Technique may fool bodies into accepting artificial implants

UW researchers are one step closer to creating artificial bones, tissue and organs that the human body will recognize as its own, they reported in the April 15 issue of Nature.

Doctors place more than a half billion medical implants into patients every year-from simple catheters to heart valves and artificial hips. While these devices save or improve the lives of millions of people, they often deliver only a temporary fix. The body’s natural response to foreign material is to wall it off with scar-like tissue. Frequently, this reaction disrupts the device’s performance and the patient has to start over again.

To confuse the body’s reaction to foreign material, UW Bioengineering Professor Buddy Ratner and graduate student Galen Shi have invented a technique for coating a surface with tiny indentions. These indentions only attract specific, healing proteins. Tests were done using proteins of similar sizes and only the healing protein with the appropriate shape and chemistry adhered to the coating.

“We’ve achieved with ordinary synthetic materials the highly specific, lock-and-key fit we see in natural healing, and that has been one of the toughest hurdles,” Ratner says. “The next step is to see if an implant coated using our process actually turns on healing in the body.” Ratner directs the UW Engineered Biomaterials Center, a $25 million National Science Foundation initiative to create next-generation medical implants.

One of the proteins to be tested next is osteopontin, which plays a critical role in preventing calcification of heart valves but typically is not present in high concentrations on artificial valve implants. Researchers hope that valve implants coated using the UW process will bind enough osteopontin to inhibit calcification. This may reduce the need for dangerous and expensive valve replacement surgery in tens of thousands of patients.