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Doxorubicin (DOX), an anthracycline anticancer drug, was successfully incorporated into the polymeric nanoparticles (NPs) based on poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL) amphiphilic triblock copolymers by thin-film hydration and ultrasonic dispersion method. The prepared DOX-loaded polymeric NPs showed spherical shapes with apparent core-shell morphology. The average particle size of DOX-loaded NPs was 130.8 nm with a narrow size distribution (PDI = 0.200). DOX was entrapped in the polymeric NPs with encapsulation efficiency and loading content of 86.71 ± 2.05% and 8.72 ± 0.57%, respectively. DOX-release from the NPs was in a sustained and long-term fashion up to several weeks, and achieved faster release at pH5.5 than that at pH7.0. In vitro cytotoxicity assay against EMT6 cells demonstrated that the cytotoxic effect of DOX-loaded NPs gradually approached that of free DOX as increasing the concentration and the incubation time. Confocal laser scanning microscopy results showed that the DOX fluorescence was distributed both in cytoplasm and nucleus for DOX-loaded NPs treated cells, while the red fluorescence was observed mostly in the nucleus for free DOX treated cells. In cell analyzer was used to further quantitatively analyze the intracellular distribution of DOX-loaded NPs on a cell-by-cell basis, indicating that the DOX fluorescence in nucleus was lower than that in cytoplasm for 1 h incubation, but higher than that in cytoplasm for long-time incubation (4 h and 24 h). Furthermore, ex vivo DOX fluorescence imaging revealed that DOX-loaded NPs had highly efficient targeting and accumulation at the implanted site of EMT6 xenograft tumor in vivo through an enhanced permeation and retention mechanism. These results suggested that the DOX-loaded polymeric NPs based on PCL-PEG-PCL triblock copolymer would be a promising nanosized drug delivery system for cancer therapy. successfully prepared by thin-film hydration and ultrasonic dispersion method. The obtained NPs exhibited apparent core-shell morphology with satisfactory size (130 nm), which was favorable for intravenous injection. Ex vivo DOX fluorescence imaging revealed that DOX-loaded NPs had highly efficient targeting and accumulation at the implanted site of EMT6 xenograft tumor in vivo through an enhanced permeation and retention mechanism. The prepared DOX-loaded polymeric NPs would be a promising nanosized drug delivery system for cancer therapy.

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The mixing on a single-particle level of chemically incompatible nanoparticles is an outstanding challenge for many applications. Burgeoning research activity suggests that entropic templating is a potential strategy to address this issue. Herein, using systematic computer simulations of model nanoparticle systems, we show that the entropy-templated interfacial organization of nanoparticles significantly depends on the stiffness of tethered chains. Unexpectedly, the optimal chain stiffness can be identified wherein a system exhibits the most perfect mixing for a certain compression ratio. Our simulations demonstrate that entropic templating regulated by chain stiffness precisely reflects various entropic repulsion states that arise from typical conformation regimes of semiflexible chains. The physical mechanism of the chain stiffness effect is revealed by analyzing the entropic repulsion states of tethered chains and quantitatively estimating the resulting entropy penalties, which provides direct evidence that supports the key role of entropic transition in the entropic templating strategy, as suggested in experiments. Moreover, the model nanoparticle systems are found to evolve into binary nanoparticle superlattices by remixing at extremely high stiffness. The findings facilitate the wide application of the entropic templating strategy in creating interfacially reactive nanomaterials with ordered structures on the single-nanoparticle level as well as mechanomutable responses.

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