The new biological bomb sniffers on the block, well at least in a lab in St Louis, are grasshoppers. Utilizing the insect’s sophisticated olfactory system (sense of smell), a team from Washington University, Missouri, have “bio-hacked” grasshoppers to detect explosive chemicals.
Traditional chemical sensing instruments, popularly referred to as electronic noses, have been developed for decades, with applications in medicine, homeland security, and environmental monitoring. However, biological olfactory systems have abilities that completely outperform the engineered devices gone before. Barani Raman and his colleagues have investigated American grasshoppers, in order to advance chemical sensing methods.
In a pre-print article on bioRxiv, the researchers describe how they exposed the grasshoppers to different chemical vapors including; explosives trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT), as well as non-explosives like hot air and benzaldehyde (which provides almond flavor to foods).
Olfactory receptor neurons (ORNs) on the insect’s antennae, of which there are around 50,000 in each, detect these chemical odors. Electrical signals are then transmitted to the antennal lobe, part of the insect’s brain. Using electrodes attached to this part of the brain, the researchers were then able to distinguish different responses of the grasshopper, and correlate them with the different chemical odors.
These signals were amplified and wirelessly transmitted from the insects via a tiny, lightweight backpack. The whole chemical recognition process was achieved pretty much instantaneously, in only a few hundred milliseconds.
However, there were some stumbling blocks for the team. After 7 hours of bomb detection, the grasshoppers grew fatigued and died. Carrying the backpack also meant that the insects were immobilized. Therefore, in order for the team to test whether the bomb detection worked in different locations, the grasshoppers were placed on a “moveable car” that traveled through areas of high and low concentrations of odor.
As for their success, every lone grasshopper outperformed a naïve classifier. However, only one grasshopper managed to classify the chemical odors with over 60 percent accuracy. In what the researchers call the “wisdom of the swarm”, they found that combining data from multiple insects led to “significant improvements in performance”. With just seven grasshoppers, the average accuracy reached 80 percent.
With a $750,000 grant from the US Office of Naval Research, these cyborg grasshoppers could be utilized in homeland security. However, further research to explore the insect’s explosive-detecting abilities, such as when multiple odors are present, will first need to be carried out.
[H/T: New Scientist]