OICC Press Progress in Biomaterials 2194-0517 2 1 (December 2013) 2013 03 09 Optimization of monomethoxy poly(ethylene glycol) grafting on Langerhans islets capsule using response surface method 10.1186/2194-0517-2-7 EN Hamideh Aghajani-Lazarjani Biotechnology Group, Department of Chemical Engineering, Faculty of Engineering, Tarbiat Modares University, Tehran, 1411713116, IR Ebrahim Vasheghani-Farahani Biotechnology Group, Department of Chemical Engineering, Faculty of Engineering, Tarbiat Modares University, Tehran, 1411713116, IR Sameereh Hashemi-Najafabadi Biotechnology Group, Department of Chemical Engineering, Faculty of Engineering, Tarbiat Modares University, Tehran, 1411713116, IR Seyed Abbas Shojaosadati Biotechnology Group, Department of Chemical Engineering, Faculty of Engineering, Tarbiat Modares University, Tehran, 1411713116, IR Saleh Zahediasl Endocrine Physiology Laboratory, Endocrine Research Centre, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, 3197619751, IR Taki Tiraihi Department of Anatomy, School of Medical Sciences, Tarbiat Modares University, Tehran, 1411713116, IR Fatemeh Atyabi Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, 1419733171, IR Journal Article 2013 03 09 Abstract Langerhans islet transplantation is a much less invasive approach compared with the pancreas transplantation to ‘cure’ diabetes. However, destruction of transplanted islets by the immune system is an impediment for a successful treatment. Chemical grafting of monomethoxy poly(ethylene glycol) onto pancreatic islet capsule is a novel approach in islet immunoisolation. The aim of this study was to determine an optimized condition for grafting of monomethoxy poly(ethylene glycol) succinimidyl propionate (mPEG-SPA) on islets capsule. Independent variables such as reaction time, the percentage of longer mPEG in the mixture, and polymer concentration were optimized using a three-factor, three-level Box-Behnken statistical design. The dependent variable was IL-2 (interleukin-2) secretion of lymphocytes co-cultured with PEGylated or uncoated control islets for 7 days co-culturing. A mathematical relationship is obtained which explained the main and quadratic effects and the interaction of factors which affected IL-2 secretion. Response surface methodology predicted the optimized values of reaction time, the percentage of longer mPEG in the mixture, and polymer concentration of 60 min to be 63.7% mPEG 10 and 22 mg/mL, respectively, for the minimization of the secreted IL-2 as response. Islets which were PEGylated at this condition were transplanted to diabetic rats. The modified islets could survive for 24 days without the aid of any immunosuppressive drugs and it is the longest survival date reported so far. However, free islets (unmodified islets as control) are completely destroyed within 7 days. These results strongly suggest that this new protocol provides an effective clinical means of decreasing transplanted islet immunogenicity.