Essay Example on Biosensors Using Insect Odorant Receptors for Chemosensory Perception

A biosensor can be described as an instrument that rapidly and easily measures molecules for monitoring or diagnostic purposes (Malhotra et al., 2017). The presentation focused on the development of biosensors using insect odorant receptors, particularly chemosensory perception. Insects have an exquisite sense of smell and are capable of detecting single molecules, and hence are preferred in chemosensory perception. Studies have shown that the antennae of insects have the most selective and sensitive chemical-sensing organs in the whole of the animal kingdom. Owing to this feature, insects can perceive minute levels of compounds in a very short time. The function exceeds the threshold of currently used analytical devices by far. Resultantly, insect biotechnology is gaining more interest and is greatly being utilized in the field of biosensors (Khadka et al., 2020).

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The presentation first describes the structure of the insect's olfactory system. Following years of research, it has been established that the antennae of insects are covered by little hair-like structures known as sensilla. They also contain olfactory receptor neurons, and the sensilla are greatly innervated. Compounds from the environment enter the sensillum through pores that surround it and travel across the lymph. In the lymph, they interact with the odorant receptors, which are bound on the dendritic membrane. It is believed that insect odorant receptors operate as a ligand-gated heteromeric ion channel. The odorant receptors subunits bind to the ligand and communicate with the orco subunit, which, in turn, opens, allowing ions to flow. The neuron is depolarized, and signals are sent to the brain. According to the presentation, transferring the receptors from the insect membrane to a sensor surface has been the main challenge faced by researchers. Recombinantly reproducing them, instead of harvesting from flies, is one of the solutions that the study explored.

A number of organisms, such as E. coli, baculovirus Sf9 cells, and wheat germ cell-free, have been tried in the quest to overcome the challenge. After producing the receptors in Sf9 cells, the next challenge was isolating them from the cells in a workable format. Nanodiscs provided the solution to this challenge. Nanodiscs are small discoidal lipid fats held together by a scaffold protein. Though they have been extensively and successfully used in structural biology, their application in the biosensor field is relatively new. For the study, a panel of four ORs from drosophila was inserted into the nanodiscs. The four ORs are DmelOR10a, DmelOR22a, DmelOR35a, and DmelOR71a (Murugathas et al., 2019). They can detect aldehydes, esters, and phenolic compounds.

After their expression in Sf9 cells, the ORs were purified, and reconstitution into lipid nanodiscs carried out. Then using help from experts, CNT-FETs were fabricated. Liquid gating was used since the electrolyte offers a gating medium. CNT films can also be fabricated on a wide variety of substrates. To ensure that the nanodiscs were bound, the ORs on the device was checked using AFM. It was determined that the nanodiscs were exclusively attached to the CNTs. The injection of electrons in the CNT-FET device led to a negative shift in threshold voltage. Nanodisc functionalization also led to an increase in the on-current and on-off ratio. Empty nanodiscs were tested against all compounds, while each OR-triplicate was tested against both known ligands and non-targets. Liposomes did not work on CNTs probably because they were too big for the surface and hence disrupted the signal. It was determined that graphene could have provided a better surface for sensing liposomes. However, the study conclusively proved that the integration of insect ORs into lipid nanodiscs could be useful in bioelectronics technologies (Murugathas et al., 2019).

Different studies have also found results similar to those in the presentation and the research paper. First, the high sensitivity and selectivity of insect antennae have been studied for a long time (Schott et al., 2013). Its use in selective sensors has also been extensively studied. In the past, the application of insect ORs in a wide range of fields such as early medical diagnosis and landmine detection has been explored. A variety of insects, including cockroaches, have also been used in the studies. For instance, in a study seeking to examine the usefulness of insects in detecting landmines, the German cockroach, which has superior olfactory systems, was used (CORDIS, 2018).

In this light, therefore, the study discussed above was a continuation of studies that have been ongoing for years. Its results compare with other studies since the ability of the insect OR to be used as biosensors was proven. However, the study can also be termed as revolutionary since it found new ways of solving some of the challenges that have been encountered in the application of insect ORs in biosensors. For instance, the study found a way of transferring the receptors from the insect membrane to a sensor surface. The researchers also overcame the challenge of isolating the receptors in a workable condition since extensive use of detergents has been shown to hurt their quality (Murugathas et al., 2019). Though the presentation made use of scientific jargon that might not be familiar to a non-technical audience, the study and its findings are presented in a way that can be easily understood.

References

CORDIS. (2018, February 13). Could insects become biosensors of the future? Retrieved from CORDIS: https://cordis.europa.eu/article/id/218654-could-insects-become-biosensors-of-the-future

Khadka, R., Carraher, C., Hamiaux, C., Travas-Sejdic, J., & Kralicek, A. (2020). Synergistic improvement in the performance of insect odorant receptor-based biosensors in the presence of Orco. Biosensors and Bioelectronics, 153, 112040. Retrieved from https://www.sciencedirect.com/science/article/pii/S0956566320300373

Malhotra, S., Verma, A., Tyagi, N., & Kumar, V. (2017). Biosensors: principle, types and applications. Int. J. Adv. Res. Innov. Ideas Educ, 3(2), 3639-3644. Retrieved from https://pdfs.semanticscholar.org/abdf/cda1f047ff7388692623a660706e83d35510.pdf

Murugathas, T., Zheng, H. Y., Colbert, D., Kralicel, A. V., Carraher, C., & Plank, N. O. (2019). Biosensing with Insect Odorant Receptor Nanodiscs and Carbon Nanotube Field-Effect Transistors. ACS applied materials & interfaces, 11(9), 9530-9538. Retrieved from https://pubs.acs.org/doi/abs/10.1021/acsami.8b19433

Schott, M., Wehrenfennig, C., Gasch, T., & Vilcinskas, A. (2013). Insect antenna-based biosensors for in situ detection of volatiles. Yellow Biotechnology II, 101-122. Retrieved from https://link.springer.com/chapter/10.1007/10_2013_210