transplant

Coating inspired by a spider web could revolutionise transplant of insulin cells

by Barbara Hewitt on January 8, 2018

A coating inspired by the silk used by spiders to create their webs could improve the management of diabetes by revolutionising the implanting of insulin producing islet cells.

Scientists from Cornell University in New York, USA, have developed a device that they believe could revolutionise management of type 1 diabetes.

Spider Web

(By Filimages/Shutterstock.com)

In type 1 diabetes, insulin producing pancreatic cell clusters, known as islets, are destroyed by the body’s immune system. The new development means there could be a new way of implanting thousands of these cells into a patient.

This is because they are protected by a thin hydrogel coating and, more importantly, the coated cells are attached to a polymer thread and can be removed or replaced easily when they have outlived their usefulness.

The research group, led by assistant professor Minglin Ma from the Department of Biological and Environmental Engineering in the College of Agriculture and Life Sciences, explained that the 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’re not connected to each other, and there are hundreds of thousands of them.

And the ability to remove the transplant is key because of the potential of tumours forming when stem cell derived, insulin producing cells, the most promising cell source for type 1 diabetes cell therapies, are used.

‘When they fail or die, they need to come out. You don’t want to put something in the body that you can’t take out. With our method, that’s not a problem,’ said Ma.

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.

The device starts with two sterile nylon sutures twisted in a helix, then folded over to facilitate the subsequent nanoporous structure coatings. Placed onto that thread is a thin layer of islet cell containing alginate hydrogel, which adheres to the helical, nanoporous thread, similar to dew drops sticking to the spider silk. Alginate is a seaweed extract commonly used in encapsulated cell transplantation.

This thread, which the group have called TRAFFIC (Thread-Reinforced Alginate Fiber For Islets enCapsulation), was inspired by a spider’s web but Ma said it is even better because the hydrogel covers the thread uniformly.

‘You don’t 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 pointed out. He added that since the thread is twisted and porous, the hydrogel won’t slip off as it would on a single, smooth piece of material.

The team say that treatment would involve minimally invasive laparoscopic surgery to implant approximately six feet of hydrogel coated thread into the patient’s peritoneal cavity and it has the potential to improve treatment as TRAFFIC’s large surface area promotes better mass transfer and diffusion is good because all the islet cells are near the surface.

In experiments with mice blood glucose levels were returned to normal two days after implantation of a one inch length of TRAFFIC and remained normal for at least three months when the experiment ended.

The team believe they have a potentially game changing medical device and it shows more promise than others because , it is minimally reactive, it protects the islet cells, it allows them to sense glucose, they don’t attach to anything, and it can be easily removed.

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