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Office of News and Information
212 Whitehead Hall / 3400 N. Charles Street
Baltimore, Maryland 21218-2692
Phone: (410) 516-7160 / Fax (410) 516-5251

July 6, 1995
CONTACT: Ken Keatley

Hopkins Researchers Find Polymers Can Control
Medication, Strengthen Bones

Researchers in the School of Engineering at The Johns Hopkins University are creating polymers -- complex chemical compounds formed from a number of simpler molecules -- that may help to revolutionize medical treatment. Here are two examples:

1. It's All in the Timing

Cancer patients often require treatment in one isolated area of the body. Targeting the delivery of medication to that area, without hurting surrounding healthy tissue, is a problem Mark Saltzman, professor of chemical engineering at Hopkins, is working to solve.

He is developing biocompatible polymers that release drugs, proteins, antibodies, antigens and other molecules into a targeted area of the body at precisely controlled rates over a period of weeks or months.

For instance, as Saltzman and Hopkins neurosurgeon Henry Brem are learning, polymeric delivery may make it possible to introduce therapeutic drugs directly into solid masses, like brain tumors, that are difficult to treat. Eventually, these polymeric drug delivery systems could be applied to the treatment of other diseases, including AIDS and Alzheimer's.

"A device that releases agents at a controlled rate has many advantages," said Saltzman, who has a joint appointment in biomedical engineering. "It doesn't need to flood the entire body with agents to protect one area. And the agents are non-toxic and don't cause hormonal changes."

He has also discovered, in collaboration with Hopkins biophysics professor Richard Cone, that polymer systems can provide long-term female contraceptive and prophylactic protection. They are combining the system's contraceptive function with prevention against sexually transmitted diseases, by using a vaginal ring made of an ethylene vinyl-acetate copolymer. Preliminary testing on mice has generated encouraging results.

2. Breakthrough for Better Bones

Kam Leong, associate professor of biomedical engineering at Hopkins, is developing synthetic polymers to speed and improve the healing of broken or brittle bones.

Leong, who holds a joint appointment in the Department of Materials Science and Engineering, is perfecting a biodegradable polymer for use in bone grafts that would eliminate the need for metal plates, pins and screws used in treatment now. Unlike metal, the polymers -- based on a foam fabrication technique -- contain pores into which bone tissue grow; these pores can also be filled with bone growth enhancers.

As the bone solidifies, the polymer implants -- which are both biodegradable and biocompatible -- dissolve, gradually allowing the bone to support more weight. This is an improvement over the use of metal plates, which support all the weight normally carried by the bone; when the metal is removed, the still-weak bone must suddenly carry all of the weight, increasing the likelihood of reinjury. Also, metal implants require two operations (one to insert them, one to remove them), and, as foreign substances, carry the long-term risk of infection.

"Polymeric prosthesis devices enjoy the advantage of having tailor-made properties," explained Leong, who is working in collaboration with Hari Reddi and Edmund Chao in the Hopkins School of Medicine. "The structural support function of a polymer device can be integrated with the drug-carrier function to enhance bone union."

He added that biodegradable polymers also have the potential for a number of environmental applications.

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