Effect of polymer concentration on camouflaging of pancreatic islets with mPEG-succinimidyl carbonate

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.