Featured Research

from universities, journals, and other organizations

Carbon nanotubes show promise for high-speed genetic sequencing

Date:
January 3, 2010
Source:
Arizona State University
Summary:
Scientists have demonstrated the potential of a new DNA sequencing method in which a single-stranded ribbon of DNA is threaded through a carbon nanotube.

In the current issue of Science, Stuart Lindsay, director of Arizona State University's Center for Single Molecule Biophysics at the Biodesign Institute, along with his colleagues, demonstrates the potential of a new DNA sequencing method in which a single-stranded ribbon of DNA is threaded through a carbon nanotube.
Credit: The Biodesign Institute at Arizona State University

Faster sequencing of DNA holds enormous potential for biology and medicine, particularly for personalized diagnosis and customized treatment based on each individual's genomic makeup. At present however, sequencing technology remains cumbersome and cost prohibitive for most clinical applications, though this may be changing, thanks to a range of innovative new techniques.

In the current issue of Science, Stuart Lindsay, director of Arizona State University's Center for Single Molecule Biophysics at the Biodesign Institute, along with his colleagues, demonstrates the potential of one such method in which a single-stranded ribbon of DNA is threaded through a carbon nanotube, producing voltage spikes that provide information about the passage of DNA bases as they pass through the tube -- a process known as translocation.

Carbon nanotubes are versatile, cylindrical structures used in nanotechnology, electronics, optics and other fields of materials science. They are composed of carbon allotropes -- varied arrangements of carbon atoms, exhibiting unique properties of strength and electrical conductivity.

Traditional methods for reading the genetic script, made up of four nucleotide bases, adenine, thymine, cytosine and guanine (labeled A,T,C,&G), typically rely on shredding the DNA molecule into hundreds of thousands of pieces, reading these abbreviated sections and finally, reconstructing the full genetic sequence with the aid of massive computing power. A decade ago, the first human genome -- a sequence of over 3 billion chemical base pairs -- was successfully decoded, in a biological tour de force. The undertaking required around 11 years of painstaking effort at a cost of $1 billion dollars. In addition to the laboriousness of existing techniques, accuracy is compromised, with errors accumulating in proportion to the number of fragments to be read.

A new strategy involves the use of nanopores -- orifices of molecular diameter that connect two fluid reservoirs. A constant voltage can be applied between two electrodes located at either end of the nanopore , inducing an ionic current to flow through the length of the nanopore's enclosed channel. At this scale, the passage of even a single molecule generates a detectable change in the flow of ionic current through the pore. This current is then electronically amplified and measured. Only fairly recently have state of the art micro-manufacturing techniques enabled researchers to construct nanopores at the scale of individual molecules, opening up many new possibilities for single-molecule manipulation and research.

In the current study, single walled carbon nanotubes, 1-2 nm in diameter, were used for the conducting channels. When a current was induced through the nanotube, segments of single-stranded DNA (known as oligomeres) made up of either 60 or 120 nucleotides, were drawn into the opening of the nanotube and translocated from the anode side of the nanotube to the output cathode side, due to the negative charge carried by the DNA molecule. The velocity of DNA translocation is dependent on both the nucleotide structure and molecular weight of the DNA sample.

The carbon nanotubes were grown on an oxidized silicon wafer. Results indicate that among the successfully formed nanotubes -- those fully opened and without leakage along their length -- a sharp spike in electrical activity is detected during the process of DNA translocation. Further, reversing the bias of the electrodes causes the current spikes to disappear; restoring the original bias caused the spikes to reappear.

Lindsay stresses that the transient current pulses, each containing roughly 10x7charges, represent an enormous amplification of the translocated charge. A technique known as quantitative polymerase chain reaction (qPCR) was used to verify that the particular carbon nanotubes displaying these anomalously sharp current spikes -- around 20 percent of the total sample, were indeed those through which DNA translocation had occurred.

The team carried out molecular simulations to try to determine the mechanism for the anomalously large ionic currents detected in the nanotubes. Observation of current-voltage curves registered at varying ionic concentrations showed that ion movement through some of the tubes is very unusual, though understanding the precise mechanism by which DNA translocation gives rise to the observed current spikes will require further modeling. Nevertheless, the characteristic electrical signal of DNA translocation through tubes with high ionic conductance may provide a further refinement in ongoing efforts to apply nanopore technology for rapid DNA sequencing.

Critical to successful rapid sequencing through nanopores is the precise control of DNA translocation. The hope is that genetic reading can be significantly accelerated, while still allowing enough time for DNA bases to be identified by electrical current traces. Carbon nanotubes provide an attractive alternative, making the control of nanopore characteristics easier and more reliable.

If the process can be perfected, Lindsay emphasizes, DNA sequencing could be carried out thousands of times faster than through existing methods, at a fraction of the cost. Realizing the one-patient-one-genome goal of personalized medicine would provide essential diagnostic information and help pioneer individualized treatments for a wide range of diseases.


Story Source:

The above story is based on materials provided by Arizona State University. The original article was written by Richard Harth, Biodesign Institute science writer. Note: Materials may be edited for content and length.


Cite This Page:

Arizona State University. "Carbon nanotubes show promise for high-speed genetic sequencing." ScienceDaily. ScienceDaily, 3 January 2010. <www.sciencedaily.com/releases/2009/12/091231164745.htm>.
Arizona State University. (2010, January 3). Carbon nanotubes show promise for high-speed genetic sequencing. ScienceDaily. Retrieved September 1, 2014 from www.sciencedaily.com/releases/2009/12/091231164745.htm
Arizona State University. "Carbon nanotubes show promise for high-speed genetic sequencing." ScienceDaily. www.sciencedaily.com/releases/2009/12/091231164745.htm (accessed September 1, 2014).

Share This




More Health & Medicine News

Monday, September 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Get on Your Bike! London Cycling Popularity Soars Despite Danger

Get on Your Bike! London Cycling Popularity Soars Despite Danger

AFP (Sep. 1, 2014) Wedged between buses, lorries and cars, cycling in London isn't for the faint hearted. Nevertheless the number of people choosing to bike in the British capital has doubled over the past 15 years. Duration: 02:27 Video provided by AFP
Powered by NewsLook.com
We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com
Liberia Continues Fight Against Ebola

Liberia Continues Fight Against Ebola

AFP (Aug. 30, 2014) Authorities in Liberia try to stem the spread of the Ebola epidemic by raising awareness and setting up sanitation units for people to wash their hands. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
California Passes 'yes-Means-Yes' Campus Sexual Assault Bill

California Passes 'yes-Means-Yes' Campus Sexual Assault Bill

Reuters - US Online Video (Aug. 30, 2014) California lawmakers pass a bill requiring universities to adopt "affirmative consent" language in their definitions of consensual sex, part of a nationwide drive to curb sexual assault on campuses. Linda So reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins