Abstract: Apparatus is provided which includes a housing, configured for insertion into a body of a subject. The apparatus includes functional cells coupled to the housing and a source of oxygen configured to supply oxygen to the functional cells. The apparatus further includes an oxygen delivery interface configured to receive oxygen from the source of oxygen, and to facilitate passage of the oxygen to the functional cells, while the housing is disposed within the body of the subject. Other embodiments are also described.

Abstract: Apparatus is provided, including a housing (60), configured for insertion into a body of a subject, one or more photosynthetic oxygen supplies (24), disposed within the housing (60), and at least one layer (70 and 74) of functional cells, disposed within the housing (60). The at least one layer (70 and 74) of functional cells is configured to receive oxygen from the one or more oxygen supplies (24). The housing (60) also includes a gas (40 and 43) configured to permit passage therethrough of the oxygen from the one or more oxygen supplies (24) to the cells (70 and 74). The gas (40) is disposed at least in part between the layer (70 and 74) of functional cells and at least one of the oxygen supplies (24). Other embodiments are also described.