Injectable gel: Poly(ethylene glycol)-sebacic acid polyester

In order to develop an injectable material for drug delivery that has both formulation advantages of a sol-to-gel transition system and minimal burst release of a drug, a soft thermogel of poly(ethylene glycol)-sebacic acid polyester was synthesized. The polymer aqueous solution (25 wt%) undergoes 'clear sol-to-gel' transition as the temperature increases from 5 to 65 °C. The drug can be mixed in a low viscous sol state at low temperature (<15 °C). In particular, the thermogel is soft enough to be injected through a 21-gauge syringe needle even as a gel state. The model hydrophilic drug, FITC-dextran (molecular weight: 40,000 Da), was released from the gel over 24 h. The biodegradable poly(ethylene glycol)-sebacic acid polyester soft thermogel is believed to be promising for the hydrophilic drug delivery where an initial burst of a drug might be a concern.