Sequencing an entire genome is currently a highly complex, time-consuming process – the DNA must be broken down into segments and replicated, utilizing chemicals that destroy the original sample. Scientists from Imperial College London, however, have just announced the development of a prototype device that could lead to technology capable of sequencing a human genome within minutes, at a cost of just a few dollars. By contrast, when sequencing of the genome of Dr. James Watson (co-discoverer of the structure of DNA) was completed in 2007, it had taken two years and cost US$1 million.
At the heart of the Imperial College device is a silicon chip, with a 50-nanometer nanopore bored through it. DNA strands are propelled at high speed through this hole, and get their coding sequence read by a “tunneling electrode junction” as they come out the other side. This junction consists of a 2-nanometer gap between two platinum wires, with an electrical current passing between them, across the gap. The current interacts with the unique electrical signal given off by each of the DNA strand’s base codes, and the resulting data is then processed by a computer to determine the complete genome sequence.
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The chips are reportedly quite durable, standing up to repeated uses and washings with no loss in performance.
“We haven't tried it on a whole genome yet, but our initial experiments suggest that you could theoretically do a complete scan of the 3,165 million bases in the human genome within minutes, providing huge benefits for medical tests, or DNA profiles for police and security work,” said study co-author Dr. Joshua Edel. “It should be significantly faster and more reliable, and would be easy to scale up to create a device with the capacity to read up to 10 million bases per second, versus the typical 10 bases per second you get with the present day single molecule real-time techniques.”
While passing DNA strands through nanopores has shown promise as a genome-sequencing technique for some time now, this is reportedly the first time it has been paired up with such a fast and accurate reading system – the American creators of a similar system announced this August, however, might dispute that claim. In any case, a practical commercial device could still be up to ten years away.
“The next step will be to differentiate between different DNA samples and, ultimately, between individual bases within the DNA strand,” said study co-author Dr. Tim Albrecht. “I think we know the way forward, but it is a challenging project and we have to make many more incremental steps before our vision can be realized.”
The research was recently published in the journal Nano Letters.