Drug-doped silicone may stop implants from being rejected
Even though electronic implants such as pacemakers may save people's lives, the body's immune system sees those same implants as unwanted foreign objects. An experimental new drug-doped coating, however, may help keep that from happening.
Ordinarily, when an object is surgically placed within the human body, the immune system mounts a defensive inflammatory response. As part of that response, collagen-fiber-producing cells known as macrophages build a capsule of scar tissue around the object, in order to isolate it from the surrounding tissue.
Unfortunately, in the case of implants that need to stimulate nerves or otherwise interact with bodily systems, that scar tissue limits their functionality. Eventually, the coating may become so thick that the implant has to be replaced.
Seeking to better understand the inflammatory response, scientists from the University of Cambridge implanted a small electrical device in mice, in order to compensate for damage to their sciatic nerve. After the device had been in place long enough to produce a response, the scientists analyzed the tissue surrounding it, plus they analyzed the tissue in that same area of a control group of mice that had not received an implant.
By comparing the two groups, it was found that a naturally occurring molecule called NLRP3 was playing a key role in the inflammation process. Previous research, however, showed that another molecule by the name of MCC950 inhibits the activity of NLRP3.
With that fact in mind, the researchers proceeded to coat another batch of the implants with MCC950-doped silicone, after which those implants were placed in another group of mice. This time around, no inflammatory response occurred, so no scar tissue formed around the implants.
Importantly, the MCC950 also did not impede the nerve regeneration process. By contrast, the broad-spectrum anti-inflammatory drugs that are currently used to limit the rejection of implants also block the regeneration of nerves and other tissue.
It is now hoped that MCC950-containing medications could be used in coatings that will keep implants from being rejected, while still allowing the tissue around them to heal.
"Combining these drugs with different materials and softer coatings for devices could transform the lives of individuals who need long-term implants to overcome serious disability or illness," said Prof. Clare Bryant, joint senior author of a paper on the research. "In particular, this could make a huge difference to neuroprosthetics – prosthetics that connect to the nervous system – where the technology exists, but scarring has not yet made their widespread use viable."
The paper was recently published in the journal Proceedings of the National Academy of Sciences.