Stimuli-responsive terpolymer mPEG-b-PDMAPMA-b-PAH mediated co-delivery of adriamycin and siRNA to enhance anticancer efficacy

Combination of chemotherapy and small interfering RNA (siRNA)-based therapy has emerged as a promising approach for cancer treatment with the synergistic effect. In this study, a novel terpolymer methoxy poly(ethylene glycol)-block-poly(N,N-dimethylaminopropyl methacrylamide)-block-poly(acrylhydrazine) (mPEG-b-PDMAPMA-b-PAH) with a disulfide linkage between mPEG and PDMAPMA blocks was developed for the intracellular targeted co-delivery of adriamycin and P-gp siRNA. The terpolymer was synthesized by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization of N,N-dimethylaminopropyl methacrylamide and N-tert-butoxycarbonyl-N′-acryl hydrazine (Boc-acrylhydrazine) in the presence of a PEGylated macro-RAFT agent, followed by Boc-deprotection. The terpolymer could chemically conjugate adriamycin via an acid-cleavable hydrazone bond and simultaneously condense the negatively charged siRNA through electrostatic interactions at an N/P ratio of 2. The resultant adriamycin-conjugated nanoparticles/siRNA complexes (ADR-NPs/siRNA complexes) showed a spherical morphology and had an average diameter of 186 nm. The release profiles of the two payloads from the ADR-NPs/siRNA complexes exhibited a pH/reduction dual-dependent sustained release behavior. The ADR-NPs/siRNA complexes could simultaneously deliver adriamycin and siRNA efficiently into MCF-7/ADR cells and significantly inhibit their growth in a synergistic fashion. All the results indicated that the terpolymer mPEG-b-PDMAPMA-b-PAH could serve as a potential vehicle for the combination of chemotherapy and gene therapy.