May 6, 2002 COLUMBUS, Ohio -- Engineers at Ohio State University have developed a computer model to help tiny medical implants dispense drugs on demand -- electrically.
This research may lead to more effective -- and more convenient -- forms of chemotherapy.
Though nanotechnology shows a great deal of promise for delivering drugs inside the body, researchers have had difficulty pumping fluid through the tiny passages that would have to be constructed inside such devices, explained Terry Conlisk, professor of mechanical engineering at Ohio State.
In the journal Analytical Chemistry, Conlisk and his colleagues report that a very small amount of electrical current may solve that problem.
The engineers have developed the first comprehensive computer model to address electrically driven fluids in channels.
Conlisk worked with Derek Hansford, assistant professor of materials science and engineering and biomedical engineering, doctoral student Zhi Zheng, and undergraduate research associate Jennifer McFerran.
Tests with actual nanometer-sized channels were conducted at iMEDD, Inc. -- a commercial company co-founded by Mauro Ferrari, professor of mechanical engineering and director of Ohio State's Biomedical Engineering Center -- using patented iMEDD/Ohio State technology.
The model was proven effective in tests where electrical potentials as small as one volt were able to drive saline through channels only a few nanometers wide.
"Pushing fluid through a very small channel requires a lot of pressure," Conlisk said. "Of course, you can't use pressures like that inside the body. So if we can drive fluid safely and effectively with electricity instead of pressure, that's a real advantage."
"The basic principle has been around for a long time. If a fluid is positively or negatively charged, and we apply a like charge to the inner surfaces of a channel, the charges will repel each other," he continued. "The fluid will flow down the channel."
Other researchers have studied electrical techniques for transporting fluid, Hansford said, but no other projects were as broad in scope.
"Other research has involved either purely theoretical or purely experimental work, but our approach combines both, for channels in a wide range of sizes," said Hansford.
The computer model closely matched results from the iMEDD experiments, in which engineers were able to flush nearly 0.5 nanoliters of saline per minute through a channel only seven nanometers wide. In a 20-nanometer channel, the flow rate was nearly 0.8 nanoliters per minute.
Though the computer models were based on electrical potentials as large as 6 volts, the experiments showed that much smaller voltages could be just as effective.
In practice, the voltage needed would depend on the size of the implantable device and the amount of drug that had to be dispensed, Conlisk said.
These electrical charges would not be dangerous to a patient, Hansford said, because they are extremely small, and would not even contact the patient's body. Rather, the charges would flow only along the tiny channels inside the device.
"You could run the device continually, and not even get a buildup of heat," Hansford said.
Ideally, this research will lead to a device that can target sites of disease in the body, such as tumors, and dispense medication.
For some kinds of chemotherapy, the device could make for better treatments and improve a cancer patient's quality of life, Hansford said.
He cited recent studies of colon cancer that showed chemotherapy to be more effective if it was administered at night, while a patient was sleepingaccording to the patient's sleep cycle. With traditional chemotherapy, the patient would have to be awakened several times in the night. But an implant could be programmed to dispense medication automatically after the patient falls asleep.
The same technology could be used to improve medical tests, where tiny samples of a substance could be analyzed more precisely inside a narrow channel.
This work is being funded by the Defense Advanced Research Projects Agency, Defense Sciences Office.
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