Abstract
Poly(vinylpyrrolidone) (PVP) hydrogels were crosslinked by gamma irradiation to add structure and rigidity, and then rheological and mucoadhesive properties were evaluated. The effects of PVP concentration, radiation dose, and additives, such as poly(ethylene glycol) (PEG) and glycerol, on rheological properties were investigated. In an oscillatory analysis, an increase in polymer concentrations increased the storage modulus (G') and the loss modulus (G") but decreased the loss tangent (tan delta < 1). The relationships between G' or G" and the frequency levelled off at higher frequencies, which is indicative of polymer chain entanglement and network formation. Each of the 6% PVP hydrogels exhibited plastic flow with rheopectic behavior. PVP concentration, radiation dose, and the presence of PEG or glycerol influenced the rheological and mucoadhesive properties of the hydrogels. However, adding acyclovir to the formulation did not have a profound effect on the rheological behavior of the hydrogels. The results suggest that a 3% PVP hydrogel with 1% PEG crosslinked with 20 kGy is the most appropriate hydrogel. The results demonstrated the successful complementary application of oscillatory and flow rheometry to characterize and develop a hydrogel for mucosal drug administration.