Characterisation and controlled drug release from a novel two-phase hydrogel system

In this work, a two-phase hydrogel system was prepared by physically imbedding a xerogel in the core of a cryogel which was freeze thawed. The cryogels were prepared with poly (vinyl alcohol) (PVA) and poly (acrylic acid) (PAA) while the xerogels were prepared by UV polymerisation of 1-vinyl-2-pyrrolidinone (NVP), acrylic acid (AA) and various percentages of ibuprofen sodium salt. Mechanical and thermal properties were determined by parallel plate rheometry and differential scanning calorimetry (DSC). The results indicated that hydrogels which contained increased percent concentrations of PAA (in the xerogel) were significantly stiffer than those synthesised using PVP alone at test temperatures between 30 and 80°C. The chemical structure of the hydrogels was confirmed by means of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). In all cases, drug dissolution analysis showed that the active agent was released at a slower rate with hydrogels that contained acrylic acid.