Researchers in Japan have built what is arguably the most eccentric chemical sensor to date: a living cell whose membrane is embedded with insect pheromone receptors, which, when activated by a whiff of pheromone, produce a current that causes a robotic mannequin to shake its head (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1004334107). Equipped with different receptors, this biorobotic sensor prototype could one day have applications in environmental and health monitoring.
The proof-of-principle apparatus, which includes a frog oocyte (egg) containing silkworm, fruit fly, or moth receptors, was developed by a team of researchers led by Shoji Takeuchi, a bioengineer at the University of Tokyo. The sensor—which provides electrical current that is used for data readout and also, in a bit of fun, to control a mannequin—can detect a handful of molecules present in only parts per billion in a solution. It can also distinguish slight differences in double bond isomerism or in functional group composition, such as the presence of —OH, —CHO or —C(=O)—groups.
Although other researchers have built similar cell-based detectors using biological molecules as receptors, "hooking up the frog egg expressing insect odorant receptors to a robotic head that shakes when the odor is present certainly is novel," comments Leslie B. Vosshall, of Rockfeller University. "I can certainly imagine an optimized version of this technology being used as a biosensor in military, food safety, and transportation safety uses," she adds.
So far Takeuchi's group has made a sensor that can detect only insect pheromones, but "we think that our sensor can potentially be applied to detect a ketone odor that is caused by diabetes or to detect allergens [in food] such as aldehydes," he says.