Release of Hydrophobic Substances from Polystyrene-Methacrylic Acid Block Copolymer Micelles into Aqueous Media

Block copolymer micelles are potential carriers for controlled-release drug delivery. In this study, the fundamental aspects of the release of a model compound from the micelles into the surrounding media were explored. A fluorescence-based technique was developed for following the release of the model compound from the cores of block copolymer micelles into aqueous media. The experimental release curves were compatible with theoretical dependences for diffusion controlled release from spherical particles. The diffusion coefficients found were of the order of 1018 cm2/s, which was expected for molecules with sizes of our probes and glassy polystyrene. The partition coefficients are also of the expected order of 105 magnitude. The fraction of the probe present outside of the cores at the start of the experiment may serve to characterize the efficiency of various procedures for the loading of various agents into the core.