Pluronic F127, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer is a representative material for showing reversible sol-gel transition by temperature change. This behavior is achieved by micelle packing mechanism above critical gelation concentration. Micelle structure is obtained around 15 C and more micelles are formed as temperature increases because each blocks have different low critical solution temperature. This thermoreversible hydrogel has attractive characteristics for therapeutic agent delivery carriers due to its high water contents and similar mechanical property like the extracellular matrix. However, it has limitation for using in clinical application due to its low stability.
To overcome the critical drawback of Pluronic F127 hydrogel, the host-guest interaction was utilized to enhance packing ability of micelles. Due to strong host-guest interaction, it was possible to achieve highly improved mechanical stability. However, the viscosity of the blended solution was too high for injection due to existing strong host-guest interaction at injection condition (at 4 C). Thus, the system was still hard to deliver therapeutic proteins and cells.
To maintain long-term stability of hydrogel and improve injection ability, multi-guest molecules were conjugated at the end of Pluronic F127 for strengthening the micelle packing while reducing the number of polymers needed. Because of increased host-guest complex at a reduced concentration, critical gelation concentration of blended solution decreased comparing with conventional Pluronic F127 hydrogel and mono guest conjugated F127 hydrogel system. As a result, the viscosity of the injectable condition largely decreased comparing with the conventional method and the high stability was achieved in the physiological condition. In addition, this host-guest interaction based gel system enabled affinity based protein release. Host molecule modified protein showed sustained protein release profile in this system. Consequently, multi-guest conjugated Pluronic F127 hydrogel which has overcome its limitations while maintaining existing merits is expected to be used for various biomedical application