Amphiphilic poly(caprolactone--hydroxyethyl acrylamide) micelles for controlled drug delivery.

To increase the bioavailability and water solubility of hydrophobic medicine, an amphiphilic block copolymer, polycaprolactone--polyhydroxyethyl acrylamide (PCL--PHEAA), was synthesized. The copolymer can self-assemble into micelles by dialysis. The micelles were characterized by the Tyndall effect, static drop method, fluorescence spectrometry, dynamic light scattering, scanning electron microscopy and transmission electron microscopy. Ibuprofen was encapsulated inside the micelles by dialysis as a model medicine. The results show that the amphiphilic copolymer forms a uniform micelle system, with spherical micelles dispersed well in solution which have a low critical micelle concentration. In addition, the system shows good amphipathic behavior. Average particle size of a micelle is 104 nm, which increases a lot after drug loading and standing for half a month. In the first few hours, the cumulative release of the drug increases gradually; the rate of increase in the first ten hours is faster, then reaching a plateau which tends to be flat finally. It is similar under two different pH conditions. This biocompatible, biodegradable amphiphilic block copolymer has potential applications in the biomedical field.