A Cornell fiber and biomaterials scientist working with a trio of graduate students has developed novel biodegradable and biologically active hydrogels that can be used for delivering many kinds of medications inside and outside the body. The jellylike substance can be used for anchoring biological substances such as skin and vascular tissues and might even be able to deliver viruses into the body for gene therapy.

"These new biomaterials not only contain enormous amounts of water, which make them more biocompatible with the human body, but also have greater mechanical strengths, integrity and stability than other hydrogels," says C. C. Chu, professor of fiber science in the textiles and apparel department in Cornell's College of Human Ecology and the university's Biomedical Engineering Program. Chu and his graduate students can manipulate various properties of the hydrogels, including how much they swell. Their hydrophilicity (the ability to attract and absorb water) and their hydrophobicity (the ability to repel water) are the chief means by which they control drug release. Strength and biodegradation rates also can be changed over a wide range.

The hydrogels not only are useful for controlling and delivering medications and serving as biodegradable networks for implants, tissue engineering and regeneration but also may have applications for coatings in agricultural products. They might even be used for coating fabrics, such as diapers, to absorb liquid, says Chu, whose research on the biodegradable hydrogels will appear in coming months in two scientific journals.

Jellylike hydrogels, non-biodegradable polymers like polyacrylates, can absorb and retain many times their weight without dissolving. They are commonly used as food-thickening agents, coatings for textiles and contact lenses, wound dressings and for delivering medications. Chu has engineered two much stronger and versatile hydrogels -- both have patents pending -- by chemically combining synthetic biodegradable polymers like polylactide and dextran, a polymer of sucrose commonly produced in fermentation, and carbohydrates called polysaccharides.

In one of the new hydrogel inventions from his lab, Chu combined dextran and maleic acid to develop one type of hydrogel that can increase its swelling without lessening its structural stability and mechanical strength. These properties allow the controlled release of medications with large or small molecular weights, such as peptides and proteins that are normally difficult to deliver through diffusion from non-biodegradable carriers.

About the other new class of hydrogel inventions from his lab that has both polysaccharide and synthetic biodegradable components, Chu says: "We have found that the release profile of medications is not only controlled by molecular weight but also by manipulating the composition ratio of these two hydrogel components. Thus, we can develop a release profile to suit any medication or rate of release we want."

Chu and his students have used these hydrogels to deliver the anti-inflammatory drug indomethacin and the cancer drug doxorubicin as well as human insulin and bovine serum albumin. A paper on one of the hydrogels will be published in the Journal of Biomedical Materials Research this year. Chu's co-authors are graduate students Sin-Hee Kim and Chee-Youb Won.

Another hydrogel, both biologically active and biodegradable, is derived from dextran and synthetic biodegradable polylactides. Chu says it can serve as a three -dimensional porous network with a large surface area on which to anchor cells and tissues like skin, cartilage, compounds for healing wounds and repairing blood vessels and introducing viruses in gene therapy. The porous 3-D network hydrogel not only provides much more surface area than currently used nonwoven fiber-based substrates but also has controllable pore sizes. In addition, the hydrogel has sites onto which bioactive substances, such as materials for tissue engineering, can be attached. It is engineered by forcing together a natural and a synthetic compound to form an homogenous gel that does not separate and has both hydrophilic and hydrophobic properties.

A paper on this hydrogel will be published early next year in the Journal of Polymer Sciences, Polymer Chemistry. Chu's co-authors are graduate students Yeli Zhang and Won.

Chu also is working with undergraduate student Renee Wong of Honolulu on testing the hydrogels as a coating for textiles and agricultural applications. The hope is that coated fabrics could be used to absorb sweat or urine in diapers or incontinence products.

Chu reported on both hydrogels last August at the American Chemical Society annual meeting in New Orleans.

Related World Wide Web sites:

• For more information about the College of Human Ecology - http://www.human.cornell.edu/