Synthesis, characterization, and drug delivery research of an amphiphilic biodegradable star-shaped block copolymer

An amphiphilic biodegradable three-arm star-shaped diblock copolymer containing poly(epsilon-caprolactone) (PCL) and poly(N-vinylpyrrolidone) (PVP) (TEA(PCL-b-PVP)(3)) has been successfully synthesized by the ring-opening polymerization of epsilon-caprolactone (epsilon-CL), RAFT polymerization of N-vinylpyrrolidone and a coupling reaction of PCL with carboxyl-terminated PVP (PVP-COOH). In aqueous media, the star-shaped copolymer self-assembled into spherical micelles with diameters of near 106 nm. The critical micelle concentration of TEA(PCL-b-PVP)(3) copolymer was determined to be 5.96 x 10(-3) mg/mL. Folic acid was then used as a model drug to incorporate into TEA(PCL-b-PVP)(3) micelles, the drug loading content and encapsulation efficiency is 16.36 and 49.08 %, respectively. In vitro release experiments of the drug-loaded micelles exhibited sustained release behavior and it was affected by the pH of release media. These results indicate that the copolymer may serve as a promising "intelligent" drug delivery alternative.