A route towards immune protection

This work describes a route towards an immune protective device for islet of Langerhans transplantation. We developed a protocol to use MIN6 β cells aggregates as pseudo-islets to overcome the donor shortage issue (chapter 3). In this thesis we explored two different immune protective strategies; a multibore hollow fiber and flat microwell membranes. In chapter 4 we investigated the possibility to use a commercial multibore hollow fiber. In this chapter we showed that we were capable to physically separate islets using agarose macrospheres. Photoacoustic imaging in chapter 5 confirmed these findings. The flat membrane microwell device was developed based on work of Buitinga et al. (1) who developed a poly(ethylene glycol terephthalate)-poly(butylene terephthalate) (PEOT/PBT) microwell scaffold, made by micro thermoforming of dense thin films. We developed a microwell device that consisted of a thin PES/PVP membrane for islet encapsulation and a 0.45μm pore sized PES lid (chapter 6). These membranes were sealed prior to seeding by a custom made seal device. Encapsulated human islets were still responsive to glucose stimulation after 7 days of culture. As a lack of proper vascularization after transplantation and thereby hypoxia is a major contributor to islet death, we studied solutions to overcome this issue. In chapter 7 we showed that micropatterned membranes in combination with MSCs could be used to enhance vascularization in vivo. Finally, we combined the oxygen generating materials of Pedraza et al. (2) with the microwell membrane device of chapter 6 in chapter 8. We showed, similar to Pedraza et al. that the oxygen generating disk had a positive effect on islet viability and function. In this thesis we took the first steps towards an immune protective device, although successful in many aspects additional work is needed to further optimize the devices developed in this work. Therefore in chapter 9 an outlook is presented of different options in order to reach a functional immune protective device for islet encapsulation.