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Integrated biosensing with polymers.

Cheap, reliable and portable biosensing for medical applications is a step closer thanks to a polymer-based biosensor reported online in the Journal of Polymer Science: Polymer Physics. The fully integrated approach of David Leuenberger and colleagues combines excitation source, sensor and detection system into a single miniature device.

"We feel that this work is an important step on the way from a 'chip-in-a-lab' to an actual 'lab-on-a-chip', explains Leuenberger. "The integrated mini-spectrometer as the key element of the sensor proves that the vision of a fully-organic bio-chip is not as far-fetched as it might seem."


The device is formed around a waveguide, which is also used as the substrate. An iridium-complex-doped polymer light-emitting diode is the excitation source, which excites a layer of light-emitting polymer on the opposite side of the waveguide. The emission from the polymer is coupled into the waveguide and travels to the point where it interacts with the analyte.

At the opposite end, the mini-spectrometer is integrated into the system. A grating is inscribed into the waveguide, which diffracts the light into wavelength-specific angles: different wavelengths are diffracted to a different extent, so they end up spatially separated. An array of polymer photodiodes, made in this instance from the well-known solar cell combination of poly(3-hexylthiophene) and a fullerene derivative, can then detect the wavelengths for reconstruction into a spectrum.

Sensing of the analyte in the central section is achieved in one of two ways. In the first approach, the analyte attaches to a molecule functionalized on the surface of the waveguide, modifying the spectrum of the waveguided light. In the second, analyte adsorbed to a 'surface plasmon stack' changes the final measured spectrum. Leuenberger and colleagues demonstrate the sensing of mouse immunoglobin at levels as low as 333 nanomolar using the device.

"We see the main application in selected areas of diagnostics where accurate results are needed at an economical price," says Leuenberger. "The proposed system is, due to its compactness, very suitable for point-of-care applications."

In the future, he says, the researchers will continue to bring different organic electronic components together: "So far people mostly focused on the development and performance of individual building blocks such as organic light-emitting diodes, organic photodiodes and organic field-effect transistors. There has been little work on integrating different organic building blocks into actual systems, especially in the domain of diagnostics."

Marc Ramuz et al., J. Polym. Sci. Part B: Polym. Phys., DOI: 10.1002/polb.22111
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Title Annotation:Materials Views
Author:Cleave, V.
Publication:Plastics Engineering
Geographic Code:1USA
Date:Nov 1, 2010
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