Micelles of hyaluronic acid-hexadecylamine derivatives for ocular release of hydrophobic durgs

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Abstract

The topical route is the ideal way to release drugs to the eye. Unfortunately, the low ocular drug bioavailability associated with this route of administration, makes not very efficient the treatment of several ocular diseases. Nowadays, polymeric micelles occupy a significant role in the field of ocular drug delivery thanks to the advantages that they offer in comparison with the administration of drugs in the free form. Indeed, polymeric micelles are suitable for delivering hydrophobic drugs and they seem to be very promising in ocular drug delivery for their high kinetic and thermodynamic stability. Also, micellar systems are able to give a controlled drug release and to act as absorption enhancers that can improve drug permeability across ocular epithelia [1, 2]. To this aim, the objective of this study was to obtain new hyaluronic acid-based micellar systems capable to act as solubility enhancers and as a platform to release hydrophobic drugs to the eye. Three amphiphilic copolymers of hyaluronic acid bearing side chains of hexadecylamine (C16), named HA-C16 a, HA-C16 b and HA-C16 c with a molar derivatization degree equal to 15, 12 and 7% respectively, have been synthesised and characterized. The critical aggregation concentration (CAC) values of these amphiphilic copolymers was determined in water and isotonic buffer by fluorescence technique. Micellar systems have been obtained through co-solvent evaporation method and they have been characterized for physicochemical properties including size and zeta potential values. Also, different mucoadhesion tests have been performed to demonstrate the affinity of prepared micelles towards mucin. All HA-C16 derivatives have shown the ability of self-assembling in aqueous media and resulted potentially useful for encapsulating and dissolving hydrophobic drugs. In particular, dexamethasone and triamcinolone loaded micelles have been prepared and characterized using HA-C16 a, HA-C16 b and HA-C16 c copolymers. In vitro drug release studies have been carried out until 48 hours and results have demonstrated that micellar systems modulate drug release. At last, studies of cytocompatibility performed with human corneal epithelial cells (HCECs), have demonstrated that the prepared systems do not cause toxic effects.
Original languageEnglish
Publication statusPublished - 2016

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