Researchers at Tokyo Tech recently demonstrated graphene-based olfactory sensors that can detect odor molecules based on peptide sequence design. The results indicated that graphene field-effect transistors (GFETs) operating with designable peptides can be used to develop electronic devices that mimic olfactory receptors and mimic the sense of smell by selective detection of odor molecules.
Olfactory sensing, or odor sensing, is an integral part of many industries including healthcare, food, cosmetics, and environmental monitoring. Nowadays, the most common method for detecting and quantifying odor molecules is gas chromatography and mass spectrometry (GC-MS). Although very effective, GC-MS has some limitations, such as bulky setup and limited sensitivity. As a result, scientists have been looking for alternatives that are more sensitive and easy to use.
In recent years, graphene field-effect transistors (GFETs) have begun to be used to develop highly sensitive and selective odor sensors by combining with olfactory receptors, also known as electronic noses. The atomically flat surfaces and high electron mobility of graphene surfaces make GFETs ideal for the adsorption of odor molecules. However, the application of GFETs as electrical biosensors with receptors is severely limited by factors, such as the fragility of the receptors and the lack of alternative synthetic molecules that can function as olfactory receptors.
A team of researchers from the Tokyo Institute of Technology (Tokyo Tech) led by Professor Yohei Hayamizu set out to tackle these problems using GFET-based olfactory receptors. In their recent study published in Biosensors and BioelectronicsAnd The team designed and developed three new peptides for graphene biosensors that can detect odor molecules. Professor Hayamizu explains, “The sequence of peptides we designed needed to perform two main functions – acting as a biomolecular scaffold for self-assembly on the graphene surface and acting as a bioprobe for the binding of odorant molecules. This would allow the peptides to cover the graphene surface in a self-assembling manner and operate the surface uniformly to capture odorant molecules.” “
The team performed atomic force microscopy, which showed that the peptides uniformly coated the surface of the graphene with a thickness of one molecule. Then functionalized graphene was used to construct a GFET setup to detect odor molecules. After assembly, the team injected limonene, menthol, and methyl salicylate as representative odor molecules into the GFET. Electrochemical measurements indicated that binding to odorant molecules reduces the conductivity of graphene. The observations also revealed that the interaction between the three peptide sequences and the odorant molecule gave rise to highly distinct signals. This confirmed that the response of the GFET to odorant molecules is dependent on peptide design.
Furthermore, the team performed real-time electrical measurements to monitor the motor response to the GFET. The observations indicated that the time limitation associated with the uptake and desorption of odorant molecules was unique to both peptide chains. This behavior was further confirmed by principal component analysis. These observations confirmed that the new GFET setup was successful in detecting odor molecules electrochemically with the help of the designed peptides.
“Our approach is simple and scalable for the 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 an electronic nose.” Professor Hayamizu.
The powerful approach presented in this study opens new doors for the development of highly selective and sensitive GFET-based odor sensing systems. These insights can also be used when designing advanced peptide sensors that can perform multidimensional analysis of a range of odorant molecules.