Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ultrasensitive detector promises improved treatment of viral respiratory infections

30.06.2009
A Vanderbilt chemist and a biomedical engineer have teamed up to develop a respiratory virus detector that is sensitive enough to detect an infection at an early stage, takes only a few minutes to return a result and is simple enough to be performed in a pediatrician's office.

Writing in The Analyst – a journal published by the Royal Society of Chemistry – the developers report that their technique, which uses DNA hairpins attached to gold filaments, can detect the presence of respiratory syncytial virus (RSV) – a leading cause of respiratory infections in infants and young children – at substantially lower levels than the standard laboratory assay.

"We hope that our research will help us break out of the catch-22 that is holding back major advances in the treatment of respiratory viruses," says Associate Professor of Chemistry David Wright, who is working with Professor of Biomedical Engineering Frederick "Rick" Haselton on the new detection method.

According to the chemist, major pharmaceutical companies are not investing in the development of antiviral drugs for RSV and the other major respiratory viruses because there is no way to detect the infections early enough for the drugs to work effectively without harmful side-effects. "There are antiviral compounds out there – we have discovered some of them in my lab – that would work if we can detect the virus early enough, before there is too much virus in the system," he says.

In addition, the lack of a reliable early detection system adds to the growing problem of antibiotic resistance. The symptoms of respiratory infections caused by viral agents are nearly identical to those caused by bacteria. As a result, antibiotics, which target bacteria, are often incorrectly prescribed for viral infections. Not only is this ineffective, but it also increases the number of antibiotic-resistant strains.

Currently, there are several standard tests for RSV including culturing the virus, polymerase chain reaction (PCR) and the enzyme-linked immunosorbent assay (ELISA). To have any of these tests done, doctors must send a mucous sample from a patient to a special laboratory. When combined with delivery times, backlogs and other delays, it frequently takes a day or more to get the results. Unfortunately, respiratory viruses multiply so rapidly that this can be too late for antiviral drugs to work, Wright says.

By contrast, "our system could easily be packaged in a disposable device about the size of a ballpoint pen," says Haselton. To perform a test, all that would be required is to pull off a cap that will expose a length of gold wire, dip the wire in the sample, pull the wire through the device and put the exposed wire into a fluorescence scanner. If it lights up, then the virus is present.

The new detector design is a combination of two existing technologies.

One is the filament-based antibody recognition assay (FARA) developed several years ago by Haselton and patented by Vanderbilt. FARA uses antibodies – special proteins produced by the immune system that binds to specific foreign substances – that are coated on the surface of a polyester filament. When the coated filament is exposed to a sample, if it contains any of the target molecules, they stick to the antibodies, forming complexes that can be detected with fluorescent dyes. One advantage of this approach is that a sample can be put through different processing steps simply by pulling the filament through a series of small chambers. In the RSV detection application, the chambers contain washing solutions that remove non-specific binding molecules.

"Originally we thought that we would have to put special seals between the chambers but we found that if we make the openings small enough, then the solutions in the chambers stay in place as we pull the wire through," says Haselton.

The second technology is based on molecular beacon probes, an approach often used in PCR. The probes consist of short lengths of single-strand DNA that normally form a hairpin shape but straighten out when they are bound to a target molecule. A fluorescent dye molecule is attached to one leg of the hairpin and a molecule that quenches its fluorescence is attached to the other. When the probe is in its hairpin configuration, the dye and quencher molecules lay side by side so the probe does not fluoresce. When it is bound to a target, such as a piece of viral RNA, the ends spring apart, turning on the probe's fluorescence.

The Vanderbilt researchers realized that if they attached molecular beacons to a gold-coated filament, the gold could theoretically replace the quencher molecule and inhibit the beacon's fluorescence. However, they had to find a linking molecule – the molecule that attaches the beacon to the wire – that was just the right length to make it work.

Once they solved this problem, the researchers tested the sensitivity of the new system. They found that it could detect the presence of RSV virus particles at levels that are 200 times below the minimum detection level of the standard ELISA method. This extreme sensitivity combined with the basic simplicity of the approach makes it "attractive for further development as a viral detection platform," the scientists write in the Analyst article, which was published online May 15.

According to Haselton, there are two areas where further development is needed. One is sample preparation. Commercial RNA sample preparation kits are available, but they are more expensive and complex than desirable. The team is currently examining the design of a simple pull-through RNA isolation chamber. The team is also exploring ways to reduce false detections. There are a lot of other molecules in mucous besides viral RNA that can bind to some extent with the molecular beacons. However, the researchers argue that it should be possible to reduce the number of false positives significantly by adding a heating step that is calibrated to drive off the molecules that are less strongly bound to the beacons than the viral RNA.

The next major step in the development process is to see how the device performs with real patient samples.

This research was supported by grants from Vanderbilt University and the National Institutes of Health.

David F. Salisbury | EurekAlert!
Further information:
http://www.vanderbilt.edu

More articles from Health and Medicine:

nachricht Antibiotic effective against drug-resistant bacteria in pediatric skin infections
17.02.2017 | University of California - San Diego

nachricht Tiny magnetic implant offers new drug delivery method
14.02.2017 | University of British Columbia

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>