Medical implant designs have always strived to be as small and unobtrusive as possible. After all, the body tends not to like cumbersome foreign objects floating around. But there may be a big new trend on the rise: researchers at MIT recently published a study that disproves the common sense belief that smaller is better.
In the study, scientists implanted rats with spherical sugar polymer-coated packages of specially designed cells which are meant to take on the function of the pancreas in people with diabetes, releasing the necessary amount of insulin. Quite often, immune systems interpret these implants as a threat, building up scar tissue around them until they stop working.
The test consisted of two sizes of implants, one with a .5 millimeter diameter and another with a 1.5 millimeter diameter. To their surprise, the .5 millimeter cells were surrounded by scar tissue and failed within a month, while the 1.5 millimeter implants continued to function for more than six months. Scientists have found similar results in tests with non-human primates.
Since these results have been shown to be consistent across different materials, this work has great potential to influence the way new implants are designed. And if larger implants are indeed better in some cases, it could offer enhanced performance in the form of carrying longer battery life, extra dosages of medicine, or more powerful sensors.
“We were surprised by how much the size and shape of an implant can affect its triggering of an immune response. What it’s made of is still an important piece of the puzzle, but it turns out if you really want to have the least amount of scar tissue you need to pick the right size and shape,” Daniel Anderson, the Samuel A. Goldblith Associate Professor in MIT’s Department of Chemical Engineering and the senior author of the study said.
“We realized that regardless of what the composition of the material is, this effect still persists, and that made it a lot more exciting because it’s a lot more generalizable,” says Omid Veiseh, another author of the paper. Considering these factors will help scientists who are designing drug delivery devices and other implants that fight disease inside the body to make sure that their inventions work.