Evaluation of polymeric micelles from brush polymer with poly(epsilon-caprolactone)-b-poly(ethylene glycol) side chains as drug carrier.

Brush polymers PHEMA-g-(PCL-b-PEG) with poly(2-hydroxyethyl methacrylate) (PHEMA) as the backbone and poly(epsilon-caprolactone)-b-poly(ethylene glycol) (PCL-b-PEG) block copolymers as side chains were synthesized and evaluated as drug delivery vehicles. Two brush polymers were synthesized, and their structures were confirmed by gel permeation chromatography analyses and (1)H NMR measurements. The brush polymers self-assembled into micelles in aqueous solution, and the critical micellization concentrations of brush polymers were 2-fold lower than that of the linear diblock copolymer PCL-b-PEG with structure similar to that of the grafted side chains of brush polymers, indicating the higher aqueous stability of brush polymer micelles. The micelles were spherical with average diameters below 100 nm. Brush polymer micelles exhibited higher loading doxorubicin capacity compared with micelles from linear PCL-b-PEG block copolymer by the dialysis method, and the burst doxorubicin release from the brush polymer micelles was significantly suppressed. Doxorubicin-loaded brush polymer micelles can be effectively internalized by A549 human lung carcinoma cells and slowly released the encapsulated drug molecules as demonstrated by the drug accumulation in cytoplasm, which was opposite to free doxorubicin, which accumulated rapidly in the cell nuclei.