A multidisciplinary team of medical researchers, engineers, and materials scientists based at Cornell University have created an implant with the potential to provide long-term treatment of the insulin deficiency that stems from type 1 diabetes (T1D).
Patients with T1D are unable to produce adequate levels of insulin due to a poorly understood autoimmune reaction that destroys insulin-secreting beta cells within the pancreas. The disease often onsets during childhood, and affected individuals must continuously supplement with injections or an insulin pump to survive.
Instead of delivering insulin into the bloodstream, the new invention transplants hundreds of thousands of stem cell-derived beta cells into the abdomen. The clusters of cells, called islets, are encased in a water-soluble hydrogel made from brown algae, reinforced by a central thread of modified nylon polymer suture.
The string-like implant has been titled TRAFFIC, for Thread-Reinforced Alginate Fiber For Islets enCapsulation. The team shared in a statement that the concept was inspired by how drops of water cling to spider webs.
TRAFFIC’s innovative design confers several key advantages over previous islet implants. The cells are protected from the body’s immune system, meaning potential patients would not require long-term immunosuppressants, a type of medication known for its serious side effects. Ironically, several anti-rejection drugs given to organ transplant patients can actually induce insulin resistance and lead to a form of type 2 diabetes (post-transplant diabetes mellitus).
Tidily encased in hydrogel, the cells can also be easily removed when production of the insulin hormone decreases or the islets begin to degrade. According to the study's leader Minglin Ma, PhD, implanted cells are at risk of forming tumors.
"When they fail or die, they need to come out," Ma said. "You don't want to put something in the body that you can't take out. With our method, that's not a problem."
Finally, the thread’s outer layer is coated with nanopores (holes on the scale of one billionth of a meter in diameter) that release calcium ions. First author and PhD candidate in Cornell's biological and environmental engineering department, Duo An, told IFLScience that this uniform distribution of the calcium is critical, as it ensures a tighter and more secure binding between the thread and the alginate hydrogel, as well as a minimal and uniform thickness of the hydrogel layer. This property is believed to facilitate the efficient diffusion of insulin produced by embedded islets out of the gel, where it can be absorbed by surrounding tissue.
A series of early experiments evaluating TRAFFIC, published ahead of print in Proceedings of the National Academy of Sciences, showed the biocompatible device provided symptom control in mice with chemically-induced diabetes for 3 to 4 months. The study also demonstrated that the device could be scaled up for larger animals and that it could be easily removed through minimally invasive laparoscopic surgery, following successful tests on dogs.
If the technology advances to human testing, the group plans to implant approximately 6 feet of TRAFFIC thread into a patient’s peritoneal cavity, a space between the linings of the abdominal wall and the tissue surrounding the internal organs.
TRAFFIC has received patent protection under the pharmaceutical company Novo Nordisk, who also collaborated on its development.