Abstract. Studies of swelling and release of naproxen sodium (NAP) solution by polyurethane nanocomposite hydrogels containing Cloisite 30B (organically modified montmorillonite (OMMT)) have been performed. Polyurethane nanocomposite hydrogels are hybrid, nontoxic biomaterials with unique swelling and release properties in comparison with unmodified hydrogels. These features enable to use nanocomposite hydrogels as a modern wound dressing. The presence of nanoparticles significantly improves the swelling. On the other hand, their presence hinders drug diffusion from polymer matrix and consequently causes delay of the drug release. The kinetics of swelling and release were carefully analyzed using the Korsmeyer-Peppas and the modified Hopfenberg models. The models were fitted to precise experimental data allowing accurate quantitative and qualitative analysis. We observed that 0.5% admixture of nanoparticles (Cloisite 30B) is the best concentration for hydrogel swelling properties. The release process was studied using fluorescence excitation spectra of NAP. Furthermore, we studied swelling hysteresis; polymer chains have not been destroyed after the swelling and part of swelled solution with active substances which remained absorbed in the polymer matrix after the drying process. We have found that the amount of solution with NAP remained in the nanocomposite matrix is greater than in pure hydrogel, as a consequence of NAP-OMMT interactions (nanosize effect).

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Polyurethane hydrogels are potentially attractive materials for biomedical applications. They are able to absorb large amount of water, biological fluids or active substances, and thus, they have potential to be used as absorbents or wound-healing dressings. They are also used for the controlled release of therapeutics because of their capacity to embed biologically active agents in their water-swollen network. The presence of organofillized montmorillonite (Cloisite® 30B) in polyurethane nanocomposite hydrogels remarkably improves the swelling capability, but on the other hand slows down the release process of an active substance from the matrix. The swelling of paracetamol solution by the nanocomposite matrix and the release process of this active substance from the hydrogel were investigated using gravimetric analysis and spectroscopic method. The kinetics of both these processes were accurately analyzed by the use of Korsmeyer-Peppas and modified Hopfenberg and Weibull models. In the present paper, three different nanocomposite systems with various amounts of Cloisite® 30B were studied. The results of these studies confirm beneficial impact of the nanosize effect on the drug diffusion processes in polyurethane nanocomposite hydrogels.