A device containing transplanted tissue includes a housing, having a chamber configured for insertion into a body of a subject and protecting the transplanted tissue from the subjects immune system. The housing includes an oxygen supply container, a hydrogel layer, a port, and an access port. The oxygen supply container has a chamber defined by top and bottom surfaces and sides, disposed within the chamber of the housing. The top surface and the bottom surface of the oxygen supply container include a gas-permeable membrane. The hydrogel layer has inner and outer surfaces. The inner surface of the hydrogel layer contacts the top surface of the oxygen supply container or the bottom surface of the oxygen supply container. The port is configured to deliver oxygen to the oxygen supply container. The access port is configured to receive an exogenous supply of gas and is fluidly connected to the port.
