NIST team advances in translating language of nanopores

June 24, 2010
Each molecule passing through the nanopore can be identified by monitoring the change it causes in an ionic current flowing across the membrane. When different molecules (purple and green objects) enter the pore (green shown in inset), each reduces the current by a certain amount and time period (shown by corresponding color scheme in the current diagram below), depending on both its size and ability to attract nearby ions (red dots). The NIST model can be used to extract this information, which might be used to identify and characterize biomarkers for medical applications. Credit: NIST

National Institute of Standards and Technology scientists have moved a step closer to developing the means for a rapid diagnostic blood test that can scan for thousands of disease markers and other chemical indicators of health. The team reports it has learned how to decode the electrical signals generated by a nanopore -- a "gate" less than 2 nanometers wide in an artificial cell membrane.

Nanopores are not new themselves; for more than a decade, scientists have sought to use a nanopore-based electrical detector to characterize single-stranded DNA for genetic sequencing applications. More recently, NIST scientists turned their attention to using nanopores to identify, quantify and characterize each of the more than 20,000 proteins the body produces—a capability that would provide a snapshot of a patient's overall health at a given moment. But while nanopores permit to enter into them one at a time, determining what specific individual molecule has just passed through has not been easy.

To address this problem, members of the NIST team that previously developed a method to distinguish both the size and concentration of each type of molecule the nanopore admits have now answered the question of just how these single molecules interact with the nanopore. Their new theoretical model describes the physics and chemistry of how the nanopore, in effect, parses a molecule, an understanding that will advance the use of nanopores in the medical field.

"This work brings us one step closer to realizing these nanopores as a powerful for medical science," says Joseph Reiner, who performed the work with Joseph Robertson, and John Kasianowicz, all of NIST's Semiconductor Electronics Division. "It adds to the 'Rosetta Stone' that will allow us to read what molecules have just passed through a nanopore."

Using their new methods, the team was able to model the interaction of a particular type of large molecule through a nanopore's opening with great accuracy. The molecules were polyethylene glycol (PEG), a well-understood polymer that forms chains of varying length.

"PEG chains can be very long, but each link is very small," Kasianowicz says. "It was a good test because we wanted to see if the nanopore could differentiate between two nearly identical large molecules that differ in length by only a few atoms."

The team's device was able to distinguish among different-sized PEG chains easily, and the model they have developed to describe the PEG-nanopore interactions is encouraging them to think that with further effort, the minuscule sensors can be customized to measure many different molecules quickly. "We could conceivably build an array of many nanopores, each one created to measure a specific substance," Kasianowicz says. "Because each is so small, an array with one for every in the body would still be tiny."

Explore further: Lollipops and Ice Fishing: Molecular Rulers Used to Probe Nanopores

More information: J.E. Reiner, J.J. Kasianowicz, B.J. Nablo, and J.W. F. Robertson. Theory for polymer analysis using nanopore-based single-molecule mass spectrometry. Proceedings of the National Academy of Sciences, Published online on June 21, 2010, doi: 10.1073/pnas.1002194107

Related Stories

Faster, cheaper DNA sequencing method developed

December 20, 2009

( -- Boston University biomedical engineers have devised a method for making future genome sequencing faster and cheaper by dramatically reducing the amount of DNA required, thus eliminating the expensive, time-consuming ...

DNA gripped in nanopores

May 14, 2009

Molecular biologists, including the cool dudes from CSI, use gel electrophoresis to separate DNA fragments from each other in order to analyze the DNA. A team of researchers under the leadership of Vici winner Serge Lemay, ...

Artificial Nanopores Take Analyte Pulse

July 31, 2007

Resistive pulse sensing represents a very attractive method for identifying and quantifying biomedical species such as drugs, DNA, proteins, and viruses in solution.

Recommended for you

Injectable plant-based nanoparticles delay tumor progression

June 28, 2017

Researchers from Case Western Reserve University School of Medicine in collaboration with researchers from Dartmouth Geisel School of Medicine and RWTH Aachen University (Germany) have adapted virus particles—that normally ...

A levitated nanosphere as an ultra-sensitive sensor

June 28, 2017

Sensitive sensors must be isolated from their environment as much as possible to avoid disturbances. Scientists at ETH Zurich have now demonstrated how to remove from and add elementary charges to a nanosphere that can be ...

Ruthenium rules for new fuel cells

June 28, 2017

Rice University scientists have fabricated a durable catalyst for high-performance fuel cells by attaching single ruthenium atoms to graphene.

Researchers create very small sensor using 'white graphene'

June 28, 2017

Researchers from TU Delft in The Netherlands, in collaboration with a team at the University of Cambridge (U.K.), have found a way to create and clean tiny mechanical sensors in a scalable manner. They created these sensors ...


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jun 25, 2010
This is very interesting and promising research. Would it be possible to use nanopores as dynamic filters, recycling fluid through and watching for a particular kind of molecule to pass through the pore? As soon as it "sees" a target molecule, could the "next layer" of the process divert that selected molecule that just passed through into a molecular cache or vacuole of some kind. This is sort of like Maxwell's daemon but here it would work much like panning for gold at the molecular level.
not rated yet Jun 25, 2010
On another note, if the signature of a molecule passing through the nanopore can be recognized and identifed .. and if all 20,000 proteins have different signatures, then I would think you would only need one good nanopore, rather than a whole chip-full of different ones?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.