Biocompatible nanomatrices composed of peptide amphiphiles are provided for the embedding of cell populations for their implantation into a recipient animal or human. To confine the nanomatrix to a site of implantation, the nanomatrix can be encapsulated in a nanofiber sack formed from an electrospun nanofiber sheet. The nanofiber sheets are porous and have surface indentations that promote the vascularization of the implant, thereby maintain the viability and biofunctions of the cells, as wells as delivering cell-product products to the circulatory system to the benefit of the recipient subject. The implants may further include cell growth factors that can be beneficial to the survival of the cells as to promote angiogenesis and infiltration of the implant by new blood vessels.
