pH-Responsive Amphiphilic Polyether Micelles with Superior Stability for Smart Drug Delivery

Despite widespread interest in the amphiphilic polymeric micelles for drug delivery systems, it is highly desirable to achieve high loading capacity and high efficiency to reduce the side effects of therapeutic agents while maximizing their efficacy. Here, we present a novel hydrophobic epoxide monomer, cyclohexyloxy ethyl glycidyl ether (CHGE), containing an acetal group as a pH-responsive cleavable linkage. A series of its homopolymers, poly(cyclohexyloxy ethyl glycidyl ether)s (PCHGEs), and block copolymers, poly(ethylene glycol)-block-poly(cyclohexyloxy ethyl glycidyl ether)s (mPEG-b-PCHGE), were synthesized via anionic ring-opening polymerization in a controlled manner. Subsequently, the self-assembled polymeric micelles of mPEG-b-PCHGE demonstrated high loading capacity, excellent stability in biological media, tunable release efficiency, and high cell viability. Importantly, quantum mechanical calculations performed by considering prolonged hydrolysis of the acetal group in CHGE indicated that the CHGE monomer had higher hydrophobicity than three other functional epoxide monomer analogues developed. Furthermore, the preferential cellular uptake and in vivo therapeutic efficacy confirmed the enhanced stability and the pH-responsive degradation of the amphiphilic block copolymer micelles. This study provides a new platform for the development of versatile smart polymeric drug delivery systems with high loading efficiency and tailorable release profiles.