Recently, scientists at Tokyo Tech illustrated how graphene-based olfactory sensors could detect odor molecules depending on the design of peptide sequences.
Designable peptides on graphene field-effect transistors for selective detection of odor molecules. Image Credit: Homma et al. (2023) | Biosensors and Bioelectronics| doi.10.1016/j.bios.2022.115047
The study outcomes showed that graphene field-effect transistors (GFETs) functionalized with designable peptides could be utilized to develop electronic devices that imitate olfactory receptors and then emulate the sense of smell by selectively detecting odor molecules.
In numerous industries like food, cosmetics, healthcare, and environmental monitoring, olfactory sensing or odor sensing is considered an integral part. Currently, the majority of the commonly utilized method for detecting and evaluating odor molecules is called gas chromatography–mass spectrometry (GC–MS).
Although GC–MS is known to be effective, it has certain limitations like its confined sensitivity and heavy setup. As a result, researchers are in the search of user-friendly and highly sensitive alternatives.
In the past few years, graphene field-effect transistors (GFETs) have started being used to come up with highly sensitive and selective odor sensors. This was done by combining with olfactory receptors, also called electronic noses.
GFETs are considered perfect for adsorbing odor molecules because of the presence of the high electron mobility of graphene surfaces and atomically flat surfaces. However, the application of GFET as electrical biosensors with the receptors has been subjected to extreme limitations by factors such as the delicacy of receptors and the lack of alternate synthetic molecules that can serve as olfactory receptors.
A research group from the Tokyo Institute of Technology (Tokyo Tech) headed by Professor Yuhei Hayamizu set out to fulfill such problems with GFET-based olfactory receptors. Three new peptides for graphene biosensors that have the potential to detect odor molecules were developed and designed by the team. This was recently reported in the Biosensors and Bioelectronics journal.
The sequence of peptides we designed needed to perform two main functions—acting as a biomolecular scaffold for self-assembly on a graphene surface and functioning as a bio-probe to bind the odor molecules. This would allow the peptides to cover the graphene surface in a self-assembling manner and functionalize the surface uniformly to capture odor molecules.
Yuhei Hayamizu, Professor, Tokyo Institute of Technology
Atomic force microscopy was used by the research group, which displayed that the peptides evenly covered the graphene surface with a single-molecule thickness. Then, the functionalized graphene was utilized to construct a GFET setup for the odor molecules to be detected.
Following the assembly, the team injected menthol, limonene, and methyl salicylate as GFET’s odor molecules. The electrochemical measurements showed that binding with the odor molecules helped decrease the conductivity of the graphene.
Also, the observations disclosed that the interaction between the three peptide sequences and the odor molecule increased to highly diverse signatures. This verified that the GFET’s response to the odor molecules relied on the design of the peptide.
Moreover, the group performed real-time electrical measurements to track the kinetic response of the GFET. The observations showed that the time constraint linked to the adsorption and desorption of odor molecules was known to be special for every peptide sequence.
Furthermore, this behavior was verified by principal component analysis. Such observations verified that the new GFET setup was successful in the electrical detection of the odor molecules using 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 a step closer to realizing the concept of electronic noses.
Yuhei Hayamizu, Professor, Tokyo Institute of Technology
In this study, the strong method presented sets the stage for the development of highly sensitive and selective GFET-based odor-sensing systems. Also, these insights could be utilized while developing advanced peptide sensors that perform multi-dimensional analysis of a variety of odor molecules.
Journal Reference:
Homma, C., et al. (2023) Designable peptides on graphene field-effect transistors for selective detection of odor molecules. Biosensors and Bioelectronics. doi.org/10.1016/j.bios.2022.115047.