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Simple, Sensitive Biosensors Derived from Engineered Viruses

Seung-Wuk Lee

Seung-Wuk Lee (Univ of California, Berkeley)

Bioengineers at University of California in Berkeley developed a process for making sensors from genetically-engineered viruses simple enough to package in a smartphone app, yet can discriminate among volatile chemical vapors. The team from the lab of bioengineering professor Seung-Wuk Lee, with colleagues from Lawrence Berkeley National Lab — where Lee is also on the faculty — and universities in Korea, published their findings today in the journal Nature Communications (paid subscription required).

Lee and colleagues simulated processes like those found in nature where cells in animal tissue, such as collagen fiber, change color when exposed to external stimuli, such as changes in blood flow. In turkeys, for example, the space between collagen fibers on the heads of turkeys changes when blood vessels contract or expand, changing the turkey’s skin color from red to while or blue.

The Berkeley team in earlier work studied viruses attacking bacteria known as M13 bacteriophages, which can be turned into bioengineered building blocks that assemble into a structure acting like collagen. The nanoscale M13 bacteriophages are harmless to humans and cylindrical in shape, somewhat resembling collagen fibers. The process first devised by Lee and colleagues engineered the viruses to express different peptides, and then assemble into the desired molecular composition on demand.

In the new study, the researchers expanded on those characteristics, but exploited another property of the engineered bacteriophages — their ability to expand and contract, and like the collagen in skin on the heads of turkeys, change color in response to external stimuli, in this case chemical vapors. Lee and colleagues hypothesize this property is a reaction of the water in the viruses to the chemicals in the vapors.

The team packaged their engineered viruses in bundles that act as biosensors, and tested the sensors with various volatile chemicals: hexane, isopropyl alcohol, and methanol. The researchers also tested the biosensors with vapor emitted by trinitrotoluene, better known as the chemical TNT used to make explosives since World War I, at concentrations of 300 parts per billion.

Lee and colleagues found engineered viruses in the biosensors react quickly to vapors in various volatile chemicals, with the reactions varying from one chemical to the next. These reactions result in unique displays of colors, thus making it possible to construct individual color profiles for each chemical. The biosensors are sensitive enough to distinguish TNT from molecularly similar compounds dinitrotoluene (DNT) and mononitrotoluene (MNT).   In addition, the biosensors react to humidity, displaying more red when humidity increases and blue when humidity decreases.

The Berkeley team is creating a smartphone app, called iColour Analyser that incorporates the biosensor technology. “Our system is convenient, and it is cheap to make,” says Lee in a university statement. “In the future, we could potentially use this same technology to create a breath test to detect cancer and other diseases.”

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