Drier Diapers and Drug Delivery-Cornell

A Cornell University fiber and biomaterials scientist, working with a trio of graduate students, has developed a number of novel biodegradable and biologically active hydrogels that can be used for delivering many kinds of medications inside and outside the body. The jelly-like substance also shows promise as a coating for agricultural products, or, because of its absorbent qualities, for fabrics, such as diapers.

"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–Sin-Hee Kim, Chee-Youb Won, and Yeli Zhan–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.

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 a 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.
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The other new class of hydrogels developed in his lab 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.

Another hydrogel, both biologically active and biodegradable and derived from dextran and synthetic biodegradable polylactides, 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. As Chu explains, the porous 3-D network hydrogel not only provides much more surface area than currently used non-woven 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 asynthetic compound to form an homogenous gel that does not separate and has both hydrophilic and hydrophobic properties.

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.

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