This paper presents some findings from the rheological and drug dissolution characterizations of hyaluronic acid (HyA)-based colloidal drug delivery systems. During this investigations the widely applied, non-steroidal, anti-inflammatory ketoprofen (KP) has been used as model drug. For the moderation of the hydrophilic character of HyA and encapsulation of the hydrophobic drug the cross-linked derivatives at different cross-linking ratio have been synthesized. To achieve the increasing encapsulation efficiency, the hydrophobized variants of HyA have also been prepared in aqueous medium by modifying the structure with positively charged cetyltrimethylammonium bromide (CTAB) at different polymer/surfactant mass ratios. It was established that the original coherent gel-like structure of the hydrophilic and well-solvated polymer chains change into an incoherent colloidal system due to modifications that were verified by rheological investigations. Taking into account the dissolution profiles of covalent and ionic systems it can be concluded that nearly 70% of the encapsulated KP molecules dissolve from the totally cross-linked HyA systems after 8h, while the dissolved amount of KP is about 20% from the surfactant modified colloidal system at near 1:1 molar ratio. It was also established that increasing the amount of surfactant the drug release turns to diffusion and erosion controlled way. It has been confirmed that the ionically modified HyA may be a potential candidate for controlled drug release of KP.Keywords: Hyaluronic acid, ketoprofen, encapsulation, controlled drug release
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