12:00pm

Tue August 14, 2012
Science

Say Goodbye To Germs With Cold Plasma

Imagine a machine that could disinfect your toothbrush or clean a skin laceration in a matter of seconds—without using any liquid disinfectants or heat. It’s not a reality yet, but researchers at the University of Colorado in Denver are getting close.

The key ingredient for this new sterilizing machine is the same thing at the heart of the most iconic weapon in the science fiction film canon: the lightsaber.

Of course, the lightsabers in Star Wars aren’t real. But if they were, they’d be made from plasma. And plasma is very much a real thing. In fact, it’s the most common form of matter found in the universe, even if most Earthlings don’t give it much thought.

Mark Golkowski, a professor of electrical engineering and bioengineering at the University of Colorado-Denver, is an expert on plasma.

“So we have solid, liquid, gas and if you keep adding energy to the system, you get a plasma state,” says Golkowski.

For this reason, plasma is usually very hot, like our nearly 10,000 degree sun (Fahrenheit).

“But using electric fields we can create what’s called non-thermal or cold plasma,” says Golkowski, where only a small fraction of the molecules are excited to the plasma state.

Creating cold plasma results in chemical reactions that make free radicals, reactive molecules that in turn can kill pathogens like bacteria. But instead of being thousands of degrees, it’s at room temperature. That, of course, is critical if you’re trying to clean your iPhone or a cut on your hand.

A closer view of a machine at CU-Denver that can sterilize without using high heat or liquid disinfectants.
Credit Jessica McDonald / KUNC

Several research groups across the world are working on similar plasma-based sanitizing machines. Many focus on the direct application of plasma and cost tens to hundreds of thousands of dollars to make and use.

Golkowski’s machine is much cheaper—his components total around $2,000. And while it may not look like much mounted on pieces of black-painted plywood, it’s quick and versatile, capable of sterilizing from about 10 feet away.

One reason for its success in the lab is that Golkowski can boost the number of hydroxyl radicals that do the sterilizing by feeding hydrogen peroxide into the device, and recirculating the stream.

“So air goes through the plasma discharge, then part of it goes on to our hydrogen peroxide solution,” says Golkowski. “And then finally, it goes into where the sterilization takes place.”

Right now, the sterilization chamber is a modified Tupperware-like container, with a tube going in and a tube going out.

Golkowski has placed ID badges, like those worn by doctors in hospitals, in the chamber, and in 15 to 30 seconds, has killed more than 99% of the bacteria.

"You're essentially taking a bullet to the cell."

Exactly how the radicals kill bacteria is not yet known, but it is thought to involve breaking open the fatty membranes that surround the cells.

“You’re essentially taking a bullet to the cell,” explains Reed Plimpton, one of Golkowski’s graduate students.

He says that this process is fundamentally different from how most antibiotic drugs work.

“It’s really not something you’d see an evolutionary response to, at least in how we understand it,” says Plimpton.

That means bacteria most likely wouldn’t be able to develop resistance to this type of sterilization—and that the drug resistant strains that are the most troublesome for hospitals now, like methicillin-resistant Staphylococcus aureus (MRSA), could be easily killed.

Sterilizing an ID badge is one thing, but animal cells are made of fatty membranes, too. So as a first safety test, Golkowski turned to a veterinarian at CU-Denver, Dr. Jori Leszczynski. They exposed the backs of mice to the plasma stream and looked for any damage.

“They looked perfectly normal, and if you compared them to the control mice, you wouldn’t have known just looking at the skin,” says Leszczynski.

Many more tests will be required before a device like this ever makes it to a clinic or a commercial setting, but this early result bodes well.

In the meantime, Mark Golkowski is still trying to optimize his machine, and understand how it works. For example, humidity can drastically change the number of hydroxyl radicals produced. And sterilizing may not be its only purpose. Other types of radicals may actually be able to promote faster healing.

Which may mean you could soon pick up a real plasma weapon to fight legions of microbes for a fraction of the price of Darth Vader’s lightsaber.