Preparation and characterization of scleroglucan drug delivery films: The effect of freeze‐thaw cycling

This study examined the effect of the freeze‐thaw process on the physical properties of films prepared from scleroglucan (Scl) hydrogels, suitable for drug delivery applications. Films made from Scl, using glycerol as plasticizer, were prepared from hydrogels by two procedures: a room temperature drying (RTD) method and a freeze‐thaw cyclic process, before the application of RTD, which results in a reinforced physically cross‐linked network. Films were characterized by studies of water vapor transmission (WVT), swelling, tensile tests, ESEM microscopy, FTIR, and drug release measurements. These determinations showed significant differences between films obtained by both treatments. The films prepared through freeze‐thaw cycles showed an important increase of the tensile strength with respect to those corresponding to films only air dried and a decreasing swelling degree in direct relationship to the number of freeze‐thaw cycles. A model drug, Theophylline, was included in these biocompatible films for in vitro drug release measurements, using a flat Franz cell. The physical differences observed between Scl films prepared with both methods can be explained proposing that the number of crosslinking points by hydrogen bonding increase when increasing the number of freezing and thawing cycles used for film preparation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009