Encapsulated islet transplantation is a promising therapy for Type I Diabetes Mellitus as it has the potential to extend graft lifetime and mitigate the need for immunosuppressants by preventing direct cell-cell contact between the transplanted islets and host immune cells. Efforts have been made over the past 30 years to investigate various barrier systems. Early research focused on natural polymers such as alginate-polylysine systems, however variable polymer compositions and biocompatibility issues directed the field towards synthetic polymers, such as poly(ethylene glycol) (PEG). Much work has been done with the photopolymerization of acrylate functionalized PEG hydrogel systems on both the micro- and macro- scale and cell-compatible reaction conditions have been identified for these systems.
We believe that PEG hydrogels formed via the emerging thiol-ene step-growth photopolymerization reactions are an attractive alternative to the chain-growth acrylate hydrogels and are investigating their use for islet transplantation. The step-growth reactions have more ideal network structures, allow for facile incorporation of biological moieties, are not inhibited by oxygen and form very rapidly needing less time and lower radical numbers to form a complete network. Initial work is focusing on how the differences in polymerization conditions between the acrylate and thiol-ene systems affect the encapsulated cells.