Turkey's Color Changing Skin InspiresToxin-Detecting Biosensor

Inspired by the color changing ability of Turkeys, the native American bird, a team of international scientists has created biosensors capable of detecting volatile chemicals.

Inspired by the color changing ability of Turkeys, a team of bioengineers at the University of California, Berkeley has developed a new type of biosensor that alters its color on being exposed to chemical vapors. This helps in detecting airborne pathogens or specific chemicals like explosive TNT.

In countries like Korea and Japan, turkeys are often referred to as the 'seven-faced birds'. This is because of their color changing characteristic. The male turkeys, also called 'Gobblers' or 'Tom Turkey', can change the color of their head depending on mood and level of excitement. This ability is due to the presence of a pack of collagen spread within the blood vessels.

Contraction and swelling of the bird's blood vessels changes the spacing between the collagen fibers of the bird. The change in collagen fiber spacing is responsible for altering the manner in which light waves are scattered, causing a change in the color of the bird's head.

This inspired the team led by Seung-Wuk Lee, UC Berkeley associate professor of bioengineering, to mimic this characteristic to develop biosensors that would alter color on being exposed to certain chemicals.

 "In our lab, we study how light is generated and changes in nature, and then we use what we learn to engineer novel devices," said Lee, who is also a faculty scientist at the Lawrence Berkeley National Laboratory.

To proceed further, they relied on a technique developed a few years ago that allows mimicking nanostructures like collagen fibers. They worked with M13 bacteriophages-a benign virus that has a shape similar to collagen fibers. Expansion and contraction of the tightly held bundles of these nanostructures changed color.

In the current study, the researchers coated the silicon wafers with the virus and then exposed them to multiple volatile organic compounds that included hexane, isopropyl alcohol and methanol. The biosensors were also exposed to vapors of explosive chemical TNT ( concentration of 300 parts per billion).

The researchers noticed that viruses swelled rapidly on exposure to chemicals, leading to a noticeable change in color. Apart from this, the sensors also reacted to humidity, becoming redder in moist air and bluer in dry air.  The changes ranged from 20 percent to 90 percent.

To make this easily available, the researchers have developed an iColour Analyser app that shows how a Smartphone photo of a sensor's color band can be used to identify the toxins.

"Our system is convenient, and it is cheap to make," said Lee. "We also showed that this technology can be adapted so that smartphones can help analyze the color fingerprint of the target chemical. In the future, we could potentially use this same technology to create a breath test to detect cancer and other diseases."

The findings were published in the journal Nature Communications.