Tri-component diblock copolymers of poly(ethylene glycol)-poly(ε-caprolactone-co-lactide):: synthesis, characterization and loading camptothecin

Biodegradable tri-component diblock copolymer was synthesized by bulk copolymerization of epsilon-caprolactone (CL) and D, L-lactide (LA) in the presence of methoxy poly(ethylene glycol) (MePEG), using stannous octoate as catalyst. Their chemical structure and physical properties were investigated by GPC, NMR, DSC, TGA and XRD. The increase of CL/LA ratio in the diblock copolymer leads to lower T-g, higher decomposition temperature and crystallinity. Nanoparticles formulated from MePEG-poly(CL-co-LA) (PCAE) possess spherical structure, which was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The DLS results indicate that the particle size increased with the increase of CL/LA ratio and the hydrophobic fragment length in the copolymer. The drug encapsulation efficiency and the drug release behavior in vitro conditions of camptothecin were measured by high performance liquid chromatography (HPLC). The encapsulation efficiency can be achieved as high as 84.4% and the release behavior can be made well-controlled. MePEG-poly(CL-co-LA) nanoparticles might have a great potential as carriers for hydrophobic drugs.