Nucleic Acid Amplification Methods Research Articles

Simultaneous detection of bovine viral diarrhea virus (BVDV) and bovine herpesvirus 1 (BoHV-1) using recombinase polymerase amplification

Bovine viral diarrhea virus (BVDV) is considered to be the most common agent of severe diarrhea in cattle worldwide, causing fever, diarrhea, ulcers, and abortion. Bovine herpesvirus 1 (BoHV-1) is also a major bovine respiratory disease agent that spreads worldwide and causes extensive damage to the livestock industry. Recombinase polymerase amplification (RPA) is a novel nucleic acid amplification method with the advantages of high efficiency, rapidity and sensitivity, which has been widely used in the diagnosis of infectious diseases. A dual RPA assay was developed for the simultaneous detection of BVDV and BoHV-1. The assay was completed at a constant temperature of 37 °C for 30 min. It was highly sensitive and had no cross-reactivity with other common bovine viruses. The detection rate of BVDV RPA in clinical samples (36.67%) was higher than that of PCR (33.33%), the detection rate of BoHV-1 RPA and PCR were equal. Therefore, the established dual RPA assay for BVDV and BoHV-1 could be a potential candidate for use as an immediate diagnostic.

Establishment of a Multiplex Detection Method for Common Bacteria in Blood Based on Human Mannan-Binding Lectin Protein-Conjugated Magnetic Bead Enrichment Combined with Recombinase-Aided PCR Technology

ObjectiveRecombinase-aided polymerase chain reaction (RAP) is a sensitive, single-tube, two-stage nucleic acid amplification method. This study aimed to develop an assay that can be used for the early diagnosis of three types of bacteremia caused by Staphylococcus aureus (SA), Pseudomonas aeruginosa (PA), and Acinetobacter baumannii (AB) in the bloodstream based on recombinant human mannan-binding lectin protein (M1 protein)-conjugated magnetic bead (M1 bead) enrichment of pathogens combined with RAP. MethodsRecombinant plasmids were used to evaluate the assay sensitivity. Common blood influenza bacteria were used for the specific detection. Simulated and clinical plasma samples were enriched with M1 beads and then subjected to multiple recombinase-aided PCR (M-RAP) and quantitative PCR (qPCR) assays. Kappa analysis was used to evaluate the consistency between the two assays. ResultsThe M-RAP method had sensitivity rates of 1, 10, and 1 copies/μL for the detection of SA, PA, and AB plasmids, respectively, without cross-reaction to other bacterial species. The M-RAP assay obtained results for < 10 CFU/mL pathogens in the blood within 4 h, with higher sensitivity than qPCR. M-RAP and qPCR for SA, PA, and AB yielded Kappa values of 0.839, 0.815, and 0.856, respectively (P < 0.05). ConclusionAn M-RAP assay for SA, PA, and AB in blood samples utilizing M1 bead enrichment has been developed and can be potentially used for the early detection of bacteremia.

The distribution of hrHPV genotypes among cervical cancer cases diagnosed across Ghana: a cross-sectional study

BackgroundThe burden of cervical cancer in Ghana is high due to a lack of a national screening and vaccination program. Geographical variations in high-risk Human Papilloma Virus incidence and type should be considered for vaccine improvement and screening in LMICs.MethodsA descriptive, multi-center cross-sectional study with purposive sampling of cases with cervical cancer diagnosed from January 2012 through to December 2018 was employed relying on archived Formalin Fixed Paraffin Embedded (FFPE) tissues from four (4) Teaching Hospitals. Cervical cancers were assessed for histopathological features following WHO guidelines. In addition, the novel Tumour Budding and Nest Size Grade (TBNS) for SCC, SILVA pattern of invasion for EAC and Tumour Infiltrating Lymphocytes (TILs) were assessed. High Risk HPV testing was performed using an isothermal, multiplex nucleic acid amplification method from ATILA biosystem (Mountain View California, USA). The FFPE blocks were tested for 15 hrHPV genotypes. Results were analyzed using SPSS v.26.0, with descriptive statistics and cross-tabulation and chi-square tests done with significance established at p < 0.05.ResultsA total of 297 cases were identified for the study with ages ranging from 20 to 95 years. The peak age group for cervical cancer was 46 to 55 years. For those tested, hrHPV positivity rate was 85.4% [EAC (84.6%) and SCC (85.6%)]. The top five hrHPV serotypes for both histological cancers were 59 (40.0%), 35 (32.0%), 18 (30.0%), 16 (15.0%), and 33 (10.0%) respectively. Approximately, 58.2% of infections were multiple. Single hrHPV infections were mostly caused by hrHPV 59 (28.9%), and 16 (26.3%). TBNS grade for SCC, SILVA pattern of invasion for EAC and TILs did not show any statistically significant relationship with hrHPV.ConclusionWe affirm reported differences in hrHPV types associated with cervical cancer in Ghana with hrHPV types such as 59, 35, and 33 forming a significant proportion of hrHPV types associated with cervical cancer. This difference in hrHPV types should guide vaccine improvement and triaging of hrHPV positives. Though multiple infections are more common, some hrHPV types such as hrHPV 16 and 59 are responsible for most single infections associated with cervical cancer. Simple haematoxylin and eosin-based morphological assessments can improve the prognostication of patients with cervical cancer.

Isothermal strand displacement polymerase reaction (ISDPR)-assisted microchip electrophoresis for highly sensitive detection of cancer associated microRNAs

More and more studies have found that microRNAs (miRNAs) are markers of cancer, and detection of miRNAs is beneficial for early diagnosis and prognosis of cancer. In this paper, the isothermal strand displacement polymerase reaction (ISDPR), which is an enzyme-assisted nucleic acid amplification method, was studied to combine with microchip electrophoresis (MCE) for a simultaneously detection of two cancer related miRNAs named microRNA-21 (miR-21) and microRNA-221 (miR-221). In the ISDPR amplification, two different DNA hairpins (HPs) were specifically designed, so that miR-21 and miR-221 could respectively bind to HPs and started ISDPR amplification to generate two different products which were ultimately detected by MCE. The optimal conditions of ISDPR were carefully investigated, and the limits of detection (LOD) of miR-21 and miR-221 were as low as 0.35 fM and 0.25 fM (S/N = 3) respectively under these conditions. The human lung tumor cells and serum samples were analyzed by this ISDPR-MCE method and satisfactory results were obtained, which means that this method is of high sensitivity, high efficiency, low reagent consumption and simple operation in miRNAs detection.

Comprehensive evaluation of nucleic acid amplification methods widely used for generic detection of sandfly-borne phleboviruses.

Virus nucleic acid testing is the primary diagnostic method, particularly in the early stages of illness. Virus-specific or syndromic tests are widely used for this purpose. The use of generic primers has had a considerable impact on the discovery, identification, and detection of Old World sandfly-borne phleboviruses (OWSBP). The study is significant because it is the first to carry out a comparative evaluation of all published OWSBP generic primer sets.

Enhanced selective discrimination of point-mutated viral RNA through false amplification regulatory direct insertion in rolling circle amplification

Coronaviruses are single-stranded RNA viruses with high mutation rates. Although a diagnostic method for coronaviruses has been developed, variants appear rapidly. Low test accuracy owing to single-point mutations is one of the main factors in the failure to prevent the early spread of coronavirus infection. Although reverse transcription-quantitative polymerase chain reaction can detect coronavirus infection, it cannot exclude the possibility of false positives, and an additional multiplexing kit is needed to discriminate single nucleotide polymorphism (SNP) variants. Therefore, in this study, we introduced a new nucleic acid amplification method to determine whether an infected person has a SNP mutation using a lateral flow assay (LFA) as a point-of-care test. Unlike traditional DNA amplification methods, direct insertion into rolling circle amplification amplifies the target genes without false amplification. After SNP-selective nucleic acid amplification, nuclease enzymes are used to make double-stranded DNA fragments that the LFA can detect, where specific mismatched DNA is found and cleaved to show different signals when a SNP-type is present. Therefore, wild- and SNP-type variants can be selectively detected. In this study, the limit of detection was 400 aM for viral RNA, and we successfully identified a dominant SNP variant selectively. Clinical tests were also conducted.

Detection of food contaminants: A review of established rapid analytical techniques and their applications and limitations

AbstractFood contaminants have consistently posed a serious threat to human health and have caused various food safety problems. The most common techniques currently used for the detection of food contaminants, include instrumental and immunoassay methods; however, these traditional methods have shown some limitations when applied to the analysis of food contaminants. Therefore, in recent years, more and more researchers have been devoted to the development of rapid, reliable, sensitive, and suitable detection techniques for the detection of food contaminants in food matrices. In this review, we first classify the analytical methods proposed in recent years into colorimetric methods, fluorescence methods, photoelectrochemical methods, electrochemical methods, nucleic acid amplification methods, and other methods, and illustrate their detection principles. In addition, the paper highlights the strategies and recent research advances for each method through typical application examples. Finally, the future perspectives of these analytical methods are presented. We hope that this review will provide researchers with valuable insights to guide the sensitive detection of food contaminants.

Progress in polymerase chain reaction technology and its contribution to the tuberculosis diagnostic ecosystem in India: A mini review

The advent of Polymerase Chain Reaction (PCR) has revolutionized the human molecular diagnostic scenario. Its ability to exponentially generate desired stretch of DNA from chromosomal or complimentary DNA has laid the foundation for sensitive and specific detection of a pathogen or an aberrant stretch of DNA. Importantly, PCR technology has helped generate diagnostic immunity from phenotypic variation of pathogenic targets. The technological evolution of conventional end-point PCR to its real time version further added clinically important features such as enhanced sensitivity and quantification of target DNA molecules. Two important chemistries became prominent in the real-time PCR domain. The intercalating dye-based chemistry comes with convenience, economy and feature such as melt curve analysis but also carries the disadvantage of overestimation of signal due to unwanted signal from primer dimers. Dual labelled probe on the other hand provides unprecedented sensitivity and specificity. Isothermal method of genome nucleic acid amplification has also evolved as a parallel and convenient method of amplification-based detection of nucleic acid targets. Tuberculosis diagnostics has immensely benefitted from these technologies. However, unmet need exists in sputum handling methods and in its adaptation for molecular diagnostics in resource limited settings. Significant dependence for diagnostic needs on the western world is a matter of concern in India. The country will benefit from rapid and indigenous research and development of molecular diagnostic solutions by way of formulating kits for rapid extraction of DNA and RNA from various clinical sources and developing detection technologies that can compete international products in its category. A solution to address sputum transportation, storage and DNA extraction that has enhanced advantages compared to current methods will also be helpful in the efforts to make India free from tuberculosis.

Bacterial vaginosis as a factor associated with adverse pregnancy outcomes

Bacterial vaginosis is the most common disease of the genitals and affects 20–70% of women. This non-inflammatory syndrome is characterized by dysbiosis of the vaginal microbiota and is accompanied by a decrease in the number of lactobacilli. Bacterial vaginosis in 60% of pregnant women is asymptomatic, but can lead to obstetric complications such as late miscarriage, premature birth, fetal growth restriction, premature rupture of membranes, choriominionitis, postpartum endometritis, and sepsis. The clinical picture of bacterial vaginosis in pregnant women is the same as in non-pregnant women, namely homogeneous whitish-gray discharge from the genital tract, often with an unpleasant “fishy” smell, rarely itching and/or burning in the genital area and urethra, as well as soreness during urination (dysuria), with no signs of an inflammation detected in the genitals. Diagnosis of bacterial vaginosis in pregnant women, as well as in non-pregnant women, is based on the use of clinical and laboratory methods. Multiplex tests based on the nucleic acid amplification method, such as real-time polymerase chain reaction, are very popular for the diagnosis of bacterial vaginosis in this country. The Femoflor-16 Reagent Kit (DNA Technology CJSC, Moscow, Russia) is designed to detect the DNA of opportunistic microorganisms, lactobacilli DNA and human genomic DNA (as a control for taking biological material). Examination of pregnant women, especially in case of complaints of vaginal discharge, should be carried out when registering for pregnancy in order to start treatment early and prevent adverse pregnancy outcomes for the mother and fetus. Biofilms formed by microorganisms in bacterial vaginosis, especially G. vaginalis, limit the penetration of antibacterial agents to bacteria, their concentration being lower than therapeutic one, which leads to ineffective treatment. There remain many unexplored issues related to changes in the epidemiology of bacterial vaginosis, an increase in the frequency of relapses against the background of increasing resistance of microorganisms associated with bacterial vaginosis to antibiotics, and the development of agents that affect bacterial films.

Prognostic factors of virus-associated pneumonia other than COVID-19 in adults

ObjectiveTo determine prognostic factors of virus-associated pneumonia other than coronavirus disease 2019. MethodsWe retrospectively studied patients suffering from virus-associated community-acquired pneumonia, and who were admitted to Saitama Cardiovascular and Respiratory Center from 2002 to 2020. Prognostic factors were analyzed by univariable and multivariable regression analysis of patient demographics, laboratory data, chest imaging, severity on admission, and initial treatment. PatientsHIV-positive patients, those with non-resected lung cancer or receiving chemotherapy, and those with COVID-19 were excluded. Included were 363 patients diagnosed by nucleic acid amplification method, paired sera, and rapid diagnostic tests. ResultsA CURB-65 score of ≥3 was significant by univariable analysis for 60-day mortality but was nonsignificant by multivariable analysis. The poor prognostic factors that were significant by multivariable analysis (p < 0.05) included immunosuppressive state due to systemic corticosteroid or immunosuppressant administration, acute kidney injury on admission, and corticosteroid administration initiated within 5 days or 5 days to 2 weeks from onset. ConclusionA CURB-65 score of ≥3, which is considered to indicate severe pneumonia, was of limited value for predicting mortality of virus-associated pneumonia. We showed patients’ underlying diseases and complications to be independent factors of poor prognosis for 60-day mortality. Timing of the initiation of corticosteroid administration remains to be elucidated.

Rapid Minimum Inhibitory Concentration (MIC) Analysis Using Lyophilized Reagent Beads in a Novel Multiphase, Single-Vessel Assay.

Antimicrobial resistance (AMR) is a global threat fueled by incorrect (and overuse) of antibiotic drugs, giving rise to the evolution of multi- and extreme drug-resistant bacterial strains. The longer time to antibiotic administration (TTA) associated with the gold standard bacterial culture method has been responsible for the empirical usage of antibiotics and is a key factor in the rise of AMR. While polymerase chain reaction (PCR) and other nucleic acid amplification methods are rapidly replacing traditional culture methods, their scope has been restricted mainly to detect genotypic determinants of resistance and provide little to no information on phenotypic susceptibility to antibiotics. The work presented here aims to provide phenotypic antimicrobial susceptibility testing (AST) information by pairing short growth periods (~3-4 h) with downstream PCR assays to ultimately predict minimum inhibitory concentration (MIC) values of antibiotic treatment. To further simplify the dual workflows of the AST and PCR assays, these reactions are carried out in a single-vessel format (PCR tube) using novel lyophilized reagent beads (LRBs), which store dried PCR reagents along with primers and enzymes, and antibiotic drugs separately. The two reactions are separated in space and time using a melting paraffin wax seal, thus eliminating the need to transfer reagents across different consumables and minimizing user interactions. Finally, these two-step single-vessel reactions are multiplexed by using a microfluidic manifold that allows simultaneous testing of an unknown bacterial sample against different antibiotics at varying concentrations. The LRBs used in the microfluidic system showed no interference with the bacterial growth and PCR assays and provided an innovative platform for rapid point-of-care diagnostics (POC-Dx).

Development and application of the MIRA and MIRA-LFD detection methods of Spiroplasma eriocheiris

The tremor disease (TD) caused by Spiroplasma eriocheiris is the most destructive disease of the Chinese mitten crab, Eriocheir sinensis. This study attempts to construct Multienzyme Isothermal Rapid Amplification (MIRA), a quick and simple nucleic acid amplification method that operates at room temperature. Based on the gene sequences of S. eriocheiris, appropriate amplification primers were constructed and screened in this investigation. Both the relevant specific probe and the chosen specific amplification primers were designed and labeled. The MIRA and MIRA-LFD reaction conditions were then optimized. The result showed MIRA and MIRA-FFD could identify S. eriocheiris at 37 °C in 30 min and 15 min, respectively. To investigate the specificity of MIRA and MIRA-LFD, three Gram-negative bacteria (Bacillus subtilis, Bacillus thuringiensis, and Staphylococcus aureus), three Gram-positive bacteria (Escherichia coli, Aeromonas hydrophila, and Salmonella typhimurium) and S. eriocheiris were selected. The result showed MIRA and MIRA-LFD were highly specific to S. eriocheiris and did not react with other six pathogens. The sensitivities of PCR, MIRA, and MIRA-LFD were then evaluated. The result showed the detection limit of PCR is 1 ng/L whereas the detection limit of MIRA and MIRA-LFD is 10 pg/L. Finally, the established MIRA and MIRA-LFD detection methods had the advantages of being quick, sensitive, and specific for S. eriocheiris detection, as well as not requiring any specialized equipment.

Whole genome enrichment approach for genomic surveillance of Toxoplasma gondii

Pathogenic bacteria, viruses, fungi, and protozoa can cause food and waterborne diseases. Surveillance methods must therefore screen for these pathogens at various stages of water distribution and of food from production to consumption. Detection using nucleic acid amplification methods offer rapid identification, but such methods have limited utility for characterizing populations, variant types or virulence traits of pathogens. Whole genome sequencing (WGS) can be used to determine this information. However, pathogens must be isolated and cultured to yield sufficient DNA for WGS, which is laborious or not feasible for certain stages of parasites like oocysts of Toxoplasma gondii. We previously developed the Circular Nucleic acid Enrichment Reagent (CNER) method to make whole genome enrichment (WGE) baits for difficult-to-grow bacterial pathogens. WGE using CNERs facilitates direct sequencing of pathogens from samples without the need to isolate and grow them. Here, we made WGE-CNERs for T. gondii to demonstrate the use of the CNER method to make baits to enrich the large genomes of water and foodborne protozoan pathogens. By sequencing, we detected as few as 50 parasites spiked in an oyster hemolymph matrix. We discuss the use of WGE-CNERs for genomic surveillance of food and waterborne pathogens.

Integration of Isothermal Enzyme-Free Nucleic Acid Circuits for High-Performance Biosensing Applications.

The isothermal enzyme-free nucleic acid amplification method plays an indispensable role in biosensing by virtue of its simple, robust, and highly efficient properties without the assistance of temperature cycling or/and enzymatic biocatalysis. Up to now, enzyme-free nucleic acid amplification has been extensively utilized for biological assays and has achieved the highly sensitive detection of various biological targets, including DNAs, RNAs, small molecules, proteins, and even cells. In this Review, the mechanisms of entropy-driven reaction, hybridization chain reaction, catalytic hairpin assembly and DNAzyme are concisely described and their recent application as biosensors is comprehensively summarized. Furthermore, the current problems and the developments of these DNA circuits are also discussed.

Retraction Note: Polymerase Spiral Reaction (PSR): A novel isothermal nucleic acid amplification method

Retraction Note: Polymerase Spiral Reaction (PSR): A novel isothermal nucleic acid amplification method

New technologies provide innovative opportunities to enhance understanding of major virus diseases threatening global food security.

Plant viruses pose a continuous and serious threat to crop production worldwide, while globalization and climate change are exacerbating the establishment and rapid spread of new viruses. Simultaneously, developments in genome sequencing technology, nucleic acid amplification methods, and epidemiological modeling are providing plant health specialists with unprecedented opportunities to confront these major threats to the food security and livelihoods of millions of resource-constrained smallholders. In this perspective, we have used recent examples of integrated application of these technologies to enhance understanding of the emergence of plant viral diseases of key food security crops in low- and middle-income countries. We highlight how international funding and collaboration have enabled high-throughput sequencing-based surveillance approaches, targeted field and lab-based diagnostic tools, and modeling approaches that can be effectively used to support surveillance and preparedness against existing and emerging plant viral threats. The importance of national and international collaboration and the future role of CGIAR in further supporting these efforts, including building capabilities to make optimal use of these technologies in low- and middle-income countries is discussed.

Optimization and Validation of Reverse Transcription Recombinase-Aided Amplification (RT-RAA) for Sorghum Mosaic Virus Detection in Sugarcane.

Sorghum mosaic virus (SrMV) causes sugarcane mosaic disease and has significant adverse economic impacts on the cultivation of sugarcane. This study aimed to develop a rapid isotherm nucleic acid amplification method for detecting SrMV. Specific primers were designed to target the conserved region of the P3 gene of SrMV. The reverse transcription recombinase-aided amplification (RT-RAA) method was developed by screening primers and optimizing reaction conditions. Comparative analyses with RT-PCR demonstrated that the RT-RAA method exhibited superior specificity, sensitivity, and reliability for SrMV detection. Notably, using a standard plasmid diluted 10-fold continuously as a template, the sensitivity of RT-RAA was 100-fold higher than that of RT-PCR. Moreover, the RT-RAA reaction displayed flexibility in a temperature range of 24-49 °C, eliminating the need for expensive and complex temperature control equipment. Thus, this method could be utilized at ambient or even human body temperature. Within a short duration of 10 min at 39 °C, the target sequence of SrMV could be effectively amplified. Specificity analysis revealed no cross-reactivity between SrMV and other common sugarcane viruses detected via the RT-RAA. With its high sensitivity, rapid reaction time, and minimal equipment requirements, this method presents a promising diagnostic tool for the reliable and expedited detection of SrMV. Furthermore, it indicates broad applicability for successfully detecting other sugarcane viruses.

CRISPR-Cas13a-Based Assay for Accurate Detection of OXA-48 and GES Carbapenemases.

Carbapenem-resistant pathogens have been recognized as a health concern as they are both difficult to treat and detect in clinical microbiology laboratories. Researchers are making great efforts to develop highly specific, sensitive, accurate, and rapid diagnostic techniques, required to prevent the spread of these microorganisms and improve the prognosis of patients. In this context, CRISPR-Cas systems are proposed as promising tools for the development of diagnostic methods due to their high specificity; the Cas13a endonuclease can discriminate single nucleotide changes and displays collateral cleavage activity against single-stranded RNA molecules when activated. This technology is usually combined with isothermal pre-amplification reactions in order to increase its sensitivity. We have developed a new LAMP-CRISPR-Cas13a-based assay for the detection of OXA-48 and GES carbapenemases in clinical samples without the need for nucleic acid purification and concentration. To evaluate the assay, we used 68 OXA-48-like-producing Klebsiella pneumoniae clinical isolates as well as 64 Enterobacter cloacae complex GES-6, 14 Pseudomonas aeruginosa GES-5, 9 Serratia marcescens GES-6, 5 P. aeruginosa GES-6, and 3 P. aeruginosa (GES-15, GES-27, and GES-40) and 1 K. pneumoniae GES-2 isolates. The assay, which takes less than 2 h and costs approximately 10 € per reaction, exhibited 100% specificity and sensitivity (99% confidence interval [CI]) for both OXA-48 and all GES carbapenemases. IMPORTANCE Carbapenems are one of the last-resort antibiotics for defense against multidrug-resistant pathogens. Multiple nucleic acid amplification methods, including multiplex PCR, multiplex loop-mediated isothermal amplification (LAMP) and multiplex RPAs, can achieve rapid, accurate, and simultaneous detection of several resistance genes to carbapenems in a single reaction. However, these assays need thermal cycling steps and specialized instruments, giving them limited application in the field. In this work, we adapted with high specificity and sensitivity values, a new LAMP CRISPR-Cas13a-based assay for the detection of OXA-48 and GES carbapenemases in clinical samples without the need for RNA extraction.

Detection of Listeria monocytogenes in Food Using the Proofman-LMTIA Assay.

Microbial factors, including bacteria, viruses, and other pathogens, are significant contributors to foodborne illnesses, posing serious food safety risks due to their potential for rapid growth and contamination. Listeria monocytogenes is one of the most common types of foodborne bacteria that can cause serious foodborne diseases or even fatalities. In this study, a novel nucleic acid amplification method called Proofman-LMTIA was employed to detect Listeria monocytogenes contamination in food. This method combines proofreading enzyme-mediated probe cleavage with ladder-shape melting temperature isothermal amplification. A positive recombinant plasmid was used as a control to ensure the accuracy of the detection results, and primers and Proofman probes were specifically designed for the LMTIA. Genomic DNA was extracted, the reaction temperature was optimized, and the primers' specificity was verified using foodborne pathogens like Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella. The sensitivity was assessed by testing serial dilutions of genomic DNA, and the method's applicability was confirmed by detecting artificially contaminated fresh pork. The established LMTIA method exhibited both high specificity and sensitivity. At the optimal reaction temperature of 63 °C, the primers specifically identified Listeria monocytogenes contamination in pork at a concentration of 8.0 ± 0.7 colony-forming units (CFUs) per 25 g. Furthermore, the Proofman-LMTIA method was applied to test Listeria monocytogenes DNA in 30 food samples purchased from a Chinese retail market, and reassuringly, all results indicated no contamination. Proofman-LMTIA can serve as a reliable and rapid method for detecting Listeria monocytogenes in food, contributing to public health by safeguarding consumers from foodborne illnesses, and strengthening food safety regulations.

Ultrasensitive detection of exosomes by microchip electrophoresis combining with triple amplification strategies

The analysis of exosomes is significant as they can be used for various pathophysiological processes, especially cancer related intercellular communication. Therefore, a convenient, reliable, and sensitive detection method is urgently needed. Strand displacement amplification (SDA) and catalytic hairpin assembly (CHA) are two kinds of effective isothermal nucleic acid amplification methods. In this article, an efficient quantitative MCE method for detecting human breast cancer cell (MCF-7) exosomes assisted by triple amplification strategies combining cholesterol probe (Chol-probe) with SDA-CHA was first developed. CD63 aptamer was immobilized on the avidin magnetic beads to specifically capture exosomes and then Chol-probe with high affinity was spontaneously inserted into the exosome membrane, which was the first step of amplification strategy to improve detection sensitivity. After magnetic separation, Chol-probe could complement ssDNA and trigger SDA, producing a large number of DNA sequences (Ta) to trigger CHA, achieving SDA-CHA amplification. Under optimal conditions, the detection limit (LOD) for MCF-7 exosomes was as low as 26 particle/μL (S/N = 3). This method provides an effective approach for sensitive and accurate quantification of tumor exosomes, and can be expected to detect exosomes in clinical samples.