The influence of freeze-thawing conditions on swelling and long-term stability properties of poly(vinyl alcohol) hydrogels for controlled drug release

Abstract

The preparation of poly(vinyl alcohol) (PVA) hydrogels was succeeded via the freeze-thawing (F/T) method by varying the synthesis parameter conditions. The swelling capacity and long-term stability of the hydrogels were determined as a function of time at pH 2.1, 5.5 and 7.4 and found to be mainly affected by the synthesis parameter conditions. These studies showed that the swelling ratio generally increased with a low number of F/T cycles (2 and 3), high freezing temperature (- 5 and - 16 degrees C) and freeze-dried of drying type for all three pH mediums. The dried hydrogels at room temperature were found to be more stable hydrogels. In addition, the drug release studies of salicylic acid as a drug model were investigated at pH 7.4 and displayed controlled release for 120 h. The release kinetic studies obtained from drug release data demonstrated that the PVA hydrogel fits well into the Higuchi model. The release mechanism of PVA hydrogel was also determined as super case II type.