When a female moth decides she is ready to mate, she sends out a leading signal - a chemical cocktail that makes male moths drop everything and fly toward her, sometimes from over a kilometre away.

Given the sophistication of the chemical communication system, our electromagnetic signal driven gadget world actually seems rather rudimentary. I am sure dropping your phone in water is something that haunts you! If your phone were to use chemical signals, well you wouldn't worry so much.

"Can we connect our digital world to nature, through communication at the molecular level?" asked an international group of researchers, including Shannon Olsson from NCBS. They have come up with a technology that can send out a chemical signal, which can be used paired with another technology that can receive and interpret the signal.

Such a 'biologically inspired' system can be used to monitor bodily processes at the cellular level, and in drug delivery for therapy. It can even be used to determine the ripening time of a fruit based on its odor or to monitor pollutants in the air. It could potentially operate effectively even in areas where the conventional electromagnetic systems fail us, such as in water and other liquid media.

Biological systems offer exceptional specificity with respect to signal generation, detection and transduction through highly specialized biosynthetic pathways and protein receptors. The paper uses the classic moth pheromone system as a template pathway to study the communication cascade. The female moth releases certain pheromones into the environment when it is ready to mate; the chemicals that form the signal are present in a definite ratio for accurate detection, giving it the name 'ratiometric infochemical communication'.

The production, transmission, detection and processing of the molecular signal are the major steps in the communication cascade. The research team has built a prototype that can carry out all these steps effectively.

The Egyptian cotton leaf worm moth (Spodoptera littoralis) is capable of producing a large variety of chemicals, and generates signals by using specific combinations of its chemicals. Using the moth's chemical repertoire as a database, the team used a specialised microreactor with immobilised enzymes capable of biosynthesis, to come up with ratiometric signals - chemicals in appropriate ratios.

To transmit the signal, the researchers used the female moth's pheromone gland as inspiration. They needed a device that would send out controlled amounts of chemicals as 'signals'. Their artificial gland was made of silicon-glass, perforated with about 40,000 tiny pores.

The microreactor and the artificial gland together made the 'chemoemitter', which then underwent the ultimate test - a bioassay. It was able to elicit a response equal to three virgin female moths!

The next step was to design a 'chemoreceiver' - a system to detect the emitted signals. The sensor used needs to be specific enough to detect very small amounts of signal; at the same time, it needs to be sensitive to a broad variety of signals. The research team came up with the idea of directly borrowing from the insect system. The olfactory receiver of the male moth has both these desirable properties. The researchers used a pheromone receptor from Drosophila, expressed in Spodoptera frugiperda cells, embedded in a microsensor. A normal cell was used as a control.

Now for the final step - we need to make sense of the signal received. Take our bodies reacting to coffee. Odour receptors in our noses get activated by a bunch of different smell molecules, and the signals fuse in our brains for us to realise that it is indeed coffee. The same step needs to be reproduced in the chemoreceiver, for the device to be able to figure out what the signals from the sensor mean. The researchers turned to computation for this complex step.

Following this, the scientists integrated emitter and receiver technologies into two mobile robots: a chemoemitter robot that generated and emitted certain chemical compounds in specific ratios, and a chemoreceiver robot that detected and processed the signal.

The mere complexity of this system poses a number of challenges. "The major hurdle we still face is coordinating all the components," says Dr. Shannon B. Olsson, the first author of this paper who is a currently a Reader at NCBS, Bangalore. She adds that the system must create, transmit, deliver, detect, and decode chemical signals all in real time.

The advantages of this approach are endless. Molecules can be transported over very short periods of time while the power consumed is almost negligible. The energy consumed by a single molecular reaction is reported to be 10,000 times lesser than that consumed by a conventional microelectronic transistor.

Future technologies can be developed that can work on the emitted and detected biochemical signals in nature. This intergration of our digital technologies with nature can open up breathtaking avenues. "Our concept is not to replace our current means of communication, but to offer ways to link technology and biology more closely to allow us unprecedented insights into nature", says Dr. Olsson.

The paper can be accessed at IOPscience .

About the Study

The iCHEM (Biosynthetic Infochemical Communication) Consortium was formed as part of an EU "Future Emerging Technologies" project in 2006. The consortium is represented by 5 different institutes:  U. Warwick, UK; U. Leicester, UK; Max Planck Institute for Chemical Ecology, DE:  U. Twente, NL; and the Institute of Advanced Chemistry of Catalonia, ES.  The paper is a large collaboration between the faculty members of the above universities.

About the authors

Dr. Marina Cole, the corresponding author of this paper was the coordinator of the consortium. She is currently an Associate Professor at the University of Warwick, UK.

Contact: Marina.Cole@warwick.ac.uk

Dr. Shannon Olsson was a project leader for the Max Planck Institute of Chemical Ecology under Prof. Bill Hansson. She is continuing and expanding this work with several of the consortium members as a Reader here at NCBS.

Contact: shannon@ncbs.res.in

Harini Aiyer is a writer with the Research Media Services Division of Gubbi Labs.