Magnetic Fluids Offer Hope for Damaged Retinas

Contact: Charmayne Marsh 202-872-4445 in Washington

April 4--11, 2002, in Orlando407-685-8070

EMBARGOED FOR RELEASE: Wednesday, April 10, 10:45 a.m., Eastern Time

Magnetic fluids offer hope for damaged retinas

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

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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.

#13183 Released 04/10/02

Embargoed: Wednesday, April 10, 10:45 p.m., Eastern TimePOLY 374 [511174] Magnetic Nanostructured Fluids

Judy S. Riffle1, Metha Rutnakornpituk1, Sheng Lin-Gibson2, James P. Dailey3, and Linda A. Harris1. (1) Department of Chemistry, Virginia Tech, 2018 Hahn Hall (0212), Blacksburg, VA 24061, Fax: 540-231-8517, Phone: 540-231-8214, (2) Polymers Division (854), NIST, (3) Dept. of Ophthalmology, Case Western Reserve University

Magnetic fluids and films are finding increased potential in a multitude of industrial and biological applications. For the past few years, we have been studying magnetic nanoparticle dispersions in biocompatible polydimethylsiloxane carrier fluids. The objectives include using such silicone fluids to treat retinal detachment disorders. Thus, we are exploring the preparation of magnetic nanoparticle dispersions in block copolymer and homopolymer liquids. The liquid silicone block copolymers can serve as both the stabilizing entities and also the carrier fluids. The feasibility of such an approach was demonstrated by using a poly(dimethylsiloxane-b-(3-cyanopropyl)methylsiloxane-b-dimethylsiloxane) (PDMS-PCPMS-PDMS) triblock copolymer with relatively long tail to anchor block lengths to stabilize cobalt particle dispersions.

The block copolymers are themselves phase separated in the nanoscale regime. When the terminal PDMS blocks are the major compositional component, these copolymers are viscous liquids. The central PCPMS component coorddinates to the surfaces of cobalt particles via specific isonitrile interactions with the electropositive metal, while the non-adhesive PDMS tail components protrude outward from the particle. These can be utilized as steric stabilizers for cobalt nanoparticles dispersed in polydimethylsiloxane carrier fluids. A further approach under current study is to prepare pentablock stabilizer molecules with trialkoxysilane containing crosslinkable blocks to disperse the cobalt particles, then to crosslink the stabilizer molecules to prepare fine cobalt core-silica shell dispersions. The objective is to use the ceramic interlayer to protect the nanoscale metal particle surfaces from oxidation. A second project involves the design and construction of biodegradable, magnetic field directable micropheres for targeted delivery of therapeutic agents. Our initial work in this area has been directed toward the generation of controlled magnetite dispersions with poly(ethylene oxide) stabilizers and the incorporation of magnetite nanoparticles into biodegradable microspheres.

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