Solubilization of Ibuprofen in Pluronic Block Copolymer F127 Micelles

We studied the effect of Pluronic F127 micelle solution on the solubility of ibuprofen (IBU). The critical micelle concentration (cmc) of F127 in both water and 0.01 mol.L-1 pH 7.4 phosphate buffer salt (PBS) solution at different temperatures was determined by the pyrene fluorescence method. The concentration of the solubilized IBU was determined using high-performance liquid chromatography (HPLC). We calculated the solubility descriptors (molar solubilization capacity, chi, and micelle-water partition coefficient, K). The influences of temperature, medium properties, and additional copolymer F68 on the micellization of F127 and the solubilization of IBU were also investigated. The results showed that the solubility of IBU increased linearly with an increase in the F127 mass fraction. With an increase in temperature, a significant decrease in the cmc was apparent and a less polar microenvironment was present in the micelle core. Slight increases in chi and K were found with an increase in temperature. The cmc of F127 in PBS solution was much less than that in water, chi was essentially the same and K decreased significantly in PBS solution. F127 micelle property and the solubilization capacity of the F127 micelles were only slightly affected in the presence of F68. An analysis of the solubility descriptors indicates that the K is particularly unique for the drug IBU, and the chi is useful in determining the solubility effectiveness of copolymer F127. We also demonstrated that IBU was predominantly in the micelle core and core-corona interface.