Reversing multidrug resistance by intracellular delivery of Pluronic® P85 unimers.

Pluronics have been demonstrated as excellent multidrug resistance (MDR) reversal agent in the form of unimers rather than micelles. However, the effective intracellular delivery of Pluronic(®) unimers to MDR cancer cells still remains a big challenge. To address this issue, a mixed micellar system based mainly on the pH-sensitive copolymer of poly (L-histidine)-poly (D,L-lactide)-polyethyleneglycol-poly (D,L-lactide)-poly (L-histidine) (PHis-PLA-PEG-PLA-PHis) and Pluronic(®) F127, some of which was conjugated with folate, was constructed to intracellularly deliver the unimers of Pluronic(®) P85 to MDR cells. The folate-mediated endosomal pH-sensitive mixed micelles (pHendoSM-P85/f) were prepared by a thin-film hydration method, by which Pluronic(®) P85 unimers and doxorubicin (DOX) were incoporated into the mixed micelles. The incorporation of Pluronic(®) P85 unimers was investigated by the surface tension test. The results indicated that the Pluronic(®) P85 unimers probably first inserted into the binary mixed micelles and then formed a triple-component mixed micelles with Pluronic(®) F127 and PHis-PLA-PEG-PLA-PHis as the loading content increased. Further analyzed with flow cytometry, confocal laser scanning microscopy (CLSM) and MTT assay, the micelles with inserted Pluronic(®) P85 unimers demonstrated much more cellular uptake and higher cytotoxicity against MDR cells than the triple-component mixed micelles and plain Pluronic(®) micelles. The enhanced MDR reversal effect was attributed to the successful intracellular delivery of Pluronic(®) P85 unimers to the MDR cells, which was confirmed by the subcellular colocalization of Pluronic(®) P85 unimers with mitochondria, the decreased ATP energy and mitochondrial membrane potential (MP) in the MCF-7/ADR cells. The pHendoSM-P85/f/DOX also demonstrated more dramatic antitumor efficiency and remarkable reduction of ATP energy in the MDR cells in tumors than the control formulations. The intracellular delivery of Pluronic(®) P85 unimers to the MDR cells based on the targeted and endosomal pH triggerd release mixed micelles has been demonstrated as a promising approach to reverse MDR.

Hong W ，Chen D ，Zhang X ，Zeng J ，Hu H ，Zhao X ，Qiao M ... -  《-》

Enhanced effect of pH-sensitive mixed copolymer micelles for overcoming multidrug resistance of doxorubicin.

P-glycoprotein (P-gp) mediated drug efflux has been recognized as a key factor contributing to the multidrug resistance (MDR) in tumor cells. To address this issue, a new pH-sensitive mixed copolymer micelles system composed of hyaluronic acid-g-poly(l-histidine) (HA-PHis) and d-α-tocopheryl polyethylene glycol 2000 (TPGS2k) copolymers was developed to co-deliver doxorubicin (DOX) and TPGS2k into drug-resistant breast cancer MCF-7 cells (MCF-7/ADR). The DOX-loaded HA-PHis/TPGS2k mixed micelles (HPHM/TPGS2k) were characterized to have a unimodal size distribution, high DOX loading content and a pH dependent drug release profile due to the protonation of poly(l-histidine). As compared to HA-PHis micelles (HPHM), the HPHM/TPGS2k showed higher and comparable cytotoxicity against MCF-7/ADR cells and MCF-7 cells, respectively. The enhanced MDR reversal effect was attributed to the higher amount of cellular uptake of HPHM/TPGS2k in MCF-7/ADR cells than HPHM, arising from the inhibition of P-gp mediated drug efflux by TPGS2k. The measurements of P-gp expression level and mitochondrial membrane potential indicate that the blank HPHM/TPGS2k inhibited P-gp activity by reducing mitochondrial membrane potential and depletion of ATP but without inhibition of P-gp expression. In vivo study of micelles in tumor-bearing mice indicate that HPHM/TPGS2k could reach the tumor site more effectively than HPHM. The pH-sensitive mixed micelles system has been demonstrated to be a promising approach for overcoming the MDR.

Qiu L ，Qiao M ，Chen Q ，Tian C ，Long M ，Wang M ，Li Z ，Hu W ，Li G ，Cheng L ，Cheng L ，Hu H ，Zhao X ，Chen D ... -  《-》

pH-sensitive micelles for the intracellular co-delivery of curcumin and Pluronic L61 unimers for synergistic reversal effect of multidrug resistance.

Hong W ，Shi H ，Qiao M ，Zhang Z ，Yang W ，Dong L ，Xie F ，Zhao C ，Kang L ... -  《Scientific Reports》

Molecular mechanism study of chemosensitization of doxorubicin-resistant human myelogenous leukemia cells induced by a composite polymer micelle.

The present study was aimed to overcome the multidrug resistance (MDR) of tumor cells which accounts for the failure of clinical chemotherapy. A novel doxorubicin (DOX)-loaded composite micelle consisting of polyethylene glycol (PEG)-polycaprolactone (PCL)/Pluronic P105 has been developed and was proved to inhibit the drug resistance of human myelogenous leukemia (K562/ADR) cells. The modulation mechanism that DOX-loaded the composite micelle inhibited MDR was for the first time investigated at cell levels. Results indicated that the cytotoxicity in K562/ADR cells treated by DOX-loaded PEG-PCL/P105 composite micelle was about 4 times higher than DOX solution at 12 μg/mL of DOX. Confocal images showed that the DOX-loaded composite micelles gradually entered into cytoplasm and nucleus, and stayed in intracellular much longer than DOX solution. All the micelles (PEG-PCL micelle, P105 micelle and PEG-PCL/P105 composite micelle) did not change Pgp expression on the surface of K562/ADR cells. However, further study revealed that micelle containing of P105 (P105 or PEG-PCL/P105 composite micelle) significantly decreased ATP level, and consequently restricted the activity of Pgp by down-regulation of mitochondrial membrane potential. On the other hand, the PEG-PCL micelle had no effect on both mitochondrial membrane potential and ATP level of the K562/ADR cells, but its access to K562/ADR cells through endocytic pathway avoided the recognition of Pgp. The PEG-PCL/P105 composite micelle was designed based on the combination of P105-mediated down regulation of mitochondrial membrane potential the malignant cells and PEG-PCL-mediated internalization effect. Therefore, the novel composite micelle is a promising drug delivery system for anticancer drug to overcome MDR.

Han M ，Diao YY ，Jiang HL ，Ying XY ，Chen DW ，Liang WQ ，Gao JQ ... -  《-》

Multifunctionalized Micelles Facilitate Intracellular Doxorubicin Delivery for Reversing Multidrug Resistance of Breast Cancer.

Cao A ，Ma P ，Yang T ，Lan Y ，Yu S ，Liu L ，Sun Y ，Liu Y ... -  《-》