NARO develops odor-sensing cultured cells that can be stored dry at room temperature

A research group led by Senior Researcher Richard Cornette and Deputy Group Leader Takahiro Kikawada of Institute of Agrobiological Sciences at the National Agriculture and Food Research Organization (NARO), in collaboration with the University of Tokyo and the University of Maryland in the United States, announced on March 17 that it has succeeded in creating odor-sensing cultured cells that can be stored dry at room temperature (abbreviated as "Pv11-Or47a"). The research group created Pv11-Or47a by introducing a Drosophila olfactory receptor gene into cells derived from the sleeping chironomid (Polypedilum vanderplanki), which is capable of surviving in a desiccated state. When water is added after dry storage, the cells respond to odors in the same way as before drying. The group aims in the future to develop a small, portable odor biosensor. The results were published in Scientific Reports.

There is demand for odor compound detection in many fields, including food quality control, medical diagnosis, and environmental monitoring. One approach that is drawing attention is the development of odor sensors that make use of the superior sense of smell found in living organisms. However, sensors that use living organisms or cells face a major challenge: the cost of keeping and storing them is high. Cultured cells, for example, require ultra-low-temperature freezers that use liquid nitrogen to maintain temperatures of minus 80 degrees Celsius.

In this study, the research group focused on the extremely high desiccation tolerance of the larvae of sleeping chironomid. For 20 years, NARO has been studying the desiccation tolerance mechanism of sleeping chironomid. The sleeping chironomid is an insect in the family Chironomidae in the order Diptera. When the water in its habitat dries up during its larval stage and its water content drops to 3% or below, it enters a dormant state with no metabolic activity. It can return to its normal larval form within about one hour after water is added back. It has been confirmed that it can survive 17 years in dry storage and that it can withstand the space environment when dry.

The research group had previously succeeded in creating a cultured cell line called Pv11 from sleeping chironomid eggs. It had shown that these cells can be stored dry at room temperature for more than one year and start growing again when water is added. Meanwhile, the University of Maryland, a partner in this research, had developed a small odor sensor using newt olfactory cells, but had difficulty keeping those cells alive over long periods.

In this study, the research group introduced the co-receptor Orco gene, which works together with the Drosophila olfactory receptor Or47a to detect pentyl acetate, an aroma component of fruits such as bananas, into Pv11 cultured cells. A gene for a fluorescent calcium marker was also inserted so that the cells would give off light when they detected an odor. Ion channels consisting of Or47a and Crco on the cell surface are closed when there is no odorant, but when an odorant is detected, calcium ions are taken in from outside the cell. Those ions then bind to the fluorescent marker, causing them to glow. When pentyl acetate was added to the same cell line, a fluorescent reaction was observed. It was also confirmed that the brightness of the fluorescence increases as the concentration of the odor rises. The sensitivity to pentyl acetate was similar to values seen with conventional animal cells (EC50: 2.2 to 50 µM).

The cell line was dried, stored at room temperature for 2 weeks, and rehydrated. The response to pentyl acetate was surveyed 24 hours later, and it was detected with the same sensitivity as before drying. Concentration-dependent responses were also maintained. It was also confirmed that when the cells are exposed to pentyl acetate repeatedly to find whether it is detected, the cells can respond over a period of several hours. The dried cell line can be stored at room temperature for a long time by vacuum-packing it in dishes. Some samples sent to research partners in the United States responded normally to pentyl acetate after water was added back.

Cornette commented: "Going forward, we want to improve the system to increase fluorescence intensity so that odor responses can be obtained right after rehydration. We also want to increase the types of cells used and combine multiple olfactory receptors in an array to allow the identification of multiple odors. Through collaborative research combining a small detection device with a sensor cell array, we hope to develop a portable odor biosensor that can be used in medical diagnosis and food evaluation."

Journal Information
Publication: Scientific Reports
Title: An anhydrobiotic cell line expressing odorant receptors shows odorant responses after dry storage
DOI: 10.1038/s41598-025-19627-x