Locusts’ sense of smell enhanced with custom-made nanoparticles

Our sensory systems are highly adaptable. A person who cannot see after turning off a light at night slowly attains a higher power allowing him to see even small objects. Women often gain an increased sense of smell during pregnancy. How can the same sensory system that was underperforming also exceed expectations based on its previous performance?

Since nature has perfected its sensory systems over time, an interdisciplinary team of researchers at the McKelvey School of Engineering at Washington University in St. Louis has harnessed these capabilities to adapt the system on demand so that it operates at peak performance. Their tools to achieve this goal: locusts and nanomaterials too small to be seen.

Srikanth Singamaneni and Barani Raman, both professors at the McKelvey School of Engineering, led a team that harnessed the power of specially designed nanostructures that can absorb light and create heat, known as the effect photothermal, and act as containers to store and release chemicals. request. They used these nanostructured materials to stimulate the neuronal response of the locust brain to specific odors and to improve their identification. The research results were published in Nature Nanotechnology January 25, 2024.

Singamaneni, the Lilyan & E. Lisle Hughes Professor in the Department of Mechanical Engineering and Materials Science, and Raman, professor of biomedical engineering, have collaborated for years with Shantanu Chakrabartty, the Clifford W. Murphy Professor in the Preston M. Green Department. Electrical and systems engineering, to exploit the superior sensing capabilities of the locust olfactory system. Recently, they demonstrated the feasibility of using a bio-hybrid electronic nose to detect explosive vapors.

“We let biology do the hard work, converting the information about the vaporized chemicals into an electrical neural signal,” Raman said. “These signals are detected in the insects’ antennae and transmitted to the brain. We can place electrodes in the brain, measure the locusts’ neural response to odors and use them as fingerprints to distinguish between chemicals.”

The idea, while valid, presents a potential obstacle.

“We are limited by the number of electrodes and where we can place them,” Singamaneni said. “Since we’ll only get a partial signal, we want to amplify that signal. That’s where we turned to heat and neuromodulation to enhance the signal we receive.”

In the new research, the team used two strategies to enhance the locusts’ ability to detect odors. First, the team created a biocompatible and biodegradable polydopamine nanoparticle that converts light into heat through a process called the photothermal effect.

“Heat affects diffusion,” Raman said. “Imagine adding cold milk to hot coffee. The idea is to use the heat generated by the nanostructures to heat locally, for example a nanowarmer, and enhance neuronal activity.”

Second, these nanostructured materials can be made to load chemicals for storage. However, they must be encapsulated by a covering material. The team used a phase change material called tetradecanol, which is solid at room temperature and turns into a liquid when heated. When heated, the same nanoheaters ooze the chemicals they contain in addition to generating heat.

Singamaneni and the team stored octopamine, a neuromodulator involved in various functions, and released it on demand. Usually, these neuromodulators are released based on the body’s needs. However, thanks to the nanostructured heating elements, they were released on demand to enhance neural signals.

“Our study presents a generic strategy to reversibly enhance neuronal signals at the brain site where we place the electrodes,” Raman said.

“The nano-enabled neuromodulation strategy we developed opens new opportunities for realizing tailored cyborg chemical sensing approaches,” said Prashant Gupta, a graduate student in Singamaneni’s lab and first author of the paper. “This approach would change an existing passive approach in which information is simply read into an active approach where the capabilities of neural circuits as a basis for information processing are fully utilized.”