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Student Tests Polymer Capsules for Curing Diabetes

Talk about precocious! A senior chemical engineering major at the University of Massachusetts Amherst is a vital cog on a research team working toward the successful treatment of diabetes and other killer diseases. Worcester resident Meenal Datta is performing key experiments on polymer capsules engineered to carry insulin-producing pancreas cells for implanting in type 1 diabetics. This procedure would inject or implant encapsulated, insulin-secreting, islets of Langerhans cells to treat the disease. The technique would be as effective as, but much safer than, a pancreas transplant, because the capsules would allow the islet cells inside to secrete insulin into the diabetic patient’s system and yet protect the encapsulated cells from attack by the immune system.

“What I’m doing is determining how that encapsulation matrix affects the oxygen supply to the islet cells, because those cells are extremely oxygen dependent,” says Datta. “What the capsule does is block out attacks from the immune system but allows the flow of necessary nutrients, oxygen, nitrogen, and water through the matrix into the islet cells.”

Besides diabetes, the cell-encapsulation technique also offers enormous potential for the treatment of many other diseases, such as atherosclerosis and cancer. Encapsulated cell systems, in which immobilized cells are protected within a biomaterial, can be implanted strategically into a patient after being engineered to do any number of health-giving or life-saving jobs.

“The capsules I’m working with right now are about 800 microns in diameter, which is a little bit larger than a grain of sand,” says Datta. “They feel like tiny plastic pellets between your fingers.”

Type 1 diabetes is an autoimmune disease in which the immune system attacks pancreatic beta cells, a subset of the islets of Langerhans that produce insulin. Datta is working in the research group of Professor Susan Roberts of the Chemical Engineering Department, a team that has developed cell encapsulation techniques specifically for cells with high oxygen demand, such as islets. The Roberts team employs a polymer known as alginate as an encapsulation matrix due to its high water content and ability to provide transplanted cells with a protective barrier from mechanical stress and immune rejection.

But alginate also inhibits oxygen from the blood stream from reaching the encapsulated cells. “If you just imagine a piece of Saran Wrap separating one part of a room from another,” explains Datta, “you would assume that oxygen wouldn’t be able to pass through that plastic barrier, even if it’s permeable, as easily as if it weren’t there at all.”

To overcome hypoxic conditions, the Roberts team has performed what Datta calls “a little trick,” incorporating oxygen vectors in the alginate matrix to facilitate the spread of oxygen to the encapsulated cells.

“These vectors allow oxygen to diffuse farther into the alginate,” says Datta. “The vectors permit more oxygen to reach the encapsulated islet cells than if there were just an alginate matrix.”

The goal of Datta’s research is to design a bioreactor that can accurately measure the oxygen consumption rates of encapsulated islets and other cell types with a high oxygen demand. After her new bioreactor is set up and tested, she’ll use it, among other tests, to analyze the oxygen intake of encapsulated HepG2, an immortalized liver carcinoma cell line, which behaves a lot like islets but is a lot easier to access and maintain in culture. Later, when she’s certain her whole testing process is working effectively, she’ll assess how much oxygen reaches much harder-to-harvest rat islets after they’re encapsulated in the alginate/oxygen vector matrix.

Eventually, encapsulated islets can be introduced into the human pancreas in two ways. One is minor surgery, in which surgeons implant the capsule into vascularized tissue. The other way of introducing the encapsulated islets is by injecting capsules directly into the pancreas with a long needle.

“This is a very important research project that could do type 1 diabetics a lot of good, including saving lives,” concludes Datta. “Everyone on the team is important. My part of the project is vital. If you don’t know the amount of oxygen made available to the islets, I mean, you can’t do anything. You can’t go forward with the project. It feels really nice to have that kind of responsibility as just an undergrad.”

Datta’s project will serve as her senior capstone thesis for the Commonwealth College honors program at the university. (January 2010)