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Olfactory biosensors

We have used rat odor-binding proteins to make olfactory biosensors sensitive to volatile organic compounds. These biosensors have a high selectivity, even at low concentrations, high reproducibility of measurements and a lifetime of up to two months.

Published on 10 July 2019
Volatile organic compounds (VOCs) are the main components of odors and are abundant in our environment. In recent decades, their monitoring has become a concern, particularly in air quality control, industrial manufacturing processes, public safety, health, etc. To meet this growing need, sensors inspired by the biological nose, such as olfactory biosensors and electronic noses, are being developed.

In order to improve the performance of these sensors, particularly sensitivity and selectivity, two families of proteins from the animal olfactory system are of particular interest to researchers: olfactory receptors and odor-binding proteins (OBP). The latter are ideal candidates for such applications. They are stable to temperature and pH variations, to some organic solvents, they are soluble, therefore easy to produce and purify, and their binding properties to their ligands are modifiable by mutagenesis.
In collaboration with the Centre des Sciences du Goût et de l'Alimentation (CSGA) in Dijon, we developed sensitive olfactory biosensors using rat OBPs. After designing and immobilizing several variants of these proteins on the chip, they demonstrated their ability to bind and recognize ß-ionone, hexanal and hexanoic acid.
The obtained olfactory biosensors have very low detection limits in both concentration and molecular weight. Such a good sensitivity is thanks to the fact that the binding of VOCs to the active sites of these OBPs would induce a change in the conformation of these proteins. This change would result in a variation in the local refractive index to which surface plasmon resonance imaging (SPRi), used here as a transducer, is extremely sensitive. Other advantages of these biosensors are their high selectivity, especially at relatively low VOC concentrations, and high repeatability, as well as good stability with a lifetime of up to two months.
Further work could pave the way for the design and use of new custom-made olfactory proteins to specifically target a wider range of VOCs with a high societal impact.
β-ionone is an aroma compound found in a variety of essential oils, contributing significantly to the odor of raspberries.
Hexanal is found in wine. It comes from the skin of the grape. Depending on its maturity, it is responsible for the more or less herbaceous notes that are sometimes found in the wine.
Hexanoic acid gives a fatty and cheesy odor.

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