Imidazole-mediated stability of block copolymer micelles and its application in drug delivery

Abstract

Block copolymer micelles have emerged as a safer alternative for delivering drugs in biomedical applications. Recent studies have shown that the stability of these micelles can significantly impact the efficiency of drug delivery. Here, we propose a method to regulate the stability of block copolymer micelles by introducing a third monomer. Specifically, we synthesized the block copolymer PDPA18-b-P(Vim18-co-P(EG)5MA21) through reversible addition-cracking chain transfer (RAFT) polymerization based on PDPA19-b-P(P(EG)5MA)18. The diblock three-component copolymer is a unique copolymer, in which the hydrophilic block being doped the third monomer with pH-sensitive property, resulting in distinctive physiological properties. Both PDPA18-b-P(Vim18-co-P(EG)5MA21) and PDPA19-b-P(P(EG)5MA)18 can self-assemble into micelles with a core-shell structure. In the case of PDPA19-b-P(P(EG)5MA)18 micelles, the solvophobic PDPA19 block forms the core, while the solvophilic P(P(EG)5MA)18 block forms the shell. To regulate the stability of the block copolymer micelles, an imidazole intermediate layer with pH-responsiveness is introduced between PDPA core and P(P(EG)5MA) shell. The introduction of the imidazole monomer affect the stability of block copolymer micelles and the release kinetics of drugs. We validated that these PDPA18-b-P(Vim18-co-P(EG)5MA21) micelles exhibit higher stability under neutral conditions and show enhanced drug release in mildly acidic conditions compared to PDPA19-b-P(P(EG)5MA)18 micelles. Overall, this report demonstrates that copolymerization of imidazole monomer is a powerful approach to mediated the stability of block copolymer micelles for drug delivery applications.