Synchronized delivery of dual-drugs for potentiating combination chemotherapy based on smart triple-responsive polymeric micelles

Here, we combined reversible addition-fragmentation chain transfer (RAFT) polymerization and amide coupling reaction to develop a novel drug-polymer conjugate using poly(AMA-co-IMMA)-b-poly(OEGMA) (termed as PAIPO) as nanocarriers. In order to enhance cellular uptake and obtain subsequent endo/lysosomal escape ca-pacity, the dual-drugs-conjugated prodrug was then coupled with 2,3-dimethylmaleimide (DA) moieties and implanted with imidazolyl groups, respectively. Paclitaxel (PTX) was conjugated to PAIPO via 3,3 '-dithiodi-propionic acid (DPA) to construct a GSH-responsive moiety, while doxorubicin (DOX) was conjugated to PAIPO via 4-formyl benzoic acid to construct a pH-responsive moiety, which synergistically enabled a synchronized and precise drug delivery. The micelles self-assembled from DOX/PTX@PAIPODA showed an ideal average diameter (163.2-178.3 nm), contributing to passive targeting by the EPR effect. Moreover, a switch of the surface Zeta potential of micelles from steady negatively charged (-9.74 +/- 0.54 mV) at pH 7.4 to positively charged (+ 6.33 +/- 1.25 mV) at pH 6.5, facilitated the long blood circulation and cellular endocytosis of micelles, respectively. More importantly, in vitro studies confirmed that DAM(DOXn/PTX) exhibited a strong synergism against tumor cells, and under slightly acidic conditions (pH 6.5), the combination index (CI) values for DAM(DOX1/PTX) on HeLa and Skov-3 cells were estimated to be 0.47 and 0.49 (previous to be 0.50 and 0.56 at pH 7.4), respectively. And in vivo results showed effective tumor accumulation potential, remarkable biosafety, and biocompatibility. Combined, such synchronized delivery approach based on multi-responsive micelles might potentiate the effi-cacy of combination chemotherapy in clinical cancer treatment.