The instructions for building all of the body's proteins are contained in a person's DNA, a string of chemicals that, if unwound and strung end to end, would form a sentence 3 billion letters long. Each person's sentence is unique, so learning how to read gene sequences as quickly and inexpensively as possible could pave the way to countless personalized medical applications.
heir DNA sensor is based on graphene, an atomically thin lattice of carbon. Earlier versions of the technique only made use of graphene's unbeatable thinness, but the Penn team's research shows how the Nobel Prize-winning material's unique electrical properties may be employed to make faster and more sensitive sequencing devices.
Critically, the team's latest study shows how to drill these nanopores without ruining graphene's electrical sensitivity, a risk posed by simply looking at the material through an electron microscope.
The team includes Marija Drndić, professor of physics in the School of Arts and Sciences, and members in her laboratory, including graduate student Matthew Puster and postdoctoral researchers Julio Rodríguez-Manzo and Adrian Balan.
Their research was published in the journal ACS Nano.
Drndić's group has previously demonstrated a series of advancements towards reading genes by passing them through a tiny hole, or nanopore. Their 2010 study involved drilling a hole in a sheet of graphene, then putting it in an ionic bath along 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 could then interpret the sequence of the DNA's bases by measuring the electrical signal of the ions. However, those current signals are weak, limiting the speed at which DNA could be sequenced.
Many research groups are now exploring multiple ways to improve the sensitivity and speed of the technique, including new materials and new ways of fashioning nanopores in them. Drndić's group has experimented with different membranes, as well as adding improved electronics to measure at faster speeds, but its latest study represents an entirely new way of generating an electrical signal unique to each base.
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