Nanosensors detect thousands of multiple proteins at low cost

Researchers at Johannes Gutenberg University Mainz (JGU) have developed a new device for parallel protein analysis that can identify as many as thousands of different proteins, with help from a spectrometer.

Content Dam Bow Online Articles 2013 07 09 Physchem Protein Sensor Scheme Web

Researchers at Johannes Gutenberg University Mainz (JGU; Mainz, Germany) have developed a new device for parallel protein analysis that can identify as many as thousands of different proteins, with help from a spectrometer. The method could be used to rapidly detect viruses and identify their type in tiny samples at low cost.

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"It would be almost as easy to use as a pregnancy test strip," says Professor Carsten Sönnichsen of the Institute of Physical Chemistry at JGU. The test involves placing a tiny drop of blood, saliva, or other bodily fluid on a small test strip they developed, which is then placed in a tiny device that identifies specific proteins in the fluid and thus quickly and reliably differentiates between harmless microorganisms and dangerous pathogens.

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Sönnichsen's research team designed a sensor that is capable of performing a hundred different individual tests on a surface that is only of one-tenth of a square millimeter in area. The test strips consist of glass capillary tubes that have gold nanoparticles as sensor elements on their internal surfaces. "We first prepare our nanoparticles using short DNA strands, each of which binds to a specific type of protein," explains Janak Prasad, who developed the functionalization method. When a protein docks with one of these special DNA strands, called aptamers, the corresponding nanoparticle changes its color. The color changes can be detected with the aid of a spectrometer. For this purpose, the capillary tubes are placed under a microscope designed, constructed, and provided with the necessary software by the JGU scientists.

Content Dam Bow Online Articles 2013 07 09 Physchem Protein Sensor Scheme Web
When proteins dock with the specifically functionalized nanoparticles, the sensor elements change color. (Image courtesy of the Institute of Physical Chemistry, JGU)

"We demonstrate a new approach for a multiplexed assay that detects multiple proteins simultaneously by letting a fluid flow past the randomly positioned gold nanorods," explains Christina Rosman, first author of the study. The research team used four different target proteins to demonstrate the viability of the new concept, its ability to detect concentrations in the nanomolar range, and the possibility of recycling the sensors for more than one analysis. "We see the potential to extend our method to the simultaneous detection of hundreds or even thousands of different target substances," the authors say. Low-cost serial production of the sensors is feasible if advanced nano-fabrication methods such as nanoprinting or optical trapping are used.

The low-cost nanosensors could be directly used by physicians in their practices in order to detect and discriminate various types of flu viruses. They could also detect the presence of toxins in the environment or in food (particularly in liquids such as milk or baby food), or the presence of doping or other illicit drugs.

For more information on the work, which has been published in a paper in the journal Nano Letters, please visit http://pubs.acs.org/doi/abs/10.1021/nl401354f.

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