A Nose Fit for a Bionic Man

The mainstream use of Artificial Noses–which could conceivably replace drug, bomb, and even diabetes and cancer-sniffing dogs–may finally be on the horizon, thanks to biological engineers at MIT, who have discovered a way to mass-produce smell receptors in the laboratory. Moreover, the discovery may help researchers to understand how the sense of smell is able to recognize a seemingly infinite range of odors.

Previous efforts to map the molecular basis of smell have been thwarted by the difficulty of working with olfactory receptors, which are highly hydrophobic (literally “afraid of water”). According to Liselotte Kaiser, lead author of a paper detailing the study which will appear this week in the Proceedings of the National Academy of Sciences (PNAS), when these receptor proteins are placed in water-based solutions, they clump up and lose their structure, making it extremely difficult to isolate the proteins in sufficient quantities to study them in detail. Kaiser and her team spent several years developing a technique to isolate and purify the proteins by utilizing a hydrophobic detergent solution, which permits the proteins to maintain their structure and function. Later, last August, they demonstrated a method which utilized engineered mammalian cells to produce the receptors. Both methods proved time and labor intensive.

Their newly published technique involves a cell-free synthesis using common wheat germ extract to produce a particular receptor, then isolating the protein through a series of purification steps. This method quickly produces large amounts of proteins, according to the researchers, more than enough for structural and functional studies.

“The main barrier to studying smell is that we haven’t been able to make enough receptors and purify them to homogeneity,” says Brian Cook, who defended his MIT PhD thesis based on this research. “Now, it’s finally available as a raw material for people to utilize, and should enable many new studies into smell research.”

As the Defense Advanced Research Projects Agency (DARPA) recently approved funding for the team’s MIT (microfluidic-integrated transduction) RealNose project, they now plan to work alongside researchers worldwide, including MIT’s Media Lab and Department of Biology, to develop a “portable microfluidic device” capable of identifying a large array of odors.

The possibilities are virtually endless for such a portable smell-based biosensing device. Besides the obvious security and diagnostic applications, it would also prove invaluable in such areas as safety, law enforcement, and yes–marketing. On a less-grand scale, a portable e-nose would be invaluable to anosmia-sufferers, who are otherwise unable to scent out spoiled foods or gas leaks. We at Whiff! will watch with great interest for further developments in MIT’s RealNose project.