The development of loop-mediated isothermal amplification (LAMP) assays for the rapid authentication of five forbidden vegetables in strict vegetarian diets

Authentication of olive oil in commercial products using specific, sensitive, and rapid loop-mediated isothermal amplification

Olive oil is an important and popularly used plant oil in the daily diet or chemical industry. Due to its biological benefits on human health and higher selling prices, adulteration of olive oil for commercial fraud by other plant oils is becoming a serious issue. In this study, a specific, sensitive and rapid loop-mediated isothermal amplification (LAMP) was first developed for the detection of Olea europaea DNA for olive oil authentication. The oleosin gene was used for the primer design of the LAMP assay. After primer validation, the results showed that the LAMP primers were specific and rapid to isothermally authenticate the oleosin gene of Olea europaea within 1 h at 62 °C and had no cross-reaction with other DNA of plant oils. The sensitivity of LAMP was 1 ng of genomic DNA in olive oil, and only 1% olive oil in the sample was requisite during DNA amplification. Additionally, positive detection by LAMP in all the collected commercial olive oil products was practically performed but not in PCR assays. In conclusion, herein, the established LAMP assay with specificity could not only be capable for rapid identification but also applicable for olive oil authentication for precluding adulteration in plant oil products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05726-y.

Loop-mediated isothermal amplification for Candida species surveillance in under-resourced setting: a review of evidence

INTRODUCTION

Non-albicans Candida species (NACS) have emerged as a major public health burden although they are still underappreciated. Some NACS have intrinsic antifungal resistance, requiring constant surveillance to improve patient care and thwart outbreaks of recalcitrant candida infections. However, effective Candida species surveillance has relied on PCR-based or other high-end techniques that are largely unaffordable in under-resourced countries. Loop-mediated isothermal amplification (LAMP) has emerged as a potentially effective and affordable technique for infectious disease surveillance, especially in under resourced settings.

AREAS COVERED

We critically reviewed current literature on application of LAMP for Candida species identification in pure fungal isolates, and in clinical and non-clinical samples.

EXPERT OPINION

LAMP has been studied for Candida species identification, including the NACS. Besides a short turnaround time, LAMP has analytical sensitivity and specificity that are not only higher than culture method but also comparable with conventional and quantitative PCR techniques. However, extensive evaluation of LAMP for Candida species detection using various types of clinical and environmental samples are required before deploying the technique for Candida species surveillance.

Loop-Mediated Isothermal Amplification (LAMP) as a Promising Point-of-Care Diagnostic Strategy in Avian Virus Research

Simple Summary

Many of the existing screening methods of avian viruses depend on clinical symptoms and pathological gross examinations that still necessitate confirmatory microscopic testing. Confirmation of a virus is often conducted at centralized laboratories that are well-equipped with instruments for virus isolation, hemagglutinin inhibition, virus neutralization, ELISA, PCR and qPCR. These assays are known for their great accuracy and sensitivity, and hence are set as standard practices. Nevertheless, limitations arise due to the time, cost and on-site applicability. As the technology progresses, molecular diagnostics should be more accessible to isolated areas and even practicable for use by non-skilled personnel such as farmers and private breeders. One of the point-of-care diagnostic strategies to consider for such matters is loop-mediated isothermal amplification (LAMP).

Abstract

Over the years, development of molecular diagnostics has evolved significantly in the detection of pathogens within humans and their surroundings. Researchers have discovered new species and strains of viruses, while mitigating the viral infections that occur, owing to the accessibility of nucleic acid screening methods such as polymerase chain reaction (PCR), quantitative (real-time) polymerase chain reaction (qPCR) and reverse-transcription qPCR (RT-qPCR). While such molecular detection methods are widely utilized as the benchmark, the invention of isothermal amplifications has also emerged as a reliable tool to improvise on-field diagnosis without dependence on thermocyclers. Among the established isothermal amplification technologies are loop-mediated isothermal amplification (LAMP), recombinant polymerase amplification (RPA), strand displacement activity (SDA), nucleic acid sequence-based amplification (NASBA), helicase-dependent amplification (HDA) and rolling circle amplification (RCA). This review highlights the past research on and future prospects of LAMP, its principles and applications as a promising point-of-care diagnostic method against avian viruses.

Specific, sensitive and rapid Curcuma longa turmeric powder authentication in commercial food using loop-mediated isothermal nucleic acid amplification

Turmeric (Curcuma longa) is a rhizomatous plant of the ginger family Zingiberaceae that is usually dried and ground into powder for use as a seasoning. Because turmeric has become increasingly popular in the functional food market, adulteration of C. longa by other turmeric species is becoming an increasingly significant problem. In this study, loop-mediated isothermal amplification (LAMP) was developed for the detection of C. longa DNA for turmeric authentication. ITS2-26S rDNA was used for the LAMP primer designation. The results demonstrated that the specific primers exhibited high specificity, authenticated C. longa DNA within 30 min at 65 °C isothermally and had no cross-reaction with other adulterants. LAMP was sensitive to 0.1 ng of turmeric C. longa DNA, and only 0.01% of C. longa turmeric powder in the sample was required for DNA amplification. The sensitivity of LAMP was 10-fold higher than that of PCR (0.1%) from a previous report. Moreover, all the collected commercial turmeric products were positively detected by LAMP and RtF-LAMP (real-time fluorescence LAMP). The developed LAMP assay not only had higher specificity and rapidity than that of other methods but could also be applied to authenticate turmeric to prevent adulteration in food products.

Critical review of methods for isothermal amplification of nucleic acids for environmental analysis

The past 30 years have seen the emergence and proliferation of isothermal amplification methods (IAMs) for rapid, sensitive detection and quantification of nucleic acids in a variety of sample types. These methods share dependence on primers and probes with quantitative PCR, but they differ in the specific enzymes and instruments employed, and are frequently conducted in a binary, rather than quantitative format. IAMs typically rely on simpler instruments than PCR analyses due to the maintenance of a single temperature throughout the amplification reaction, which could facilitate deployment of IAMs in a variety of environmental and field settings. This review summarizes the mechanisms of the most common IAM methods and their use in studies of pathogens, harmful algae and fecal indicators in environmental waters, feces, wastewater, reclaimed water, and tissues of aquatic animals. Performance metrics of sensitivity, specificity and limit of detection are highlighted, and the potential for use in monitoring and regulatory contexts is discussed.

Development of a specific isothermal nucleic acid amplification for the rapid and sensitive detection of shrimp allergens in processed food

Food allergens that cause anaphylactic reactions have become an important health problem worldwide. Among them, shrimp is a popular seafood in many cuisines. The best way to avoid allergic reactions is to mitigate the intake of food allergens. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the detection of shrimp DNA. Using LAMP primers, the identification of shrimp DNA by the LAMP assay was specific and rapid (within 30 min). It exhibited no cross-reaction with the DNA of other Crustacea, including crabs and lobster, and at least 0.01% shrimp DNA existed in the test sample. Additionally, the sensitivity of LAMP for detecting shrimp DNA was 100-fold greater than that of conventional PCR. LAMP for the detection of shrimp DNA was reproducible regardless of whether the genomic DNA was extracted from boiled, steamed or roasted shrimp samples. In summary, the LAMP assay established herein not only could be potentially used for diagnosing shrimp DNA but could also be applicable for identifying shrimp allergens in commercial food products in marketplaces.

Specific, sensitive and rapid authentication of donkey-hide gelatine (Colla corii asini) in processed food using an isothermal nucleic acid amplification assay

Donkey-hide gelatine (DHG) is a well-known, animal-derived traditional Chinese medicine material called Colla corii asini (known in Chinese as "E'jiao"). Because DHG is claimed to have properties that are beneficial to health, its consumption has increased, but its production has decreased. Thus, the incidence of DHG adulteration has become increasingly serious. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the authentication of DHG. Identification of donkey DNA from DHG was performed specifically and rapidly within one hour by LAMP primers. Moreover, the sensitivity of LAMP in authenticating DHG was 10^-3 ng, which revealed a 10⁵-fold higher sensitivity than that of conventional PCR. The relative detection limit was 0.1% DHG in the adulterants, including gelatines of horse, cow, pork, goat, sheep or chicken origins. When genomic DNAs extracted from heat-treated DHG samples, including boiling or autoclaving for 40 min, were used as templates, DHG detection by LAMP was unchanged and reproducible. In conclusion, the LAMP assay established herein could potentially be applied for the authentication of DHG and DHG-related products in herbal or food markets.

Review of Recent DNA-Based Methods for Main Food-Authentication Topics

Adulteration and mislabeling of food products and the commercial fraud derived, either intentionally or not, is a global source of economic fraud to consumers but also to all stakeholders involved in food production and distribution. Legislation has been enforced all over the world aimed at guaranteeing the authenticity of the food products all along the distribution chain, thereby avoiding food fraud and adulteration. Accordingly, there is a growing need for new analytical methods able to verify that all the ingredients included in a foodstuff match the qualities claimed by the manufacturer or distributor. In this sense, the improved performance of most recent DNA-based tools in term of sensitivity, multiplexing ability, high-throughput, and relatively low-cost give them a game-changing role in food-authenticity-related topics. Here, we provide a thorough and updated vision on the recently reported approaches that are applying these DNA-based tools to assess the authenticity of food components and products.

Specific and rapid identification of the Pheretima aspergillum by loop-mediated isothermal amplification

Guang-dilong (Pheretima aspergillum) is a traditional Chinese animal medicine that has been used for thousands of years in China. In the present study, we purposed to establish a new rapid identification method for Guang-dilong. We provided a useful technique, loop-mediated isothermal amplification (LAMP), to differentiate Guang-dilong from other species. Four specific LAMP primers were designed based on mitochondrial cytochrome c oxidase I (COI) gene sequences of Guang-dilong. LAMP reaction, containing DNA template, four primers, 10× Bst DNA polymerase reaction buffer, dNTPs, MgSO₄, and Bst DNA polymerase, was completed within 60 min at 63°C. The LAMP product can be visualized by adding SYBR Green I or detected by 2% gel electrophoresis. LAMP technology was successfully established for rapid identification of Guang-dilong. In addition, DNA template concentration of 675 fg/μl was the detection limit of LAMP in Guang-dilong, which was 1000-times higher than conventional PCR. The simple, sensitive, and convenient LAMP technique is really suited for on-site identification of Guang-dilong in herbal markets.

A Multiplex PCR Assay Mediated by Universal Primers for the Detection of Adulterated Meat in Mutton

This study aimed to establish a multiplex PCR detection system mediated by "universal primers," which would be able to determine whether mutton meat contained nonmutton ingredients from rats, foxes, and ducks. Based on the sequence variation of specific mitochondrial genes, nine different multiplex PCR primers were designed, and four kinds of meat products were rapidly identified by electrophoresis using an optimized multiplex PCR system based on the molecular weight differences of the amplified products. Multiplex PCR applications optimized for meat food source from food samples for testing was used to verify the accuracy of the identification method. The results showed that the primers in multiple PCR system mediated by universal primers could be used for the rapid identification of rat, fox, duck, and sheep meat in mutton products, and the detection sensitivity could reach 0.05 ng/μL. The identification of food samples validated the practical value of this method. Therefore, a multiplex PCR system mediated by universal primers was established, which can be used to quickly identify the origin of animal ingredients from rats, foxes, and ducks in mutton products.

A Loop-mediated Isothermal Amplification (LAMP) Assay for Rapid Identification of Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) is an invasive pest of considerable importance, affecting the production of vegetable and ornamental crops in many countries around the world. Severe yield losses are caused by direct feeding, and even more importantly, also by the transmission of more than 100 harmful plant pathogenic viruses. As for other invasive pests, increased international trade facilitates the dispersal of B. tabaci to areas beyond its native range. Inspections of plant import products at points of entry such as seaports and airports are, therefore, seen as an important prevention measure. However, this last line of defense against pest invasions is only effective if rapid identification methods for suspicious insect specimens are readily available. Because the morphological differentiation between the regulated B. tabaci and close relatives without quarantine status is difficult for non-taxonomists, a rapid molecular identification assay based on the loop-mediated isothermal amplification (LAMP) technology has been developed. This publication reports the detailed protocol of the novel assay describing rapid DNA extraction, set-up of the LAMP reaction, as well as interpretation of its read-out, which allows identifying B. tabaci specimens within one hour. Compared to existing protocols for the detection of specific B. tabaci biotypes, the developed method targets the whole B. tabaci species complex in one assay. Moreover the assay is designed to be applied on-site by plant health inspectors with minimal laboratory training directly at points of entry. Thorough validation performed under laboratory and on-site conditions demonstrates that the reported LAMP assay is a rapid and reliable identification tool, improving the management of B. tabaci.

The rapid and sensitive detection of edible bird's nest (Aerodramus fuciphagus) in processed food by a loop-mediated isothermal amplification (LAMP) assay

Edible bird’s nest (EBN) is a well-known and precious traditional Chinese herbal material (CHM). Because of this, preventing the adulteration of EBN efficiently and precisely is crucial to protect consumers’ interests and health. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the detection of EBN using specifically designed LAMP primers. The results demonstrated that the identification of EBN by LAMP assay was specific and rapid (within 1 h). It had no cross-reaction with EBN adulterants, including white fungus, egg white and pig skin, in different ratios. The relative detection limit was 0.01% EBN in the adulterants. Moreover, the sensitivity of LAMP in authenticating EBN was 10⁻⁸ μg, it showed higher sensitivity than that of conventional PCR with 10⁵ fold. When genomic DNAs extracted from boiled or steamed EBN samples were used as templates, LAMP for EBN detection was not affected and was reproducible after heat processing. In conclusion, the LAMP assay established herein could be applicable for authenticating EBN and for identifying commercial EBN products in herbal markets.

Development of loop-mediated isothermal amplification (LAMP) assays for the rapid detection of allergic peanut in processed food

Peanut is a widely and common used in many cuisines around the world. However, peanut is also one of the most important food allergen for causing anaphylactic reaction. To prevent allergic reaction, the best way is to avoid the food allergen or food containing allergic ingredient such as peanut before food consuming. Thus, to efficient and precisely detect the allergic ingredient, peanut or related product, is essential and required for maintain consumer's health or their interest. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the detection of allergic peanut using specifically designed primer sets. Two sets of the specific LAMP primers respectively targeted the internal transcribed sequence 1 (ITS1) of nuclear ribosomal DNA sequence regions and the ara h1 gene sequence of Arachia hypogeae (peanut) were used to address the application of LAMP for detecting peanut in processed food or diet. The results demonstrated that the identification of peanut using the newly designed primers for ITS 1 sequence is more sensitive rather than primers for sequence of Ara h1 gene when performing LAMP assay. Besides, the sensitivity of LAMP for detecting peanut is also higher than the traditional PCR method. These LAMP primers sets showed high specificity for the identification of the peanut and had no cross-reaction to other species of nut including walnut, hazelnut, almonds, cashew and macadamia nut. Moreover, when minimal 0.1% peanuts were mixed with other nuts ingredients at different ratios, no any cross-reactivity was evident during performing LAMP. Finally, genomic DNAs extracted from boiled and steamed peanut were used as templates; the detection of peanut by LAMP was not affected and reproducible. As to this established LAMP herein, not only can peanut ingredients be detected but commercial foods containing peanut can also be identified. This assay will be useful and potential for the rapid detection of peanut in practical food markets.