Third-generation arnphiphilic conetworks. III. Permeabilities and mechanical properties

While two of our earlier papers on poly(dimethyl acryl amide)/polymethylhydrosiloxane/polydimethylsiloxane (PDMAAm/PMHS/PDMS) amphiphilic conet-works concerned synthesis and biological properties, respectively, the present contribution focuses on oxygen and insulin permeabilities, and select mechanical properties. We show that by increasing the PDMA-Am content from 20 to 60% (i.e., by decreasing the hydrophobic content from 80 to 40%), oxygen permeabilities decrease from similar to 240 to similar to 130 barrers. Evidently, oxygen permeability is a function of the sum of the oxyphilic components, PDMS + PMHS, in the conetworks. In contrast, insulin permeability is a function of the hydrophilic component, and reaches a desirable 1.5 x 10(-7) cm(2)/s at 61% PDMAAm. We also studied the permeabilities of glucose, dextran, and albumin through a PDMAAm(61)/PMHS(6)/PDMS(33) membrane and found, unsurprisingly, that the permeability of these molecules follows their hydrodynamic radii, and we project that the permeability of IgG is infinitesimally low. Tensile strengths and ultimate elongations of water-swollen membranes are also a function of conetwork composition: by increasing the PDMAAm content from 30 to 60%, strengths decrease from 1.6 to 1.2 MPa, and elongations from similar to 60 to similar to 40%. Overall, the permeabilities and the mechanical properties of these membranes are appropriate for implantation and, specifically, for immunoisolation of living tissue. (c) 2007 Wiley Periodicals, Inc.