Macroencapsulation of rat islets without alteration of insulin secretion kinetics

Transplantation of encapsulated islets may restore endogenous insulin secre tion in type 1 diabetics with no need of lifetime immunosuppression of the recipient. A biomaterial should be developed which combined immunoisolation with rapid and efficient diffusion of glucose and insulin. Rat islets were macroencapsulated in capillaries (molecular cut off 50 kD) of differently modified polysulphone. Macroencapsulated islets were perifused to study the kinetics of glucose induced insulin secretion into the perifusion medium. Blending polysulphone (PSU) with poly vinyl pyrrolidone or sodium dodecyl. sulphate was not suited for islet macroencapsulation since glucose induced insulin release was absent after encapsulation. Hydroxy methylation (CH2OH) of PSU improved the secretory behaviour of macroencapsulated islets depend ing on the degree of substitution (DS). At 0.8 DS glucose induced insulin s ecretion was delayed and inefficient. At maximal degrees of PSU-substitutio n (1.8) the kinetics of insulin release and the efficiency of insulin relea se were very similar to that observed of free floating islets. In conclusio n, highly substituted hydroxgy methylated polysulphone allows a rapid and e fficient insulin release after macroencapsulation and is suited for the fur ther development of a bioartificial pancreas.