Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > DNA 'barcodes'

Abstract:
Cornell researchers make synthetic DNA 'barcodes' to tag pathogens, providing an inexpensive, off-the-shelf monitoring system

DNA 'barcodes'

June 13, 2005

A supermarket checkout computer can identify thousands of different items by scanning the tiny barcode printed on the package. New technology developed at Cornell University could make it just as easy to identify genes, pathogens, illegal drugs and other chemicals of interest by tagging them with color-coded probes made out of synthetic tree-shaped DNA.

A research group headed by Dan Luo, Cornell assistant professor of biological engineering, has created "nanobarcodes" that fluoresce under ultraviolet light in a combination of colors that can be read by a computer scanner or observed with a fluorescent light microscope.

Cornell University
When DNA chains interact, adenine always bonds to thymine, and cytosine always bonds to guanine. Three DNA chains with complementary patterns along half their length will combine to form a Y.
Copyright Cornell University. Click for higher-resolution version.

Other methods of identifying biological molecules that are available or being developed mostly involve expensive equipment, Luo said. "We wanted something that could be done with inexpensive, readily available equipment," he said. Several years ago researchers created probes consisting of nanoscale bars of metal actually etched with conventional bar codes. Since then, most molecular tagging devices have been referred to as "barcodes," even though there are no bars involved.

The researchers have tested their system using samples containing various combinations of E. coli, anthrax and tularemia bacteria and ebola and SARS viruses, and have found the color codes could clearly distinguish several different pathogens simultaneously.

The research is described in a paper, "DNA fluorescence nanobarcodes for multiplexed pathogen detections," by Luo, Yougen Li, a former Cornell graduate student now at California Institute of Technology, and Yen Thi Hong Cu, a current graduate student, to be published in the July 2005 issue of the journal Nature Biotechnology and available after June 12 in the online version of the journal.

The idea is one of several applications the researchers have found for what they call "dendimer-like DNA," consisting of many short Y-shaped strands of DNA linked together in a treelike structure. The DNA that carries the genetic code in living cells consists of two complementary strands that attach to one another along their length. But Luo's research purposely and completely ignores the DNA's genetic coding properties. He uses DNA, he said, as a "generic instead of a genetic material."

Cornell University
Several Ys can be joined to form a tree with many open ends, to which dye molecules or probes can be attached with precision.
Copyright Cornell University. Click for higher-resolution version.

By synthesizing three short strands of DNA, each of which is complementary to one of the others along half its length, the researchers can create a Y-shaped structure. Combining several of these structures creates a web with many branching ends. "While DNA is flexible, the short strands used here are quite rigid," Luo said. "A long piece of spaghetti is floppy, but a short bit of it is quite stiff."

An antibody or some other molecule that will bind to the molecule to be detected is attached to one of the loose ends of the DNA. To other ends are attached molecules of fluorescent dye in a predetermined pattern. For example, one probe might contain four molecules of green dye and one of red. Another might have three molecules of green and two of red, and so on. If a mixture of several probes is added to a solution containing, for example, E. coli bacterial DNA, only probes with a particular color code will be programmed to bind to that DNA. The results can be seen under a fluorescent light microscope using colored filters that pass only one color at a time. A signal in which the ratio of intensity of green light is four times that of red light, for example, identifies a "4G1R" probe. The researchers say that up to 1,000 different codes can be created using only three fluorescent dyes.

To amplify the signals, the researchers attached many DNA probes to the surface of polystyrene microbeads 5.5 microns (millionths of a meter) in diameter. The results can be read in several ways. One is in a flow cytometer, in which samples move rapidly past a window where a computer reads the color codes of individual beads. Another is by dot blotting, in which the sample is spread on a sheet of absorbent paper and made visible to the naked eye. Or the color can be observed directly through a fluorescent light microscope, which is useful in situations where the geographic distribution of the target molecules is important, Luo said.

Cornell University
Probes with different combinations of dye molecules will produce different ratios of color intensity that can be read by a computer scanner or in some cases seen with the naked eye.
Copyright Cornell University. Click for higher-resolution version.

For convenience, a computer can convert the subtle differences in light intensity between, say 4G1R and 3G1R, into "pseudo colors," perhaps making one appear as orange and the other as pink, to make the difference clear to a human eye.

The researchers point out that the nanobarcode detection system does not require complex preparation of a sample and can be applied to living cells. The technology could be used in genomic research, clinical diagnosis, drug testing, environmental monitoring and monitoring for biological terrorism, they suggest.

Further details on "tree-shaped" DNA appear in a paper in Nature Materials (Vol. 3, Pg. 38-42, 2004).

Related World Wide Web sites: Dan Luo's Molecular Bioengineering Lab at Cornell

####

Contact:
Bill Steele
Office: (607) 255-7164
ws21@cornell.edu

Media Contact:
Blaine P. Friedlander Jr.
Phone: (607) 254-8093
E-mail: bpf2@cornell.edu

Copyright Cornell University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

Possible Futures

Clay nanotube-biopolymer composite scaffolds for tissue engineering May 1st, 2016

Cooling graphene-based film close to pilot-scale production April 30th, 2016

Personal cooling units on the horizon April 29th, 2016

Exploring phosphorene, a promising new material April 29th, 2016

Nanomedicine

Clay nanotube-biopolymer composite scaffolds for tissue engineering May 1st, 2016

Nanoparticles hold promise as double-edged sword against genital herpes April 28th, 2016

Arrowhead Pharmaceuticals Files for Regulatory Clearance to Begin Phase 1/2 Study of ARC-521 April 28th, 2016

The Translational Research Center at the University Hospital of Erlangen in Germany uses the ZetaView from Particle Metrix to quantify extracellular vesicles such as exosomes April 28th, 2016

Announcements

Spintronics for future information technologies: Spin currents in topological insulators controlled May 2nd, 2016

Nanoparticles present sustainable way to grow food crops May 1st, 2016

Clay nanotube-biopolymer composite scaffolds for tissue engineering May 1st, 2016

Cooling graphene-based film close to pilot-scale production April 30th, 2016

Homeland Security

Team builds first quantum cascade laser on silicon: Eliminates the need for an external light source for mid-infrared silicon photonic devices or photonic circuits April 21st, 2016

Nanoporous material's strange "breathing" behavior April 7th, 2016

Sniffing out a dangerous vapor: University of Utah engineers develop material that can sense fuel leaks and fuel-based explosives March 28th, 2016

Detecting and identifying explosives with single test December 10th, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic