Prolongation of graft survival via layer-by-layer assembly of collagen and immunosuppressive particles on pancreatic islets.

Pancreatic islet transplantation holds great potential as a curative therapy for treating type 1 diabetes. However, the need for lifelong systemic immunosuppression with inevitable side effects is an obstacle to clinical success. Here we devised a strategy for the site-specific delivery of an immunosuppressant (tacrolimus) using layer-by-layer assembly of polymeric particles and collagen on the islet surface. This approach aims to provide a continuous and sustained supply of tacrolimus in the vicinity of transplanted cells while avoiding systemic drug exposure. The dose and release rate of tacrolimus can be tunable to achieve therapeutic windows by varying layer-by-layer construction and chemistry of polymers. Transplanting 400 IEQ of pancreatic islets coated with particles containing ∼3 μg of TAC per recipient provided controlled drug release and rectified diabetes for up to 5 months in a xenogeneic rodent model of type 1 diabetes. We anticipate that the findings of this study will be found useful by those developing local immunomodulation strategies aimed at improving the outcomes and safety of cell therapies for curing type 1 diabetes.