by Melissa Crytzer Fry

Super glue, organic solvents, and stainless steel springs seem better suited for high school science competitions than for treatment of defective blood vessels and cancerous tissues. Such products, however, are frequently used to repair the human body.

Brent Vernon is focused on creating a safer, more efficient alternative. A bioengineering professor at Arizona State University’s Ira Fulton School of Engineering, Vernon is developing temperature-sensitive polymer gels that can be injected into the vascular system to stop unwanted blood flow. They can also be used to deliver drugs to targeted areas of the body.

The gels are particularly useful in treating dangerous, bulging blood vessels known as aneurysms. “With an aneurysm, a bubble forms off the blood vessel,” Vernon explains. “You could use the gel to fill up that bubble and keep it from rupturing.”

Other uses include delivery of chemotherapy drugs. “Because the drugs are toxic, you can’t give a very high concentration,” Vernon says. “But if you put the drug inside a gel and it can diffuse out slowly, then you can give a lot more drug. One dose could contain enough for slow release delivery over an entire week or even a month.”

Many materials, when under constant stress and temperature in the body, begin to swell or flow out of the target region. As a result, they block undesirable vessel regions. Others gel too quickly before they enter the blood stream. They get trapped in catheters and never reach their destination. Other materials don’t solidify quickly enough in the blood vessel. They end up being distributed elsewhere in the body away from where they are needed.

Vernon has developed gels that solve many of those problems. To make them, he creates long chains of molecules called polymers in his laboratory. To create polymers, he combines a series of smaller molecules in organic solvents. He then purifies the new substances and dries them to remove unwanted solvent.

The end result is a powdery material that dissolves when combined with liquid. It remains as a liquid at room temperature, but gels at body temperature when injected.

These temperature-responsive materials are known as in situ gels. Such gels form in two ways: physical and chemical. The material begins to gel when injected, but solidifies over time. This helps help the gel stay in place.

“At body temperature, the polymers in physical gels precipitate into a solid form out of the injectable solution. They entangle around each other, creating a spaghetti-like mass,” explains Vernon. “Conversely, chemical gels involve a chemical bond, or cross-link, between the polymers. Materials that are both physical and chemical will gel by entanglement and by cross-linking.” The result will be stronger, more effective gels.

While degradable gels have been used in drug delivery for years, the non-degradable endovascular application is unique. Within three to four years, Vernon expects that patients with vascular problems will benefit from the myriad computer analyses and cell culture studies conducted in his lab.

“The implications are far-reaching,” says Vernon. He and fellow ASU researchers at the Harrington Department of Bioengineering, Michael Caplan, Bae Hoon Lee, and Christine Pauken, are beginning to study the relationship between polymer gels and stem cell production.

ASU’s polymer gels could feature a scaffold that is ideal for carrying signals that “tell” stem cells to divide and grow, he says. Mass production of stem cells could impact maladies ranging from Parkinson’s disease and arthritis to cancer and diabetes.

Brent Vernon’s research is supported by the National Institutes of Health and Arizona Technology Enterprises, in collaboration with the Barrow Neurological Institute in Phoenix.