Personalised medicine and the DNA transistor

In an effort to build a nanoscale DNA sequencer, IBM scientists are drilling nano-sized holes in computer-like chips and passing DNA strands through them to read the information contained within their genetic code.

The research is to demonstrate that a silicon-based 'DNA transistor' could help pave the way to read human DNA easily and quickly, generating advancements in health condition diagnosis and treatment.

The challenge in the effort is to slow and control the motion of the DNA through the hole so the reader can accurately decode what is in the DNA.

If successful, the project could improve throughput and reduce cost to achieve the vision of personalised genome analysis at a cost of $100 to $1000.

The first sequencing ever done by the human genome project cost $3 billion.

Having access to an individual's personal genetic code could advance personalised medicine by using genomic and molecular data to facilitate the discovery and clinical testing of new products and help determine a person's predisposition to a particular disease or condition.

A team of scientists from four fields - nanofabrication, microelectronics, physics and biology - are converging to master the technique that threads a long DNA molecule through a three-nanometre-wide hole, known as a nanopore, in a silicon chip.

A nanometre is one one-billionth of a metre or about 100,000 times smaller than the width of a human hair. As the molecule is passed through the nanopore, it is ratcheted one unit of DNA at a time, as an electrical sensor 'reads' the DNA.

This sensor that identifies the genetic information is the subject of intense ongoing research. The information gathered from the reader could be used to gain a better understanding of an individual's medical make-up to help further the pursuit of personalised healthcare.

IBM Research is working to optimise a process for controlling the rate at which a DNA strand moves through a nano-scale aperture on a thin membrane during analysis for DNA sequencing.

While scientists around the world have been working on using nanopore technology to read DNA, nobody has been able to work out how to have complete control of a strand as it travels through the nanopore.

Slowing the speed is critical to being able to read the DNA strand. IBM scientists believe they have a unique approach that could tackle this challenge.

To control the speed at which the DNA flows through the nanopore, researchers have developed a device consisting of a multilayer metal/dielectric nanostructure that contains the nanopore.

Voltage biases between the electrically addressable metal layers will modulate the electric field inside the nanopore. This device uses the interaction of discrete charges along the backbone of a DNA molecule with the modulated electric field to trap DNA in the nanopore.

By cyclically turning on and off these gate voltages, scientists showed theoretically and computationally, and expect to be able to prove experimentally, the plausibility of moving DNA through the nanopore at a rate of one nucleotide per cycle - a rate that IBM scientists believe would make DNA readable.