Biosingularity

Fast and ultrasensitive optical virus sensor

Posted on: January 23, 2007

Scientists of the Biophysical Engineering Group of the University of Twente in The Netherlands have developed an ultrasensitive sensor that can be used in a handheld device to, within minutes, detect various viruses and measure their concentration. The sensor could be used to quickly screen people at hospitals, airports and emergency clinics to control outbreaks of diseases such as SARS and the bird flu. All it would take is a tiny sample of saliva, blood, or other body fluid.

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In a new virus-detecting sensor, waveguides in a silicon substrate split light into four parallel beams. The beams then form an interference pattern that changes when viruses bind to the antibodies placed on one of the light channels. Researchers at the University of Twente, in the Netherlands, made the device, which can detect low virus concentrations in minutes.
Credit: Credit: Aurel Ymeti

Dr. Aurel Ymeti and others present their results in February’s issue of Nano Letters.

Currently available methods to detect viruses are also sensitive. But they require laborious preparation of the fluid sample and only give results after several days. Since viral diseases can spread rapidly, researchers are looking for easier, faster ways to directly detect viruses. “You want a tool on which you apply the [fluid] sample on-site and in a few minutes say whether or not the person has the SARS virus,” says Aurel Ymeti, a postdoctoral researcher in biophysical engineering and the sensor’s lead developer.

The essential innovation in the technique reported in this paper is the combining of an integrated optics interferometric sensor with antibody-antigen recognition approaches to yield a very sensitive, very rapid test for virus detection. The technology is amenable to miniaturization and mass-production, and thus has significant potential to be developed into a handheld, point-of-care device.

The attention this sensor is currently achieving in the international scientific and nanotechnology community can be understood in the light of recent serious virus outbreaks such as SARS and H5N1 bird flu virus. Future viral outbreaks are a major threat to the societal and economic development throughout the world. Therefore a rapid, sensitive, and easy-to-use test for viral infections is essential to prevent and to control such viral pandemics. Furthermore, a compact, portable device is potentially very useful in remote or developing regions without easy access to sophisticated laboratory facilities.

The technique is better than traditional methods such as PCR (polymerase chain reaction) because of its speed and ease of use without compromising sensitivity. In principle, with a device such as this, minimal pre-processing of samples is required, and one could imagine having several different, interchangeable, detection modules for rapid detection. It’s also possible to consider configuring the device to detect multiple analytes.

So far, the researchers have only tested the sensor for the herpes-simplex virus. On one of the four light-guiding channels, the researchers attach antibodies that bind to the virus. Then they slowly flow a saline solution of the virus along that channel. As the microbes attach to the antibodies, the interference pattern changes. The higher the concentration, the more the interference pattern shifts.

By measuring the change in the pattern for different virus concentrations, the researchers establish a fixed relationship between the two factors. Once this relationship is known, Ymeti says they can estimate the concentration of a new virus solution by analyzing the sensor’s response for a few minutes.

Read more about this story at MIT Technology Review

Souce: The article, entitled, ‘Fast, ultrasensitive virus detection using a young interferometer sensor’ by A. Ymeti, J. Greve, P.V. Lambeck, Th. Wink, S.W.F.M. van Höwell, T.A.M. Beumer, R.R. Wijn, R.G. Heideman, V. Subramaniam, and J.S. Kanger will be published in the February issue of Nano Letters and is already online for subscribers.

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7 Responses to "Fast and ultrasensitive optical virus sensor"

If you have something that binds to whatever, high resolution surface plasmon resonance can detect 10 nM concentrations, and modified single nanotube resistance changes from conformal changes from binding can be detected. What advantage does this technique have over those?

The resolution of this technique is 100 X better than surface plasmon resonance!

Something seems strange, though. The paper claims detection of 850 particles/mL, but the MIT page says that it can only detect particles at high concentrations currently, and much higher concentrations in serum. Using refraction as a detection mechanism and not at a surface like SPR does means that you can’t distinguish between different particles very well; you can only detect the difference in total amounts of particles due to some of them binding to antibodies. When the concentration of other particles is much higher than the concentration of particles to be detected, noise is too high, unlike in SPR or nanotube conformation changes. Further, at 850/mL, there’s a good chance you will not get a single bound particle.

If you read the original article carefully, you will notice the high SNR at 850 particles/mL. Given the detection limit of the sensor, detection of a few virus particles is possible.

You will also notice that the detection mechanism in this sensor has also to do with binding of viruses at a surface coated with an antobody like SPR.

In an intereferometer sensor, the information obtained from different channels can be used to correct for non-specific binding and other factors such as temperature, which is impossible to be perfomed with an SPR based sensor.

I would advice you to better study the working principle of this type of sensors before you draw conclusions based on poor knowledge. Otherwise the comparison you are making is nonsense.

Couldn’t get the paper at the time, somehow I was thinking of running the laser through the fluid…anyway, it does seem very clever. Sort of a “sideways SPR” to stack phase delays to improve sensitivity and cancel some effects.

Sorry about that.

Perhaps it would even be possible to distinguish between a small number of particles apart from binding by comparing phase delay at different wavelengths.

It is over two years since this article was posted and I am wondering if there are any news/updates available by now? I just found out the the mentioned venture company “Paradocs Group B.V.” (www.paradocsgroup.com) seams not to exist anymore. Does anybody has more information about this project?

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