A low-cost novel lateral flow nucleic acid assay (LFNAA) for yak milk authentication

Rapid authentication of characteristic milk powders by recombinase polymerase amplification assays

The authentication of dairy species has great significance for food safety. This study focused on a more rapid method for identifying major dairy species, and specific recombinase polymerase amplification (RPA)-based assays for cattle, goat, sheep, camel and donkey were developed. Through the developed RPA-based assays, goats and sheep could be simultaneously identified and bovine families could be differentiated. The performances of the RPA assays were validated using 37 milk powder samples, of which 16.2% (6/37) were suspected of being adulterated and 24.3% (9/37) were potentially at risk of being wrongly identified as adulteration. The effectiveness of the developed assays for crude DNA detection was also validated by a rapid nucleic acid extraction kit, and results showed that the presence of large amounts of protein and fat did not affect the qualitative results. Therefore, these assays could combine with the rapid nucleic acids extraction methods for being used in field detection.

Amplification-free quantitative detection of genomic DNA using lateral flow strips for milk authentication

With the globalization and complexity of the food supply chain, the market is becoming increasingly competitive and food fraudulent activities are intensifying. The current state of food detection faced two primary challenges. Firstly, existing testing methods were predominantly laboratory-based, requiring complex procedures and precision instruments. Secondly, there was a lack of accurate and efficient quantitative detection methods. Taking cow's milk as an example, this study introduced a novel method for nucleic acid quantification in dairy products, based on lateral flow strips (LFS). The core idea of this method is to design single-stranded DNA (ssDNA) probes to hybridize with mitochondrial genes, which are abundant, stable, and species-specific in dairy products, as detection targets. Drawing inspiration from the principles of nucleic acid amplification, this research innovatively established a new DNA hybridization method, named LAMP-Like Hybridization (HybLAMP-Like). Leveraging the denaturation and DNA polymerization functions of the bst enzyme, efficient binding of the probe and template strand was achieved. This method eliminated the need for nucleic acid amplification, simplifying the procedure and mitigating aerosol contamination, thereby ensuring the accuracy of the detection results. The method exhibited exceptional sensitivity, capable of detecting extremely low to 12.5 ng in visual inspection and 3.125 ng when using a reader. In terms of practicality, it could achieve visual detection of cow's milk content as low as 1% in adulterated dairy products. When combined with a portable LFS reader, it also enabled precise quantitative analysis of milk adulteration.

The potential of tailed amplicons for SARS-CoV-2 detection in Nucleic Acid Lateral Flow Assays

Nucleic Acid Lateral Flow Assays (NALFAs) are a promising solution for the point-of-care detection of viruses like SARS-CoV-2. However, they show some drawbacks, such as the great dependency on the use of antibodies and the need for post-amplification protocols that enable the preparation of amplicons for effective readings, as well as low sensitivity. Here, we developed amplicons of a specific SARS-CoV-2 gene tailed with single-strand DNA (ssDNA) sequences to hybridize with DNA probes immobilized on the NALFA strips, thus overcoming the aforementioned problems. Results have shown that tailed primers have not compromised the amplification efficiency and allowed the correct detection of the amplicons in the lateral flow strip. This approach has presented a limit of detection (LOD) of 25 RNA copies /reaction mix (1 copy/μL) and the test of cross-reactivity with other related viruses has not shown any cross-reactivity. Twenty clinical samples were evaluated by NALFA and simultaneously compared with the gold standard RT-qPCR protocol, originating equal results. Although the number of clinical specimens tested being relatively small, this indicates a sensitivity and specificity both of 100%. In short, an alternative NALFA was successfully implemented, rendering an accurate route for SARS-CoV-2 diagnosis, compatible with low-resource settings.

An instrument-free, integrated micro-platform for rapid and multiplexed detection of dairy adulteration in resource-limited environments

In dairy industry, expensive yak's milk, camel's milk, and other specialty dairy products are often adulterated with low-cost cow's milk, goat's milk and so on. Currently, the detection of specialty dairy products typically requires laboratory settings and relies on skilled operators. Therefore, there is an urgent need to develop a multi-detection technology and on-site rapid detection technique to enhance the efficiency and accuracy of the detection of specialty dairy products. In this study, we introduced a fully integrated and portable microfluidic detection platform called Sector Self-Driving Microfluidics (SDM), designed to simultaneously detect eight common species-specific components in milk. SDM integrated nucleic acid extraction, purification, loop-mediated isothermal amplification (LAMP), and lateral flow strip (LFS) detection functions into a closed microfluidic system, enabling contamination-free visual detection. The SDM platform used a constant-temperature heating plate, powered by a mobile battery, eliminated the need for additional power support. The SDM platform achieved nucleic acid enrichment and transfer through magnetic force and liquid flow driven by capillary forces, operating without external pumps. The standalone SDM platform could detect dairy components with as low as 1% content within 1 h. Validation with 35 commercially available samples demonstrated 100% specificity and accuracy compared to the gold standard real-time PCR. The SDM platform provided the dairy industry with an efficient, convenient, and accurate detection tool, enabling rapid on-site testing at production facilities or sales points. This facilitated real-time monitoring of quality issues during the production process, quickly identifying potential risks and preventing substandard products from entering the market.

Rapid analysis technologies with chemometrics for food authenticity field: A review

In recent years, the problem of food adulteration has become increasingly rampant, seriously hindering the development of food production, consumption, and management. The common analytical methods used to determine food authenticity present challenges, such as complicated analysis processes and time-consuming procedures, necessitating the development of rapid, efficient analysis technology for food authentication. Spectroscopic techniques, ambient ionization mass spectrometry (AIMS), electronic sensors, and DNA-based technology have gradually been applied for food authentication due to advantages such as rapid analysis and simple operation. This paper summarizes the current research on rapid food authenticity analysis technology from three perspectives, including breeds or species determination, quality fraud detection, and geographical origin identification, and introduces chemometrics method adapted to rapid analysis techniques. It aims to promote the development of rapid analysis technology in the food authenticity field.

Microfluidic-assisted integrated nucleic acid test strips for POCT

Numerous diseases have posed significant threats to public health, notably the global pandemic of COVID-19, resulting in widespread devastation due to its high infectivity and severity. The nucleic acid lateral flow assay (NALFA) addresses challenges of complexity, cost, and time associated with traditional assays, offering a reliable platform for rapid and precise nucleic acid target detection. NALFA is gaining prominence as a point-of-care testing (POCT) technique, thanks to its user-friendly operation and rapid results. Nevertheless, conventional NALFA relies on specialized technicians and involves labor-intensive steps like DNA extraction and PCR processes, impeding its efficiency. To overcome these limitations, integrating NALFA with microfluidic technology, widely employed in rapid field detection, holds promise. This review comprehensively outlines prevailing strategies for integrating NALFA, encompassing both research initiatives and commercial applications. Addressing the bottleneck of nucleic acid amplification as a rate-limiting step, the review delves into progress in amplification-free NALFA and highlights prevalent signal amplification techniques. Ultimately, the review outlines the future prospect of integrated NALFA development, capturing the technology's evolution and providing valuable insights for academic and commercial endeavors.

CRISPR-Based Colorimetric Nucleic Acid Tests for Visual Readout of DNA Barcode for Food Authenticity

Food authenticity is a critical issue associated with the economy, religion, and food safety. Herein, we report a label-free and colorimetric nucleic acid assay for detecting DNA barcodes, enabling the determination of food authenticity with the naked eye. This method, termed the CRISPR-based colorimetric DNA barcoding (Cricba) assay, utilizes CRISPR/Cas12a (CRISPR = clustered regularly interspaced short palindromic repeats; Cas = CRISPR associated protein) to specifically recognize the polymerase chain reaction (PCR) products for further trans-cleavaging the peroxidase-mimicking G-quadruplex DNAzyme. Based on this principle, the presence of the cytochrome oxidase subunit I gene could be directly observed with the naked eye via the color change of 3,3',5,5'-tetramethylbenzidine sulfate (TMB). The whole detection process, including PCR amplification and TMB colorimetric analysis, can be completed within 90 min. The proposed assay can detect pufferfish concentrations diluted to 0.1% (w/w) in a raw pufferfish mixture, making it one of the most sensitive methods for food authenticity. The robustness of the assay was verified by testing four common species of pufferfish, including Lagocephalus inermis, Lagocephalus spadiceus, Takifugu bimaculatus, and Takifugu alboplumbeus. The assay is advantageous in easy signal readout, high sensitivity, and general applicability and thus could be a competitive candidate for food authenticity.

Critical insight into recombinase polymerase amplification technology

INTRODUCTION

Recombinase polymerase amplification (RPA) is a promising and emerging technology for rapidly amplifying target nucleic acid from minimally processed samples and through small portable instruments. RPA is suitable for point-of-care testing (POCT) and on-site field testing, and it is compatible with microfluidic devices. Several detection assays have been developed, but limited research has dug deeper into the chemistry of RPA to understand its kinetics and fix its shortcomings.

AREAS COVERED

This review provides a detailed introduction of RPA molecular mechanism, kits formats, optimization, application, pros, and cons. Moreover, this critical review discusses the nonspecificity issue of RPA, highlights its consequences, and emphasizes the need for more research to resolve it. This review discusses the reaction kinetics of RPA in relation to target length, product quantity, and sensitivity. This critical review also questions the novelty of recombinase-aided amplification (RAA). In short, this review discusses many aspects of RPA technology that have not been discussed previously and provides a deeper insight and new perspectives of the technology.

EXPERT OPINION

RPA is an excellent choice for pathogen detection, especially in low-resource settings. It has a potential to replace PCR for all purposes, provided its shortcomings are fixed and its reagent accessibility is improved.

Characterization of ACE inhibitory and antioxidant peptides in yak and cow milk hard chhurpi cheese of the Sikkim Himalayan region

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Yak and cow hard chhurpi cheese of Sikkim Himalaya.

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ACE-inhibitory activities of undigested and GI digested yak and cow hard chhurpi.

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Bioactive peptides identified by LC-MS/MS peptidomics of yak and cow hard chhurpi.

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In silico prediction and molecular docking of potential ACE-inhibitory peptides.

In this study, simulated in vitro GI digestion of the Himalayan hard chhurpi cheese resulted in the increase of hydrolyzed protein content, antioxidant and ACE-inhibitory activities. LC-MS/MS-based peptidomics revealed a total of 1473 peptides in the samples originating from different milk proteins, including α-S1-casein, α-S2-casein, β-casein, κ-casein, α-lactalbumin, and β-lactoglobulin, out of which 60 peptides have been reported for different functional properties. A total of 101 peptides were predicted to be antihypertensive using the bioactivity prediction web servers, AHTpin and mAHTPred. In silico molecular docking studies predicted 20 antihypertensive peptides, exhibiting non-bond interactions between hard chhurpi peptides and ACE catalytic residues. A peptide, SLVYPFPGPI, identified in GI digested cow hard chhurpi and undigested, and GI digested samples of yak hard chhurpi, showed a stronger binding affinity towards ACE. Identifying antioxidant and ACE inhibitory peptides in hard cheese products adds value to them as functional foods of the Himalayan region.

An Overview for the Nanoparticles-Based Quantitative Lateral Flow Assay

The development of the lateral flow assay (LFA) has received much attention in both academia and industry because of their broad applications to food safety, environmental monitoring, clinical diagnosis, and so forth. The user friendliness, low cost, and easy operation are the most attractive advantages of the LFA. In recent years, quantitative detection has become another focus of LFA development. Here, the most recent studies of quantitative LFAs are reviewed. First, the principles and corresponding formats of quantitative LFAs are introduced. In the biomaterial and nanomaterial sections, the detection, capture, and signal amplification biomolecules and the optical, fluorescent, luminescent, and magnetic labels used in LFAs are described. The invention of dedicated strip readers has drawn further interest in exploiting the better performance of LFAs. Therefore, next, the development of dedicated reader devices is described and the usefulness and specifications of these devices for LFAs are discussed. Finally, the applications of LFAs in the detection of metal ions, biotoxins, pathogenic microorganisms, veterinary drugs, and pesticides in the fields of food safety and environmental health and the detection of nucleic acids, biomarkers, and viruses in clinical analyses are summarized.

Rapid developments in lateral flow immunoassay for nucleic acid detection

Recently, lateral flow assay (LFA) for nucleic acid detection has drawn increasing attention in the point-of-care testing fields. Due to its rapidity, easy implementation, and low equipment requirement, it is well suited for use in rapid diagnosis, food authentication, and environmental monitoring under source-limited conditions. This review will discuss two main research directions of lateral flow nucleic acid tests. The first one is the incorporation of isothermal amplification methods with LFA, which ensures an ultra-high testing sensitivity under non-laboratory conditions. The two most commonly used methodologies will be discussed, namely Loop-mediated Isothermal Amplification (LAMP) and Recombinase Polymerase Amplification (RPA), and some novel methods with special properties will also be introduced. The second research direction is the development of novel labeling materials. It endeavors to increase the sensitivity and quantifiability of LFA testing, where signals can be read and analyzed by portable devices. These methods are compared in terms of limits of detection, detection times, and quantifiabilities. It is anticipated that future research on lateral flow nucleic acid tests will focus on the integration of the whole testing process into a microfluidic system and the combination with molecular diagnostic tools such as clustered regularly interspaced short palindromic repeats to facilitate a rapid and accurate test.