Integrated DNA and RNA extraction using magnetic beads from viral pathogens causing acute respiratory infections

Optimizing total RNA extraction method for human and mice samples

Background

Extracting high-quality total RNA is pivotal for advanced RNA molecular studies, such as Next-generation sequencing and expression microarrays where RNA is hybridized. Despite the development of numerous extraction methods in recent decades, like the cetyl-trimethyl ammonium bromide (CTAB) and the traditional TRIzol reagent methods, their complexity and high costs often impede their application in small-scale laboratories. Therefore, a practical and economical method for RNA extraction that maintains high standards of efficiency and quality needs to be provided to optimize RNA extraction from human and mice tissues.

Method

This study proposes enhancements to the TRIzol method by incorporating guanidine isothiocyanate (GITC-T method) and sodium dodecyl sulfate (SDS-T method). We evaluated the effectiveness of these modified methods compared to the TRIzol method using a micro-volume UV-visible spectrophotometer, electrophoresis, q-PCR, RNA-Seq, and whole transcriptome sequencing.

Result

The micro-volume UV-visible spectrophotometer, electrophoresis, and RNA-Seq demonstrated that the GITC-T method yielded RNA with higher yields, integrity, and purity, while the consistency in RNA quality between the two methods was confirmed. Taking mouse cerebral cortex tissue as a sample, the yield of total RNA extracted by the GITC-T method was 1,959.06 ± 49.68 ng/mg, while the yield of total RNA extracted by the TRIzol method was 1,673.08 ± 86.39 ng/mg. At the same time, the OD260/280 of the total RNA samples extracted by the GITC-T method was 2.03 ± 0.012, and the OD260/230 was 2.17 ± 0.031, while the OD260/280 of the total RNA samples extracted by the TRIzol method was 2.013 ± 0.041 and the OD260/230 was 2.11 ± 0.062. Furthermore, q-PCR indicated that the GITC-T method achieved higher yields, purity, and greater transcript abundance of total RNA from the same types of animal samples than the TRIzol method.

Conclusion

The GITC-T method not only yields higher purity and quantity of RNA but also reduces reagent consumption and overall costs, thereby presenting a more feasible option for small-scale laboratory settings.

Direct Zeptomole Detection of RNA Biomarkers by Ultrabright Fluorescent Nanoparticles on Magnetic Beads

Nucleic acids are important biomarkers in cancer and viral diseases. However, their ultralow concentration in biological/clinical samples makes direct target detection challenging, because it leads to slow hybridization kinetics with the probe and its insufficient signal-to-noise ratio. Therefore, RNA target detection is done by molecular (target) amplification, notably by RT-PCR, which is a tedious multistep method that includes nucleic acid extraction and reverse transcription. Here, a direct method based on ultrabright dye-loaded polymeric nanoparticles in a sandwich-like hybridization assay with magnetic beads is reported. The ultrabright DNA-functionalized nanoparticle, equivalent to ≈10 000 strongly emissive rhodamine dyes, is hybridized with the magnetic bead to the RNA target, providing the signal amplification for the detection. This concept (magneto-fluorescent sandwich) enables high-throughput detection of DNA and RNA sequences of varied lengths from 48 to 1362 nt with the limit of detection down to 0.3 fm using a plate reader (15 zeptomoles), among the best reported for optical sandwich assays. Moreover, it allows semi-quantitative detection of SARS-CoV-2 viral RNA directly in clinical samples without a dedicated RNA extraction step. The developed technology, combining ultrabright nanoparticles with magnetic beads, addresses fundamental challenges in RNA detection; it is expected to accelerate molecular diagnostics of diseases.

The surface modification of the silica-coated magnetic nanoparticles and their application in molecular diagnostics of virus infection

The study presents a series of examples of magnetic nanoparticle systems designed for the diagnosis of viral diseases. In this interdisciplinary work, we describe one of the most comprehensive synthetic approaches for the preparation and functionalization of smart nanoparticle systems for rapid and effective RT-PCR diagnostics and isolation of viral RNA. Twelve different organic ligands and inorganic porous silica were used for surface functionalization of the Fe3O4 magnetic core to increase the number of active centres for efficient RNA binding from human swab samples. Different nanoparticle systems with common beads were characterized by HRTEM, SEM, FT-IR, XRD, XPS and magnetic measurements. We demonstrate the application of the fundamental models modified to fit the experimental zero-field cooling magnetization data. We discuss the influence of the nanoparticle shell parameters (morphology, thickness, ligands) on the overall magnetic performance of the systems. The prepared nanoparticles were tested for the isolation of viral RNA from tissue samples infected with hepatitis E virus-HEV and from biofluid samples of SARS-CoV-2 positive patients. The efficiency of RNA isolation was quantified by RT-qPCR method.

Palm-Sized Lab-In-A-Magnetofluidic Tube Platform for Rapid and Sensitive Virus Detection

Simple, sensitive, and accurate molecular diagnostics are critical for preventing rapid spread of infection and initiating early treatment of diseases. However, current molecular detection methods typically rely on extensive nucleic acid sample preparation and expensive instrumentation. Here, a simple, fully integrated, lab-in-a-magnetofluidic tube (LIAMT) platform is presented for "sample-to-result" molecular detection of virus. By leveraging magnetofluidic transport of micro/nano magnetic beads, the LIAMT device integrates viral lysis, nucleic acid extraction, isothermal amplification, and CRISPR detection within a single engineered microcentrifuge tube. To enable point-of-care molecular diagnostics, a palm-sized processor is developed for magnetofluidic separation, nucleic acid amplification, and visual fluorescence detection. The LIAMT platform is applied to detect SARS-CoV-2 and HIV viruses, achieving a detection sensitivity of 73.4 and 63.9 copies µL-1, respectively. Its clinical utility is further demonstrated by detecting SARS-CoV-2 and HIV in clinical samples. This simple, affordable, and portable LIAMT platform holds promise for rapid and sensitive molecular diagnostics of infectious diseases at the point-of-care.

A semi-automated and high-throughput approach for the detection of honey bee viruses in bee samples

Deformed wing virus (DWV) was first detected in dead honey bees in 1982 but has been in honey bees for at least 300 years. Due to its high prevalence and virulence, they have been linked with the ongoing decline in honey bee populations worldwide. A rapid, simple, semi-automated, high-throughput, and cost-effective method of screening colonies for viruses would benefit bee research and the beekeeping industry. Here we describe a semi-automated approach that combines an RNA-grade liquid homogenizer followed by magnetic bead capture for total virus nucleic acid extraction. We compare it to the more commonly applied nucleic acid column-based purification method and use qPCR plus Oxford Nanopore Technologies sequencing to evaluate the accuracy of analytical results for both methods. Our results showed high reproducibility and accuracy for both approaches. The semi-automated method described here allows for faster screening of viral loads in units of 96 samples at a time. We developed this method to monitor viral loads in honey bee colonies, but it could be easily applied for any PCR or genomic-based screening assays.

Silica-coated magnetic particles for efficient RNA extraction for SARS-CoV-2 detection

Molecular diagnostic methods to detect and quantify viral RNA in clinical samples rely on the purification of the genetic material prior to reverse transcription polymerase chain reaction (qRT-PCR). Due to the large number of samples processed in clinical laboratories, automation has become a necessity in order to increase method processivity and maximize throughput per unit of time. An attractive option for isolating viral RNA is based on the magnetic solid phase separation procedure (MSPS) using magnetic microparticles. This method offers the advantage over other alternative methods of making it possible to automate the process. In this study, we report the results of the MSPS method based on magnetic microparticles obtained by a simple synthesis process, to purify RNA from oro- and nasopharyngeal swab samples of patients suspected of COVID-19 provided by three diagnostic laboratories located in the Buenos Aires Province, Argentina. Magnetite nanoparticles of Fe3O4 (MNPs) were synthesized by the coprecipitation method and then coated with silica (SiO2) produced by hydrolysis of tetraethyl orthosilicate (TEOS). After preliminary tests on samples from the A549 human lung cell line and swabs, an extraction protocol was developed. The quantity and purity of the RNA obtained were determined by gel electrophoresis, spectrophotometry, and qRT-PCR. Tests on samples from naso- and oropharyngeal swabs were performed in order to validate the method for RNA purification in high-throughput SARS-CoV-2 diagnosis by qRT-PCR. The method was compared to the spin columns method and the automated method using commercial magnetic particles. The results show that the method developed is efficient for RNA extraction from nasal and oropharyngeal swab samples, and also comparable to other extraction methods in terms of sensitivity for SARS-CoV-2 detection. Of note, this procedure and reagents developed locally were intended to overcome the shortage of imported diagnostic supplies as the sudden spread of COVID-19 required unexpected quantities of nucleic acid isolation and diagnostic kits worldwide.

Combination of nucleic acid amplification and CRISPR/Cas technology in pathogen detection

Major health events caused by pathogenic microorganisms are increasing, seriously jeopardizing human lives. Currently PCR and ITA are widely used for rapid testing in food, medicine, industry and agriculture. However, due to the non-specificity of the amplification process, researchers have proposed the combination of nucleic acid amplification technology with the novel technology CRISPR for detection, which improves the specificity and credibility of results. This paper summarizes the research progress of nucleic acid amplification technology in conjunction with CRISPR/Cas technology for the detection of pathogens, which provides a reference and theoretical basis for the subsequent application of nucleic acid amplification technology in the field of pathogen detection.

A preliminary exploration for co-detecting RNA virus and STR type on capillary electrophoresis in forensic practice

RNA virus infection such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection shows severe respiratory symptoms on human and could be an obvious individual characteristic for investigations in forensic science. As for biological samples suspected to contain RNA virus in forensic casework, it requires respective detection of viral RNA and human DNA: reverse transcriptase polymerase chain reaction and DNA type (short tandem repeat [STR] analysis). Capillary electrophoresis (CE) has been shown to be a versatile technique and used for a variety of applications, so we preliminarily explored the co-detection of RNA virus and STR type on CE by developing a system of co-detecting SARS-CoV-2 and STR type under ensuring both the efficiency of forensic DNA analysis and safety of the laboratory. This study investigated the development and validation of the system, including N and ORF1ab primer designs, polymerase chain reaction amplification, allelic ladder, CE detection, thermal cycling parameters, concordance, sensitivity, species specificity, precision, and contrived and real SARS-CoV-2 sample studies. Final results showed the system could simultaneously detect SARS-CoV-2 and STR type, further indicating that CE has possibilities in the multi-detection of RNA viruses/STR type to help to prompt individual characteristics (viral infection) and narrow the scope of investigation in forensic science.

CRISPR Assays for Disease Diagnosis: Progress to and Barriers Remaining for Clinical Applications

Numerous groups have employed the special properties of CRISPR/Cas systems to develop platforms that have broad potential applications for sensitive and specific detection of nucleic acid (NA) targets. However, few of these approaches have progressed to commercial or clinical applications. This review summarizes the properties of known CRISPR/Cas systems and their applications, challenges associated with the development of such assays, and opportunities to improve their performance or address unmet assay needs using nano-/micro-technology platforms. These include rapid and efficient sample preparation, integrated single-tube, amplification-free, quantifiable, multiplex, and non-NA assays. Finally, this review discusses the current outlook for such assays, including remaining barriers for clinical or point-of-care applications and their commercial development.

Graphene Oxide/Nitrocellulose Non-Covalent Hybrid as Solid Phase for Oligo-DNA Extraction from Complex Medium

A nitrocellulose-graphene oxide hybrid that consists of a commercially nitrocellulose (NC) membrane non-covalently modified with graphene oxide (GO) microparticles was successfully prepared for oligonucleotide extraction. The modification of NC membrane was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), which highlighted the principal absorption bands of both the NC membrane at 1641, 1276, and 835 cm^-1 (NO₂) and of GO in the range of 3450 cm^-1 (CH₂-OH). The SEM analysis underlined the well-dispersed and uniform coverage of NC membrane with GO, which displayed thin spider web morphology. The wettability assay indicated that the NC-GO hybrid membrane exhibited slightly lower hydrophilic behavior, with a water contact angle of 26.7°, compared to the 15° contact angle of the NC control membrane. The NC-GO hybrid membranes were used to separate oligonucleotides that had fewer than 50 nucleotides (nt) from complex solutions. The features of the NC-GO hybrid membranes were tested for extraction periods of 30, 45, and 60 min in three different complex solutions, i.e., an aqueous medium, an α-Minimum Essential Medium (αMEM), and an αMEM supplemented with fetal bovine serum (FBS). The oligonucleotides were desorbed from the surface of the NC-GO hybrid membrane using Tris-HCl buffer with a pH of 8.0. Out of the three media utilized, the best results were achieved after 60 min incubation of the NC-GO membranes in αMEM, as evidenced by the highest fluorescence emission of 294 relative fluorescence units (r.f.u.). This value corresponded to the extraction of approximately 330-370 pg (≈7%) of the total oligo-DNA. This method is an efficient and effortless way to purify short oligonucleotides from complex solutions.

On-Chip Nucleic Acid Purification Followed by ddPCR for SARS-CoV-2 Detection

We developed a microfluidic chip integrated with nucleic acid purification and droplet-based digital polymerase chain reaction (ddPCR) modules to realize a 'sample-in, result-out' infectious virus diagnosis. The whole process involved pulling magnetic beads through drops in an oil-enclosed environment. The purified nucleic acids were dispensed into microdroplets by a concentric-ring, oil-water-mixing, flow-focusing droplets generator driven under negative pressure conditions. Microdroplets were generated with good uniformity (CV = 5.8%), adjustable diameters (50-200 μm), and controllable flow rates (0-0.3 μL/s). Further verification was provided by quantitative detection of plasmids. We observed a linear correlation of R² = 0.9998 in the concentration range from 10 to 10⁵ copies/μL. Finally, this chip was applied to quantify the nucleic acid concentrations of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The measured nucleic acid recovery rate of 75 ± 8.8% and detection limit of 10 copies/μL proved its on-chip purification and accurate detection abilities. This chip can potentially be a valuable tool in point-of-care testing.

Improved DNA extraction on bamboo paper and cotton is tightly correlated with their crystallinity and hygroscopicity

DNA extraction, a vital pre-requisite for most biological studies, continues to be studied extensively. According to some studies, DNA shows a certain degree of absorbability on filter paper made of plant fiber-based adsorbent material. However, the principle underlying such specific adsorption as well as plant species associated with plant fiber-based adsorbents and optimized extraction conditions have not yet been studied. This study demonstrates the tight correlation between crystallinity and hygroscopicity in plant fiber-based adsorbents used for DNA extraction and proposes the concept of DNA adsorption on plant fiber-based adsorbents, for the first time. We also explored optimal extracting and eluting conditions and developed a novel plant fiber-based DNA extraction method that was quadruple times more powerful than current approaches. Starting with the screening of various types of earthed plant fiber-based adsorbents, we went on to mine new plant fiber-based adsorbents, bamboo paper and degreased cotton, and succeeded in increasing their efficiency of DNA extraction to 4.2 times than that of current approaches. We found a very strong correlation between the crystallinity and hygroscopicity of plant fiber-based adsorbents which showed efficiency for DNA extraction, and thus propose a principle that potentially governs such specific adsorption processes, in the hope that this information may guide related multidisciplinary research studies in the future. Nanodrop, electrophoresis and PCR were selected to demonstrate the quantity, quality, integrity and utility of the extracted DNA. Furthermore, crystallinity, hygroscopicity, pore size distribution and composition of plant fiber-based adsorbents were studied to explore their correlation in an attempt to understand the principle underlying this particular type of adsorption. The findings of this study may be further extended to the extraction of other types of nucleic acids with similar biochemical properties.

Research on safety and compliance of imported microbial inoculants using high-throughput sequencing

Microbial inoculants are widely used in wastewater treatment, soil remediation, and biological control. Safety and compliance for active constituents are considered to be the most important measures of imported microbial inoculants. Microbial inoculants composition was commonly identified by phenotypic culture, which is time-consuming and labor intense with occasionally false negative results provided, and can only be tested for specific species. High-throughput sequencing (HTS), known for its non-targeted detection of unknown species composition in samples, is suitable for composition consistency identification and biosafety analysis of imported microbial inoculants. In this study, the application of HTS for microflora distribution and resistance gene was verified in microbial inoculants for environmental protection and then applicated in imported microbial inoculants. Both Illumina- and Nanopore-based HTS methods identified the same dominant bacterial species successfully in the imported microbial inoculants. The main component of bacterial species was Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Enterococcus faecium, and further confirmed with traditional methods. The antibiotic resistance genes Bacillus subtilis mprF, bcrA, blt, lmrB, rphB, tet(L), tmrB, vmlR, ykkC, and ykkD were detected in all samples. Our results indicated that HTS processes the application potential to identify the active ingredients of microbial inoculants. Therefore, rapid and accurate identification of the microbial compositions in microbial formulation products is of high importance for port biosafety supervision.

Rapid Nucleic Acid Extraction for Aquatic Animal DNA Virus Determination Using Chelex 100 Resin via Conventional PCR and Digital Droplet PCR Detection

Simple Summary

Convenient, fast, and high-quality nucleic acid extraction methods are urgently needed in molecular diagnostic testing for viral pathogens in aquaculture. We developed a viral DNA extraction method from diseased tissues and cells using the Chelex 100 resin solution workflow. The only extraction reagents required are the Chelex 100 resin and phosphate-buffered saline. The whole extraction process only takes about 15 min from the tissue homogenate to obtain the DNA. The concentration of extracted DNA is at least 100 ng/µL. This methodology has clear benefits in terms of cost and time saving compared to the commercial kit extraction for aquatic animal DNA virus determination by PCR in the laboratory. In addition, the simplified method using Chelex 100 resin with a pH value of 10–11 presented excellent results in PCR application and could be a standard for the DNA extraction for DNA virus testing in the future.

Abstract

Molecular diagnostic testing for viral pathogens is crucial in aquaculture. The efficient and convenient preparation of pathogenic microbial nucleic acids is the basis of molecular diagnosis. Here, we developed a simplified deoxyribonucleic acid (DNA) extraction method from aquatic animal DNA viruses using the Chelex 100 resin. The nucleic acid was extracted from infected tissues and cell culture for the detection of three common aquatic viral pathogens (CEV, CyHV-2, and GSIV). We compared the extraction effects of a current commercial kit extraction method and the Chelex 100 resin extraction method according to nucleic acid concentration, conventional polymerase chain reaction (PCR), and digital droplet PCR (ddPCR). The results indicated that both extraction procedures could obtain high-quality nucleotide samples. Extracting DNA using the Chelex 100 resin led to better detective efficiency for ddPCR molecular diagnostic testing. The whole process took less than 20 min, and only Chelex 100 resin solution was added to the tissues or cells without multiple tubes being transferred several times. The extracted DNA concentration and the detection sensitivity were high. These results indicated that the Chelex 100 resin solution has the advantages of speed, efficiency, and economy compared to the commercial kit. In addition, the higher pH value (10–11) of the Chelex 100 resin solution markedly improved the detection sensitivity compared to a lower pH value (9–10). In conclusion, the comparison of the Chelex 100 Resin and commercial viral DNA extraction kits revealed the good performance of the Chelex 100 resin solution at pH 10–11 in DNA extraction for PCR amplification from aquatic animal viral samples of tissues and cells in molecular diagnostic testing. It is both rapid and cost-effective.

A comparison of SARS-CoV-2 RNA extraction with the QuickGene-810 Nucleic Acid Isolation System compared to the EZ1 Advanced DSP Virus Kit

The QuickGene-810 Nucleic Acid Isolation System is a semi-automated extraction platform which may be used for RNA extraction. New methods were required to support the rapid increase in respiratory virus testing during the SARS-CoV-2 pandemic. The aim of this study was to assess SARS-CoV-2 RNA extraction using the QuickGene-810 kit compared to the EZ1 Advanced Extraction Platform for use on the AusDiagnostics SARS-CoV-2, Influenza and RSV 8-well RT-PCR assay. Qualitative results from all clinical samples were concordant between the QuickGene-810 and the EZ1 extraction methods, demonstrating that the QuickGene-810 kit is suitable for use in pathogen diagnostics. However, there was an average difference of approximately two cycles between the cycle threshold (Ct) values for both SARS-CoV-2 targets, suggesting that the EZ1 kit yields a higher concentration of nucleic acid extract, possibly related to its use of carrier RNA and/or smaller elution volume, which infers the possibility of false negative results for samples with very low viral loads.

Development and application of LAMP assays for the detection of enteric adenoviruses in feces

Loop-mediated isothermal amplification (LAMP) is an alternative to PCR that is faster and requires fewer resources. Here, we describe two LAMP assays for the detection of human adenoviruses in the feces of children with acute intestinal infections. We designed сolorimetric LAMP (c-LAMP) and real-time LAMP (f-LAMP) with fluorescent probes to detect the DNA of the adenovirus F human adenovirus 40/41 (hAdV40/41) hexon gene. The detection limit of both developed methods was 10³ copies/mL, which is comparable to the sensitivity of PCR. The specificities of both c-LAMP and f-LAMP were high, with no false-positive results for clinical samples that do not contain adenovirus F, when testing other viruses and microorganisms. Comparative tests of PCR and LAMP on clinical samples from patients with acute gastroenteritis were carried out. For all samples with a PCR threshold cycle (C_T) of up to 36, the PCR and LAMP results completely coincided; however, at low viral loads, the diagnostic sensitivity of LAMP, especially c-LAMP with colorimetric detection, was inferior to that of PCR. The combination of LAMP with modern methods of nucleic acid extraction, both in manual and automatic modes, can reduce the time for a complete study, including extraction of nucleic acid material and amplification, to 60 min.

IMPORTANCE In April 2022, several cases of acute hepatitis of unknown origin were reported in children from 12 countries. In many cases, enteric adenovirus or SARS-CoV-2 and adenovirus coinfection were detected. It is known that human adenoviruses can cause different infections of varying severity, from asymptomatic to severe cases with lethal outcomes. There is a need to increase the diagnostic capabilities of clinical laboratories to identify such an underestimated pathogen as adenovirus. Although PCR remains the gold standard for pathogen detection, this method requires specialized equipment and has a long turnaround time to process samples. Previously, LAMP assays for the detection of human adenovirus have been based on measuring the turbidity, the fluorescence of intercalated dyes, or electrophoretic separation. Herein, we present LAMP-based assays with colorimetric or fluorescent detection and perform a detailed assessment of their sensitivity, specificity, and diagnostic performance.

Advancements in Testing Strategies for COVID-19

The SARS-CoV-2 coronavirus, also known as the disease-causing agent for COVID-19, is a virulent pathogen that may infect people and certain animals. The global spread of COVID-19 and its emerging variation necessitates the development of rapid, reliable, simple, and low-cost diagnostic tools. Many methodologies and devices have been developed for the highly sensitive, selective, cost-effective, and rapid diagnosis of COVID-19. This review organizes the diagnosis platforms into four groups: imaging, molecular-based detection, serological testing, and biosensors. Each platform's principle, advancement, utilization, and challenges for monitoring SARS-CoV-2 are discussed in detail. In addition, an overview of the impact of variants on detection, commercially available kits, and readout signal analysis has been presented. This review will expand our understanding of developing advanced diagnostic approaches to evolve into susceptible, precise, and reproducible technologies to combat any future outbreak.

Contribution of magnetic particles in molecular diagnosis of human viruses

Viral diseases are the primary source of death, making a worldwide influence on healthcare, social, and economic development. Thus, diagnosis is the vital approach to the main aim of virus control and elimination. On the other hand, the prompt advancement of nanotechnology in the field of medicine possesses the probability of being beneficial to diagnose infections normally in labs as well as specifically. Nanoparticles are efficiently in use to make novel strategies because of permitting analysis at cellular in addition to the molecular scale. Henceforth, they assist towards pronounced progress concerning molecular analysis at the nanoscale. In recent times, magnetic nanoparticles conjugated through covalent bonds to bioanalytes for instance peptides, antibodies, nucleic acids, plus proteins are established like nanoprobes aimed at molecular recognition. These modified magnetic nanoparticles could offer a simple fast approach for extraction, purification, enrichment/concentration, besides viruses' recognition precisely also specifically. In consideration of the above, herein insight and outlook into the limitations of conventional methods and numerous roles played by magnetic nanoparticles to extract, purify, concentrate, and additionally in developing a diagnostic regime for viral outbreaks to combat viruses especially the ongoing novel coronavirus (COVID-19).

Photo-Cross-Linked Probe-Modified Magnetic Particles for the Selective and Reliable Recovery of Nucleic Acids

Polymerase chain reaction (PCR) assays are used to diagnose various infectious diseases such as Coronavirus disease 2019 by detecting the nucleic acids of the pathogen. However, in practice, the yield of the extraction process and the inhibition of the reverse transcription reaction and PCR by foreign substances reduce the sensitivity and may yield false negative results. The sensitivity of the PCR test can be improved by using technologies that can reliably capture the target nucleic acid and remove foreign substances. In this study, we developed photo-cross-linkable probe-modified magnetic particles (PPMPs) for the sequence-specific recovery of target nucleic acids using photo-cross-linkable artificial nucleic acid probes and magnetic particles. Nucleic acid probes modified with photo-cross-linkable artificial nucleic acids can hybridize with the target nucleic acids in a sequence-specific manner and then securely capture the target nucleic acids by UV irradiation-mediated covalent bonding. Then the target nucleic acid is detected by trapping the target-bound probe on the surface of the magnetic particles and subjecting these collected magnetic particles to PCR. Recovery of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) N gene pseudo-DNA (120 bp) was performed using PPMPs. We confirmed that the PPMPs captured the target consistently even after washes were done with denaturing agents and surfactants. Even in the presence of foreign DNA fragments, PPMPs were able to specifically recover the target DNA. This method allows for a more accurate detection by recovering only the target DNA for PCR. Hence, PPMPs can be successfully used for PCR-mediated detection of SARS-CoV-2 and other pathogens whose nucleic acid sequences are known.

Advances in Nucleic Acid Amplification-Based Microfluidic Devices for Clinical Microbial Detection

Accurate and timely detection of infectious pathogens is urgently needed for disease treatment and control of possible outbreaks worldwide. Conventional methods for pathogen detection are usually time-consuming and labor-intensive. Novel strategies for the identification of pathogenic nucleic acids are necessary for practical application. The advent of microfluidic technology and microfluidic devices has offered advanced and miniaturized tools to rapidly screen microorganisms, improving many drawbacks of conventional nucleic acid amplification-based methods. In this review, we summarize advances in the microfluidic approach to detect pathogens based on nucleic acid amplification. We survey microfluidic platforms performing two major types of nucleic acid amplification strategies, namely, polymerase chain reaction (PCR) and isothermal nucleic acid amplification. We also provide an overview of nucleic acid amplification-based platforms including studies and commercialized products for SARS-CoV-2 detection. Technologically, we focus on the design of the microfluidic devices, the selected methods for sample preparation, nucleic acid amplification techniques, and endpoint analysis. We also compare features such as analysis time, sensitivity, and specificity of different platforms. The first section of the review discusses methods used in microfluidic devices for upstream clinical sample preparation. The second section covers the design, operation, and applications of PCR-based microfluidic devices. The third section reviews two common types of isothermal nucleic acid amplification methods (loop-mediated isothermal amplification and recombinase polymerase amplification) performed in microfluidic systems. The fourth section introduces microfluidic applications for nucleic acid amplification-based detection of SARS-CoV-2. Finally, the review concludes with the importance of full integration and quantitative analysis for clinical microbial identification.

Filtration-assisted magnetofluidic cartridge platform for HIV RNA detection from blood

The ability to detect and quantify HIV RNA in blood is essential to sensitive detection of infections and monitoring viremia throughout treatment. Current options for point-of-care HIV diagnosis (i.e. lateral flow rapid tests) lack sensitivity for early detection and are unable to quantify viral load. HIV RNA diagnostics typically require extensive pre-processing of blood to isolate plasma and extract nucleic acids, in addition to expensive equipment for conducting nucleic acid amplification and fluorescence detection. Therefore, molecular HIV diagnostics is still mainly limited to clinical laboratories and there is an unmet need for high sensitivity point-of-care screening and at-home HIV viral load quantification. In this work, we outline a streamlined workflow for extraction of plasma from whole blood coupled with HIV RNA extraction and quantitative polymerase chain reaction (qPCR) in a portable magnetofluidic cartridge platform for use at the point-of-care. Viral particles were isolated from blood using manual filtration through a 3D-printed filter module in seconds followed by automated nucleic acid capture, purification, and transfer to qPCR using magnetic beads. Both nucleic acid extraction and qPCR were integrated within cartridges using compact instrumentation consisting of a motorized magnet arm, miniaturized thermocycler, and image-based fluorescence detection. We demonstrated detection down to 1000 copies of HIV viral particles from whole blood in <30 minutes.

Conserved MicroRNAs in Human Nasopharynx Tissue Samples from Swabs Are Differentially Expressed in Response to SARS-CoV-2

The use of high-throughput small RNA sequencing is well established as a technique to unveil the miRNAs in various tissues. The miRNA profiles are different between infected and non-infected tissues. We compare the SARS-CoV-2 positive and SARS-CoV-2 negative RNA samples extracted from human nasopharynx tissue samples to show different miRNA profiles. We explored differentially expressed miRNAs in response to SARS-CoV-2 in the RNA extracted from nasopharynx tissues of 10 SARS-CoV-2-positive and 10 SARS-CoV-2-negative patients. miRNAs were identified by small RNA sequencing, and the expression levels of selected miRNAs were validated by real-time RT-PCR. We identified 943 conserved miRNAs, likely generated through posttranscriptional modifications. The identified miRNAs were expressed in both RNA groups, NegS and PosS: miR-148a, miR-21, miR-34c, miR-34b, and miR-342. The most differentially expressed miRNA was miR-21, which is likely closely linked to the presence of SARS-CoV-2 in nasopharynx tissues. Our results contribute to further understanding the role of miRNAs in SARS-CoV-2 pathogenesis, which may be crucial for understanding disease symptom development in humans.

Comparison of in-house SARS-CoV-2 genome extraction procedures. A need for COVID-19 pandemic

Among the methods used to diagnose COVID-19, those based on genomic detection by q(RT)-PCR are the most sensitive. To perform these assays, a previous genome extraction of the sample is required. The dramatic increase in the number of SARS-CoV-2 detection assays has increased the demand for extraction reagents hindering the supply of commercial reagents. Homemade reagents and procedures could be an alternative. Nasopharyngeal samples were extracted by seven different methods as well as the automatic method MagNaPure96, to detect SARS-CoV-2. All protocols show sensitivity higher than 87 %, in comparison with reference method, for detecting SARS-CoV-2 as well as human β- globin. Our results support that these procedures, using common and cheap reagents, are effective to extract RNA (from SARS-CoV-2) or DNA (from human β-globin) genome from nasopharyngeal swabs. Furthermore, these procedures could be easily adopted by routine diagnostic laboratories to implement detection methods to help to fight against COVID-19 pandemic.

Optimization of magnetic bead-based nucleic acid extraction for SARS-CoV-2 testing using readily available reagents

The COVID-19 pandemic has highlighted the need for generic reagents and flexible systems in diagnostic testing. Magnetic bead-based nucleic acid extraction protocols using 96-well plates on open liquid handlers are readily amenable to meet this need. Here, one such approach is rigorously optimized to minimize cross-well contamination while maintaining sensitivity.

An overview of magnetic ionic liquids: From synthetic strategies to applications in microextraction techniques

Remarkable progress has been achieved in the application of magnetic ionic liquids in microextraction-based procedures. These materials exhibit unique physicochemical properties of ionic liquids featuring additional responses to magnetic fields by incorporating a paramagnetic component within the chemical structure. This intriguing property can open new horizons in analytical extractions because the solvent manipulation is facilitated. Moreover, the tunable chemical structures of magnetic ionic liquids also allow for task-specific extractions that can significantly increase the method selectivity. This review aimed at providing an up-to-date overview of articles involving synthesis, physicochemical properties, and applications of magnetic ionic liquids highlighting recent developments and configurations. Moreover, a section containing critical evaluation and future trends in magnetic ionic liquid-based extractions is included.

Impact of Preanalytical and Analytical Methods on Cell-Free DNA Diagnostics

While tissue biopsy has for the longest time been the gold-standard in biomedicine, precision/personalized medicine is making the shift toward liquid biopsies. Cell-free DNA (cfDNA) based genetic and epigenetic biomarkers reflect the molecular status of its tissue-of-origin allowing for early and non-invasive diagnostics of different pathologies. However, selection of preanalytical procedures (including cfDNA isolation) as well as analytical methods are known to impact the downstream results. Calls for greater standardization are made continuously, yet comprehensive assessments of the impact on diagnostic parameters are lacking. This study aims to evaluate the preanalytic and analytic factors that influence cfDNA diagnostic parameters in blood and semen. Text mining analysis has been performed to assess cfDNA research trends, and identify studies on isolation methods, preanalytical and analytical impact. Seminal and blood plasma were tested as liquid biopsy sources. Traditional methods of cfDNA isolation, commercial kits (CKs), and an in-house developed protocol were tested, as well as the impact of dithiothreitol (DTT) on cfDNA isolation performance. Fluorimetry, qPCR, digital droplet PCR (ddPCR), and bioanalyzer were compared as cfDNA quantification methods. Fragment analysis was performed by qPCR and bioanalyzer while the downstream application (cfDNA methylation) was analyzed by pyrosequencing. In contrast to blood, semen as a liquid biopsy source has only recently begun to be reported as a liquid biopsy source, with almost half of all publications on it being review articles. Experimental data revealed that cfDNA isolation protocols give a wide range of cfDNA yields, both from blood and seminal plasma. The addition of DTT to CKs has improved yields in seminal plasma and had a neutral/negative impact in blood plasma. Capillary electrophoresis and fluorometry reported much higher yields than PCR methods. While cfDNA yield and integrity were highly impacted, cfDNA methylation was not affected by isolation methodology or DTT. In conclusion, NucleoSnap was recognized as the kit with the best overall performance. DTT improved CK yields in seminal plasma. The in-house developed protocol has shown near-kit isolation performance. ddPCR LINE-1 assay for absolute detection of minute amounts of cfDNA was established and allowed for quantification of samples inhibited in qPCR. cfDNA methylation was recognized as a stable biomarker unimpacted by cfDNA isolation method. Finally, semen was found to be an abundant source of cfDNA offering potential research opportunities and benefits for cfDNA based biomarkers development related to male reproductive health.

Oil immersed lossless total analysis system for integrated RNA extraction and detection of SARS-CoV-2

The COVID-19 pandemic exposed difficulties in scaling current quantitative PCR (qPCR)-based diagnostic methodologies for large-scale infectious disease testing. Bottlenecks include lengthy multi-step processes for nucleic acid extraction followed by qPCR readouts, which require costly instrumentation and infrastructure, as well as reagent and plastic consumable shortages stemming from supply chain constraints. Here we report an Oil Immersed Lossless Total Analysis System (OIL-TAS), which integrates RNA extraction and detection onto a single device that is simple, rapid, cost effective, and requires minimal supplies and infrastructure to perform. We validated the performance of OIL-TAS using contrived SARS-CoV-2 viral particle samples and clinical nasopharyngeal swab samples. OIL-TAS showed a 93% positive predictive agreement (n = 57) and 100% negative predictive agreement (n = 10) with clinical SARS-CoV-2 qPCR assays in testing clinical samples, highlighting its potential to be a faster, cheaper, and easier-to-deploy alternative for infectious disease testing.

Bottlenecks in qPCR-based COVID-19 diagnostics include the lengthy multistep process and reagent shortages. Here the authors report OIL-TAS which integrates RNA extraction and detection into a single device.

Application of Magnetic Nanoparticles Coated with Crosslinked Zwitterionic Poly(ionic liquid)s for the Extraction of Oligonucleotides

Magnetic nanoparticles coated with zwitterionic poly(ionic liquid)s were applied for dispersive solid-phase extraction of oligonucleotides. The materials were synthesized by miniemulsion copolymerization of ionic liquids and divinylbenzene on magnetic nanoparticles. The functional monomers contain a positively charged imidazolium ring and one of the anionic groups: derivatives of acetate, malonate, or butyl sulfonate ions. Adsorption of unmodified DNA oligonucleotide on obtained materials was possible in ion-exchange (IE) and hydrophilic interactions (HI) mode. The adsorption in IE was possible at low pH and was almost complete. The adsorption in HI mode required the usage of appropriate addition of organic solvent but did not provide full adsorption. Studies on the desorption of the analytes included determining the impact of ammonium acetate concentration and pH and organic solvents addition on the recovery. The material containing acetic fragments as an anionic group was selected for the final procedure with the use of 10 mM ammonium acetate (pH = 9.5)/methanol (50/50, v/v) as an elution solution. The magnetic dispersive solid-phase extraction procedure was tested for the oligonucleotides with various modifications and lengths. Moreover, it was applied to extract DNA oligonucleotide and its synthetic metabolites from enriched human plasma without any pre-purification, with recoveries greater than 80%.

Nucleic acid amplification-based microfluidic approaches for antimicrobial susceptibility testing

Because of the global spread of antimicrobials, there is an urgent need to develop rapid and effective tools for antimicrobial susceptibility testing to help clinicians prescribe accurate and appropriate antibiotic doses sooner. The conventional methods for antimicrobial susceptibility testing are usually based on bacterial culture methods, which are time-consuming, complicated, and labor-intensive. Therefore, other approaches are needed to address these issues. Recently, microfluidic technology has gained significant attention in infection management due to its advantages including rapid detection, high sensitivity and specificity, highly automated assay, simplicity, low cost, and potential for point-of-care testing in low-resource areas. Microfluidic advances for antimicrobial susceptibility testing can be classified into phenotypic (usually culture-based) and genotypic tests. Genotypic antimicrobial susceptibility testing is the detection of resistant genes in a microorganism using methods such as nucleic acid amplification. This review (with 107 references) surveys the different forms of nucleic acid amplification-based microdevices used for genotypic antimicrobial susceptibility testing. The first section reviews the serious threat of antimicrobial-resistant microorganisms and the urgent need for fast check-ups. Next, several conventional antimicrobial susceptibility testing methods are discussed, and microfluidic technology as a promising candidate for rapid detection of antimicrobial-resistant microorganisms is briefly introduced. The next section highlights several advancements of microdevices, with an emphasis on their working principles and performance. The review concludes with the importance of fully integrated microdevices and a discussion on future perspectives.

Prolonged Unfrozen Storage and Repeated Freeze-Thawing of SARS-CoV-2 Patient Samples Have Minor Effects on SARS-CoV-2 Detectability by RT-PCR

Reliable transportation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) patient samples from a swabbing station to a diagnostics facility is essential for accurate results. Therefore, cooling or freezing the samples is recommended in case of longer transportation times. In this study, SARS-CoV-2 detectability by RT-PCR was assessed after prolonged unfrozen storage or repetitive freeze-thawing of SARS-CoV-2 samples. SARS-CoV-2–positive patient swabs stored in viral transport medium were exposed to different temperatures (4°C, 25°C, and 35°C) and to repetitive freeze-thawing, to assess the effect of storage conditions on RT-PCR detection. SARS-CoV-2 RNA was still reliably detected by RT-PCR after 21 days of storage in viral transport medium, even when the samples had been stored at 35°C. The maximum observed change in cycle threshold value per day was 0.046 (±0.019) at 35°C, and the maximum observed change in cycle threshold value per freeze-thaw cycle per day was 0.197 (±0.06). Compared with storage at 4°C, viral RNA levels deviated little but significantly when stored at 25°C or 35°C, or after repeated freeze-thawing. The results of this study indicate that viral RNA levels are relatively stable at higher temperatures and repetitive freeze-thawing.

Microfluidic-based virus detection methods for respiratory diseases

With the recent SARS-CoV-2 outbreak, the importance of rapid and direct detection of respiratory disease viruses has been well recognized. The detection of these viruses with novel technologies is vital in timely prevention and treatment strategies for epidemics and pandemics. Respiratory viruses can be detected from saliva, swab samples, nasal fluid, and blood, and collected samples can be analyzed by various techniques. Conventional methods for virus detection are based on techniques relying on cell culture, antigen-antibody interactions, and nucleic acids. However, these methods require trained personnel as well as expensive equipment. Microfluidic technologies, on the other hand, are one of the most accurate and specific methods to directly detect respiratory tract viruses. During viral infections, the production of detectable amounts of relevant antibodies takes a few days to weeks, hampering the aim of prevention. Alternatively, nucleic acid-based methods can directly detect the virus-specific RNA or DNA region, even before the immune response. There are numerous methods to detect respiratory viruses, but direct detection techniques have higher specificity and sensitivity than other techniques. This review aims to summarize the methods and technologies developed for microfluidic-based direct detection of viruses that cause respiratory infection using different detection techniques. Microfluidics enables the use of minimal sample volumes and thereby leading to a time, cost, and labor effective operation. Microfluidic-based detection technologies provide affordable, portable, rapid, and sensitive analysis of intact virus or virus genetic material, which is very important in pandemic and epidemic events to control outbreaks with an effective diagnosis.

Evaluation of two automated low-cost RNA extraction protocols for SARS-CoV-2 detection

Background

Two automatable in-house protocols for high-troughput RNA extraction from nasopharyngeal swabs for SARS-CoV-2 detection have been evaluated.

Methods

One hundred forty one SARS-CoV-2 positive samples were collected during a period of 10-days. In-house protocols were based on extraction with magnetic beads and designed to be used with either the Opentrons OT-2 (OT-2_in-house) liquid handling robot or the MagMAX^TM Express-96 system (MM_in-house). Both protocols were tested in parallel with a commercial kit that uses the MagMAX^TM system (MM_kit). Nucleic acid extraction efficiencies were calculated from a SARS-CoV-2 DNA positive control.

Results

No significant differences were found between both in-house protocols and the commercial kit in their performance to detect positive samples. The MM_kit was the most efficient although the MM_in-house presented, in average, lower Cts than the other two. In-house protocols allowed to save between 350€ and 400€ for every 96 extracted samples compared to the commercial kit.

Conclusion

The protocols described harness the use of easily available reagents and an open-source liquid handling system and are suitable for SARS-CoV-2 detection in high throughput facilities.

Antigen tests for COVID-19

PCR diagnosis has been considered as the gold standard for coronavirus disease 2019 (COVID-19) and other many diseases. However, there are many problems in using PCR, such as non-specific (i.e., false-positive) and false-negative amplifications, the limits of a target sample volume, deactivation of the enzymes used, complicated techniques, difficulty in designing probe sequences, and the expense. We, thus, need an alternative to PCR, for example an ultrasensitive antigen test. In the present review, we summarize the following three topics. (1) The problems of PCR are outlined. (2) The antigen tests are surveyed in the literature that was published in 2020, and their pros and cons are discussed for commercially available antigen tests. (3) Our own antigen test on the basis of an ultrasensitive enzyme-linked immunosorbent assay (ELISA) is introduced. Finally, we discuss the possibility that our antigen test by an ultrasensitive ELISA technique will become the gold standard for diagnosis of COVID-19 and other diseases.

Detection of COVID-19: A review of the current literature and future perspectives

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the coronavirus disease 2019 (COVID-19) worldwide pandemic. This unprecedented situation has garnered worldwide attention. An effective strategy for controlling the COVID-19 pandemic is to develop highly accurate methods for the rapid identification and isolation of SARS-CoV-2 infected patients. Many companies and institutes are therefore striving to develop effective methods for the rapid detection of SARS-CoV-2 ribonucleic acid (RNA), antibodies, antigens, and the virus. In this review, we summarize the structure of the SARS-CoV-2 virus, its genome and gene expression characteristics, and the current progression of SARS-CoV-2 RNA, antibodies, antigens, and virus detection. Further, we discuss the reasons for the observed false-negative and false-positive RNA and antibody detection results in practical clinical applications. Finally, we provide a review of the biosensors which hold promising potential for point-of-care detection of COVID-19 patients. This review thereby provides general guidelines for both scientists in the biosensing research community and for those in the biosensor industry to develop a highly sensitive and accurate point-of-care COVID-19 detection system, which would be of enormous benefit for controlling the current COVID-19 pandemic.

Point-Of-Care or Point-Of-Need Diagnostic Tests: Time to Change Outbreak Investigation and Pathogen Detection

In the recent years, the progress of international trade and travel has led to an increased risk of emerging infections. Around 75 percent of the pathogens causing these infections are of animal origin. Point-of-care tests (POCT) and point-of-need tests (PONT) have been established in order to directly provide accurate and rapid diagnostics at field level, the patient bed-side or at the site of outbreaks. These assays can help physicians and decision makers to take the right action without delay. Typically, POCT and PONT rely on genomic identification of pathogens or track their immunological fingerprint. Recently, protocols for metagenomic diagnostics in the field have been developed. In this review, we give an overview of the latest developments in portable diagnostic methods. In addition, four mobile platforms for the implementation of these techniques at point-of-care and point-of-need are described. These approaches can provide reliable diagnostics and surveillance, especially in low resource settings as well as at the level of one health.

Improvement of Mycobacterium tuberculosis detection in sputum using DNA extracted by sonication

Tuberculosis (TB) is one of the infectious diseases with high mortality in the world. DNA amplification techniques have been used to overcome barriers to the diagnosis of this disease. However, the success of these methodologies is highly dependent on the DNA obtained from the sample. This study was carried out to verify whether the DNA extracted by sonication (in house method) could yield suitable DNA for amplification by real-time PCR (qPCR). Sixty sputum samples were submitted to DNA extraction using sonication compared to a commercial method (Detect-TB kit, Labtest/MG-Brazil). All DNA samples were amplified by qPCR for IS6110 region (IS6110-qPCR/SYBR Green assay). Out of 60 samples, 40 were positive for TB; of these, all had positive results when extracted by sonication (100%) and 80% when extracted by the commercial method. The limit of detection (LOD) of Mycobacterium tuberculosis (H37Rv strain) by qPCR was 14 CFU/mL when the DNA was extracted by sonication, compared to countless colonies when extracted by commercial kit. In conclusion, the sonication protocol (without purification step) proved to be a simple, fast, and suitable method for obtaining DNA for use in qPCR from sputum samples.

Development of a multiplex isothermal amplification molecular diagnosis method for on-site diagnosis of influenza

Influenza, which is an acute respiratory disease caused by the influenza virus, represents a worldwide public health and economic problem owing to the significant morbidity and mortality caused by its seasonal epidemics and pandemics. Sensitive and convenient methodologies for the detection of influenza viruses are important for clinical care and infection control as well as epidemiological investigations. Here, we developed a multiplex reverse transcription loop-mediated isothermal amplification (RT-LAMP) with quencher/fluorescence oligonucleotides connected by a 5' backward loop (LF or LB) primer for the detection of two subtypes of influenza viruses: Influenza A (A/H1 and A/H3) and influenza B. The detection limits of the multiplex RT-LAMP assay were 103 copies and 102 copies of RNA for influenza A and influenza B, respectively. The sensitivities of the multiplex influenza A/B/IC RT-LAMP assay were 94.62% and 97.50% for influenza A and influenza B clinical samples, respectively. The specificities of the multiplex influenza A/B/IC RT-LAMP assay were 100% for influenza A, influenza B, and healthy clinical samples. In addition, the multiplex influenza A/B/IC RT-LAMP assay had no cross-reactivity with other respiratory viruses.

Fighting COVID-19: Integrated Micro- and Nanosystems for Viral Infection Diagnostics

The pandemic of coronavirus disease 2019 (COVID-19) highlights the importance of rapid and sensitive diagnostics of viral infection that enables the efficient tracing of cases and the implementation of public health measures for disease containment. The immediate actions from both academia and industry have led to the development of many COVID-19 diagnostic systems that have secured fast-track regulatory approvals and have been serving our healthcare frontlines since the early stage of the pandemic. On diagnostic technologies, many of these clinically validated systems have significantly benefited from the recent advances in micro- and nanotechnologies in terms of platform design, analytical method, and system integration and miniaturization. The continued development of new diagnostic platforms integrating micro- and nanocomponents will address some of the shortcomings we have witnessed in the existing COVID-19 diagnostic systems. This Perspective reviews the previous and ongoing research efforts on developing integrated micro- and nanosystems for nucleic acid-based virus detection, and highlights promising technologies that could provide better solutions for the diagnosis of COVID-19 and other viral infectious diseases. With the summary and outlook of this rapidly evolving research field, we hope to inspire more research and development activities to better prepare our society for future public health crises.

Validation of a single-step, single-tube reverse transcription loop-mediated isothermal amplification assay for rapid detection of SARS-CoV-2 RNA

Introduction. The SARS-CoV-2 pandemic of 2020 has resulted in unparalleled requirements for RNA extraction kits and enzymes required for virus detection, leading to global shortages. This has necessitated the exploration of alternative diagnostic options to alleviate supply chain issues.Aim. To establish and validate a reverse transcription loop-mediated isothermal amplification (RT- LAMP) assay for the detection of SARS-CoV-2 from nasopharyngeal swabs.Methodology. We used a commercial RT-LAMP mastermix from OptiGene in combination with a primer set designed to detect the CDC N1 region of the SARS-CoV-2 nucleocapsid (N) gene. A single-tube, single-step fluorescence assay was implemented whereby 1 µl of universal transport medium (UTM) directly from a nasopharyngeal swab could be used as template, bypassing the requirement for RNA purification. Amplification and detection could be conducted in any thermocycler capable of holding 65 °C for 30 min and measure fluorescence in the FAM channel at 1 min intervals.Results. Assay evaluation by assessment of 157 clinical specimens previously screened by E-gene RT-qPCR revealed assay sensitivity and specificity of 87 and 100%, respectively. Results were fast, with an average time-to-positive (Tp) for 93 clinical samples of 14 min (sd±7 min). Using dilutions of SARS-CoV-2 virus spiked into UTM, we also evaluated assay performance against FDA guidelines for implementation of emergency-use diagnostics and established a limit-of-detection of 54 Tissue Culture Infectious Dose 50 per ml (TCID50 ml-1), with satisfactory assay sensitivity and specificity. A comparison of 20 clinical specimens between four laboratories showed excellent interlaboratory concordance; performing equally well on three different, commonly used thermocyclers, pointing to the robustness of the assay.Conclusion. With a simplified workflow, The N1 gene Single Tube Optigene LAMP assay (N1-STOP-LAMP) is a powerful, scalable option for specific and rapid detection of SARS-CoV-2 and an additional resource in the diagnostic armamentarium against COVID-19.

SARS-CoV-2 RNA Extraction Using Magnetic Beads for Rapid Large-Scale Testing by RT-qPCR and RT-LAMP

Rapid large-scale testing is essential for controlling the ongoing pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The standard diagnostic pipeline for testing SARS-CoV-2 presence in patients with an ongoing infection is predominantly based on pharyngeal swabs, from which the viral RNA is extracted using commercial kits, followed by reverse transcription and quantitative PCR detection. As a result of the large demand for testing, commercial RNA extraction kits may be limited and, alternatively, non-commercial protocols are needed. Here, we provide a magnetic bead RNA extraction protocol that is predominantly based on in-house made reagents and is performed in 96-well plates supporting large-scale testing. Magnetic bead RNA extraction was benchmarked against the commercial QIAcube extraction platform. Comparable viral RNA detection sensitivity and specificity were obtained by fluorescent and colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) using a primer set targeting the N gene, as well as RT-qPCR using a primer set targeting the E gene, showing that the RNA extraction protocol presented here can be combined with a variety of detection methods at high throughput. Importantly, the presented diagnostic workflow can be quickly set up in a laboratory without access to an automated pipetting robot.

Evaluation of Viral RNA Recovery Methods in Vectors by Metagenomic Sequencing

Identification and characterization of viral genomes in vectors including ticks and mosquitoes positive for pathogens of great public health concern using metagenomic next generation sequencing (mNGS) has challenges. One such challenge is the ability to efficiently recover viral RNA which is typically dependent on sample processing. We evaluated the quantitative effect of six different extraction methods in recovering viral RNA in vectors using negative tick homogenates spiked with serial dilutions of tick-borne encephalitis virus (TBEV) and surrogate Langat virus (LGTV). Evaluation was performed using qPCR and mNGS. Sensitivity and proof of concept of optimal method was tested using naturally positive TBEV tick homogenates and positive dengue, chikungunya, and Zika virus mosquito homogenates. The amount of observed viral genome copies, percentage of mapped reads, and genome coverage varied among different extractions methods. The developed Method 5 gave a 120.8-, 46-, 2.5-, 22.4-, and 9.9-fold increase in the number of viral reads mapping to the expected pathogen in comparison to Method 1, 2, 3, 4, and 6, respectively. Our developed Method 5 termed ROVIV (Recovery of Viruses in Vectors) greatly improved viral RNA recovery and identification in vectors using mNGS. Therefore, it may be a more sensitive method for use in arbovirus surveillance.

Low-Resource Nucleic Acid Extraction Method Enabled by High-Gradient Magnetic Separation

Nucleic acid-based diagnostic tests often require isolation and concentration of nucleic acids from biological samples. Commercial purification kits are difficult to use in low-resource settings because of their cost and insufficient laboratory infrastructure. Several recent approaches based on the use of magnetic beads offer a potential solution but remain limited to small volume samples. We have developed a simple and low-cost nucleic acid extraction method suitable for isolation and concentration of nucleic acids from small or large sample volumes. The method uses magnetic beads, a transfer pipette, steel wool, and an external magnet to implement high-gradient magnetic separation (HGMS) to retain nucleic acid-magnetic bead complexes within the device's steel wool matrix for subsequent processing steps. We demonstrate the method's utility by extracting tuberculosis DNA from both sputum and urine, two typical large volume sample matrices (5-200 mL), using guanidine-based extraction chemistry. Our HGMS-enabled extraction method is statistically indistinguishable from commercial extraction kits when detecting a spiked 123-base DNA sequence. For our HGMS-enabled extraction method, we obtained extraction efficiencies for sputum and urine of approximately 10 and 90%, whereas commercial kits obtained 10-17 and 70-96%, respectively. We also used this method previously in a blinded sample preparation comparison study published by Beall et al., 2019. Our manual extraction method is insensitive to high flow rates and sample viscosity, with capture of ∼100% for flow rates up to 45 mL/min and viscosities up to 55 cP, possibly making it suitable for a wide variety of sample volumes and types and point-of-care users. This HGMS-enabled extraction method provides a robust instrument-free method for magnetic bead-based nucleic acid extraction, potentially suitable for field implementation of nucleic acid testing.

Adsorption of DNA by using polydopamine modified magnetic nanoparticles based on solid-phase extraction

A polydopamine magnetic composite (PDA@Fe₃O₄) was prepared for the extraction of human genomic DNA and characterized by transmission electron microscopy, X-ray diffraction, FT-IR spectrometer, zeta potential and vibrating sample magnetometry. PDA@Fe₃O₄ based on magnetic solid phase extraction (MSPE) method have highly efficient capture of genomic deoxyribonucleic acid (DNA)and gene fragments ranging from about 100 bp to 200 bp. Compared with commercial beads (Shenggong, China) and spin column nucleic acid extraction kit (Tiangen, China), the PDA coated magnetic nanoparticles display superior genomic DNA extraction capacity (116 mg/g) and yield (90.2%). The isolation protocol used the solutions (composed of PEG and NaCl) with a specific pH for the binding and release of DNA. The procedure can be attributed to the charge switch of amino and hydroxyl groups on surface of the magnetic particle. The extracted DNA with high quality (A260/A280 = 1.82 ± 0.04) can be directly used as template for polymerase chain reaction (PCR) followed by agarose gel electrophoresis. The results showed the new composite to be an ideal adsorbent for separation of DNA which had the advantage of its low cost, high extraction capacity and yield.

Elimination of bacterial DNA during RNA isolation from sputum: Bashing bead vortexing is preferable over prolonged DNase treatment

Sputum often contains large amounts of contaminating bacterial DNA that, if not eliminated during RNA isolation, may interfere with gene expression studies. During RNA isolation only repeated DNase treatment can effectively remove contaminating bacterial DNA from samples, but this compromises RNA quality. In this study we tested alternative methods to facilitate the removal of DNA and improve the quality of RNA obtained. Sputum samples obtained from patients with chronic obstructive pulmonary disease were processed with dithiothreitol and subjected to various RNA isolation methods, yet with modified protocols. Modifications included prolonged DNase treatment or vortexing of sputum cells in the presence of beads prior to RNA isolation. Bacterial DNA contamination was tested by PCR using universal bacterial primers, while RNA quality was assessed by real-time PCR using GAPDH primers for amplicons of different length. We found that the RNeasy Plus Mini kit equipped with the gDNA eliminator spin column was able to completely eliminate bacterial DNA, if sputum cells were lysed in the presence of bashing beads. Notably, compared with the standard protocol, the modified procedure yielded better quality RNA as well, as indicated by improved threshold profiles of qPCR. Bead vortexing of cells was less effective when combined with other RNA isolation methods, and the repeated DNase treatment needed to completely remove contaminating DNA from the samples reduced the quality of RNA markedly. Bead vortexing in combination with certain RNA extraction methods greatly facilitates the isolation of sputum RNA that is free of contaminating bacterial DNA, and is suitable for downstream applications.

All in One High Quality Genomic DNA and Total RNA Extraction From Nematode Induced Galls for High Throughput Sequencing Purposes

Meloidogyne spp. are plant-parasitic nematodes that form a very complex pseudo-organ, called gall, which contains the giant cells (GCs) to nourish them. During the last decade, several groups have been studying the molecular processes accompanying the formation of these structures, combining both transcriptomics and cellular biology. Among others, it was confirmed that a generalized gene repression is a hallmark of early developing GCs formed by Meloidogyne javanica in Arabidopsis and tomato. One of the main mechanisms behind this gene repression involve small RNAs (sRNAs) directed gene silencing. This is supported not only by the described action of several microRNAs differentially expressed in galls, but by the differential abundance of 24-nucleotide sRNAs in early developing Arabidopsis galls, particularly those rasiRNAs which are mostly involved in RNA-directed DNA methylation. Their accumulation strongly correlates to the repression of several retrotransposons at pericentromeric regions of Arabidopsis chromosomes in early galls. However, the contribution of this global gene repression to GCs/galls formation and maintenance is still not fully understood. Further detailed studies, as the correlation between gene expression profiles and the methylation state of the chromatin in galls are essential to raise testable working hypotheses. A high quality of isolated DNA and RNA is a requirement to obtain non-biased and comprehensive results. Frequently, the isolation of DNA and RNA is performed from different samples of the same type of biological material. However, subtle differences on epigenetic processes are frequent even among independent biological replicates of the same tissue and may not correlate to those changes on the mRNA population obtained from different biological replicates. Herein, we describe a method that allows the simultaneous extraction and purification of genomic DNA and total RNA from the same biological sample adapted to our biological system. The quality of both nucleic acids from Arabidopsis galls formed by M. javanica was high and adequate to construct RNA and DNA libraries for high throughput sequencing used for transcriptomic and epigenetic studies, such as the analysis of the methylation state of the genomic DNA in galls (MethylC-seq) and RNA sequencing (RNAseq). The protocol presents guidance on the described procedure, key notes and troubleshooting.

Efficient targeted cancer cell detection, isolation and enumeration using immuno-nano/hybrid magnetic microgels

Magnetic nano/hybrid structures have drawn ample attention in the field of biotechnology due to their excellent magnetic properties and biocompatibility.