According to a November 14 news release from Penn State University, researchers have paved the way for a new gene sequencing technique that is based on threading the 3 billion letter-long DNA sequences unique to each and every human through a tiny hole and using a nearby sensor to read each letter as it passes through.
The new DNA sensor uses graphene, a lattice of carbon roughly the thickness of an atom. While earlier iterations of the technique leveraged graphene’s unparalleled thinness, the University of Pennsylvania research team shows how the Nobel Prize-wining material’s unique electrical properties may be used to produce faster and more sensitive gene sequencing machines.
Most importantly, the team’s most recent evaluation of the technology shows how to drill the nanopores without adulterating graphene’s electrical sensitivity – a severe risk posed by merely looking at the material through an electron microscope.
Led by Marija Drndić, professor of physics in the School of Arts and Sciences, the team’s research appears in the latest issue of the journal ACS Nano.
Drndić’s team previously validated a series of developments towards reading genes by passing them through a tiny hole, or nanopore. Their 2010 study comprised drilling a hole in a sheet of graphene, then submerging it in an ionic bath with the strands of DNA to be detected. Because each of the four bases, the letters in DNA’s alphabet, have a different size, a different number of ions would be expected to squeeze through along with each base as the strand passes through the pore. Researchers then could interpret the sequence of the DNA’s bases by measuring the electrical signal of the ions. However, those current signals are weak, and limit the speed at which DNA could be sequenced.
“Our latest attempt at improving the technique is a departure from our previous work, however,” Drndić said. “We’re now trying to measure current directly from the graphene, whereas before we measured ionic current in the solution as it goes through the pore.”
The University of Pennsylvania researchers wanted to evaluate whether nanopores in graphene would be capable of sensing the variance between bases directly. In lieu of their different sizes, this method would rely on the bases varying the electric charge in the nearby material – a thin, wire-like ribbon of graphene. As each base travels through the pore, it would control the electrical current flowing through the ribbon. The changes in current would then be matched to their respective bases, permitting the researchers to decode the sequence.
To take on this challenging endeavor, the University of Pennsylvania researchers received support from the National Science Foundation and the National Institutes of Health.