Graphene-based odor sensors that can detect odor molecules based on the design of peptide sequences were recently demonstrated by Tokyo Tech researchers. Results showed that graphene field-effect transistors (GFETs) functionalized with designable peptides can be used to design electronic devices that mimic olfactory receptors and emulate the sense of smell by selectively recognizing odorant molecules.
Smell or odor detection is an integral part of many industries including healthcare, food, cosmetics and environmental monitoring. The currently most widely used technique for detecting and estimating odor molecules is gas chromatography-mass spectrometry (GC-MS). Although GC-MS is very effective, it has some limitations, such as B. its bulky structure and its limited sensitivity. As a result, scientists have been looking for more sensitive and easy-to-handle alternatives.
In recent years, graphene field effect transistors (GFETs) have been used to develop highly sensitive and selective olfactory sensors by integrating them with olfactory receptors, also known as electronic noses. The atomically flat surfaces and high electron mobility of graphene surfaces make GFETs ideal for adsorbing odor molecules. However, the application of GFETs as electrical biosensors with the receptors is severely limited by factors such as the fragility of the receptors and the lack of alternative synthetic molecules that can act as olfactory receptors.
A team of researchers from the Tokyo Institute of Technology (Tokyo Tech) led by Prof. Yuhei Hayamizu set out to address these issues with GFET-based olfactory receptors. In their recently published study in biosensors and bioelectronics, The team designed and developed three new peptides for graphene biosensors that can detect odor molecules. Prof. Hayamizu explains: “The sequence of peptides that we designed had to fulfill two main functions – to act as a biomolecular scaffold for self-assembly on a graphene surface and to act as a bioprobe to bind the odorant molecules. This would allow the peptides to self-assemble to cover the graphene surface and uniformly functionalize the surface to capture odor molecules.”
The team performed atomic force microscopy, which showed that the peptides evenly covered the graphene surface with a thickness of a single molecule. The functionalized graphene was then used to build a GFET assembly to detect odor molecules. After assembly, the team injected limonene, menthol, and methyl salicylate as representative odor molecules into the GFET. The electrochemical measurements showed that binding with the odor molecules reduced the conductivity of the graphene. The observations also showed that the interaction between the three peptide sequences and the odorant molecule resulted in very different signatures. This confirmed that the response of the GFET to the odor molecules depended on the peptide design.
In addition, the team performed real-time electrical measurements to monitor the kinetic response of the GFET. The observations indicated that the time constraint associated with the adsorption and desorption of odorant molecules was unique to each of the peptide sequences. This behavior was further confirmed by principal component analysis. These observations confirmed that the new GFET assembly was successful in electrically detecting the odorant molecules using the designed peptides.
“Our approach is simple and can be scaled up for mass production of peptide-based olfactory receptors that can mimic and miniaturize the natural protein receptors responsible for our sense of smell. We are one step closer to realizing the concept of the electronic nose,” says Prof. Hayamizu.
The robust approach presented in this study opens new doors for the development of highly selective and sensitive GFET-based odor detection systems. These findings can also be used in the development of advanced peptide sensors that can perform multidimensional analysis of a range of odorant molecules.