For the development of a liposome that takes in and out a drug in response to stimuli, 2,4‐diaminoxylose (Xyl), which allows stimuli‐responsive conformational switches between 4C1 and 1C4, was incorporated into a lipid structure: Xyl derivatives with C8 and C16 methylene chains at the 1,3‐positions (C8Xyl and C16Xyl) were synthesized. 1H NMR spectroscopy indicates that the addition of Zn2+ and then H+ induces conformational switches from the chair (4C1) to the reverse chair (1C4) and 1C4‐to‐4C1, respectively, at Xyl; this leads to transformation of the lipids between linear and bent structures. Osmotic pressure and electron microscopy studies demonstrate that C8Xyl in water forms spherical solid aggregates (C8Xyl?Zn), which are converted into liposomes (C8Xyl+Zn) upon the addition of Zn2+, and C16Xyl forms liposomes regardless of the presence of Zn2+. The aggregates of C8Xyl±Zn incorporated a fluorophore and only C8Xyl+Zn released the content upon the addition of HCl. This study shows that Xyl could be a stimuli‐responsive component of a liposome. 相似文献
Flexible and self-standing multilayered films made of nanoperforated poly(lactic acid) (PLA) layers separated by anodically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) conducting layers have been prepared and used as electrodes for supercapacitors. The influence of the external layer has been evaluated by comparing the charge storage capacity of four- and five-layered films in which the external layer is made of PEDOT (PLA/PEDOT/PLA/PEDOT) and nanoperforated PLA (PLA/PEDOT/PLA/PEDOT/PLA), respectively. In spite of the amount of conducting polymer is the same for both four- and five-layered films, they exhibit significant differences. The electrochemical response in terms of electroactivity, areal specific capacitance, stability, and coulombic efficiency was greater for the four-layered electrodes than for the five-layered ones. Furthermore, the response in terms of leakage current and self-discharge was significantly better for the former electrodes than for the latter ones. 相似文献
An analytical methodology based on the use of a polyethylene layflat tube filled with activated carbon and Florisil (ACFL-VERAM) was employed for the passive sampling of volatile organic compounds (VOCs) in the air of working areas of packing industries. VOCs amount in the ACFL-VERAM sampler was directly determined through head-space-gas chromatography-mass spectrometry (HS-GC-MS) allowing a direct determination in only 20 min without the need of any previous treatment. Uptake parameters, like sampling rate (RS) and sampler-air partition coefficient (KSA), were determined for every studied VOC from adsorption isotherm data. Additionally, experimental equations have been proposed to predict RS and KSA from the octanol-air partition coefficients reported in the literature. The proposed methodology reaches method detection levels from 0.007 to 0.2 mg m−3 for the studied VOCs. 相似文献
The partitioning of non-polar analytes into the silicone polydimethylsiloxane (PDMS) is the basis for many analytical approaches such as solid phase microextraction (SPME), stir bar sorptive extraction (SBSE) and environmental passive sampling. Recently, the methods have been applied to increasingly complex sample matrices. The present work investigated the possible effect of complex matrices on the sorptive properties of PDMS. First, SPME fibers with a 30 μm PDMS coating were immersed in 15 different matrices, including sediment, suspensions of soil and humic substances, mayonnaise, meat, fish, olive oil and fish oil. Second, the surface of the fibers was wiped clean, and together with matrix-free control fibers, they were exposed via headspace to 7 non-polar halogenated organic chemicals in spiked olive oil. The fibers were then solvent-extracted, analyzed, and the ratios of the mean concentrations in the matrix-immersed fibers to the control fibers were determined for all matrices. These ratios ranged from 92% to 112% for the four analytes with the highest analytical precision (i.e. polychlorinated biphenyls (PCBs) 3, 28, 52 and brominated diphenyl ether (BDE) 3), and they ranged from 74% to 133% for the other three compounds (i.e. PCBs 101, 105 and γ-hexachlorocyclohexane (HCH)). We conclude that, for non-polar, hydrophobic chemicals, the sorptive properties of the PDMS were not modified by the diverse investigated media and consequently that PDMS is suited for sampling of these analytes even in highly complex matrices. 相似文献
A multitasking fluorescent device can be obtained by forming micelles of Triton X‐100, containing a lipophilic macrocyclic Cu2+ complex and the coordinating fluorophore Coumarin 343 (C343), which features a COOH moiety. At low pH the two micellised components do not interact, and the fluorescence of Courmarin 343 (C343) is intense. At intermediate pH, C343 is deprotonated and coordinates to the Cu2+ centre in its apical position, with fluorescence quenching. At higher pH the deprotonated C343 is displaced from Cu2+ by the formation of an OH? complex, and the fluorescence is revived. This allows the system to carry out its first task as it behaves as an “on–off–on” fluorescent sensor for pH windows. The “off” part of the window ranges from pH 6 to 8. In this interval, in which the carboxylate form of C343 is apically coordinated to the Cu2+ complex inside micelles, the device carries out its second task, that is, it behaves as a gauge for lipophilicity. For pHs between 6 and 8, molecules containing a COOH group are in their COO? form and distribute between bulk water and micelles proportionally to their lipophilicity. Upon entering the micelle, their COO? moiety competes for coordination with C343, displacing it from the Cu2+ centre, and this results in fluorescence revival, the intensity of which is also proportional to the lipophilicity of the examined molecule. We have chosen the physiological pH value (7.4) as the working pH, and we have examined the lipophilicity of fatty acids and of the widely used family of non‐steroidal anti‐inflammatory drugs (NSAIDs). The device successfully measures their lipophilicity, expressing it with an “off–on” type fluorescent signal, as demonstrated by the correlation of the fluorescence increase with the logarithmic water/octanol partition coefficient (log P) and with the difference between the pKa observed in micelles and that measured in water for NSAIDs. 相似文献
Enlightening the memory : The integration of a crosslinkable photochromic dithienylperfluorocyclopentene (DTE) into organic light‐emitting diodes (OLED) allows for the individualization of the emissive area of the OLED device, for example, for signage applications. The operation principle is based on switching the injection barrier for holes (positive charge carriers). Very large ON/OFF ratios of up to 3000 for current as well as electroluminescence have been achieved.
Zn2+ release from Zn and ZnO particles with different sizes in simulated uterine solution were investigated by absorbance measurements. The effects of pH and human serum albumin (HSA) on Zn2+ release were also studied. The morphology of Zn and ZnO particles was observed by scanning electron microscopy, and the corrosion products of zinc nanoparticles were analyzed by XRD. The results indicate that the maximum release ratios of Zn2+ from Zn and ZnO nanoparticles are higher than those from Zn and ZnO microparticles. Zn2+ release ratio depends not only on the pH of the simulated uterine solution but also the presence of human serum albumin. It decreases as the pH of the uterine solution increases. The trends of Zn2+ release ratios are almost the opposite for solutions with and without HSA. XRD analysis results indicate that zinc oxide is the main corrosion product of zinc particles. 相似文献