A novel macroencapsulating immunoisolatory device: the preparation and properties of nanomat-reinforced amphiphilic co-networks deposited on perforated metal scaffold

This paper describes the design and preparation of the non-biological components (the hardware) of a conceptually novel bioartificial pancreas (BAP) to correct diabetes. The key components of the hardware are (1) a thin (5-10 mu m) semipermeable amphiphilic co-network (APCN) membrane [i.e., a membrane of cocontinuous poly(dimethyl acryl amide) (PDMAAm)/polydimethylsiloxane (PDMS) domains cross-linked by polymethylhydrosiloxane (PMHS)] expressly created for macroencapsulation and immunoisolation of a tissue graft; (2) an electrospun nanomat of PDMS-containing polyurethane to reinforce the water-swollen APCN membrane; and (3) a perforated hollow-ribbon nitinol scaffold to stiffen and provide geometric stability to the construct. The reinforcement of water-swollen hydrogels with an electrospun nanomat is a generally applicable new method for hydrogel reinforcement. Details of device design and preparation are discussed. The advantages and disadvantages of micro- and macro-immunoisolation are analyzed, and the requirements for the ideal immunoisolatory membrane are presented. Burst pressure, and glucose and insulin permeabilities of representative devices have been determined and the effect of device composition and wall thickness on these properties is discussed.