2.2. Preparation of Micelles

A simple thin-film rehydration method was used to prepare micelles of Pluronic F127 and Cremophor EL. The procedure is schematically presented in the Figure 1.

Schematic representation of the obtaining procedure for the Norfloacin loaded Pluronic F127—Cremophor EL mixed micelles.

Suitable amounts of surfactants or surfactant mixtures were dissolved in ethanol in a round-bottom flask. The vial was attached to a rotatory evaporator (Rotavapor-R-300^®, Buchi Labortechnik AG, Flawil, Switzerland) and heated at 45 °C under vacuum to produce a thin film of micelle forming material deposited on the walls. After the total removal of the solvent, the required volume of distilled water was added to rehydrate the film under moderate magnetic stirring at 45 °C, for 30 min. The as prepared micellar dispersion was further filtered through sterile syringe filter Minisart^® 0.2 µm (Sartorius, Gottingen, Germany). For the mixed micelles, the two surfactants were added in ethanol solvent to obtain molar ratio 0.2, 0.4, 0.6 and 0.8 in the final aqueous dispersions.

The drug loaded pure and mixed micelles were prepared following the same procedure and Norfloxacin was dissolved together with the polymeric surfactants in alcohol. The dissolution of the Norfloxacin in the deposited thin film before the rehydration step ensure the maximum solubilization of the drug inside the micelle core.