Cicada Secrets

Researchers work to unlock the secrets of summer’s favorite insect — the cicada. Cicada wings kill microbes on contact, and the design could hold engineering secrets for nanotechnology scientists.

GREENSBORO — You will find a refrigerator or two in most laboratories, and they are not just where researchers keep their lunches cold.

Many of the appliances have large warning stickers on the front, which read “NOT FOR STORAGE OF FOOD” or some words to that effect. The refrigerators are often used to store and keep test materials cold. That’s not the best place to keep your PB&J sandwich.

There’s a very plain looking refrigerator in the lab of Dr. Dennis LaJeunesse at the Joint School of Nanoscience and Nanotechnology in Greensboro. The school is an academic collaboration between the University of North Carolina at Greensboro and North Carolina Agricultural and Technical State University. But this is not just any refrigerator. It’s jokingly referred to as the "Freezer of Death.”

“This sample is actually three years old,” says Dr. LaJeunesse as he opens the refrigerator’s freezer compartment and begins looking through the collection of frost colored tubes and containers. “These are brood two that came out last year; you can see the bright orange on the eyes and wings. These are all cicadas.”

For the past couple of years Dr. LaJeunesse and his students have collected cicadas from around Greensboro. The researcher says he wanted to study the insects because they are so large, and big bugs are easier to study. But the other reason — the real reason — has to do with the structure of cicada wings. It turns out cicada wings have anti-microbial properties that one day, researchers hope, could be used in medical devices and other products.

“Flying insects have been around for 400-450 million years, and so during evolution you have this selection for different properties in their materials,” explains Dr. LaJeunesse. “It makes sense to take advantage of 450 million years of testing and understand how these structures work, their properties, how cells interact with them, and then apply those properties for human benefits.”

To study what is so amazing about cicada wings involves the discipline of nanoscience, which is the study of super small things. The primary tool is a scanning electron microscope.

“We call this a splat,” says Adam Boseman, a doctoral student in nanoscience at the University of North Carolina at Greensboro. “I know that’s not too scientific sounding, but it’s pretty accurate when you look at the image.”

The image Boseman is studying on the screen adjacent to the microscope is of a yeast cell on a cicada wing. The wing structures on the surface resemble a mass of tiny spikes. But the reality is those spikes are about 50 nanometers tall. That’s about 1000 times smaller than the width of a human hair. Researchers want to understand the dynamics of the wing structure to figure out the property that kills microbes on contact. That explains why the cell looks like a splattered egg sitting atop the spikes.

“In every image we study, the cell appears to be breaking down as it rests on the wing,” explains Boseman. “So the questions are pretty basic: what allows a cell to adhere to the wing surface and then what tears it apart.”

Researchers are studying the wing’s structure — its surface features, mechanical properties and chemical makeup to understand what gives cicada wings what appear to be anti-microbial properties.

And sometimes the best way to understand how something works is to build it. That’s what Kyle Nowlin, another doctoral student, decided. He designed and is creating tiny cicada wings in the lab. They are made out of plastic and even have those 50 nanometer tall structures.

“We discovered that cicadas native to Greensboro have an anti-microbial property and an anti-reflective property on their wings,” says Nowlin. “And so what I did was attempt to mimic that in the lab with polymeric surfaces, in hopes of transferring the function of a cicada wing to everyday materials.”

Nowlin holds up a tiny tube to the light to show the man-made wing floating in a solution.

“The anti-microbial phenomena was discovered in nature and we’re applying it in the lab,” explains Nowlin. “I used PET, which is a polymer, and I fabricated nanostructures that we find on a cicada wing on the surface of these wings. There are also brewer’s yeast cells incubating on the surface and when the time is right, we’ll look at everything under the microscope and see if the cells have attached and how they have behaved.”

Whether or not the cell adheres to the wing and dies, or whether the wing simply repels the cell, researchers believe that understanding the mechanics and makeup of cicada wings could lead to scientific breakthroughs in the creation of medical instruments and in the fight against dangerous pathogens.

"The properties of cicada wings we have discovered so far are pretty amazing and it makes you wonder what else is out there," says Dr.LaJeunesse, putting yet another cicada sample into the "Freezer of Death."

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