MIT scientists discover size of implant can affect immune system rejection

1.5 mm biomedical implants made of sugar polymers and other materials could be used to efficiently treat diseases such as diabetes(Credit: Andrew Bader, Omid Veiseh, Arturo Vegas, Anderson/Langer Laboratory, Koch Institute at MIT)

A team of researchers from MIT has discovered that creating body implants at a certain size maximizes the amount of time they can spend operational in the body before being neutralized by the immune system. In the future, the research could lead to longer term treatment avenues for diseases that could do away with the need for painful and repeated injections.

Without doubt, the human immune system is a wondrous thing. Over the course of our species' short existence, it has protected us and evolved with us, but it also has the capacity to interfere and stymie avenues of treatment offered by advances in medical science. Such is the case with body implants, which are increasingly used as a long-term drug delivery method.

The study that led to the discovery started seven years ago as an attempt to create an artificial pancreas, in order to treat diabetes. The study aimed to replace an individual's islet cells, which are responsible for detecting high concentrations of blood sugar and trigger the release of insulin from the pancreas. These cells cease to function in individuals suffering from Type 1 diabetes, preventing the body from coping with the sugar build-up.

During the trial, the team implanted a series of pancreatic islet cells encased in alginate implants directly into the abdominal cavity of diabetic mice, which would mimic the functions of a healthy pancreas, making insulin injections a thing of the past. However, the newly-implanted cells would be incapable of performing their new function if they were covered by scar tissue.

The team discovered that larger implants measuring 1.5 mm in diameter were better suited to avoiding scar tissue build-up when compared to smaller 0.5-mm variants. The smaller implants were found to be engulfed in scar tissue and ceased to function at around the four-week mark, however the 1.5-mm implant continued to function for an impressive six months after insertion. Furthermore, the larger implants were able to respond to changes in glucose levels while attracting less attention from the rat's immune cells.

Over the course of the study, the team trialled the two sizes of implants constructed out of stainless steel, glass, polystyrene, and polycaprolactone. It was discovered that the results invariably favored the larger analogue. The research represents a promising step forward in implant survivability, and could change the lives of millions suffering from diseases such as Type 1 diabetes

A paper on the team's research is available on the online journal Nature Materials.

Source: MIT

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