A non-enzymatic, isothermal strand displacement and amplification assay for rapid detection of SARS-CoV-2 RNA.
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ABSTRACT:
SUBMITTER: Mohammadniaei M
PROVIDER: S-EPMC8385016 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been spreading rapidly all over the world. In the absence of effective treatments or a vaccine, there is an urgent need to develop a more rapid and simple detection technology of COVID-19. We describe a WarmStart colorimetric reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for the detection of SARS-CoV-2. The detection limit for this assay was 1 copy/µL SARS-CoV-2. To test the clinical sensitivity and specificity of the assay, 37 positive and 20 negative samples were used. The WarmStart colorimetric RT-LAMP had 100% sensitivity and specificity. End products were detected by direct observation, thereby eliminating the need for post-amplification processing steps. WarmStart colorimetric RT-LAMP provides an opportunity to facilitate virus detection in resource-limited settings without a sophisticated diagnostic infrastructure.
| S-EPMC8437165 | biostudies-literature
Project description:The current diagnosis of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) relies on laboratory-based tests since its clinical features are nonspecific, unlike other respiratory pathogens. Therefore, the development of a rapid and simple method for on-site detection of SARS-CoV is crucial for the identification and prevention of future SARS outbreaks. In this study, a simple colorimetric and multiplex loop-mediated isothermal amplification (LAMP) assay was developed to rapid screening of severe acute respiratory syndrome-associated coronavirus (SARS-CoV). It can be visually detected based on color change and monitored in real-time with fluorescent signals. The performance of this assay, based on six primers targeting open reading frame (ORF1b) and nucleocapsid (N) genes located in different regions of the SARS-CoV, was compared with real-time RT-PCR assay using various concentrations of target genes. The detection limit of the LAMP assay was comparable to that of real-time RT-PCR assay and therefore a few target RNA to 104-105 copies could be detected within a short period of time (20-25 min). In addition, we established a multiplex real-time LAMP assay to simultaneously detect two target regions within the SARS-CoV genome. Two target sequences were amplified by specific primers in the same reaction tube and revealed that it was able to detect down to 105 copies. The standard curve had a linear relationship with similar amplification efficiencies. The LAMP assay results in shorter "sample-to-answer" time than conventional PCR method. Therefore, it is suitable not only for diagnosis of clinical test, but also for surveillance of SARS virus in developing countries.Electronic supplementary materialSupplementary material is available for this article at 10.1007/s13206-019-3404-3 and is accessible for authorized users.
| S-EPMC7097549 | biostudies-literature
Project description:The COVID-19 pandemic provides an urgent example where a gap exists between availability of state-of-the-art diagnostics and current needs. As assay protocols and primer sequences become widely known, many laboratories perform diagnostic tests using methods such as RT-PCR or reverse transcription loop mediated isothermal amplification (RT-LAMP). Here, we report an RT-LAMP isothermal assay for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and demonstrate the assay on clinical samples using a simple and accessible point-of-care (POC) instrument. We characterized the assay by dipping swabs into synthetic nasal fluid spiked with the virus, moving the swab to viral transport medium (VTM), and sampling a volume of the VTM to perform the RT-LAMP assay without an RNA extraction kit. The assay has a limit of detection (LOD) of 50 RNA copies per μL in the VTM solution within 30 min. We further demonstrate our assay by detecting SARS-CoV-2 viruses from 20 clinical samples. Finally, we demonstrate a portable and real-time POC device to detect SARS-CoV-2 from VTM samples using an additively manufactured three-dimensional cartridge and a smartphone-based reader. The POC system was tested using 10 clinical samples, and was able to detect SARS-CoV-2 from these clinical samples by distinguishing positive samples from negative samples after 30 min. The POC tests are in complete agreement with RT-PCR controls. This work demonstrates an alternative pathway for SARS-CoV-2 diagnostics that does not require conventional laboratory infrastructure, in settings where diagnosis is required at the point of sample collection.
| S-EPMC7502724 | biostudies-literature
Project description:The COVID-19 pandemic provides an urgent example where a gap exists between availability of state-of-the-art diagnostics and current needs. As assay details and primer sequences become widely known, many laboratories could perform diagnostic tests using methods such as RT-PCR or isothermal RT-LAMP amplification. A key advantage of RT-LAMP based approaches compared to RT-PCR is that RT-LAMP is known to be robust in detecting targets from unprocessed samples. In addition, RT-LAMP assays are performed at a constant temperature enabling speed, simplicity, and point-of-use testing. Here, we provide the details of an RT-LAMP isothermal assay for the detection of SARS-CoV-2 virus with performance comparable to currently approved tests using RT-PCR. We characterize the assay by introducing swabs in virus spiked synthetic nasal fluids, moving the swab to viral transport medium (VTM), and using a volume of that VTM for performing the amplification without an RNA extraction kit. The assay has a Limit-of-Detection (LOD) of 50 RNA copies/μL in the VTM solution within 20 minutes, and LOD of 5000 RNA copies/μL in the nasal solution. Additionally, we show the utility of this assay for real-time point-of-use testing by demonstrating detection of SARS-CoV-2 virus in less than 40 minutes using an additively manufactured cartridge and a smartphone-based reader. Finally, we explore the speed and cost advantages by comparing the required resources and workflows with RT-PCR. This work could accelerate the development and availability of SARS-CoV-2 diagnostics by proving alternatives to conventional laboratory benchtop tests.
| S-EPMC7263486 | biostudies-literature
Project description:CRISPR-Cas technology has widely been applied to detect single-nucleotide mutation and is considered as the next generation of molecular diagnostics. We previously reported the combination of nucleic acid amplification (NAA) and CRISPR-Cas12a system to distinguish major severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. However, the mixture of NAA and CRISPR-Cas12a reagents in one tube could interfere with the efficiency of NAA and CRISPR-Cas12a cleavage, which in turn affects the detection sensitivity. In the current study, we employed a novel photoactivated CRISPR-Cas12a strategy integrated with recombinase polymerase amplification (RPA) to develop one-pot RPA/CRISPR-Cas12a genotyping assay for detecting SARS-CoV-2 Omicron sub-lineages. The new system overcomes the potential inhibition of RPA due to early CRISPR-Cas12a activation and cleavage of the target template in traditional one-pot assay using photocleavable p-RNA, a complementary single-stranded RNA to specifically bind crRNA and precisely block Cas12a activation. The detection can be finished in one tube at 39℃ within 1 h and exhibits a low limit of detection of 30 copies per reaction. Our results demonstrated that the photocontrolled one-pot RPA/CRISPR-Cas12a assay could effectively identify three signature mutations in the spike gene of SARS-CoV-2 Omicron variant, namely, R346T, F486V, and 49X, and distinguish Omicron BA.1, BA.5.2, and BF.7 sub-lineages. Furthermore, the assay achieved a sensitivity of 97.3% and a specificity of 100.0% and showed a concordance of 98.3% with Sanger sequencing results.IMPORTANCEWe successfully developed one-pot recombinase polymerase amplification/CRISPR-Cas12a genotyping assay by adapting photocontrolled CRISPR-Cas technology to optimize the conditions of nucleic acid amplification and CRISPR-Cas12a-mediated detection. This innovative approach was able to quickly distinguish severe acute respiratory syndrome coronavirus 2 Omicron variants and can be readily modified for detecting any nucleic acid mutations. The assay system demonstrates excellent clinical performance, including rapid detection, user-friendly operations, and minimized risk of contamination, which highlights its promising potential as a point-of-care testing for wide applications in resource-limiting settings.
| S-EPMC10913417 | biostudies-literature
Project description:Evaluation of the performance of a new set of primers defined from the ORF1ab sequence, and its combination with a previously published set of primers from the N sequence, to detect SARS-CoV-2 RNA by the loop-mediated isothermal amplification technique is presented. The ORF1ab primer set enables visual detection of SARS-CoV-2 RNA in 16 min. In addition, a simultaneous reaction with both ORF1ab and N primers allows for higher sensitivity of detection, particularly when low numbers of copies are present (250 viral RNA copies). Further, the protocol is able to detect viral RNA in saliva samples. The procedure reported could be easily implemented in the generation of a new and sensitive rapid point-of care device for SARS-CoV-2 RNA visual detection.
| S-EPMC8023013 | biostudies-literature
Project description:ObjectiveTo evaluate a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and compare it with RT-PCR.MethodsWe designed primers specific to the orf1ab and S genes of SARS-CoV-2. Total viral RNA was extracted using the QIAamp Viral RNA Mini Kit. We optimized the RT-LAMP assay, and evaluated it for its sensitivity and specificity of detection using real-time turbidity monitoring and visual observation.ResultsThe primer sets orf1ab-4 and S-123 amplified the genes in the shortest times, the mean (±SD) times were 18 ± 1.32 min and 20 ± 1.80 min, respectively, and 63°C was the optimum reaction temperature. The sensitivities were 2 × 101 copies and 2 × 102 copies per reaction with primer sets orf1ab-4 and S-123, respectively. This assay showed no cross-reactivity with 60 other respiratory pathogens. To describe the availability of this method in clinical diagnosis, we collected 130 specimens from patients with clinically suspected SARS-CoV-2 infection. Among them, 58 were confirmed to be positive and 72 were negative by RT-LAMP. The sensitivity was 100% (95% CI 92.3%-100%), specificity 100% (95% CI 93.7%-100%). This assay detected SARS-CoV-2 in a mean (±SD) time of 26.28 ± 4.48 min and the results can be identified with visual observation.ConclusionThese results demonstrate that we developed a rapid, simple, specific and sensitive RT-LAMP assay for SARS-CoV-2 detection among clinical samples. It will be a powerful tool for SARS-CoV-2 identification, and for monitoring suspected patients, close contacts and high-risk groups.
| S-EPMC7144850 | biostudies-literature
Project description:We report herein the development of a highly sensitive and selective approach for label-free DNA detection by combining target-recycled ligation (TRL), magnetic nanoparticle assisted target capture/separation, and efficient enzymatic amplification. We show that our approach can detect as little as 30 amol (600 fM in 50 ?L) of unlabelled single-stranded DNA targets and offer an exquisitely high discrimination ratio (up to >380 fold with background correction) between a perfect-match cancer mutant and its single-base mismatch (wild-type) DNA target. Furthermore, it can quantitate the rare cancer mutant (KRAS codon 12) in a large excess of coexisting wild-type DNAs down to 0.75%. This sensor appears to be well-suited for sensitive SNP detection and a wide range of DNA mutation based diagnostic applications.
| S-EPMC4576341 | biostudies-literature
Project description:We have devised a novel amplification strategy based on isothermal strand-displacement polymerization reaction, which was termed multiple cross displacement amplification (MCDA). The approach employed a set of ten specially designed primers spanning ten distinct regions of target sequence and was preceded at a constant temperature (61-65 °C). At the assay temperature, the double-stranded DNAs were at dynamic reaction environment of primer-template hybrid, thus the high concentration of primers annealed to the template strands without a denaturing step to initiate the synthesis. For the subsequent isothermal amplification step, a series of primer binding and extension events yielded several single-stranded DNAs and single-stranded single stem-loop DNA structures. Then, these DNA products enabled the strand-displacement reaction to enter into the exponential amplification. Three mainstream methods, including colorimetric indicators, agarose gel electrophoresis and real-time turbidity, were selected for monitoring the MCDA reaction. Moreover, the practical application of the MCDA assay was successfully evaluated by detecting the target pathogen nucleic acid in pork samples, which offered advantages on quick results, modest equipment requirements, easiness in operation, and high specificity and sensitivity. Here we expounded the basic MCDA mechanism and also provided details on an alternative (Single-MCDA assay, S-MCDA) to MCDA technique.
| S-EPMC4648395 | biostudies-other
Project description:The COVID-19 pandemic has illustrated the importance of simple, rapid and accurate diagnostic testing. This study describes the validation of a new rapid SARS-CoV-2 RT-LAMP assay for use on extracted RNA or directly from swab offering an alternative diagnostic pathway that does not rely on traditional reagents that are often in short supply during a pandemic. Analytical specificity (ASp) of this new RT-LAMP assay was 100% and analytical sensitivity (ASe) was between 1 × 101 and 1 × 102 copies per reaction when using a synthetic DNA target. The overall diagnostic sensitivity (DSe) and specificity (DSp) of RNA RT-LAMP was 97% and 99% respectively, relative to the standard of care rRT-PCR. When a CT cut-off of 33 was employed, above which increasingly evidence suggests there is a low risk of patients shedding infectious virus, the diagnostic sensitivity was 100%. The DSe and DSp of Direct RT-LAMP (that does not require RNA extraction) was 67% and 97%, respectively. When setting CT cut-offs of ≤33 and ≤25, the DSe increased to 75% and 100%, respectively, time from swab-to-result, CT < 25, was < 15 min. We propose that RNA RT-LAMP could replace rRT-PCR where there is a need for increased sample throughput and Direct RT-LAMP as a near-patient screening tool to rapidly identify highly contagious individuals within emergency departments and care homes during times of increased disease prevalence ensuring negative results still get laboratory confirmation.
| S-EPMC7703389 | biostudies-literature