Making Smarter Plastics

Originally Published MDDI July 2003

R&D DIGEST

Researchers at Rensselaer Polytechnic Institute (Troy, NY) are trying to create plastics that may one day improve medical care simply by being "smarter." The technique involves embedding the plastic with enzymes, says Shekhar Garde, PhD, assistant professor of chemical engineering at Rensselaer.

"Such protein-enhanced plastics might someday be able to act as ultrahygienic surfaces or sensors to detect the presence of various chemicals," says Garde.

These types of materials could have a wide range of applications, including medical use. Proteins require water to function, however. Nonwatery environments do not provide the driving force necessary to keep proteins in their normally intricately folded state; unfolded, the molecules cease to function.

To learn what it takes to successfully integrate proteins into a dry substance such as plastic, Garde and his graduate student Lu Yang use molecular dynamics simulations to create a computer model of the proteins and study the molecules in both watery and nonwatery environments, such as organic solvents.

Proteins are "molecular machines," says Garde, uniquely able to efficiently and reliably conduct chemical processes. Their powerful activity, however, is limited to relatively low temperatures and pressures. Helping proteins adapt to a non-water-based environment may actually increase the resiliency of the molecules and make them useful in situations they otherwise would not survive, such as exposure to high temperatures or other extreme conditions.

In addition to preserving proteins' known actions, the researchers speculate that they may also "discover that proteins could perform some new functions [in dry environments], something that they could not do in water," according to Yang.

The researchers are working in collaboration with Jonathan S. Dordick, the Howard P. Isermann 1942 Professor of Chemical Engineering, who conducted the initial protein research. Dordick suggests that the next hurdle in the material's development is related to manipulating enzyme functions. "We have a suite of enzymes that can be put into a plastic; however, the enzymes which are responsible for the desirable reactions are being put into a very unnatural environment. The challenge is to find ways to manipulate the enzyme to function optimally in those environments. We then have to find ways to build architectures to best support these materials," Dordick says. "We are doing this work through a combination of experimental and computational techniques. Shekhar Garde is developing computational methods to study the possible influences of the various nanoenvironments on the structure and function of the plastics. With his computations, we hope to predict ways to build better systems and go on to test them experimentally."

Dordick adds, "Computationally, we get the understanding of what's happening and the ability to predict how things might be affected. Then to validate those predictions, we do it experimentally. Together, both sides of the work provide a nice collaboration. We can do so much more with the combination of experimental and computational—there are so many more things that Shekhar can do computationally."

"Potential medical applications of this work include materials that could resist fouling due to microorganisms—this would be especially important in endotracheal tubes or other implants that involve a tube entering the body," says Dordick. Other possible applications are surfaces that resist fibrotic tissue growth when used as implants, and stent coatings that could prevent clotting or restenosis."

Use of the plastic could provide unique benefits, says Dordick, such as extending the life of implants or other in vivo materials, and reducing the risks of infection or rejection."If an antifibrotic coating is coupled with a drug-delivery system, it's more likely the system would continue to work over time, as it would not be hindered by the body's efforts to encase it in a fibrotic capsule," says Dordick.

Illustration courtesy of RENSSELAER POLYTECHNIC INSTITUTE

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