Synthesis, self-assembly, and in vitro doxorubicin release behavior of dendron-like/linear/dendron-like poly(epsilon-caprolactone)-b-poly(ethylene glycol)-b-poly(epsilon-caprolactone) triblock copolymers

Abstract

Dendron-like/linear/dendron-like poly(epsilon-caprolactone)-b-poly(ethylene glycol)-b-poly(epsilon-caprolactone) triblock copolymers with controlled molecular weights (M(n) = 9550-30 460) and low polydispersities were synthesized by a click conjugation between dendron-like poly(epsilon-caprolactone) and bifunctional azide-terminated poly(ethylene glycol) (copolymer yield = 56-89%). Their molecular structures and physicochemical and self-assembly properties were thoroughly characterized by means of FT-IR, (1)H NMR, multiangle laser light scattering coupled with gel permeation chromatography, differential scanning calorimetry, wide-angle X-ray diffraction, dynamic light scattering, and transmission electron microscopy. Using a nanoprecipitation method, these triblock copolymers self-assembled into spherical flower-like micelles with an average diameter of less than 50 nm in aqueous solution, and both the copolymer composition and the dendritic topology of the hydrophobic core had no apparent influence on the morphology of nanoparticles. The critical aggregation concentrations of these copolymers ranged from 0.034 to 0.048 mg/mL. However, the anticancer doxorubicin-loaded nanoparticles showed worm-like micelles similar to blank nanoparticles fabricated by a dialysis method, and the loaded doxorubicin drug hardly affected the final morphology of nanoparticles. Moreover, the doxorubicin-loaded nanoparticles fabricated from the dumbbell copolymer showed a higher drug loading efficiency of 18% and a longer drug-release time of 45 days than the linear counterpart. Consequently, this provides a versatile strategy not only for the synthesis of biodegradable and biocompatible dendron-like/linear/dendron-like triblock copolymers with dumbbell topology by using click chemistry but also for fabricating worm-like doxorubicin-loaded nanoparticles for anticancer drug release.