SHERLOCK 2.0: even more elementary
A group of researchers from the Broad Institute in Cambridge and the Massachusetts Institute of Technology has refined a previously created fast, inexpensive and sensitive diagnostic tool based on CRISPR technology. It consists of test strips that allow you to see the result with the naked eye: after immersion in the test sample, a strip appears indicating whether the target molecule has been detected or not.
SHERLOCK test strips. Source: Zhang lab.
SHERLOCK (from the English "Specific High Sensitivity Reporter unLOCKing"), as the developers called the test, will be indispensable in clinical practice. It was developed a year ago, and now researchers are reporting on the refinement and expansion of the possibilities of using the test.
In experiments, test strips were tested to detect tumor DNA in lung cancer, as well as to detect Zika virus and Dengue fever. But this does not exhaust SHERLOCK's potential: it can be used to diagnose infections, detect mutations, and determine drug resistance.
The principle of operation of SHERLOCK is to detect genetic markers – sequences of nucleic acids belonging to pathogens or tumor DNA. It contains the Cas13 protein associated with the CRISPR system. It can be programmed to interact with a specific part of the RNA. The target of Cas13 can be any genetic sequence, including viral genomes, genes that confer antibiotic resistance to bacteria, or mutations that cause cancer.
The Cas13 enzyme protein, when interacting with an RNA fragment, cuts it, during which signaling molecules are produced, which ensure the appearance of a strip on the test.
The most important thing, according to the developers, is that SHERLOCK can now detect several parameters simultaneously. If earlier the test determined only one sequence of nucleic acids, now it can identify up to four "targets" in one sample. This means that samples for diagnostics, as well as the tests themselves, will now need up to four times less.
For example, the new version of SHERLOCK can differentiate Zika virus and Dengue fever: both of these diseases have similar symptoms. Moreover, for an accurate diagnosis, a single sampling of material from the patient and a minimum of time spent will be required.
Animation demonstrating the definition of Zika and Dengue viruses.
In addition to improving functionality, the new version of the test has become even more sensitive. This was achieved by strengthening with additional enzymes Cas12a and Csm6. The authors report a 100-fold increase in the sensitivity of the test compared to the previous version. This revision is of fundamental importance in the practice of oncologists, when the concentration of tumor DNA in the blood can be negligible.
The potential of the SHERLOCK test is difficult to overestimate. It will help clinicians save time and effort spent on making an accurate diagnosis. This is especially important for primary care physicians, especially during outbreaks and epidemics.
Article by J.S. Gootenberg et al. Multiplexed and portable nucleic acid detection platform with Cas13, Cas12a, and Csm6 is published in the journal Science.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on the Broad Institute: SHERLOCK team advances its CRISPR-based diagnostic tool.