Novel Multiplexed Protein Sensor Developed

Chemists at Johannes Gutenberg University (Mainz, Germany) have designed a sensor that is only of one-tenth of a square millimeter in area, but capable of performing a hundred different individual tests on that surface. The 'test strips' consist of glass capillary tubes that have gold nanoparticles as sensor elements on their internal surfaces. The test involves placing a tiny drop of blood, saliva, or other bodily fluid on a small test strip, which is then placed in the device.

The scientists used the simple and direct principle of plasmons in noble metal nanoparticles, which react to protein binding by a shift of the resonance wavelength. This is the target detection method for both the mapped and the unmapped sensors by monitoring individual nanoparticles by optical dark-field spectroscopy. The team used four different target proteins to demonstrate the viability of the concept, its ability to detect concentrations in the nanomolar range, and the possibility to recycle the sensors for more than one analysis.

The four proteins tested were thrombin, immunoglobulin E (IgE), streptavidin, and fibronectin. 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 team of chemists. Low-cost serial production of the sensors is feasible if advanced nanofabrication methods such as nanoprinting or optical trapping are used.

Christina Rosman, DiplChem, first author of the study, said, “We have demonstrated a new approach for a multiplexed assay that detects multiple proteins simultaneously by letting a fluid flow past the randomly positioned gold nanorods. We see the potential to extend our method to the simultaneous detection of hundreds or even thousands of different target substances." There are manifold possible applications of a test for multiple targets in a single procedure. The low-cost sensors could be directly used by physicians in their practices in order to detect and discriminate various types of influenza viruses with which their patients could be infected. The study was published on June 21, 2013, in the journal Nano Letters.

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