MRI Maps to Track Effectiveness of Drug Releasing Implants

Drug-releasing implants may have significant benefits for treating a variety of diseases. They’re already used in a few limited applications, but wider implementation has proven to be challenging because it is difficult to know how a drug moves through the implant and into the surrounding tissues.

Now, researchers at Purdue University have developed a way to use an MRI machine to view the movement of a drug through and out of a drug eluting implant. The capability will allow drug implant developers to study how their designs work with different drugs and within the types of tissues they’re expected to be surrounded by when inside patients.

The team focused on in situ forming implants, which are tiny injectable devices, invented in the 1990s, that change from liquid to solid once inside the body. Tissues and fluids that surround the implants absorb the drugs that are contained inside the now solid implants, and the implants themselves eventually break down inside the body.

Loading these implants with fluorescent markers, which effectively stood in for a drug compound, the Purdue team was able to track how these markers moved through the implants using diffusion-weighted MRI. The technique allowed the researchers to quantify how much of the mock drug moved during a given period of time through the implant, a capability that was previously only possible via invasive means.

Results show up in the form of colorful maps of the implants that illustrate how the drug moves through the implant pores. These maps are intuitive and easy to understand, which should be immediately useful for drug eluting implant developers.

“With this platform, we have been able to better understand some of the underlying phenomena that alter drug release, and as a consequence design implants more precisely to get the drug release profiles that we want,” said Luis Solorio, a Purdue assistant professor of biomedical engineering who was involved in the research. “Being able to measure how an implant restricts drug movement across both time and space, within the implant and at the actual injection site, allows us to inform a mathematical model that can be used to predict how much of the drug is left in the implant.”

Study in Journal of Controlled Release: Noninvasive characterization of in situ forming implant diffusivity using diffusion-weighted MRI

Via: Purdue University