2011 - IPITA - Prague


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Parallel session 7 – Open mini-oral presentations Topic: Islet transplantation: Technical aspects

7.9 - Microencapsulation of the pancreatic islet within biofunctional GLP-1/PEG hydrogel

Presenter: I., Ergenc, Istanbul, Turkey
Authors: I. Ergenc, N. Marek, A. Krzystyniak, O. Cochet, C. Nazli, P. Trzonkowski, J.M. Millis, S. Kizilel, P. Witkowski


Microencapsulation of the pancreatic islet within biofunctional GLP-1/PEG hydrogel

I. Ergenc1, N. Marek2, A. Krzystyniak2, O. Cochet2, C. Nazli2, P. Trzonkowski2, J.M. Millis2, S. Kizilel1, P. Witkowski2
1 Koç University, Istanbul, Turkey; 2 University of Chicago, Surgery, Chicago, USA

Objective: Islet encapsulation as a method of immunoseparation was developed in order to immunoprotect islets after transplantation without need for toxic immunosuppresion. However, traditional technology provides capsules, which are too big to be applied intraportally and/or have too thick wall, which compromises fluid exchange and islets survival. The goal of the study is to test feasibility of a novel technology to create ultrathin microcapsule containing biofunctional molecule (GLP-1) and its influence on islet cell viability and function.

Method: Semipermeable poly(ethylene glycol) (PEG) hydrogels membranes were created around single islets applying eosin-Y and the argon-ion laser for surface initiated photopolymerization. Thickness of the capsule was 40microm. In order to additionally improve islets function active fragment of Glucagon-Like Peptide-1 (GLP-1) (7-37) was incorporated into the capsule wall. In controls, inactive GLP-1 fragment (9-37) was used instead. Islets function was evaluated in insulin release assays-static incubation as well as in dynamic perifusion.

Results: Integration of the GLP-1 into PEG hydrogel was confirmed in the FITR spectrophotometry. Application of microencapsulation did not affect islet viability (FDA/PI >96%) and function. Islets in microcapsules containing active GLP-1 fragment (7-37) or inactive (9-37) or no GLP were responding properly, without delay with insulin release according to changing glucose concentration in dynamic perifusion assay comparing to unmodified islets. In addition, PEG hydrogel coated islets containing active GLP-1(7-37) secreted 17-fold more insulin in response to high glucose comparing to low glucose solution, whereas these ratios were 2.4 and 2.7for inactive GLP-1(9-37) coated islets and non-capsulated islets.

Conclusions: Application of PEG hydrogel microencapsulation does not compromise islet viability or function. Additionally, incorporation of the active GLP-1 significantly improves islet function. For the first time, single islet ultrathin microcapsules was created with biofunctional molecule incorporated, which has a great potential for clinical applications.


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