The potential for bioabsorbable polymer implants to replace metal in many applications has generated a great deal of buzz in recent years. However, a multiuniversity consortium is taking a less-traveled approach, seeking to develop metal-based implants that degrade while in the body.
Spearheading the research endeavor is North Carolina Agricultural and Technical State University (NCAT; Greensboro, NC; www.ncat.edu), which has obtained a five-year, $18.5-million Engineering Research Center (ERC) grant conferred by the National Science Foundation. NCAT is pooling its materials knowledge with fellow collaborators at the University of Pittsburgh (www.pitt.edu) and the University of Cincinnati (UC; www.uc.edu), which are contributing expertise in biomedical applications and sensors, respectively.
“The three areas [of expertise] complement each other, and all three areas are needed to develop this technology because it is so interdisciplinary,” says UC professor and ERC deputy director, Mark Schultz.
The primary objective of the multiuniversity project is threefold: to develop biodegradable metal craniofacial and orthopedic implants, to create biodegradable metal cardiovascular devices, and to produce miniature sensing systems that can monitor and control the biodegradable metal in vivo. Engineering these biodegradable devices and smart structures can ultimately reduce implant-related complications and spare patients multiple surgeries needed for implant retrieval. Potential applications include stents, orthopedic screws, scaffolds, and pediatric devices.
To achieve these ambitious goals, the consortium is researching magnesium alloys because of magnesium’s biocompatible and degradable properties. Among the developmental challenges, however, will be determining how to control the rate of the material’s degradation, according to Schultz. “One of the problems is that when you put magnesium in the body, it corrodes too fast in the beginning,” he says. “What we want to do is slow down the corrosion at the beginning and then, maybe toward the end when [the implant] is not needed anymore, speed up the corrosion.”
Controlling the material’s degradation rate hinges on a variety of factors—among them are finding the best magnesium alloy for the application and applying the right coating to the surface of the device, according to Schultz. Determining the correct degradation rate for porous implants potentially containing an extracellular matrix or stem cells, for example, is another challenge that the team must tackle.
Facing such complicated obstacles, the consortium expects the development of these biodegradable metal implants to be a long-term project. However, the researchers are optimistic that miniature sensors capable of characterizing the metal implants in vivo can be engineered within the next few years.