Influence of lipid composition on the thermotropic behavior and size distribution of mixed cationic liposomes

Cationic liposomes are studied mainly as nonviral nucleic acid delivery systems and to a lesser extent as carriers/adjuvants of vaccines and as low-molecular-weight drug carriers. It is well established that the performance and the biological activity of liposomes in general are strongly related to their physicochemical properties. We investigated the thermotropic behavior and the size distribution of mixed cationic liposomes formulated with different percentages of 1,2 dimyristoyl-sn-glycero-3-phosphatidylcholine and one of four cationic amphiphiles characterized by a pyrrolidinium headgroup with the aim of achieving a better understanding of how the molecular structure of the cationic amphiphile and its mole percentage affect the physicochemical properties of the liposomes. Multilamellar vesicles and large unilamellar vesicles were studied by differential scanning calorimetry and turbidity, respectively, to characterize the thermotropic behavior and lipid phase, whereas dynamic light scattering was used to determine size distribution. This study shows that subtle modifications in the cationic amphiphile's molecular structure and in liposome composition may have dramatic effects on the organization of the liposome bilayer and hence on the morphological and physicochemical features of the liposomes, thus being highly relevant to the biological features investigated previously.     

A new route towards redox bistability through the inspection of manganese-porphyrin complexes

The redox and spin versatilities of manganese–porphyrin complexes [Mn^IIP] are examined to construct a redox‐switchable device. The electronic structure of [Mn^IIIP]⁺ was analyzed by using wavefunction‐based calculations (complete active spaces plus single excitations on top of the active spaces, that is, CAS+singles). A non‐negligible σ‐type electron‐transfer configuration is present in the [Mn^IIIP]⁺ S=2 ground state. By contrast, the [Mn^IIP^.]⁺ valence tautomer is a purely π‐type intramolecular charge transfer, thus reflecting an S=3 spin state as a result of the strong ferromagnetic interaction (J=30 meV) between the S=5/2 Mn^II ion and the S=1/2 porphyrin radical cation P^.+. The change of the redox‐sensitive site in the valence tautomer leads to a ‘triangular scheme’ that involves a critical step in which a simultaneous electron transfer and spin change are expected to induce bistability. From the wavefunction inspection, a meso‐substituted porphyrin candidate was designed to support this scenario. The complete active‐space second‐order perturbation theory (CASPT2) adiabatic energy difference between the S=2 and the S=3 spin states was reduced down to 0.15 eV, thereby giving rise to a metastable S=3 state characterized by a 0.10 Å extension of the porphyrin cavity radius. These results not only confirm the rather versatile nature of these inorganic systems but also demonstrate that redox and spin changes are intermingled in this class of compounds and can be used for applied devices.     

First evidence of resistive switching in polycrystalline GaV4S8 thin layers

Recently a new type of reversible and non‐volatile resistive switching was discovered in single crystals of Mott insulators AM₄X₈ (A = Ga, Ge; M = V, Nb, Ta; X = S, Se). Here we report on the first synthesis of thin layers (thicknesses in the 100 to 1000 nm range) of GaV₄S₈ by RF magnetron sputtering process. Energy dispersive spectroscopy, X‐ray diffraction and TEM analyses attest the high quality of polycrystalline GaV₄S₈ thin layers. Electrical measurements demonstrate that deposited GaV₄S₈ thin films exhibit a non‐volatile reversible resistive switching at room temperature with writing/erasing times of ～10 µs and a memory window (R_high – R_low)/ R_low > 33%. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A General Synthetic Route to High-Quality Perovskite Oxide Nanoparticles and Their Enhanced Solar Photocatalytic Activity

The main limitations of current methods for synthesizing perovskite oxide (ABO₃) nanoparticles (NPs), e.g., the high reagent costs and sophisticated equipment, the long time and high-temperature processing, or multiple post-processing and thermal treatment steps, hamper their full study and potential application. Here, we use a facile low temperature (50 °C) chemical bath synthesis and only one annealing step to successfully produce high phase purity and crystalline quality nano-shaped rare-earth-based REMO₃ NPs (RE=La, Nd, Sm, Gd; M=Fe, Mn, Al). We also show the versatility of this approach by fabricating La_0.7Sr_0.3MnO₃ solid solution and non-RE-based BiFeO₃ perovskite. To assess the potential of the as-prepared REFeO₃ and REMnO₃ NPs, they are used for photocatalytic degradation of the norfloxacin antibiotic and show high efficiency. We believe this easy, robust, versatile, and general route for synthesizing ABO₃-based NPs can be further explored in the vast perovskite family and beyond.