Speedy molecular assay to detect SARS-CoV-2-specific RNA sequences

Researchers from Israel have described a brand new molecular assay to quickly detect pathogens with excessive sensitivity in scientific samples. The tactic combines a extremely delicate magnetic modulation biosensing (MMB) system, speedy thermal biking, and a modified double-quenched hydrolysis probe to detect the presence of RNA.

Study:A magnetic modulation biosensing-based molecular assay for rapid and highly sensitive clinical diagnosis of COVID-19. Image Credit: CROCOTHERY/ ShutterstockResearch: A magnetic modulation biosensing-based molecular assay for speedy and extremely delicate scientific prognosis of COVID-19. Picture Credit score: CROCOTHERY/ Shutterstock

Revealed in The Journal of Molecular Diagnostics, the research reported speedy detection of extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with excessive sensitivity and specificity in scientific samples.


Speedy and delicate detection of human pathogens is an pressing want, particularly throughout epidemics and pandemics. The continued coronavirus illness 2019 (COVID-2019) pandemic attributable to SARS-CoV-2 has prompted the swift improvement of various speedy screening strategies for pathogen detection.

Nevertheless, the gold normal take a look at for SARS-CoV-2 is at the moment primarily based on the reverse transcription-quantitative polymerase chain response (RT-qPCR) detection of the virus-specific RNA within the pattern, with a  turnaround time of 90-120 minutes. This assay depends on course amplification by Taq polymerase and makes use of a fluorescent resonance vitality switch (FRET)-based hydrolysis probe.

Whereas as little as a single copy of a goal RNA might be detected theoretically by RT-qPCR, total, the RT part, the real-time monitoring, and the excessive variety of amplification cycles are time-consuming for speedy screening. Different challenges within the thrilling speedy screening strategies embody the excessive fee of false-negative outcomes and lengthy response occasions.

This research describes a brand new Magnetic Modulation Biosensing (MMB) assay 3-4 occasions sooner than the usual RT-qPCR and overcomes the constraints of the prevailing small footprint speedy screening.

The research

The researchers carried out MMB assay for the E-gene (envelope) and the N1-gene (nucleocapsid) targets on this research. They collected the nasopharyngeal swabs from hospitalized COVID-19-positive sufferers. They collected samples for the SARS-CoV-2 adverse set earlier than the onset of the COVID-19 pandemic in Israel.

The researchers investigated the MMB assay from RT-PCR reactions with or with out the artificial SARS-CoV-2 RNA E-gene in an amplification cycles-dependent take a look at. Whereas they detected as few as ten copies of in vitro transcribed RNA E-gene targets with 30 amplifications cycles, the optimum cycles for improved SNR are discovered to be carried out at 40 amplification cycles.

Transcribing the E-gene goal in vitro in PCR-grade water, the researchers additionally carried out a copies/reaction-dependent assay to find out the analytical sensitivity of the assay. They calculated the restrict of detection to be 1.6 copies/response.

Importantly, the researchers decided the scientific sensitivity and specificity of the MMB-based E-gene assay following 40 amplification cycles. For the 309 scientific samples, together with 170 SARS-CoV-2-negative samples (30 of that are constructive to different respiratory viruses), and the 139 RT-qPCR SARS-CoV-2-positive samples, the researchers confirmed the MMB assay had 100% specificity and 97.8% scientific sensitivity for samples with ���� ≤ 42.

Additional, the researchers examined the scientific sensitivity and specificity of the MMB-based N1-gene assay following 40 amplification cycles. They used 70 samples, together with 40  SARS-CoV-2-negative samples (30 of that are constructive for different respiratory viruses) and 30 RT-qPCR SARS-CoV-2-positive samples.

Utilizing the identical ROC cut-off calculated for the MMB-based E-gene assay, the researchers recognized all adverse samples as adverse, indicating 100% specificity by the N1-gene MMB-based assay.

Correlating the Ct worth and the MMB indicators, the researchers concluded that the assay may present, along with correct qualitative outcomes, semi-quantitative outcomes reminiscent of adverse, borderline constructive, and constructive. Considerably, in addition they reported that there was no cross-reactivity on this assay, indicative of excessive specificity. Additionally, the research appears on the related prices of the MMB assay – it’s anticipated to be cheaper than the price of a normal RT-qPCR system.


The researchers right here introduced a speedy molecular assay to detect SARS-CoV-2-specific RNA sequences primarily based on the MMB assay. They demonstrated the scientific sensitivity and specificity to be 97.8 and 100%, respectively.

In comparison with the common RT-qPCR take a look at (90–120 minutes), the MMB-based molecular assays with 40 amplification cycles took solely half-hour (together with dealing with time). The MMB-based detection is roughly 150 occasions extra delicate than the direct optical detection of fluorescent molecules (RT-qPCR).

The researchers reported that this MMB platform was beforehand described to detect the Ibaraki virus and hen intercourse in ovo. That is the primary report to explain MMB assay for molecular detection of human pathogens.

The primers and the probe set on this assay might be adjusted to detect different pathogens simply. Coupling with a excessive throughput detection gadget to quickly display massive samples in a group, this assay can alter the response to any pandemic scenario.

Journal reference:

  • Margulis, M. et al. (2021) “A magnetic modulation biosensing-based molecular assay for speedy and extremely delicate scientific prognosis of COVID-19”, The Journal of Molecular Diagnostics. doi: 10.1016/j.jmoldx.2021.08.012.

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