Effect of molecular mass of methoxypoly(ethylene glycol) activated with succinimidyl carbonate on camouflaging pancreatic islets.

The surface modification of Langerhans islets by grafting activated poly(ethylene glycol) on to their capsules in order to prevent immune-system stimulation is a novel method in diabetes cell therapy. In the present study, mPEG [methoxypoly(ethylene glycol)] with two molecular masses of 5 and 10 kDa, activated with SC (succinimidyl carbonate), was grafted on to the surface of pancreatic islets at a polymer concentration of 22 mg/ml. It was found that PEGylated islets were viable and active, and no morphological changes on the collagen capsule of islets were observed. The amount of interleukin-2 secretion from lymphocytes co-cultured with islets PEGylated with mPEG-SC of 5 and 10 kDa was 112.12 ± 23.09 pg/ml and 172.75 ± 27.94 pg/ml respectively. Thus mPEG-SC (SC-activated mPEG) with higher molecular mass was more suitable for camouflaging islets from the immune system.