This illustration accompanies a Dec. 14, 2012 Nanowerk Spotlight article by Michael Berger about the development of a nanobioelectronic tongue by Korean researchers (Note: I have removed links),
The concept of e-noses – electronic devices which mimic the olfactory systems of mammals and insects – is very intriguing to researchers involved in building better, cheaper and smaller sensor devices (read more: “Nanotechnology electronic noses”). Less well known is the fact that equivalent artificial sensors for taste – electronic tongues – are capable of recognizing dissolved substances (see for instance: “Electronic tongue identifies cava wines”).
“Even with current technological advances, e-tongue approaches still cannot mimic the biological features of the human tongue with regard to identifying elusive analytes in complex mixtures, such as food and beverage products,” Tai Hyun Park, a professor in the School of Chemical and Biological Engineering at Seoul National University, tells Nanowerk.
Park, together with Professor Jyongsik Jang and their collaborators, have now developed a human bitter-taste receptor as a nanobioelectronic tongue.
The team worked with a protein to develop the ‘tongue’,
The nanobioelectronic tongue uses a human taste receptor as a recognition element and a conducting polymer nanotube field effect transistor (FET) sensor as a sensor platform. Specifically, the Korean team functionalized carboxylated polypyrrole nanotubes with the human bitter taste receptor protein hTAS2R38. They say that the fabricated device could detect target bitter tastants with a detection limit of 1 femtomole and high selectivity.
“In the case of bitter taste, our nanobioelectronic tongue can be used for sensing quantitatively the bitter taste, for example, of coffee, chocolate drinks, drugs and oriental medicines,” says Park. “Our nanobioelectronic tongue can be used as an alternative to time-consuming and labor-intensive sensory evaluations and cell-based assays for the assessment of quality, tastant screening and basic research on the human taste system.”
Prachi Patel’s ??? 2012 article about the research for Chemical and Engineering News (C&EN) provides more technical details about the testing,
The researchers tested their device’s response to four bitter compounds: phenylthiocarbamide, propylthiouracil, goitrin, and isothiocyanate. When these compounds bound to the protein-coated nanotubes, the researchers noted, the current through the transistors changed. For solutions of phenylthiocarbamide and propylthiouracil in buffer, the researchers could detect concentrations of 1 and 10 femtomolar, respectively. The device could sense goitrin and isothiocyanate, which are found in cruciferous vegetables, at picomolar concentrations in samples taken from vegetables such as cabbage, broccoli, and kale.
The team also tested the sensor’s response to mixtures of bitter, sweet, and umami (or savory) flavor molecules. The device responded only when the bitter compounds were present in the mixtures, even at femtomolar concentrations. Park says that the researchers are now trying to make sensors for sweet and umami tastes by using human taste receptors that respond to those flavors.
Here’s a citation (not an official one) and a link to the researchers’ paper,
Human Taste Receptor-Functionalized Field Effect Transistor as a Human-Like Nanobioelectronic Tongue by Hyun Seok Song, Oh Seok Kwon, Sang Hun Lee, Seon Joo Park, Un-Kyung Kim, Jyongsik Jang, and Tai Hyun Park in Nano Lett., Article ASAP DOI: 10.1021/nl3038147 Publication Date (Web): November 26, 2012 Copyright © 2012 American Chemical Society
Access to the full article is behind a paywall.