Interpenetrating polymer networks of alginate and polyethylene glycol for encapsulation of islets of Langerhans

A mixture of alginate and polyethylene glycol acrylate was investigated as a system for the encapsulation of islets of Langerhans. This system showed dual crosslinkability: the alginate was ionically crosslinked by multivalen t cations, and the PEG was covalently crosslinked by photoactivated free ra dical polymerization. The major advantage of the dually crosslinkable syste m was the chemical stability of the resultant gels due to the presence of c ovalent bunds that maintain the integrity of the gel as opposed to reversib le ionic linkages that were the only mode of crosslinkage in previous gener ations of alginate-based encapsulation systems. The physical aspects of gel ation of such alginate/PEG compositions were investigated. Diffusion of dex trans of known molecular weights through these gels was studied in order to shed light on the hydrogel porosity and permeability. In vitro viability a nd function tests demonstrated that these gels were biocompatible. Islets e ncapsulated in these systems were healthy and retained both viability and i nsulin secretory function.