Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New nanosensor uses quantum dots to detect DNA

07.12.2005


Quick, highly sensitive method makes genetic material glow



Using tiny semiconductor crystals, biological probes and a laser, Johns Hopkins University engineers have developed a new method of finding specific sequences of DNA by making them light up beneath a microscope.

The researchers, who say the technique will have important uses in medical research, demonstrated its potential in their lab by detecting a sample of DNA containing a mutation linked to ovarian cancer.


The Johns Hopkins team described the new DNA nanosensor in a paper published in the November 2005 issue of the journal Nature Materials.

"Conventional methods of finding and identifying samples of DNA are cumbersome and time-consuming," said Jeff Tza-Huei Wang, senior author of the paper and supervisor of the research team. "This new technique is ultrasensitive, quick and relatively simple. It can be used to look for a particular part of a DNA sequence, as well as for genetic defects and mutations."

The technique involves an unusual blend of organic and inorganic components. "We are the first to demonstrate the use of quantum dots as a DNA sensor," Wang said.

Quantum dots are crystals of semiconductor material, whose sizes are only in the range of a few nanometers across. (A nanometer is one-billionth of a meter.) They are traditionally used in electronic circuitry. In recent years, however, scientists have begun to explore their use in biological projects.

Wang, an assistant professor in the Department of Mechanical Engineering and the Whitaker Biomedical Engineering Institute at Johns Hopkins, led his team in exploiting an important property of quantum dots: They can easily transfer energy. When a laser shines on a quantum dot, it can pass the energy on to a nearby molecule, which in turn emits a fluorescent glow that is visible under a microscope.

But quantum dots alone cannot find and identify DNA strands. For that, the Johns Hopkins team used two biological probes made of synthetic DNA. Each of these probes is a complement to the DNA sequence the researchers are searching for. Therefore, the probes seek out and bind to the target DNA.

Each DNA probe also has an important partner. Attached to one is a Cy5 molecule that glows when it receives energy. Attached to the second probe is a molecule called biotin. Biotin sticks to yet another molecule called streptavidin, which coats the surface of the quantum dot.

To create their nanosensor, the researchers mixed the two DNA probes, plus a quantum dot, in a lab dish containing the DNA they were trying to detect. Then nature took its course. First, the two DNA probes linked up to the target DNA strand, holding it in a sandwich-like embrace. Then the biotin on one of the probes caused the DNA "sandwich" to stick to the surface of the quantum dot.

Finally, when the researchers shined a laser on the mix, the quantum dot passed the energy on to the Cy5 molecule that was attached to the second probe. The Cy5 released this energy as a fluorescent glow. If the target DNA had not been present in the solution, the four components would not have joined together, and the distinctive glow would not have appeared. Each quantum dot can connect to up to about 60 DNA sequences, making the combined glow even brighter and easier to see.

To test the new technique, Wang’s team obtained DNA samples from patients with ovarian cancer and detected DNA sequences containing a critical mutation. "This method may help us identify people at risk of developing cancer, so that treatment can begin at a very early stage," Wang said.

Phil Sneiderman | EurekAlert!
Further information:
http://www.jhu.edu

More articles from Materials Sciences:

nachricht Spin current detection in quantum materials unlocks potential for alternative electronics
16.10.2017 | DOE/Oak Ridge National Laboratory

nachricht Missing atoms in a forgotten crystal bring luminescence
11.10.2017 | King Abdullah University of Science & Technology (KAUST)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

Im Focus: New nanomaterial can extract hydrogen fuel from seawater

Hybrid material converts more sunlight and can weather seawater's harsh conditions

It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...

Im Focus: Small collisions make big impact on Mercury's thin atmosphere

Mercury, our smallest planetary neighbor, has very little to call an atmosphere, but it does have a strange weather pattern: morning micro-meteor showers.

Recent modeling along with previously published results from NASA's MESSENGER spacecraft -- short for Mercury Surface, Space Environment, Geochemistry and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

Conference Week RRR2017 on Renewable Resources from Wet and Rewetted Peatlands

28.09.2017 | Event News

 
Latest News

A single photon reveals quantum entanglement of 16 million atoms

16.10.2017 | Physics and Astronomy

The melting ice makes the sea around Greenland less saline

16.10.2017 | Earth Sciences

On the generation of solar spicules and Alfvenic waves

16.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>