People with type 1 diabetes have to live with daily injections of insulin. As researchprogresses in this field, scientists are looking into new methods that can free, or at least partially free, patients from regular doses. One such method is pancreatic islet transplantation, something that researchers at Okinawa Institute of Technology and Science Graduate University (OIST) claim they have improved.
Current procedures involve injecting the insulin-producing islets into the liver. After an adaptation period, the cells will start producing enough insulin for the patient. The technique has advanced in recent years, but one challenging issue is the collection, preservation, and transportation of those cells, which can be damaged by sharp ice crystals during freezing and thawing.
Led by Professor Amy Shen, head of the Micro/Bio/Nanofluidics Unit at OIST, the research team, in collaboration with the University of Washington and Wuhan University of Technology, has developed a new cryopreservation method that preserves the cells without damage and makes it easier to assess their viability in real time.
The islets are encapsulated in hydrogel made from alginate, a polymer extracted from seaweed. The strong bond between water molecules and hydrogen networks prevent the formation of ice and so protects the cells from damage. As a consequence, the need for cryoprotectants, anti-freeze materials than can be toxic in higher concentrations, is reduced.
To monitor the integrity of the cells, the research team has introduced a fluorescent oxygen-sensitive dye in the hydrogel capsules. Because they are porous, the capsules do not prevent oxygen from reaching the cells. The fluorescent dye signals in real time the presence of oxygen in each cell, which indicates they are alive and healthy.
The method can also help reduce transplant rejection rates, the researchers claim. The capsules can prevent direct contact between the implanted and hosted cells, even though they are permeable enough to allow such things as nutrients and islet secretions to pass through the membrane.
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