Under the microscope: Dr. Unger's bubbles

Evan C. Unger, MD
Evan C. Unger, MD

Evan C. Unger, MD, has big plans for his tiny bubbles.

As co-leader of The University of Arizona Cancer Center Imaging Program, Dr. Unger finds himself at the forefront of nanotechnology research. He is the inventor on more than 100 issued patents and has led the development of three compounds approved by the Food and Drug Administration.

In 1990, Dr. Unger began his work with microbubble technology, well before there was even an official name for the field. The idea was that if millions of these bubbles could be injected into a patient’s bloodstream, they could act as little mirrors for ultrasound or as delivery systems for drugs or oxygen.

Thanks in large part to Dr. Unger’s work, those ideas are now becoming a reality. He is currently in the process of developing microbubbles specifically for oxygen delivery. Thus far, it is the most successful oxygen delivery system that has ever been tested.

What does this development mean for cancer research? Dr. Unger says it may turn a few untreatable forms of cancer into a thing of the past.

“We’re focusing on cancers that are hypoxic,” Dr. Unger said. “Hypoxia is a condition where an area is deprived of oxygen. A hypoxic cancer can’t be treated with radiation because the way that treatment works is by creating individual oxygen atoms, or singlets. Oxygen, of course, is O2, so the radiation splits the oxygen molecule apart and creates free radicals, which then kills the tumor. If a tumor is in a low-oxygen or no-oxygen area, then it is resistant to the radiation.”

How does it work? Billions of tiny nanodroplets, less than 1/20th the diameter of red blood cells, are injected intravenously. The nanodroplets form into microbubbles as they circulate through blood vessels in the lungs absorbing oxygen. The oxygen-carrying microbubbles will circulate in a patient’s bloodstream near the cancerous area. Each microbubble is about one micron, or 1/1000 of a millimeter, in size. If properly administered, these microbubbles give the area enough oxygen to proceed with radiation treatment.

“The average cancer patient undergoes roughly 28 radiation treatments, so we’re also hoping this oxygen therapy allows patients to undergo far fewer treatments and recover much faster,” Dr. Unger said.

In addition to cancer treatments, Dr. Unger and his team have found great success using microbubble technology to treat strokes and hemorrhagic shock.

It’s this sort of out-of-the-box thinking that led The University of Arizona to recognize Dr. Unger with the 2011 Technology Innovation Award — an honor given annually in recognition of exemplary innovative achievement in translating original ideas from the laboratory to the marketplace.

Prior to his work developing these drug- and oxygen-delivery systems, Dr. Unger was brainstorming ways to get stronger, sharper internal images, while reducing a patient’s exposure to radiation.

“As a contrast agent, this technology is much safer and much more effective than a CAT scan or an MRI,” Dr. Unger said. “Those tests use either use radiation or contrast agents that can cause kidney damage. But the microbubbles use ultrasound, which causes no kidney damage and is much cheaper for patients.”

While this technology is currently used in the United States for cardiology, it is still awaiting FDA approval for cancer imaging. It is, however, being used with great success in Canada, Japan and parts of Europe.

“I have colleagues at the Institut Gustave-Roussy [Europe’s largest oncology center] using these ultrasound contrast agents, and they tell me that they can gauge a patient’s response to treatment way before they could tell on a CAT scan,” Unger said.

As the scope of Dr. Unger’s research grows at an exponential rate, the technology continues to shrink. The future of cancer imaging and treatment may rest with these bubbles that are smaller than specks of dust.