Using stannous octoate (Sn(Oct)2) as catalyst and monomethoxy-poly(ethylene glycol) (mPEG) as macroinitiator

-caprolactone (CL) and -methyl--caprolactone (MCL) with different feed ratios were copolymerized by ring opening polymerization.By controlling the feed ratio and sequence of CL and MCL

four types of copolymers containing various hydrophobic CL/MCL ratio and distribution were obtained.1H-NMR and GPC were used to characterize the structures of these four copolymers.DSC

WAXD and FTIR were applied to investigate their crystallinity.By dialysis method

four types of polymeric micelles and drug-loaded (doxorubicin DOX) micelles were prepared and their self-assembly behavior was carefully studied.The loading and release profiles of DOX were also illustrated.The results indicated that the introduction of MCL decreased the crystallinity of copolymers

which led to the improvement in drug loading capacity and release speed.Confocal laser microscopy and flow cytometry were used to expose the endocytosis behavior of drug-loaded micelles with different core structures taken by HepG2 hepatoma carcinoma cells.The cytotoxicity of micelles was then examined by MTT.All the cell experiments revealed that both endocytosis of DOX-loaded micelles taken by HepG2 and toxic effects of DOX-loaded micelles on cells were mainly influenced by the core structure of micelles.