New amphiphilic PEG-b-P(ester-ether) micelles as potential drug nanocarriers

A range of diblock and triblock copolymers of dioxanone and methyl dioxanone (MeDX) were synthesized by ring-opening polymerization of dioxanone and MeDX initiated by hydroxyl-terminated PEG (MPEG) or di-amino-terminated PEG (Jeffamine (R)) as macroinitiator in the presence of Sn(Oct)(2). The copolymers exhibit amphiphilic behavior in water forming core-shell micelles in the size range 120-300 nm as measured by DLS. DSC measurements exhibit only one melting transition for all copolymers and confirm that increasing MeDX content of the copolymers lead to decreasing crystalline character and hydrophobic-hydrophilic chain entanglement. Anti-inflammatory drug ketoprofen was successfully loaded into the hydrophobic core of the micelles. Various key parameters such as micelle size, drug entrapment efficiency and drug release, which are dependent on crystalline structure and biodegradability characteristics of the hydrophobic core, could effectively be controlled by varying the dioxanone/MeDX ratio of the (ester-ether) copolymer.