Some embodiments of the present disclosure include an encapsulated islet for treating diabetes. The encapsulated islet may include a semi-permeable capsular membrane having a plurality of layers including an outer immunoprotection layer, a bridging layer, and an inner backbone layer, each layer having a plurality of pores, wherein the pores increase in size from the immunoprotection layer to the backbone layer, creating the tapered conduits. The semi-permeable capsular membrane may include the following layers, in order from outermost layer to innermost layer: an immunoprotection layer, a bridging layer, and a backbone layer. With proper balancing of membrane thickness and tapered pore size distribution, the encapsulated islets may offer a diabetes treatment or functional cure without immunosuppressive drugs.
