IBM’s “DNA Transistor” May Lead to Cheap, Rapid DNA Sequencing

Cheap DNA sequencing is a holy grail for geneticists and advocates of personalized medicine. IBM has embarked on its own search for a technology, capable of bringing down personalized genome sequencing to $1,000. The technique they’re currently pursuing involves running a DNA thread through a nanopore three nanometers wide. Inside would be an electrical sensor that can distinguish which of the four DNA bases is in proximity. If the DNA can be moved through the nanopore quickly enough with short pauses for base readings, the project researchers believe this approach will make genome sequencing common for clinical applications.

IBM Research is working to optimize 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 figure out how to have complete control of a DNA 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 microprocessor nanopore, IBM researchers have developed a device consisting of a multilayer metal/dielectric nano-structure that contains the nanopore. Voltage biases between the electrically addressable metal layers will modulate the electric field inside the nanopore. This device utilizes 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 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.

Image: A membrane containing the nanopore, funtionalized with metal contacts (orange) separated by dielectric materials (lime), devides a reservoir into a top part containing an ionic solution with a high concentration of single stranded DNA, and a bottom part, where the DNA will be translocated to. The DNA on the top reservoir is induced to go to the bottom reservoir by the action of a biasing voltage. In the absence of anything else, the DNA would translocate through the pore at a speed of several million bases per second. To control the passage of DNA trhough the nano-hole, voltages of appropriate polarity (not shown) are applied to the metal contacts inside the pore, which create an internal electric field that trap the DNA. By alternating the trapping voltages applied to the metal contacts, the DNA can be made ratchet from the top to the bottom reservoirs in a controlled way.