Amphiphilic biodegradable poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) triblock copolymers: synthesis, characterization and their use as drug carriers for folic acid

Amphiphilic biodegradable poly(epsilon-caprolactone)-poly(ethylene glycol)-poly (epsilon-caprolactone) (PCEC) triblock copolymers have been successfully synthesized by the ring-opening polymerization of epsilon-caprolactone (epsilon-CL) employing SnOct as catalyst and double-hydroxyl capped PEG (DHPEG) as macro-initiator. The triblock structure and copolymer composition were conformed by FT-IR, H-1-NMR, and GPC. Using a membrane dialysis method, PCEC micelles were prepared with a core-shell type. The critical micelle concentration (CMC) of PCEC triblock copolymers was determined by fluorescence technique using pyrene as probe, and CMC values decreased with the increase of PCL chain length. From the observation of transmission electron microscopy (TEM), the morphology of polymer micelles was spherical in shape. Micelles size measured by dynamic light scattering (DLS) exhibited a narrow size distribution. Folic acid (FA) was then used as a model drug to incorporate into PCEC micelles. The diameter, drug loading, and drug release rate of PCEC micelles were influenced by the feed weight ratio of FA and copolymer, and polymer composition. In addition, in vitro release experiments of the drug-loaded PCEC micelles exhibited sustained release behavior without any burst effects and the release behavior was also affected by the pH of release media.