Polymers are everywhere, from the plastic wrap that covers cooked dishes to state-of-the-art devices designed by the aerospace industry. But who would have expected to find them in pharmaceutical and biomedical products? Chemist Julian Zhu, Professor at Université de Montréal for 10 years, is a world specialist in biopolymers, compounds that are able to disappear in the body or be evacuated by natural channels after releasing the active molecules of a drug. “They are called intelligent materials,” the Chinese-born expert who came to Canada in 1983 explains. “They can be very useful for transporting a drug exactly to the place we want it to act. Or for controlled release devices.”

In the July issue of the journal Accounts of Chemical Research, the researcher discusses progress in his work on a class of polymers derived from bile acids, secreted by the gall bladder to help digest fats and lipids. These are hydrogels (which are soluble or swell in water) and biodegradable polymers (that decompose in a biological milieu). “Some hydrogels are characterized by the fact that they swell when the are activated—a bit like Jello.”

Since bile acids act in the intestine, this is where the drug has to be released. So Professor Zhu has developed a hydrogel that is sensitive to a base environment. Since the pH in the stomach does not exceed 4 and the intestine is at 6 or more, the component he has created is activated in an environment that has a pH of 5. “Take the example of aspirin, which often causes problems in the stomach,” explains the chemist. “With a polymer like ours, the product would remain intact until it reaches the intestine. The capsule would only dissolve once it reaches this milieu.”

The properties of polymers always astonish students when professor Zhu shows them some of these substances. “Some are sensitive to temperature and change colour when they are heated, for example. This characteristic fascinates my students, just as it fascinated me at the start of my career. Others break down after a certain time. They literally disappear after they reach their target. This property makes them very interesting for treating cancers.”

The chemist was recently named to the Canada Research Chair for Polymeric Biomaterials. His job will be to design polymers for the health sector and industry. One Montréal firm specializing in hospital bedding and adult diapers, Absorb-plus, has already drawn on the professor’s expertise to develop a superabsorbant, thermo sensitive polymer. “Even when it is saturated with water, it dries out quickly when heated.”

Researcher: Julian Zhu
Telephone: (514) 343-6733
Funding: National Science and Engineering Research Council