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In cancer therapy nanocargos based on star-shaped polymer exhibit unique features such as better stability, smaller size distribution and higher drug capacity in comparison to linear polymeric micelles. In this study, we developed a multifunctional star-shaped micellar system by combination of active targeting ability and redox-responsive behavior. The star-shaped micelles with good stability were self-assembled from four-arm poly(ε-caprolactone)-poly(ethylene glycol) copolymer. The redox-responsive behaviors of these micelles triggered by glutathione were evaluated from the changes of micellar size, morphology and molecular weight. In vitro drug release profiles exhibited that in a stimulated normal physiological environment, the redox-responsive star-shaped micelles could maintain good stability, whereas in a reducing and acid environment similar with that of tumor cells, the encapsulated agent was promptly released. In vitro cellular uptake and subcellular localization of these micelles were further studied with confocal laser scanning microscopy and flow cytometry against the human cervical cancer cell line HeLa. In vivo and ex vivo DOX fluorescence imaging displayed that these FA-functionalized star-shaped micelles possessed much better specificity to target solid tumor. Both the qualitative and quantitative results of the antitumor effect in 4T1 tumor-bearing BALB/c mice demonstrated that these redox-responsive star-shaped micelles have a high therapeutic efficiency to artificial solid tumor. Therefore, the multifunctional star-shaped micelles are a potential platform for targeted anticancer drug delivery., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

How to deliver the drug to the target area at the right time and at the right concentration is still a challenge in cancer therapy. In this study, we present a facile strategy to control drug release by precisely controlling the thermo-sensitivity of the nanocarriers to the variation of environmental temperature. One type of thermoresponsive Pluronic F127-poly(d,l-lactic acid) (F127-PLA, abbreviated as FP) copolymer micelles was developed and decorated with folate (FA) for active targeting. FP100 micelles assembled from FP with PLA segment having polymerization degree of 100 had a low critical solution temperature of 39.2 °C close to body temperature. At 37 °C, little amount of encapsulated anticancer drug DOX is released from the FP100 micelles, while at a slightly elevated temperature (40 °C), the shrinkage of thermoresponsive segments causes a rapid release of DOX and instantly increases the drug concentration locally. The cytocompatibility analysis and cellular uptake efficiency were characterized with the fibroblast cell line NIH 3T3 and human cervix adenocarcinoma cell line HeLa. The results demonstrate that this copolymer has excellent cytocompatibility, and FA-decorated FP100 micelles present much better efficiency of cellular uptake and higher cytotoxicity to folate receptor (FR)-overexpressed HeLa cells. In particular, under hyperthermia (40 °C) the cytotoxicity of DOX-loaded FA-FP100 micelles against HeLa cells was significantly more obvious than that upon normothermia (37 °C). Therefore, these temperature-responsive micelles have great potential as a drug vehicle for cancer therapy.

Chemotherapy is widely applied to treat cancer patients but its application is limited due to the systemic toxicity and low efficacy. Nanocarrier system, which is capable of delivering their toxic cargos specifically into cancer cells and then greatly overcomes these disadvantages, has drawn a broad attention. Here we developed a drug-conjugated micelle for a better drug delivery in which folic acid was attached to the DOX-conjugated poly(ethylene glycol)-poly(ε-caprolactone) to target tumor; DOX was further connected with a hydrazone linker (FA-hyd) for a pH-triggered drug release. Comparing to other DOX-conjugated micelles either linked with carbamate (FA-cbm) or lacking FA(m-hyd), the developed FA-hyd demonstrated excellent biocompatibility; When analyzed with Alamar blue assays, flow cytometry and confocal laser scanning microscopy (CLSM), the pH-sensitive FA-functionalized DOX-conjugated micelles presented much better efficiency of cellular uptake and higher cytotoxicity to tumor cells. In vivo pharmacokinetics and biodistribution studies indicated that FA-hyd micelles significantly prolonged the blood circulation time of drug and enriched drug into the tumors rather than normal tissues. In vivo antitumor activity demonstrated that FA-hyd micelles had the highest safety to body and the best therapeutic efficacy to tumors. Therefore, this drug delivery system is deemed as a potential nanocarrier for cancer therapy., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

For cancer therapy, optimization of carrier features is necessary to effectively deliver the targeting agents to tumor sites. Biodegradable poly(ether-anhydrides) micelles with filamentous, rod-like, and spherical shapes are fabricated. Their size and morphology are characterized by AFM and TEM. The encapsulation of doxorubicin hydrochloride (DOX) into the micelles does not impact their shape. The effect of micellar shape on the drug loading capacity and encapsulation efficiency, as well as in vitro drug release, is investigated. The cellular uptakes are evaluated using fluorescence microscopy, confocal laser scanning microscopy and flow cytometry on co-cultures of human hepatoblastoma cell line (HepG2), lung epithelial cancer cell line (A549), and human nasopharyngeal epidermoid carcinoma cells (KB) and fibroblast normal cells mixed with the different shapes of DOX-loaded micelles. The results show that the spherical DOX-loaded micelles are more readily taken up by all types of cells. The impact of micellar shape on in vivo antitumor function is also assessed from changes of tumor volume, body weight loss, and survival rate of 4T1-bearing mice and the immunostaining of tumor sections for analysis of tumor cell proliferation. The results reveal that the filamentous DOX-loaded micelles possess the highest safety to body and the best therapeutic effects to artificial solid tumors. Therefore, the filamentous shape is deemed the most suitable morphology for design and engineering of drug vehicles for cancer therapy., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Efficientdelivery of therapeutic agents with nanocarriers intothe nucleus to achieve high therapeutic efficiency is still a majorchallenge for cancer therapy due to mucosal barriers, nonspecificuptake, and intracellular drug resistance. In this study, we developa dual-responsive polymer micelle system with sheddable polyethylenimine(PEI) shells for actively targeted drug delivery. This system exhibitsan ultrasensitive negative-to-positive charge reversal in responseto the extracellular pH value, resulting in greatly enhanced uptakeby cancer cells via electrostatic interaction. Moreover, the activetargeting ability can further promote the selective uptake of thenanocarriers in the cancer cell. Once the micelles escape from thelysosomes, the disulfide linkages can be cleaved by GSH in the cytoplasm,and in turn the hydrophilic PEI shell is deshielded, leading to therapid release of the encapsulated agent into the nuclei. The antitumoractivity in 4T1 tumor-bearing mice reveals that this novel systempossesses a long blood circulation due to the originally negativelycharged surface and can significantly promote the cell internalizationand intracellular drug release, thus leading to a high therapeuticefficacy against resistant tumors and fewer side effects to normaltissues. [ABSTRACT FROM AUTHOR]