No abstract

Modifying the surface of living cells with specially selected polymers is a new method of protecting them from the immune system. Covalent attachment of polyethylene glycol (PEG) derivatives on the capsule of pancreatic islets in aqueous media under moderate conditions is an example. This study aimed to find out whether higher polymer concentration could protect PEGylated islets from immune systems more efficiently without affecting their viability and morphology. Methoxy polyethylene glycol succinimidyl carbonate (mPEG-SC) with molecular weight of 5 kDa at different concentrations was grafted onto islets capsules. It was found that at polymer concentrations higher than 22 mg/mL, islets lost their viability with changes in their surface structure as compared to free islets. At mPEG-SC concentrations less than 22 mg/mL, there was no change in morphology and viability of PEGylated islets, but PEGylation of islets at polymer concentration 7 mg/mL was not sufficient for their camouflaging. Polymer concentration of 22 mg/mL was more effective in weakening the immunogenicity of islets. It was concluded that increasing the 5kDa mPEG-SC concentration up to 22 mg/ml protected islets from the immune cells more efficiently without affecting their viability and functionality.

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.