Concentration of a microemulsion influences the mechanical properties of ibuprofen in situ microgels.

The aim of this study was to develop an ibuprofen microemulsion (IBU-ME) incorporated into in situ gels (microgels) for local delivery into periodontal pockets. The IBU-ME was prepared at a concentration of 1% w/v IBU. Various concentrations of the thermosensitive Pluronic® F127 (P127) solution and a series of combinations of the P127 solution and IBU-ME at a 1:1 ratio were initially developed and tested to determine their sol-gel transition temperatures (Tsol→gel). Based on these studies, a constant concentration of P127 (11.1% w/v) and variable concentrations of IBU-ME were used to prepare the microgels. The mechanical properties (Tsol→gel, gelling time (Tgel), viscosity, and viscoelastic properties) of the microgels were evaluated. The release of IBU from the microgels was determined in vitro. Rheological stability studies were performed to investigate the mechanical properties of the microgels after one month. The transition behavior studies demonstrated that the microgels are thermosensitive systems with pseudoplastic flow and their viscoelastic properties indicated that the elastic property was greater than the viscous property (G' > G″). The results showed that the mechanical properties of the microgels depend on the concentration of IBU-ME. In addition, rheological stability studies demonstrated that Tgel and Tsol→gel are increased after one month, whereas the viscosity and viscoelastic properties are decreased after one month. Owing to the rigid structure of the microgels, the release of IBU from the microgels followed a controlled-release pattern.