No matter what sort of wondrous implantable medical devices are created, they’re not going to do anyone much good if the recipient's body simply rejects them. With that in mind, scientists at the University of Washington have developed a synthetic biomaterial that they claim is “exceptional” at keeping implanted materials from being attacked by the immune system.

Quite often, after a foreign object is introduced into biological tissue, the body will go about isolating that object by building a thick layer of collagen around it. In the case of implantable devices such as artificial heart valves or electrode sensors, this so-called “collagen capsule” keeps them from functioning properly.

A team led by Professors Buddy Ratner and Shaoyi Jiang set out to make such implants invisible to the body’s defenses, via a special hydrogel. The gel is made from a polymer that contains both a negative and positive charge, which keeps proteins (such as collagen) from bonding to it.

In lab tests, samples of the hydrogel were implanted in the bodies of mice. Three months later, no collagen capsules had formed around the implants. What collagen there was, was evenly and loosely distributed throughout the animals’ tissue. In humans, if a capsule is going to form around an implant, it will typically be evident within three weeks. If none has formed within several weeks, then rejection is unlikely to occur at all.

“Scientists have tried many materials, and with no exception, this is the first non-porous, synthetic substance demonstrating that no collagen capsule forms, which could have positive implications for implantable materials, tissue scaffolds and medical devices,” said Jiang.

Human trials of the hydrogel are now being planned. A paper on the research was published this week in the journal Nature Biotechnology.