Functionalized Co2FeAl Nanoparticles for Detection of SARS CoV-2 Based on Reverse Transcriptase Loop-Mediated Isothermal Amplification

Rapid detection of SARS-CoV-2 RNA using a one-step fast multiplex RT-PCR coupled to lateral flow immunoassay

BACKGROUND

The COVID-19 has put emphasis on pivotal needs for diagnosis and surveillance worldwide, with the subsequent shortage of diagnostic reagents and kits. Therefore, it has become strategic for the countries to access diagnostics, expand testing capacity, and develop their own diagnostic capabilities and alternative rapid accurate nucleic acid diagnostics that are at lower costs. Here, we propose a visual SARS-CoV-2 detection using a one-step fast multiplex reverse transcription-PCR (RT-PCR) amplification coupled to lateral flow immunoassay detection on a PCRD device (Abingdon Health, UK).

METHODS

We developed various simplex fast-PCRs for screening sets of primer pairs newly designed or selected from literature or from validated WHO diagnostics, targeting S, N, E, RdRp or ORF1ab genes. We retained primers showing specific and stable amplification to assess for their suitability for detection on PCRD. Thus, fast RT-PCR amplifications were performed using the retained primers. They were doubly labeled with Fam and Biotin or Dig and Biotin to allow visual detection of the labeled amplicons on the lateral flow immunoassay PCR Detection (PCRD) device, looking at lack of interaction of the labeled primers (or primer dimers) with the test-lines in negative or no RNA controls. We set up all the assays using RNAs isolated from patients' nasopharyngeal swabs. We used two simplex assays, targeting two different viral genomic regions (N and E) and showing specific detection on PCRD, to set up a one-step fast multiplex RT-PCR assay (where both differently labeled primer pairs were engaged) coupled to amplicons' detection on a PCRD device. We evaluated this novel assay on 50 SARS-CoV-2 positive and 50 SARS-CoV-2 negative samples and compared its performance to the results of the quantitative RT-PCR (RT-qPCR) assays used for diagnosing the patients, here considered as the standard tests.

RESULTS

The new assay achieved a sensitivity of 88% (44/50) and a specificity of 98% (49/50). All patients who presented Ct values lower than 33 were positive for our assay. Except for one patient, those with Ct values above 33 returned negative results.

CONCLUSION

Our results have brought proof of principle on the usefulness of the one-step fast multiplex RT- PCR assay coupled to PCRD as a new assay for specific, sensitive, and rapid detection of SARS-CoV-2 without requiring costly laboratory equipment, and thus, at reduced costs in a format prone to be deployed when resources are limited. This assay offers a viable alternative for COVID-19 diagnosis or screening at points of need.

Hierarchical Nanobiosensors at the End of the SARS-CoV-2 Pandemic

Nanostructures have played a key role in the development of different techniques to attack severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Some applications include masks, vaccines, and biosensors. The latter are of great interest for detecting diseases since some of their features allowed us to find specific markers in secretion samples such as saliva, blood, and even tears. Herein, we highlight how hierarchical nanoparticles integrated into two or more low-dimensional materials present outstanding advantages that are attractive for photonic biosensing using their nanoscale functions. The potential of nanohybrids with their superlative mechanical characteristics together with their optical and optoelectronic properties is discussed. The progress in the scientific research focused on using nanoparticles for biosensing a variety of viruses has become a medical milestone in recent years, and has laid the groundwork for future disease treatments. This perspective analyzes the crucial information about the use of hierarchical nanostructures in biosensing for the prevention, treatment, and mitigation of SARS-CoV-2 effects.

Rapid detection of Mucorales in human blood and urine samples by functionalized Heusler magnetic nanoparticle assisted customized loop-mediated isothermal amplification

Mucormycosis is a rare disease with scarce diagnostic methods for early intervention. Available strategies employing direct microscopy using calcofluor white-KOH, culture, radiologic, and histopathologic testing often are time-intensive and demand intricate protocols. Nucleic Acid Amplification Test holds promise due to its high sensitivity combined with rapid detection. Loop-mediated isothermal amplification (LAMP) based detection offers an ultrasensitive technique that does not require complicated thermocyclers like in polymerase chain reaction, offering a straightforward means for improving diagnoses as a near-point-of-care test. The study introduces a novel magnetic nanoparticle-based LAMP assay for carryover contaminant capture to reduce false positives. Solving the main drawback of LAMP-based diagnosis techniques. The assay targets the cotH gene, which is invariably specific to Mucorales. The assay was tested with various species of Mucorales, and the limit of detections for Rhizopus microsporus, Lichtheimia corymbifera, Rhizopus arrhizus, Rhizopus homothallicus, and Cunninghamella bertholletiae were 1 fg, 1 fg, 0.1 pg, 0.1 pg, and 0.01 ng, respectively. This was followed by a clinical blindfolded study using whole blood and urine samples from 30 patients diagnosed with Mucormycosis. The assay has a high degree of repeatability and had an overall sensitivity of > 83%. Early Mucormycosis detection is crucial, as current lab tests from blood and urine lack sensitivity and take days for confirmation despite rapid progression and severe complications. Our developed technique enables the confirmation of Mucormycosis infection in < 45 min, focusing specifically on the RT-LAMP process. Consequently, this research offers a viable technique for quickly identifying Mucormycosis from isolated DNA of blood and urine samples instead of invasive tissue samples.

Single-domain Fe2CoGa0.5Al0.5 Heusler alloy nanoparticles with enhanced properties

Fine quaternary single-domain Heusler alloy nanoparticles with a composition of Fe2CoGa0.5Al0.5 have been synthesized using a simple template-less chemical route for the first time. Ab initio calculations and standard models have been used to analyze and interpret the experimental findings. The synthesized nanoparticles with an average crystallite size of 42 nm exhibited high saturation magnetization (>5 μB f.u.-1), high effective anisotropy constant (≈8 × 106 erg cc-1), high Curie temperature (>1200 K), low magnetic remanence (<0.2 μB f.u.-1) and low coercive field (<90 Oe), declaring their suitability for fabricating various nanomagnetic devices.

SARS-CoV-2 Diagnostics Based on Nucleic Acids Amplification: From Fundamental Concepts to Applications and Beyond

COVID-19 pandemic ignited the development of countless molecular methods for the diagnosis of SARS-CoV-2 based either on nucleic acid, or protein analysis, with the first establishing as the most used for routine diagnosis. The methods trusted for day to day analysis of nucleic acids rely on amplification, in order to enable specific SARS-CoV-2 RNA detection. This review aims to compile the state-of-the-art in the field of nucleic acid amplification tests (NAATs) used for SARS-CoV-2 detection, either at the clinic level, or at the Point-Of-Care (POC), thus focusing on isothermal and non-isothermal amplification-based diagnostics, while looking carefully at the concerning virology aspects, steps and instruments a test can involve. Following a theme contextualization in introduction, topics about fundamental knowledge on underlying virology aspects, collection and processing of clinical samples pave the way for a detailed assessment of the amplification and detection technologies. In order to address such themes, nucleic acid amplification methods, the different types of molecular reactions used for DNA detection, as well as the instruments requested for executing such routes of analysis are discussed in the subsequent sections. The benchmark of paradigmatic commercial tests further contributes toward discussion, building on technical aspects addressed in the previous sections and other additional information supplied in that part. The last lines are reserved for looking ahead to the future of NAATs and its importance in tackling this pandemic and other identical upcoming challenges.