Diffusional characteristics of freeze/thawed poly(vinyl alcohol) hydrogels: applications to protein controlled release from multilaminate devices.

The incorporation of a model protein, bovine serum albumin (BSA), into poly(vinyl alcohol) (PVA) hydrogel films during the freezing and thawing process and its subsequent release behavior were investigated. The effect of the number of freezing and thawing cycles as well as the stability of BSA were examined. BSA release profiles were not significantly different from gels prepared after 3 or 5 cycles. However, the rate and overall amount of PVA dissolution were considerably higher for gels prepared after 3 cycles. These observations were then applied to the development of novel, freeze/thawed PVA laminates. Laminates containing gel layers prepared after 3 or 5 cycles were successfully prepared with good stability over a 6 month swelling period. These structures, containing distinct layers of very specific properties, could be used to achieve zero-order release behavior.