The original 10 Mb Ion 314 semiconductor sequencing chip.
Credit: Jonathan Rothberg
The Ion Personal Genome Machine (PGM) released in January 2011.
Credit: Ion Torrent
FAREHAM: A new technique for sequencing the human genome developed by researchers in the U.S. uses electronic chips and is set to be low cost, portable and scaleable.
The ability to sequence, or read, DNA has revolutionised medical research, including the fields of cancer, human genetics and infectious disease. It has also led to the emerging field of personalised medicine, which could soon enable doctors to tailor therapies to patients' individual genomes.
Since the Human Genome Project was completed nearly 10 years ago, the costs of sequencing DNA have dropped steadily and the race is now on to sequence an entire human genome for just US$1,000. One of the key factors standing in the way of this milestone is the need for expensive imaging apparatus.
Fast, cheap sequencing
Jonathan Rothberg and colleagues at Life Technologies Ion Torrent in California have developed a solution to this problem in the form of an electronic sensor in an integrated circuit that is produced using low-cost semiconductor manufacturing techniques.
"The development of ion semiconductor sequencing will have as profound an effect on sequencing as the introduction of CMOS imagers had on the development of digital photography - it will make sequencing ubiquitous, fast and low cost," said Rothberg, who has described the new technology in an article published in Nature this week.
"Genome sequencing has huge potential in the diagnosis and management of disease. This semiconductor device is a very exciting development that should be able to deliver genome information to the clinic cheaply and effectively," added Dame Kay Davies from the University of Oxford, UK, who was not involved in the research.
A novel approach
Current DNA sequencing methods use optical imaging, which requires costly equipment, while other attempts to use electronic sensors to synthesise and sequence DNA have been limited by the number of sensors that could fit on a single array, which adversely affects the speed at which they can read the code.
Rothberg's team has overcome these limitations by producing simple electronic chips with a large number of fast, uniform sensors arranged in a two-dimensional array.
Unlike the current light-based sequencing techniques, which rely on the release of photons to measure when a nucleotide base has been incorporated into a DNA strand, Ion Torrent's chips have no optical components and instead use a sensor to measure the release of hydrogen ions, which cause a reduction in pH to the surrounding medium.
This pH change is converted to a voltage when each nucleotide base is incorporated, so that the code of the DNA strand can be read from the series of voltage readings by a signal processor. Each nucleotide base pair is flowed sequentially over the chip to differentiate between the four nucleotides. The results are passed through several filters to ensure that the ‘read’ of the DNA is accurate and any erroneous results are filtered out.
wrong name
Gordon Moore is the name you were meaning to report as one of the founders of Intel Corporation.