pH-sensitive pluronic micelles combined with oxidative stress amplification for enhancing multidrug resistance breast cancer therapy.

Multidrug resistance (MDR) is one of the major obstacles to clinical cancer chemotherapy. Herein, we designed new pH-sensitive pluronic micelles with the synergistic effects of oxidative therapy and MDR reversal. Pluronic (P123) was modified with α-tocopheryl succinate (α-TOS) via an acid-labile ortho ester (OE) linkage to give a pH-sensitive copolymer (POT). Self-assembled POT micelles exhibited desirable size (~80 nm), excellent anti-dilution ability, high drug loading (~85%), acid-triggered degradation and drug release behaviours. In vitro cell experiments verified that POT micelles could significantly reverse MDR through suppressing the function of drug effluxs mediated by P123 and induce more reactive oxygen species (ROS) generation mediated by α-TOS, resulting in enhanced cytotoxicity and apoptosis in MDR cells. In vivo studies further revealed that DOX-loaded POT micelles (POT-DOX) possessed the highest drug accumulation (3.03% ID/g at 24 h) and the strongest tumour growth inhibition (TGI 83.48%). Pathological analysis also indicated that POT-DOX could induce more apoptosis or necrosis at the site of tumour without distinct damage to normal tissues. Overall, these smart POT micelles have great potential as promising nano-carriers for MDR reversal and cancer treatment.