A recent study reported in Cell demonstrates a new fast and easy point-of-care device for SARS-CoV-2 testing.
Decreasing SARS-Cov-2 transmission has proven difficult due to the inability to identify pre-symptomatic, symptomatic, and asymptomatic individuals. Medical communities around the world have spearheaded efforts to develop effective treatments, but proper testing is needed to curb the spread. Current problems with available SARS-Cov-2 testing are inaccessibility, expensive costs, and lengthy result wait times. A group of researchers successfully developed a sensitive, accurate, and fast portable point-of-care device to test for SARS-Cov-2.
The current standard for SARS-Cov-2 testing is PCR. This technique measures the amount of DNA present in a sample through multiple costly steps and the use of specific laboratory equipment. Other test methods involve the use of CRISPR diagnostics. CRISPR was invented as a means to change an organism’s DNA. With this, scientists are able to target DNA sequences which can then be removed, changed, or added to other DNA. The CRISPR-Cas9 system is most commonly used; Cas-9 is a protein responsible for cutting DNA in the process. The researchers developed a new system called CRISPR-Cas13, which utilizes CRISPR-Cas gene editing technology. It functions the same as other CRISPR-Cas systems, however their protein is Cas13, which targets RNA instead of DNA.
The study was conducted to test the effectiveness of CRISPR-Cas13 and a smartphone-based detector system. Pre-extracted nasal swab samples from SARS-Cov-2 positive patients were collected and run through the test. The researchers created the CRISPR-Cas13 system such that when the Cas13 protein binds to RNA, it cuts the sequence and attaches a fluorescent probe capable of being detected by a smartphone camera. In this way, the researchers were able to tell exactly how much RNA virus was present. Measuring the number of viral particles (RNA load) within an individual is necessary to determine how infectious they are. The current Cas13 test method was able to detect as low as 30 viral particles per microliter of sample, and as much as 100 particles in 30 minutes. The CRISPR-Cas13 system was also accurately able to diagnose the set of pre-extracted patient RNA in just five minutes.
The new CRISPR-Cass13 system can provide accurate SARS-CoV-2 test results using only a smartphone reader.
Eliminating the need to detect DNA puts the CRISPR-Cas13 system above other CRISPR and PCR test methods. It circumvents the need for costly equipment, trained laboratory personnel, and long wait times. More importantly, the test is sensitive to even the slightest amount of viral RNA present. By providing a quantitative measure (the number of viral particles) versus simply “positive” and “negative” results, clinicians will be able to make better informed decisions regarding infectivity of patients. This novel point-of-care instrument provides a fast and easy SARS-CoV-2 testing system, thus allowing for better containment of viral transmission.
Written by Melody Sayrany
- CellPressNews. (n.d.). Researchers adapt cell phone camera for SARS-CoV-2 detection. Retrieved December 12, 2020, from https://www.eurekalert.org/pub_releases/2020-12/cp-rac120420.php
- Fozouni, P., Son, S., Díaz de León Derby, M., Knott, G.J., Gray, C.N., D’Ambrosio, M.V., … Ott, M., Amplification-free detection of SARS- CoV-2 with CRISPR-Cas13a and mobile phone microscopy, Cell (2021), doi: https://doi.org/10.1016/ j.cell.2020.12.001.
Reference to get you started: https://www.eurekalert.org/pub_releases/2020-12/cp-rac120420.php
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