The proposed device – a capacitor which stores electric charge – is a ribbon of molybdenum disulfide suspended over a metal electrode and immersed in water. Single-stranded DNA, containing a chain of bases, is threaded through a hole 2.5nm wide in the ribbon. The ribbon flexes only when a DNA base pairs up with and then separates from a complementary base affixed to the hole. The membrane motion is detected as an electrical signal. The DNA sequence is determined by measuring how and when electrical blips vary over time. To detect all four bases, four nanoribbons, each with a different base attached to the pore, could be stacked vertically to create an integrated DNA sensor.
Among other advantages, this material does not stick to DNA, which can be a problem with graphene. The NIST team suggests the method might even work without a nanopore, by passing DNA across the edge of the membrane.
"This approach solves the issue with DNA sticking to graphene if inserted improperly, because this approach does not use graphene," NIST theorist, Alex Smolyanitsky, said. "Another major difference is that instead of relying on the properties of graphene or any particular material used, we read motions electrically by forming a capacitor. This makes any electrically conductive membrane suitable for the application."
According to the team, it made numerical simulations and theoretical estimates to show the membrane would be 79 to 86% accurate in identifying DNA bases in a single measurement at speeds of up to about 70million bases/s.
