Ws. Dai et Ta. Barbari, Hydrogel membranes with mesh size asymmetry based on the gradient crosslinking of poly(vinyl alcohol), J MEMBR SCI, 156(1), 1999, pp. 67-79
Poly(vinyl alcohol) (PVA) hydrogel membranes with mesh size asymmetry were
prepared and their transport properties were studied. Homogeneous membranes
with water contents of 82%, 76% and 72% were prepared by crosslinking PVA
with glutaraldehyde. These membranes were then modified to create asymmetry
by establishing a glutaraldehyde concentration gradient across the hydroge
l thickness. The reaction time and magnitude of the glutaraldehyde concentr
ation gradient were varied to determine the optimum values of permeability
and selectivity. Permeation experiments with creatinine, Fab and IgG were p
erformed in a stirred diffusion cell through homogeneous and asymmetric PVA
hydrogels. A modified version of the multiple-membrane technique was used
to determine boundary layer resistance in order to determine the intrinsic
membrane permeability. As expected, the selectivity of creatinine over IgG
increased as the modification time increased. However, the selectivity of F
ab over IgG initially increased as the modification time increased, but the
n decreased at longer times, indicating that the increased crosslinking at
the surface effectively blocks both proteins. At a given value of IgG rejec
tion, the asymmetric membranes had higher creatinine and Fab permeabilities
than the corresponding homogeneous membranes. This indicates that creating
mesh size asymmetry in a hydrogel can result in a high-Bur, high-selectivi
ty membrane for cell encapsulation or bioseparations. (C) 1999 Elsevier Sci
ence B.V. All rights reserved.