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Nanotech News

March 6, 2006

Detection of DNA on Nanotubes Offers New Sensing, Sequencing Technologies

Researchers at the University of Illinois at Urbana-Champaign, who recently reported that DNA-wrapped carbon nanotubes could serve as sensors in living cells, now say that they can use carbon nanotubes to detect specific DNA sequences. Potential applications for the new sensors range from rapid detection of cancer-related genes to simpler tests to identify infectious organisms.

In January, a research team led by Michael Strano, Ph.D., reported that single-walled carbon nanotubes coated with DNA could be placed in living cells and detect trace amounts of harmful contaminants. Now, writing in the journal Nano Letters, Strano and his colleagues report they have taken the technique a significant step further.

“We have successfully demonstrated the optical detection of selective DNA hybridization on the surface of a nanotube,” said Strano. “This work opens possibilities for new types of nanotube-based sensing and sequencing technologies.”

In its natural state, DNA exists in a double stranded form, consisting of two complementary strands, each resembling the side of a ladder and having a specific sequence of nucleotide bases as rungs. Hybridization refers to the spontaneous binding of two complementary strands through base pair matching.

By wrapping one strand of DNA around the surface of a carbon nanotube, the researchers can create a sensor that is targeted for a particular piece of complementary DNA. When the complementary DNA then binds to the DNA probe, the nanotube’s natural near-infrared fluorescence is shifted slightly, and can readily be detected.

“The optical detection of specific DNA sequences through hybridization with a complementary DNA probe has many potential applications in medicine, microbiology and environmental science,” said Esther Jeng, a graduate student in Strano’s group. “For example, this system could be used in genomic screening to detect sequences that encode for genetic disorders, and that are precursors to diseases such as breast cancer.”

“Optical detection allows for passive sensing of hybridization, meaning there is no need to pass voltage or current through the system,” Jeng said. “Furthermore, optics yield high-resolution signals and require a relatively simple setup. And, because our detection setup is in solution, we can sense in a natural biological environment.”

The key to successful optical detection was developing a new technique for suspending carbon nanotubes in solution, getting them to bind to single-stranded DNA, and then removing unbound DNA from the nanotube solution. This method relies on the well-established technique of dialysis and uses readily available equipment.

This work is detailed in a paper titled, “Detection of DNA hybridization using the near-infrared band-gap fluorescence of single-walled carbon nanotubes.” This paper was published online in advance of print publication. An abstract is available at the journal’s website.
View abstract.

The initial work reported by this research team was detailed in a paper titled, "Optical detection of DNA conformational polymorphism on single-walled carbon nanotubes." An abstract of this paper is available through PubMed.
View abstract.