MENU

CRISPR-powered device promises ‘bedside’ DNA testing

CRISPR-powered device promises ‘bedside’ DNA testing

Technology News |
By Rich Pell



The device, dubbed CRISPR-Chip, could be used to rapidly diagnose genetic diseases or to evaluate the accuracy of gene-editing techniques, say the scientists. To demonstrate CRISPR-Chip’s sensitivity, the researchers used the device to detect two common genetic mutations in blood samples from Duchenne muscular dystrophy (DMD) patients.

“We have developed the first transistor that uses CRISPR to search your genome for potential mutations,” says Kiana Aran, an assistant professor at KGI who conceived of the technology while a postdoctoral scholar at UC Berkeley. “You just put your purified DNA sample on the chip, allow CRISPR to do the search, and the graphene transistor reports the result of this search in minutes.”

Unlike most forms of genetic testing, say the researchers, CRISPR-Chip uses nanoelectronics to detect genetic mutations in DNA samples without first “amplifying” or replicating the DNA segment of interest millions of times over through a time- and equipment-intensive process called polymerase chain reaction (PCR). This means it could be used to perform genetic testing in a doctor’s office or field work setting without having to send a sample off to a lab.

“CRISPR-Chip has the benefit that it is really point of care, it is one of the few things where you could really do it at the bedside if you had a good DNA sample,” says Niren Murthy, professor of bioengineering at UC Berkeley and co-author of a paper on the project. “Ultimately, you just need to take a person’s cells, extract the DNA and mix it with the CRISPR-Chip and you will be able to tell if a certain DNA sequence is there or not. That could potentially lead to a true bedside assay for DNA.”

The CRISPR – shorthand for “CRISPR-Cas9” – gene editing system gives researchers unprecedented gene-editing capabilities by being able to snip threads of DNA at precise locations. Cas9 (or “CRISPR-associated protein 9”) acts as a pair of molecular “scissors” that can cut strands of DNA at a specific location in the genome so that bits of DNA can then be added or removed.

For Cas9 to find a specific location on the genome, scientists must first equip it with a snippet of “guide ribonucleic acid (RNA),” a small piece of RNA – a nucleic acid present in all living cells – whose bases are complementary to the DNA sequence of interest. The bulky protein first unzips the double-stranded DNA and scans through until it finds the sequence that matches the guide RNA, and then latches on.

To harness CRISPR’s gene-targeting ability, the researchers took a deactivated Cas9 protein – a variant of Cas9 that can find a specific location on DNA, but doesn’t cut it – and tethered it to transistors made of graphene. When the CRISPR complex finds the spot on the DNA that it is targeting, it binds to it and triggers a change in the electrical conductance of the graphene, which, in turn, changes the electrical characteristics of the transistor, say the scientists. These changes can be detected with a hand-held device developed by the team’s industrial collaborators.

Graphene, which is built of a single atomic layer of carbon, is so electrically sensitive, say the researchers, that it can detect a DNA sequence “hit” in a full-genome sample without PCR amplification.

“Graphene’s super-sensitivity enabled us to detect the DNA searching activities of CRISPR,” says Aran. “CRISPR brought the selectivity, graphene transistors brought the sensitivity and, together, we were able to do this PCR-free or amplification-free detection.”

The researchers hope to soon “multiplex” the device, allowing doctors to plug in multiple guide RNAs at once to simultaneously detect a number of genetic mutations in minutes.

“Imagine a page with a lot of search boxes, in our case transistors, and you have your guide RNA information in these search boxes, and each of these transistors will do the search and report the result electronically,” says Aran.

Rapid genetic testing could also be used to help doctors develop individualized treatment plans for their patients, say the researchers. For example, genetic variations make some people unresponsive to expensive blood thinners, like Plavix.

Finally, say the researchers, because the CRISPR-Chip can be used to monitor whether CRISPR binds to specific DNA sequences, it could also be used to test the effectiveness of CRISPR-based gene-editing techniques. For example, it could be used to verify that guide RNA sequences are designed correctly, says Aran.

“Combining modern nanoelectronics with modern biology opens a new door to get access to new biological information that was not accessible before,” Aran says.

For more, see “Detection of unamplified target genes via CRISPR–Cas9 immobilized on a graphene field-effect transistor.”

Related articles:
World’s smallest ‘tape’ recorder uses hacked microbes
Malware in DNA could infect computers
Large-scale DNA data storage moves closer to reality
First fully automated DNA data storage demonstrated

If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :    eeNews on Google News

Share:

Linked Articles
10s