Magnetic fluids offer hope for damaged retinas

April 10, 2002

ORLANDO, Fla., April 10 -- Researchers at Virginia Tech in Blacksburg are developing injectable magnetic fluids to repair torn or detached retinas -- a technique they believe could help prevent blindness in thousands.

Their work was reported today at the 223rd national meeting of the American Chemical Society, the world's largest scientific society.

Silicone fluid is currently used to push damaged retinas back in place. A magnetized version of the fluid would make repairs easier and more precise by allowing the fluid to be moved to areas of the eye that are hard to reach, according to the researchers.

The treatment appears promising in laboratory studies, says Judy Riffle, Ph.D., head of the research team and a chemistry professor at the university. Animal studies could take place within a year and human studies could soon follow, she says.

"We are the first to develop controlled magnetic nanoparticles that are appropriate to use in the eye," says Riffle. Her lab has been developing the material for the past ten years.

Tiny particles of cobalt or magnetite are enmeshed in a silicone-based fluid (polydimethylsiloxane). When exposed to an external magnetic field, the fluid can be maneuvered in much the same way that magnetic pieces are moved around in certain toys, Riffle explains.

The retina is the thin, light-sensitive layer of tissue located at the back of the eye. When it becomes detached or torn, either due to disease or injury, impaired vision results. Blindness occurs if it is not repaired.

The conventional way to repair this disorder is to inject silicone fluid or a special gas directly into the eye to push the retina back into place. In people with more severe damage, this treatment often fails because the material cannot reach certain areas of the eye, particularly the lower parts, says J. P. Dailey, M.D., an ophthalmologist with Erie Retinal Surgery in Erie, Pa., and a major collaborator in the study.

In searching for a way to distribute the material more evenly inside the eye, Dailey came up with the concept of using magnetic fluids, which are known for their maneuverability. He discussed the concept with Riffle, a polymer chemist, who then designed the biocompatible, silicone magnetic nanofluids.

"If it works, it will be wonderful," says Dailey, who cautions that the technology still needs further safety testing. "This could be a major innovation in how retinal detachment repair is done."

"Our lab's work may open the door for a whole host of new medical applications for magnetic nanoparticles," adds Riffle. Similar fluids are being developed by her lab for use in targeted drug delivery.

Riffle and her colleagues are developing magnetic, biodegradable microspheres that can be attached to specific drugs, such as chemotherapy agents. With the aid of a magnet placed outside the body, the medicated fluid microspheres could be directed to hard-to-reach tumor sites, such as the lung, prostate and brain. Riffle believes that a similar technique can eventually be used to deliver DNA to specific cells for gene therapy.

Another possible use of magnetic fluids is magnetic hyperthermia. By passing an alternating magnetic field across a magnetic fluid, the particles will heat up, destroying tissue in their path. This method looks promising as a noninvasive means of treating brain tumors, the researcher says.

There are still problems to be worked out before the fluids are ready for human trials, says Riffle. Due to the potential toxicity of cobalt, she is now experimenting with an iron-based material, magnetite, which is believed to be less toxic to cells. Riffle and her associates are also attempting to coat the experimental nanoparticles with silica material shells so that they will not lose their magnetism over time, giving them the potential to be permanently implanted, she says.

Magnetic fluids have been used in industry for the past 40 years, most notably as a sound damper for stereo loudspeakers and as seals in motors.

Riffle and Dailey were recently awarded a patent for the use of silicone magnetic fluid for eye surgery.

Funding for this study was provided by the Carilion Biomedical Institute, the Hirtzel Memorial Foundation, the Air Force Office of Scientific Research (AFOSR) / Defense Advanced Research Projects Agency (DARPA), and the Lord Foundation.

--Mark T. Sampson

The paper on this research, POLY 374, will be presented at 10:45 a.m., Wednesday, April 10, at Convention Center, Room 314A, Level Three, during the symposium, "2002 ACS Award in Applied Polymer Science Honoring James E. McGrath."

Judy S. Riffle, Ph.D., is a professor in the department of chemistry at Virginia Tech in Blacksburg, Va., and director of the university's Macromolecular Science and Engineering Program.

J. P. Dailey, M.D., is an ophthalmologist with Erie Retinal Surgery in Erie, Pa., and assistant clinical professor at Case Western Reserve University in Cleveland, Ohio.

American Chemical Society

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