The 2D profiles of DU and Ti/TiN multilayer film under different test frequencies.

<p>The 2D profiles of DU and Ti/TiN multilayer film under different test frequencies.</p

COF value of DU substrate (a) and Ti/TiN film (b) under different test frequencies.

<p>COF value of DU substrate (a) and Ti/TiN film (b) under different test frequencies.</p

Effect of frequency on fretting wear behavior of Ti/TiN multilayer film on depleted uranium

<div><p>The Ti/TiN multi-layer film was prepared on the depleted uranium (DU) substrate by cathodic arc ion plating equipment. The character of multi-layer film was studied by SEM, XRD and AES, revealed that the surface was composed of small compact particle and the cross-section had a multi-layer structure. The fretting wear performance under different frequencies was performed by a MFT-6000 machine with a ball-on-plate configuration. The wear morphology was analyzed by white light interferometer, OM and SEM with an EDX. The result shows the Ti/TiN multi-layer film could greatly improve the fretting wear performance compared to the DU substrate. The fretting wear running and damaged behavior are strongly dependent on the film and test frequency. The fretting region of DU substrate and Ti/TiN multi-layer under low test frequency is gross slip. With the increase of test frequency, the fretting region of Ti/TiN multi-layer change from gross slip to mixed fretting, then to partial slip.</p></div

Wear morphology of Ti/TiN multilayer film after the test frequency of 50Hz (a), 2Hz (b) and 10Hz (c).

<p>Wear morphology of Ti/TiN multilayer film after the test frequency of 50Hz (a), 2Hz (b) and 10Hz (c).</p

XRD patterns (a) and element depth distribution (b) of Ti/TiN multilayer film.

<p>XRD patterns (a) and element depth distribution (b) of Ti/TiN multilayer film.</p

The wear volume of DU substrate and Ti/TiN multi-layer film (a), and the schematic diagram to explain the wear volume of DU (b) and Ti/TiN multi-layer film (c).

<p>The wear volume of DU substrate and Ti/TiN multi-layer film (a), and the schematic diagram to explain the wear volume of DU (b) and Ti/TiN multi-layer film (c).</p

SEM images of DU substrate under the frequency of 50Hz (a), 20Hz (b) and 2Hz (c).

<p>SEM images of DU substrate under the frequency of 50Hz (a), 20Hz (b) and 2Hz (c).</p

Variation of Ft–D curves as function of number of cycle under the frequency of 2Hz (a), 20Hz (b) and 50Hz (c).

<p>Variation of Ft–D curves as function of number of cycle under the frequency of 2Hz (a), 20Hz (b) and 50Hz (c).</p

Functionalization of Halloysite Nanotubes via Grafting of Dendrimer for Efficient Intracellular Delivery of siRNA

Here, polyamidoamine grafted halloysite nanotubes (PAMAM-<i>g</i>-HNTs) were synthesized for loading of siRNA in order to intracellular delivery of siRNA and treat of breast cancer via gene therapy. The successful grafting of PAMAM on HNTs was confirmed by various analytical methods. The size, zeta potential, and grafting ratio of PAMAM-<i>g</i>-HNTs is ∼206.2 nm, +19.8 mV, and 3.04%, respectively. PAMAM-<i>g</i>-HNTs showed good cytocompatibility toward HUVECs (84.7%) and MCF-7 cells (82.3%) even at high concentration of 100 μg/mL. PAMAM-<i>g</i>-HNTs/siRNA exhibited enhanced cellular uptake efficiency of 94.3% compared with Lipofectamine 2000 (Lipo2000)/siRNA (83.6%). PAMAM-<i>g</i>-HNTs/small interfering RNA-vascular endothelial growth factor (siVEGF) led to 78.0% knockdown of cellular VEGF mRNA and induced 33.6% apoptosis in the MCF-7 cells, which is also much higher than that of Lipo2000/siVEGF. In vivo anti-cancer results demonstrated that PAMAM-<i>g</i>-HNTs/siVEGF treated 4T1-bearing mice showed enhanced anti-cancer efficacy than Lipo2000/siVEGF group. Also, the nanocarrier system showed negligible toxic effects toward the major organs of mice. In vivo fluorescence imaging studies showed that there is a slight decrease in the fluorescence signal of PAMAM-<i>g</i>-HNTs/cy5-siVEGF after 72 h post-injection. Therefore, PAMAM-<i>g</i>-HNTs show promising application as novel nanovectors for siRNA delivery and gene therapy of cancer

Folate-Conjugated Halloysite Nanotubes, an Efficient Drug Carrier, Deliver Doxorubicin for Targeted Therapy of Breast Cancer

To carry doxorubicin (DOX) on breast cancer site effectively, halloysite nanotubes conjugated with poly­(ethylene glycol) and folate (HNTs-PEG-FA) is designed as a targeted drug delivery system. Halloysite nanotubes (HNTs) are shortened to ∼200 nm by ultrasonic scission and functionalized with amide groups to conjugate with <i>N</i>-hydroxylsuccinimide-polyethylene glycol carboxylic acid (NHS-PEG-COOH) and folate (FA). DOX@HNTs-PEG-FA is prepared by loading DOX on HNTs-PEG-FA via physical adsorption. The sustained and controlled release of DOX from DOX@HNTs-PEG-FA is up to 35 h in an acidic environment (pH 5.3). DOX@HNTs-PEG-FA, performed as a new nanodelivery system, shows significant inhibition of proliferation and induction of death in MCF-7 cells with positive FA receptor but not in L02 cells with negative FA receptor. Results of acridine orange/ethidium bromide and flow cytometric assay indicate that DOX@HNTs-PEG-FA induces cell death through apoptosis. Compared to the same dose of DOX, DOX@HNTs-PEG-FA generates more reactive oxygen species (ROS) in MCF-7 cells, which lead to mitochondrial damage and apoptosis. Furthermore, with fluorescence images and transmission electron microscopy, uptake of DOX@HNTs-PEG-FA by tumor cells is both through endocytosis and direct penetration mechanism. The in vivo antibreast cancer activity of DOX@HNTs-PEG-FA is further confirmed in 4T1-bearing mice. In contrast to DOX, DOX@HNTs-PEG-FA effectively reduces heart toxicity and inhibits solid tumor growth with higher cleaved caspase-3 protein level in tumor tissue of 4T1-bearing mice. DOX@HNTs-PEG-FA reveals a higher DOX fluorescence intensity in tumor tissue than in other normal tissues including heart, spleen, lung, and kidney at different time points. All these results suggest that FA-conjugated HNTs may be designed to be a novel drug delivery system for targeted therapy of breast cancer via intravenous injection