Thesis presented December 04, 2023

Abstract:
The detection of odorant molecules and volatile organic compounds (VOCs) is the subject of growing demand in various fields such as food industry, perfumery, medical diagnostics, environmental monitoring and so on. Although accurate and reliable, the most commonly used methods - gas chromatography coupled with mass spectrometry and panels of human noses or trained dogs- have a number of drawbacks, particularly in terms of cost and time. In response to these limitations, electronic noses (eNs) have emerged as promising tools for the analysis of VOCs. Inspired by the biological nose, these biomimetic devices generally consist of a set of cross-reactive chemical sensors combined with a pattern recognition system. Over the past three decades, eNs have demonstrated their great potential for VOC analysis in many areas. However, one of the main weaknesses of most existing eNs is their limited selectivity. In response to this problem, research efforts have multiplied over the last decade to explore the use of biological materials from the olfactory system as sensing materials in order to improve the performance of eNs. In this context, our team at the Molecular Systems and Nanomaterials for Energy and Health laboratory (SyMMES, UMR 5819), has conceptualized a bioelectronic nose using surface plasmon resonance imaging as a transduction technique and employing small peptides as sensing materials. This technology led to the creation of Aryballe, a company that has successfully miniaturized and commercialized the device. This thesis project is a part of the ANR project OBP-Optinose (ANR-18-CE42-0012), which aims to explore the potential of odorant binding proteins (OBPs) as novel sensing materials for the development of bioelectronic noses.
During the thesis, we used a combination of wild-type and more selective OBPs, which were designed and genetically modified to have specific binding properties for target VOCs. Our experimental approach was to study various parameters that could have an impact on the performance of OBP-based biosensors for the detection of VOCs in the gas phase. First, a complete characterization of the OBP layers after immobilization on surface was carried out. The stability of the proteins in the gas phase was assessed, which is crucial to ensure their activity. The density and orientation of the OBPs were also studied since they may have impact on the sensitivity of the system. In addition, the impact of glycerol and humidity on the OBP layers was investigated. In particular, in-depth research into the hydration mechanism of the OBP layers was carried out, which enabled us to gain a better understanding of how humidity influences the reactivity of the biosensors. Finally, we demonstrated the good performance of OBP-based bioelectronic nose in the gas phase in terms of selectivity, stability, and repeatability.

Keywords:
Bioelectronic Nose, Electronic Nose, Odorant Binding Proteins, Volatile Organic Compounds, Surface Plasmon Resonance Imaging, ​Pattern Recognition