Amphiphilic polycarbonate conjugates of doxorubicin with pH-sensitive hydrazone linker for controlled release.

Novel amphiphilic polycarbonates-graft-doxorubicin (mPEG-b-P(ATMC-co-DTC)-g-DOX) were successfully designed and synthesized for pH-triggered intercellular drug release in cancer cells. The amphiphilic block copolymer, mPEG-b-P(ATMC-co-DTC), was synthesized in bulk using immobilized porcine pancreas lipase (IPPL) as the catalyst. After allyl epoxidation of ATMC units, DOX was covalently conjugated to the hydrophobic polycarbonates block through a hydrazone linkage. The resulting mPEG-b-P(ATMC-co-DTC)-g-DOX prodrugs could self-assemble to form nano-sized micelles in aqueous solution, while DOX contents in the hydrophobic core were 9.9 and 12.5 wt.%. DOX release rate from the prodrug micelles increased in acidic medium due to the acid-cleavable hydrazone linkage between the DOX and polycarbonates. MTT assays demonstrated that DOX prodrug micelles in this study showed effective cytotoxic effects to HeLa cells. Furthermore, confocal laser scanning microscopy (CLSM) observations also revealed that mPEG-b-P(ATMC-co-DTC)-g-DOX prodrugs could efficiently deliver and release DOX into the nuclei of HeLa cells.