Chemo-enzymatic synthesis of degradable PTMC-b-PECA-b-PTMC triblock copolymers and their micelle formation for pH-dependent controlled release.

A series of degradable triblock copolymers, poly(trimethylene carbonate)-block-poly[poly(ethylene glycol)-co-cyclic acetal]-block-poly(trimethylene carbonate) (PTMC-b-PECA-b-PTMC), were chemo-enzymatically synthesized. Cyclic acetal was introduced into a poly(ethylene glycol) segment as a degradable segment to impart a pH-dependent degradation nature and to prevent the production of acidic degradation products. Amphiphilic polymeric micelles were successfully prepared, and the properties of the micelles were significantly affected by their chemical compositions and the molecular weights. A drug release study showed that the release rate increased as the pH of the buffer decreased due to the degradation of the cyclic acetal segments, indicating its high utility for pH-sensitive controlled release.