SU-8-based immunoisolative microcontainer with nanoslots defined by nanoimprint lithography

Cells can secrete biotherapeutic molecules that can replace or restore host function. The transplantation of such cells is a promising therapeutic modality for the treatment of several diseases including type 1 diabetes mellitus. These cellular grafts are encapsulated in semipermeable and immunoisolative membranes to protect them from the host immune system, while allowing the transport of nutrients and small molecules that are required for cell survival and function. The authors report on SU-8-based biocompatible immunoisolative cuboid microcontainers for cell transplantation. Each microcontainer comprises a 300×300×250 or a 1100×1100×250 microm(3) SU-8 hollowed cuboid base that houses the cells and an optically transparent SU-8-based nanoporous lid that closes the device. The hollowed cuboid base was formed by conventional optical lithography to have 8 nl (200×200×200 microm(3)) encapsulation volume for cellular payload. The lid comprises a thick SU-8 slab with an array of cylindrical wells, whose bottom surface is sealed with a thin nanoporous SU-8 membrane. The nanoporous membrane was created from a 100 nm grating (width and spacing) initial silicon mold subjected to a repeated cycle of oxidation and wet etching to achieve a 20 nm wide and 200 nm pitch nano silicon grating. Nanoimprinting and oblique-angle metal deposition, followed by inductively coupled plasma etching were utilized to create 15 nm wide and 350-450 nm deep nanoslots in the thin SU-8 membrane. Isolated mouse islets were encapsulated in the hollowed cuboid base and the nanoporous lid was assembled on top. The penetration of large and small molecules into the microcontainer was observed with fluorescence.