Transplantation of stem cell-derived, insulin-producing islet cells is an alternative to insulin therapy, but that requires long-term immunosuppressive drug administration. One well-researched approach to avoid the immune system’s response is to coat and protect the cells in tiny hydrogel capsules, hundreds of microns in diameter. However, these capsules cannot be taken out of the body easily, since they are not connected to each other, and there are hundreds of thousands of them. The ability to remove the transplant is key because of its potential to form tumours, researchers said.
“When they fail or die, they need to come out. You do not want to put something in the body that you cannot take out. With our method, that is not a problem,” said Minglin Ma, assistant professor at Cornell University. Taking inspiration from the way water beads on a spider’s web, Ma and his team first attempted to connect the islet cell-containing capsules through a string but realised that it would be better to put the hydrogel layer uniformly around a string instead. That string is an ionised calcium releasing, nanoporous polymer thread, the researchers said.
This thread — which the group has dubbed Thread — Reinforced Alginate Fiber For Islets enCapsulation (TRAFFIC) — was inspired by a spider’s web but, according to Ma, is even better because the hydrogel covers the thread uniformly. “You do not have any gaps between capsules. With a spider’s silk, you still have gaps between the water beads. In our case, gaps would be bad in terms of scar tissue and the
like,” he said. This therapy would involve minimally invasive laparoscopic surgery to implant about six feet of hydrogel-coated thread into the patient’s peritoneal cavity.