The new sensor promises earlier detection of viral infections

Vanderbilt a chemist and biomedical engineer was developing a respiratory virus detector is quite sensitive to infection at an early stage, only takes a few minutes for a result and it is easy enough for children in a medical office .

Writing in The Analyst - a magazine published by the Royal Society of Chemistry - the developers indicate that their technique, DNA with hairpins of gold filaments, may be the presence of respiratory syncytial virus (RSV) - a major cause of respiratory tract infections in infants and young children - in many cases lower the quality of laboratory testing.

"We hope our research will help us to the Catch-22, the conservation of significant progress in the treatment of respiratory tract viruses," says Junior Professor of Chemistry David Wright, in collaboration with the biomedical engineering professor Frederick "Rick" Haselton on the new detection method.

According to chemists, the pharmaceutical industry, investment in the development of antivirals for RSV and other major respiratory viruses, since there was no possibility for the infection early enough for drugs to work effectively without harmful side effects. "There are antiviral connections - we discovered that some of them in my lab - it works, if we can detect the virus early, before it is too much virus in the system," he says.

In addition, the lack of a reliable early detection complemented the growing problem of antibiotic resistance. The symptoms of respiratory tract infection by viral agents are nearly identical to those of bacteria. As a result, antibiotics, bacteria, which are often mistaken for viral infections. It is not only inefficient, but it also increases the number of antibiotic resistant strains.

Currently, there are several standard tests for RSV, including the cultivation of virus, the reaction of polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). For all these tests, physicians must be a mucosal sample from a patient to a special laboratory. In combination with the delivery time, residues and other delays, it often takes a day or more for results. Unfortunately, the respiratory viruses multiply so quickly that it's too late for the antiviral drugs work, Mr. Wright.

However, "our system could, in a single-use device, about the size of a pen," says Haselton. To perform a test, all persons who would be required, it is, drag a ceiling, which has a length of gold thread, yarn-Dip in the sample, pull the cord and exposure to a wire scanner fluorescence. When it is lit, then the virus is present.

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

One is the filament-antibody recognition test (FARA), which several years ago by Haselton and patented Vanderbilt. FARA using antibodies - proteins created by the immune system, it binds to foreign substances - on the surface of a coating of polyester filaments. If the luminous body surface is exposed to a sample, if one of the target molecules, antibodies to form complexes and are detected with fluorescent dyes. An advantage of this approach is that a sample can be through the different stages of processing by simply dragging the filament by a series of small rooms. In the RSV detection application, the rooms contain wash solutions, do not delete the specific binding of molecules.

"Initially, we thought that, for sealing joints between the boards of appeal, but we believe that if we openings small enough, then the solutions in the living room in the resort, as we get the thread "Haselton said.

The second technology is based on molecular beacon probes, often in a PCR approach. The probes are short length of each strand of DNA, usually a hairpin, but in a fair, if they are required to a target molecule. A fluorescent dye molecule is in the leg and the curves of hair a molecule that suppresses its fluorescence is on the other side. If the probe is in the configuration of hair dyes and quencher molecules together, so that the probe does not fluoresce. If it is a goal, like a piece of viral RNA, except for spring, the rotation of the probe fluorescence.

Researchers at Vanderbilt, said that, if molecular beacons to a coating of gold son, gold could theoretically replace the quencher molecule Bake and inhibit fluorescence. However, they had to link a molecule - the molecule, the key measure on the wire - it was exactly the right length to make it work.

If you solved this problem, researchers have tested the sensitivity of the new system. They found that the presence of RSV virus particles at a level 200 times below the limit of the standard ELISA method. This extreme sensitivity combined with the basic simplicity of the approach, it is attractive for development as evidence of the platform virus, "the researchers write in the article by the analyst, in the 15th line in May

After Haselton, there are two areas where development is needed. One is the sample preparation. RNA kit commercial samples are available, but they are more expensive and more complicated than desirable. The team is currently reviewing the draft of a simple pull-through RNA isolation room. The team is also exploring options for reducing false detections. There are many other molecules in the mucosa, in addition to the viral RNA can bind to a certain extent with the molecular weight Beacons. But researchers say it should be possible for the number of false positives by a stage of heating, calibrated for the molecules under the tags of the viral RNA.

The next major step in development is to see how the device with real patients.

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