High porosities, large surface areas, and tunable functionalities made metal-organic frameworks (MOFs) as effective carriers for drug delivery. One of the most promising MOFs is the zeolitic imidazolate framework (ZIF-8) crystal, an advanced functional material for small-molecule delivery, due to its high loading ability and pH-sensitive degradation. As a novel carrier, ZIF-8 nanoparticles were used in this work to control the release of an autophagy inhibitor, 3-methyladenine (3-MA), and prevent it from dissipating in a large quantity before reaching the target. The cellular uptake in HeLa cells of 3-MA encapsulated in ZIF-8 (3-MA@ZIF-8 NPs) is facilitated through the nanoparticle internalization with reference to TEM observations and the quantitative analyses of zinc by ICP-MS. The autophagy-related proteins and autophagy flux in HeLa cells treated with 3-MA@ZIF-8 NPs show that the autophagosome formation is significantly blocked, which reveals that the pH-sensitive dissociation increases the efficiency of autophagy inhibition at the equivalent concentration of 3-MA. In vivo experiments, when compared to free 3-MA, 3-MA@ZIF-8 NPs show a higher antitumor efficacy and repress the expression of autophagy-related markers, Beclin 1 and LC3. It follows that ZIF-8 is an efficient drug delivery vehicle in antitumor therapy, especially in inhibiting autophagy of cancer cells.
Twelve gemini quaternary ammonium surfactants have been employed to evaluate the antibacterial activity and in vitro cytotoxicity. The antibacterial effects of the gemini surfactants are performed on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with minimum inhibitory concentrations (MIC) ranging from 2.8 to 167.7 μM. Scanning electron microscopy (SEM) analysis results show that these surfactants interact with the bacterial cell membrane, disrupt the integrity of the membrane, and consequently kill the bacteria. The data recorded on C6 glioma and HEK293 human kidney cell lines using an MTT assay exhibit low half inhibitory concentrations (IC50). The influences of the gemini surfactants on the cell morphology, the cell migration ability, and the cell cycle are observed through hematoxylin-eosin (HE) staining, cell wound healing assay, and flow cytometric analyses, respectively. Both the values of MIC and IC50 decrease against the growth of the alkyl chain length of the gemini surfactants with the same spacer group. In the case of surfactants 12-s-12, the MICs and IC50s are found to decrease slightly with the spacer chain length changing from 2 to 8 and again to increase at higher spacer length (s = 10-12). All of the gemini surfactants show great antibacterial activity and cytotoxicity, and they might exhibit potential applications in medical fields.
Thermal cracking of a high density hydrocarbon fuel, JP-10 (exo-tetrahydrodicyclopentadiene), was studied on a batch reactor under different pressures. The effluent was cooled and collected at room temperature and atmospheric pressure. The gaseous and liquid components were quantitatively determined by gas chromatography and gas chromatography−mass spectrometry, respectively. The conversion of JP-10 has relatively low value at atmospheric pressure and increases under pressure. With an increase of the pressure, the relative content of ethene or propene decreases and that of methane, ethane, or propane increases simultaneously. In the liquid products, cyclopentane, cyclopentene, 1,3-cyclopentadiene, and cis-bicyclo[3.3.0]oct-2-ene are found to be major components. Substituted cyclopentene, benzene, toluene, and naphthalene are also observed under high pressures and temperatures. A probable mechanism of the thermal cracking of JP-10 is proposed to explain the product distribution. The process of isomerization might be dominating for liquid product formation during the thermal cracking under elevated pressure.
Alkylketene dimer (AKD), a kind of wax, has been known to form fractal surfaces spontaneously and show super water-repellency. Such formation of water-repellent and fractal surfaces was also found in this work for triglycerides. Since the crystal phase transitions of these waxes were well studied, we studied the formation of their fractal surfaces through contact angle measurements, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). From time-dependent contact angle measurements, it was found that the formation of super water-repellent surfaces with fractal structures occurred spontaneously also on the triglyceride surfaces at different temperatures. The freshly solidified triglyceride surfaces were almost transparent, and their initial contact angles of water were close to 110 degrees. The surfaces then became rough and clouded after being incubated for a certain time at a specified temperature. The super water-repellent surfaces were quite rough and showed fractal structures with the dimension of ca. 2.2 calculated from the scanning electron microscopic (SEM) images by the box-counting method. The phase transformation from a metastable state to a stable cystalline one after the solidification from the melt of triglycerides was clearly observed by DSC and XRD measurements. The fractal crystalline structures and the super water-repellency resulted from this phase transformation and the crystal growth. Ensuring the initial sample solidified into the metastable state and curing the surface at an appropriate temperature are key factors for the successful preparation of fractal triglyceride surfaces by the solidification method.
Self-assembled silver nanoparticles with an average diameter of 5 nm have been successfully fabricated by reduction of Ag + with ascorbic acid in the mixture of water, alkylamine, and oleic acid. Thermogravimetry (TG), differential scanning calorimetry (DSC), and contact angle measurements indicate that oleic acid molecules are well capped on the silver nanoparticles. The effects of temperature and reaction-medium pH on the morphology and composition of the silver nanoparticles are discussed. A decrease in pH leads to a tendency to produce silver nanorods and nanospheres. The temperature can affect the thickness of the organic layer on the surfaces of the silver nanoparticles. The stabilities of the silver nanoparticles in the nanofluids were monitored at different temperatures. Thermal conductivity enhancements were determined in kerosenebased nanofluids with the prepared silver nanoparticles. The surface-capped silver nanoparticles exhibited excellent dispersity in kerosene and conventional organic solvent such as n-hexane and chloroform. The highly dispersible silver nanoparticles are therefore suitable for the preparation of oil-based nanofluids.
A zeolitic imidazolate framework (ZIF-8) with high loading capacity and pH-responsive properties, an important subclass of metal-organic frameworks (MOFs), has become a promising material for drug delivery. A multifunctional drug delivery system (DDS) was designed in this work for effective targeting delivery of chloroquine diphosphate (CQ) as an autophagy inhibitor. The ZIF-8 nanoparticles encapsulating CQ (CQ@ZIF-8 NPs) were fabricated by a simple one-pot method and were then decorated with methoxy poly(ethylene glycol)-folate (FA-PEG), a special identifier of cancer cells, to form FA-PEG/CQ@ZIF-8. The target identification of FA-PEG/CQ@ZIF-8 NPs, compared with CQ@ZIF-8 NPs, leads to an increasing number of NPs being internalized into HeLa cells, which decreases the loss of drugs and results in high cytotoxicity of CQ for cancer cells. The lower viabilities of HeLa cells (cancer cells) and higher viabilities of HEK293 cells (healthy cells) treated with FA-PEG/CQ@ZIF-8 NPs show that the special target for cancer cells results from the combinations of folic acid and folate receptors on the surface of HeLa cells. The quantitative measurements of autophagy-related proteins and the detection of autophagy flux in HeLa cells suggest that the autophagosome formation and autophagy flux are appreciably blocked after the cells are treated with FA-PEG/CQ@ZIF-8 NPs. The ZIF-8 can disintegrate only under low pH conditions, resulting in fast and full release of CQ. The pH-responsive and tumor-targeted properties of the NPs can control the drug release and enhance the efficiency of autophagy inhibition. It indicates that the FA-PEG/CQ@ZIF-8 NPs combining target identification with controlled drug release can be used as a novel model for discussing targeted cancer therapy and inhibiting the autophagy of cancer cells.
A total of 10 new N-alkyl piperazinium-based ionic liquids (ILs) have been prepared, and they are used as extractants for removing aromatics from three kinds of hydrocarbon fuels. A total of 3 ILs, N-methyl piperazinium lactate (MPL), N-ethyl piperazinium lactate (EPL), and N-ethyl piperazinium propionate (EPP), in the liquid state at room temperature are used directly for extraction, while the other 7 ILs in the solid state at room temperature are used with methanol as the co-solvent. Effects on the extraction efficiency of the temperature and the amounts of IL and co-solvent are investigated. The results indicate that the amounts of IL and co-solvent play very important roles in the extraction process and the efficiency is greatly influenced by the cation and anion structures in the N-alkyl piperazinium-based ILs. In comparison to 1,1,3,3-tetramethylguanidinium lactate (TMGL), the extraction capability order is EPP > EPL > MPL > TMGL. The ILs with aromatic anions are found to have better extraction capability than the others. Furthermore, recycling of ILs reflects that these ILs can be recovered simply by vacuum distillation without a significant decrease in the activity of dearomatization.
The transition metal rhodium has been proved the effective catalyst to convert from NO(x) to N(2.) In the present work, we are mainly focused on the NO adsorption and decomposition reaction mechanism on the surface of the Rh(7)(+) cluster, and the calculated results suggest that the reaction can proceed via three steps. First, the NO can adsorb on the surface of the Rh(7)(+) cluster; second, the NO decomposes to N and O atoms; finally, the N atom reacts with the second adsorbed NO and reduces to a N(2) molecule. The N-O bond breaks to yield N and O atoms in the second step, which is the rate-limiting step of the whole catalytic cycle. This step goes over a relatively high barrier (TS(12)) of 39.6 kcal/mol and is strongly driven by a large exothermicity of 55.1 kcal/mol during the formation of stable compound 3, accompanied by the N and O atoms dispersed on the different Rh atoms of the Rh(7)(+) cluster. In addition, the last step is very complex due to the different possibilities of reaction mechanism. On the basis of the calculations, in contrast to the reaction path II that generates N(2) from two nitrogen atoms coupling, the reaction path I for the formation of intermediate N(2)O is found to be energetically more favorable. Present work would provide some valuable fundamental insights into the behavior of the nitric oxide adsorption and reduction reaction mechanism on the Rh(7)(+) cluster.
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