically modified crop governance, issues and challenges in Malaysia

The application of agricultural biotechnology attracts the interest of many stakeholders. Genetically modified (GM) crops, for example, have been rapidly increasing in production for the last 20 years. Despite their known benefits, GM crops also pose many concerns not only to human and animal health but also to the environment. Malaysia, in general, allows the use of GM technology applications but it has to come with precautionary and safety measures consistent with the international obligations and domestic legal frameworks. This paper provides an overview of GM crop technology from international and national context and explores the governance and issues surrounding this technology application in Malaysia. Basically, GM research activities in Malaysia are still at an early stage of research and development and most of the GM crops approved for release are limited for food, feed and processing purposes. Even though Malaysia has not planted any GM crops commercially, actions toward such a direction seem promising. Several issues concerning GM crops as discussed in this paper will become more complex as the number of GM crops and varieties commercialised globally increase and Malaysia starts to plant GM crops. © 2017 Society of Chemical Industry.

A Microneedle Functionalized with Polyethyleneimine and Nanotubes for Highly Sensitive, Label-Free Quantification of DNA

The accurate measure of DNA concentration is necessary for many DNA-based biological applications. However, the current methods are limited in terms of sensitivity, reproducibility, human error, and contamination. Here, we present a microneedle functionalized with polyethyleneimine (PEI) and single-walled carbon nanotubes (SWCNTs) for the highly sensitive quantification of DNA. The microneedle was fabricated using ultraviolet (UV) lithography and anisotropic etching, and then functionalized with PEI and SWCNTs through a dip coating process. The electrical characteristics of the microneedle change with the accumulation of DNA on the surface. Current-voltage measurements in deionized water were conducted to study these changes in the electrical properties of the sensor. The sensitivity test found the signal to be discernable from the noise level down to 100 attomolar (aM), demonstrating higher sensitivity than currently available UV fluorescence and UV absorbance based methods. A microneedle without any surface modification only had a 100 femtomolar (fM) sensitivity. All measurement results were consistent with fluorescence microscopy.

Current perspectives on genetically modified crops and detection methods

Genetically modified (GM) crops are the fastest adopted commodities in the agribiotech industry. This market penetration should provide a sustainable basis for ensuring food supply for growing global populations. The successful completion of two decades of commercial GM crop production (1996-2015) is underscored by the increasing rate of adoption of genetic engineering technology by farmers worldwide. With the advent of introduction of multiple traits stacked together in GM crops for combined herbicide tolerance, insect resistance, drought tolerance or disease resistance, the requirement of reliable and sensitive detection methods for tracing and labeling genetically modified organisms in the food/feed chain has become increasingly important. In addition, several countries have established threshold levels for GM content which trigger legally binding labeling schemes. The labeling of GM crops is mandatory in many countries (such as China, EU, Russia, Australia, New Zealand, Brazil, Israel, Saudi Arabia, Korea, Chile, Philippines, Indonesia, Thailand), whereas in Canada, Hong Kong, USA, South Africa, and Argentina voluntary labeling schemes operate. The rapid adoption of GM crops has increased controversies, and mitigating these issues pertaining to the implementation of effective regulatory measures for the detection of GM crops is essential. DNA-based detection methods have been successfully employed, while the whole genome sequencing using next-generation sequencing (NGS) technologies provides an advanced means for detecting genetically modified organisms and foods/feeds in GM crops. This review article describes the current status of GM crop commercialization and discusses the benefits and shortcomings of common and advanced detection systems for GMs in foods and animal feeds.

Simultaneous production of monoclonal antibodies against Bacillus thuringiensis (Bt) Cry1 toxins using a mixture immunization

The detections of Cry1 toxins are mainly dependent on immunoassays based on specific monoclonal antibodies (mAb). In the present study, a mixture immunization with seven Cry1 toxins was administered. The results showed that five mAbs with different characteristics, especially one mAb named 5-E8 which could recognize all the seven Cry1 toxins were obtained. Based on the 5-E8 mAb, a double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) which can specifically detect the seven Cry1 toxins without cross-reactivity to Cry2A and vip3 was developed with the limit of detection (LOD) and limit of quantification (LOQ) of 6.37-11.35 ng mL^-1 and 17.36-24.48 ng mL^-1, respectively. The recovery tests showed that the recoveries ranged from 78% to 110% within the quantitation range (LOQ-100 ng mL^-1). The established DAS-ELISA can be a useful tool for monitoring the Cry1 toxins in agricultural products. Mixture immunization opens a new path for producing diverse mAbs simultaneously in a single immunization circle.

Establishment of a sandwich enzyme-linked immunosorbent assay for specific detection of Bacillus thuringiensis (Bt) Cry1Ab toxin utilizing a monoclonal antibody produced with a novel hapten designed with molecular model

Cry1Ab toxin is commonly expressed in genetically modified crops in order to control chewing pests. At present, the detection method with enzyme-linked immunosorbent assay (ELISA) based on monoclonal antibody cannot specifically detect Cry1Ab toxin for Cry1Ab's amino acid sequence and spatial structure are highly similar to Cry1Ac toxin. In this study, based on molecular design, a novel hapten polypeptide was synthesized and conjugated to keyhole limpet hemocyanin (KLH). Then, through animal immunization with this antigen, a monoclonal antibody named 2C12, showing high affinity to Cry1Ab and having no cross reaction with Cry1Ac, was produced. The equilibrium dissociation constant (K _D) value of Cry1Ab toxin with MAb 2C12 was 1.947 × 10^-8 M. Based on this specific monoclonal antibody, a sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was developed for the specific determination of Cry1Ab toxin and the LOD and LOQ values were determined as 0.47 ± 0.11 and 2.43 ± 0.19 ng mL^-1, respectively. The average recoveries of Cry1Ab from spiked rice leaf and rice flour samples ranged from 75 to 115%, with coefficient of variation (CV) less than 8.6% within the quantitation range (2.5-100 ng mL^-1), showing good accuracy for the quantitative detection of Cry1Ab toxin in agricultural samples. In conclusion, this study provides a new approach for the production of high specific antibody and the newly developed DAS-ELISA is a useful method for Cry1Ab monitoring in agriculture products. Graphical Abstract Establishment of a DAS-ELISA for the specific detecting of Bacillus thuringiensis (Bt) Cry1Ab toxin.

Electrochemical detection of magnetically-entrapped DNA sequences from complex samples by multiplexed enzymatic labelling: Application to a transgenic food/feed quantitative survey

Monitoring of genetically modified organisms in food and feed demands molecular techniques that deliver accurate quantitative results. Electrochemical DNA detection has been widely described in this field, yet most reports convey qualitative data and application in processed food and feed samples is limited. Herein, the applicability of an electrochemical multiplex assay for DNA quantification in complex samples is assessed. The method consists of the simultaneous magnetic entrapment via sandwich hybridisation of two DNA sequences (event-specific and taxon-specific) onto the surface of magnetic microparticles, followed by bienzymatic labelling. As proof-of-concept, we report its application in a transgenic food/feed survey where relative quantification (two-target approach) of Roundup Ready Soybean® (RRS) was performed in food and feed. Quantitative coupling to end-point PCR was performed and calibration was achieved from 22 and 243 DNA copies spanning two orders of magnitude for the event and taxon-specific sequences, respectively. We collected a total of 33 soybean-containing samples acquired in local supermarkets, four out of which were found to contain undeclared presence of genetically modified soybean. A real-time PCR method was used to verify these findings. High correlation was found between results, indicating the suitability of the proposed multiplex method for food and feed monitoring.

Rapid screening of roundup ready soybean in food samples by a hand-held PCR device

Insulated isothermal PCR (iiPCR) method was recently available for rapid on-site detection of roundup ready soybean (RRS; event GTS40-3-2) in food materials and products. Performance of this method was evaluated in this study. The 100% detection endpoint for the RRS by iiPCR was found in samples containing 0.1% RRS, equivalent to the results of the reference real-time PCR (rtPCR). Analysis of nucleic acids of soybean-based processed food products indicated 95% agreement between the iiPCR and rtPCR for RRS detection. By testing soybean milk and tofu samples using simple pretreatment methods, we found that the agreements between iiPCR and rtPCR methods of the aforementioned samples were 80% and 90%, respectively. Replicated tests of all discrepant samples implied that these samples had trace amounts of RRS, suggesting that the iiPCR system is more sensitive than the rtPCR method. In conclusion, the iiPCR technology can be a useful point-of-need tool to help make a timely decision in the consumption of genetically modified organisms.

Development, Optimization, and Evaluation of a Duplex Droplet Digital PCR Assay To Quantify the T-nos/hmg Copy Number Ratio in Genetically Modified Maize

Certified reference materials (CRMs) are required to guarantee the reliability of analytical measurements. The CRMs available in the field of genetically modified organisms (GMOs) are characterized using real-time polymerase chain reaction (qPCR). This technology has limited application, because of its dependence on a calibrant. The objective of this study was to obtain a method with higher metrological quality, to characterize the CRMs for their contents of T-nos/hmg copy number ratio in maize. A duplex droplet digital PCR (ddPCR) assay was developed and optimized by a central composite design. The developed method achieved an absolute limit of detection (LOD) of 11 cP T-nos, a relative LOD of 0.034%, a limit of quantification (LOQ) of 23 cP (relative LOQ of 0.08%), and a dynamic range of 0.08%–100% T-nos/hmg ratio. The specificity and applicability of the assay were established for the analysis of low T-nos concentrations (0.9%) in several corn varieties. The convenience of DNA digestion to reduce measurement bias in the case of multiple-copy binding was confirmed through an enzymatic restriction assay. Given its overall performance, this method can be used to characterize CRM candidates for their contents of T-nos/hmg ratio.

Enzyme-assisted target recycling (EATR) for nucleic acid detection

Fast, reliable and sensitive methods for nucleic acid detection are of growing practical interest with respect to molecular diagnostics of cancer, infectious and genetic diseases. Currently, PCR-based and other target amplification strategies are most extensively used in practice. At the same time, such assays have limitations that can be overcome by alternative approaches. There is a recent explosion in the design of methods that amplify the signal produced by a nucleic acid target, without changing its copy number. This review aims at systematization and critical analysis of the enzyme-assisted target recycling (EATR) signal amplification technique. The approach uses nucleases to recognize and cleave the probe-target complex. Cleavage reactions produce a detectable signal. The advantages of such techniques are potentially low sensitivity to contamination and lack of the requirement of a thermal cycler. Nucleases used for EATR include sequence-dependent restriction or nicking endonucleases or sequence independent exonuclease III, lambda exonuclease, RNase H, RNase HII, AP endonuclease, duplex-specific nuclease, DNase I, or T7 exonuclease. EATR-based assays are potentially useful for point-of-care diagnostics, single nucleotide polymorphisms genotyping and microRNA analysis. Specificity, limit of detection and the potential impact of EATR strategies on molecular diagnostics are discussed.

Degradation and detection of transgenic Bacillus thuringiensis DNA and proteins in flour of three genetically modified rice events submitted to a set of thermal processes

This study aimed to investigate the degradation of three transgenic Bacillus thuringiensis (Bt) genes (Cry1Ab, Cry1Ac, and Cry1Ab/Ac) and the corresponding encoded Bt proteins in KMD1, KF6, and TT51-1 rice powder, respectively, following autoclaving, cooking, baking, or microwaving. Exogenous Bt genes were more stable than the endogenous sucrose phosphate synthase (SPS) gene, and short DNA fragments were detected more frequently than long DNA fragments in both the Bt and SPS genes. Autoclaving, cooking (boiling in water, 30 min), and baking (200 °C, 30 min) induced the most severe Bt protein degradation effects, and Cry1Ab protein was more stable than Cry1Ac and Cry1Ab/Ac protein, which was further confirmed by baking samples at 180 °C for different periods of time. Microwaving induced mild degradation of the Bt and SPS genes, and Bt proteins, whereas baking (180 °C, 15 min), cooking and autoclaving led to further degradation, and baking (200 °C, 30 min) induced the most severe degradation. The findings of the study indicated that degradation of the Bt genes and proteins somewhat correlated with the treatment intensity. Polymerase chain reaction, enzyme-linked immunosorbent assay, and lateral flow tests were used to detect the corresponding transgenic components. Strategies for detecting transgenic ingredients in highly processed foods are discussed.

Multiplex electrochemical DNA platform for femtomolar-level quantification of genetically modified soybean

Current EU regulations on the mandatory labeling of genetically modified organisms (GMOs) with a minimum content of 0.9% would benefit from the availability of reliable and rapid methods to detect and quantify DNA sequences specific for GMOs. Different genosensors have been developed to this aim, mainly intended for GMO screening. A remaining challenge, however, is the development of genosensing platforms for GMO quantification, which should be expressed as the number of event-specific DNA sequences per taxon-specific sequences. Here we report a simple and sensitive multiplexed electrochemical approach for the quantification of Roundup-Ready Soybean (RRS). Two DNA sequences, taxon (lectin) and event-specific (RR), are targeted via hybridization onto magnetic beads. Both sequences are simultaneously detected by performing the immobilization, hybridization and labeling steps in a single tube and parallel electrochemical readout. Hybridization is performed in a sandwich format using signaling probes labeled with fluorescein isothiocyanate (FITC) or digoxigenin (Dig), followed by dual enzymatic labeling using Fab fragments of anti-Dig and anti-FITC conjugated to peroxidase or alkaline phosphatase, respectively. Electrochemical measurement of the enzyme activity is finally performed on screen-printed carbon electrodes. The assay gave a linear range of 2-250 pM for both targets, with LOD values of 650 fM (160 amol) and 190 fM (50 amol) for the event-specific and the taxon-specific targets, respectively. Results indicate that the method could be applied for GMO quantification below the European labeling threshold level (0.9%), offering a general approach for the rapid quantification of specific GMO events in foods.

International ring trial for the validation of an event-specific Golden Rice 2 quantitative real-time polymerase chain reaction method

This article describes the international validation of the quantitative real-time polymerase chain reaction (PCR) detection method for Golden Rice 2. The method consists of a taxon-specific assay amplifying a fragment of rice Phospholipase D α2 gene, and an event-specific assay designed on the 3' junction between transgenic insert and plant DNA. We validated the two assays independently, with absolute quantification, and in combination, with relative quantification, on DNA samples prepared in haploid genome equivalents. We assessed trueness, precision, efficiency, and linearity of the two assays, and the results demonstrate that both the assays independently assessed and the entire method fulfill European and international requirements for methods for genetically modified organism (GMO) testing, within the dynamic range tested. The homogeneity of the results of the collaborative trial between Europe and Asia is a good indicator of the robustness of the method.

DNA extraction techniques compared for accurate detection of genetically modified organisms (GMOs) in maize food and feed products

In this paper, DNA extraction methods have been evaluated to detect the presence of genetically modified organisms (GMOs) in maize food and feed products commercialised in Turkey. All the extraction methods tested performed well for the majority of maize foods and feed products analysed. However, the highest DNA content was achieved by the Wizard, Genespin or the CTAB method, all of which produced optimal DNA yield and purity for different maize food and feed products. The samples were then screened for the presence of GM elements, along with certified reference materials. Of the food and feed samples, 8 % tested positive for the presence of one GM element (NOS terminator), of which half (4 % of the total) also contained a second element (the Cauliflower Mosaic Virus 35S promoter). The results obtained herein clearly demonstrate the presence of GM maize in the Turkish market, and that the Foodproof GMO Screening Kit provides reliable screening of maize food and feed products.