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This article describes the swelling and release mechanisms of paracetamol in polyurethane nanocomposite hydrogels containing Cloisite® 30B (organically modified montmorillonite). The transport mechanism, swelling and release processes of the active substance in nanocomposite matrix were studied using gravimetric and UV-Vis spectroscopic methods. Swelling and release processes depend on the amount of clay nanoparticles in these systems and the degree of crosslinking of PU/PEG/Cloisite® 30B hydrogel nanocomposites. The presence of clay causes, on the one hand, a reduction in free volumes in the polymer matrices, making the swelling process less effective; on the other hand, the high swelling and self-aggregation behavior of Cloisite® 30B and the interactions of paracetamol both with it and with the matrix, cause a change in the transport mechanism from anomalous diffusion to Fickian-like diffusion. A more insightful interpretation of the swelling and release profiles of the active substance was proposed, taking into account the "double swelling" process, barrier effect, and aggregation of clay. It was also proven that in the case of modification of polymer matrices with nanoparticles, the appropriate selection of their concentration is crucial, due to the potential possibility of controlling the swelling and release processes in drug delivery patches. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]