Sustained release of ibuprofen from polymeric micelles with a high loading capacity of ibuprofen in media simulating gastrointestinal tract fluids

Amphiphilic diblock copolymers with poly(ethylene glycol) as the hydrophilic block and a random copolymer of n-butyl methacrylate or styrene and (N,N-diethylamino)ethyl methacrylate as the hydrophobic block were prepared by atom transfer radical polymerization (ATRP). Ibuprofen, a model drug that contains a carboxylic group and hydrophobic moiety, was loaded into micelles formed from the amphiphilic diblock copolymers by a combination of ionic interaction and hydrophobic effect. The loading capacity of ibuprofen in the micelles reached 60%. Loaded ibuprofen was released in a sustained fashion into media simulating gastric fluid (pH 1.6, 2 h), small intestinal fluid (pH 7.4, 4 h), and colon fluid (pH 6.7, 18 h). Simulating the case of oral administration at 2 doses per day, loaded ibuprofen was released almost linearly against time after the second dose in media simulating human gastrointestinal tract fluids.