Soft matter dispersions with ordered inner structures, stabilized by ethoxylated phytosterols

This paper describes the formation and characterization of liquid crystalline dispersions based on the hexagonal phase of GMO/tricaprylin/water. As a stabilizer of the soft particles dispersed in the aqueous phase, a non-ionic, non-polymeric surfactant—ethoxylated phytosterol with 30 oxyethylene units (PhEO) was utilized. In contrast to Pluronic copolymers, normally utilized in the stabilization of liquid crystalline dispersions with ordered inner structure, use of such non-polymeric surfactant is not a common practice in this field. We revealed how properties of these particles, such as internal structure, size, and stability, can be rationally modified by the concentration of the stabilizing agent and processing conditions. The physical stability of the hexosomes was further examined by the LUMiFuge technique.Structural effect of PhEO solubilization on the properties of the bulk H_II mesophase system showed that phase behavior was greatly influenced following phase transitions: H_II → H_II + cubic → cubic + L_α → L_α. The decrease of hydrogen bonding of the hydroxyl and carbonyl groups of monoolein with water and simultaneous hydration of EO groups of PhEO appeared to be important for the observed behavior. The use of PhEO as a dispersant resulted in a soft matter multi-phase water dispersion with bimodal distribution of the particle population. Effective stabilization of hexosomes was obtained in an extremely narrow concentration range of PhEO (0.1–0.2 wt%), coexisting with small vesicles and disordered particles. At higher PhEO content, particles had disordered inner structure, and unilamellar and multilamellar vesicles, at the expense of hexosomes in consequence of incorporation of the dispersant into the hexosome structure. PhEO was found to induce lamellar phase formation, introducing disorder into the hexagonal LLC and reducing their domain size.Finally, hexosomes were evaluated as delivery vehicles for the therapeutic peptide desmopressin. Sustained release of this drug was observed during the first 10 h; however, permeation drastically increased in the 10–24 h range.     

Cognitive‐Performance Recovery of Alzheimer's Disease Model Mice by Modulation of Early Soluble Amyloidal Assemblies

A rationally designed oligomerization inhibitor interacts with early intermediate assemblies of amyloid‐β polypeptide (Aβ) through the aromatic elements and inhibits their assembly into the toxic oligomers that cause Alzheimer's disease by a unique C^α‐methylation β‐breakage strategy. The electrostatic potential of the low‐energy conformation of the dipeptide inhibitor bound to Aβ is shown.

     

Thermal and chemical stability of diphenylalanine peptide nanotubes: implications for nanotechnological applications

The diphenylalanine peptide, the core recognition motif of the beta-amyloid polypeptide, efficiently self-assembles into discrete, well-ordered nanotubes. Here, we describe the notable thermal and chemical stability of these tubular structures both in aqueous solution and under dry conditions. Scanning and transmission electron microscopy (SEM and TEM) as well as atomic force microscopy (AFM) revealed the stability of the nanotubes in aqueous solution at temperatures above the boiling point of water upon autoclave treatment. The nanotubes preserved their secondary structure at temperatures up to 90 degrees C, as shown by circular dichroism (CD) spectra. Cold field emission gun (CFEG) high-resolution scanning electron microscope (HRSEM) and thermogravimetric analysis (TGA) of the peptide nanotubes after dry heat revealed durability at higher temperature. It was shown that the thermal stability of diphenylalanine peptide nanotubes is significantly higher than that of a nonassembling dipeptide, dialanine. In addition to thermal stability, the peptide nanotubes were chemically stable in organic solvents such as ethanol, methanol, 2-propanol, acetone, and acetonitrile, as shown by SEM analysis. Moreover, the acetone environment enabled AFM imaging of the nanotubes in solution. The significant thermal and chemical stability of the peptide nanotubes demonstrated here points toward their possible use in conventional microelectronic and microelectromechanics processes and fabrication into functional nanotechnological devices.     

Miniature array postdetection-encoded MRI

A method for performing nuclear magnetic resonance (NMR) measurements simultaneously from more than a single radiofrequency (RF) coil is presented. The method employs the detection of magnetic resonance signals in an array of detectors, where each detector is responsible for detecting a unique frequency bandwidth or a magnetic resonance signal from a unique location in a region in a primary, substantially homogeneous, static magnetic field. The detectors may be separated logically into groups, whereby all the detectors in a given group are essentially RF-decoupled from each other to substantially eliminate cross-talk by switching circuits or by being placed from each other sufficiently remotely. Sampling of detected signals from detectors in this array is done simultaneously over groups of noninteracting detectors. The detected signals from all detectors in a given group are simultaneously transmitted to a single preamplifier, thus increasing significantly the signal-to-noise ratio (SNR) in that preamplifier. Prior to transmitting each detected NMR signal of each detector to the preamplifier, each detected signal is separately and uniquely encoded electronically. This provides a method whereby the signal of each detector is uniquely encoded. Accumulating all these encoded signals, which were simultaneously received in a number of RF detectors into a single amplifier, results in the total signal having a high SNR ratio. This total amplified signal is later decoded into each detector's original signal by a decoding circuitry. Conventional magnetic resonance imaging (MRI) techniques may be thereafter applied to obtain an image. Or else, conventional NMR techniques may be thereafter applied to obtain an improved SNR from a sample, using a single preamplifier with a multitude of detectors. Applying this method to a large number of miniature and closely packed RF detectors placed in an array-like configuration results in an MRI technique with a very fast acquisition time, an increased SNR and a high spatial resolution equivalent to the number of detectors per unit of length. Deblurring and decoupling algorithms allow for images from layers as deep as 6 mm to be acquired.     

Effect of sonochemistry: Li- and Mn-rich layered high specific capacity cathode materials for Li-ion batteries

Li- and Mn-rich layered Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode material was synthesized using sonochemical method followed by annealing at 700, 800, and 900 °C for 10 h. The material was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and electrochemical techniques. Its performance as a cathode material for Li-ion batteries was examined. With the sample annealed at 900 °C, an initial specific capacity of 240 mAh g^?1 was obtained, which decreased to 215 mAh g^?1 after 80 cycles, thus retaining about 90 % of its initial capacity. In contrast, samples annealed at lower temperatures exhibited lower capacity retention upon cycling. Thus, the final annealing temperature was found to have a significant effect on the electrochemical stability of this material in terms of capacity, average voltage, and rate capability. The advantage of this synthesis, which includes a sonochemical stage, compared with a conventional co-precipitation synthesis, was also confirmed.     

Microscopic evidence for the modification of the electronic structure at grain boundaries of Cu(In(1-x),Ga(x))Se2 films

We investigated the electronic properties around grain boundaries of polycrystalline Cu(In(1-x),Ga(x)Se(2)) films as a function of Ga content, using scanning tunneling spectroscopy. Spectra acquired on samples with low Ga content (x=0 and 0.33) reveal downward band bending with respect to adjacent p-type grains, suggesting type inversion at the surface of grain boundaries. Such a behavior was not observed for samples with high Ga contents. These results are consistent with our atomic force microscopy data and may shed light on the origin of the x-dependent efficiency for polycrystalline Cu(In(1-x),Ga(x)Se(2))-based solar cells.     

A Highly Selective and Sensitive Chemiluminescent Probe for Real-Time Monitoring of Hydrogen Peroxide in Cells and Animals

Selective and sensitive molecular probes for hydrogen peroxide (H₂O₂), which plays diverse roles in oxidative stress and redox signaling, are urgently needed to investigate the physiological and pathological effects of H₂O₂. A lack of reliable tools for in vivo imaging has hampered the development of H₂O₂ mediated therapeutics. By combining a specific tandem Payne/Dakin reaction with a chemiluminescent scaffold, H₂O₂-CL-510 was developed as a highly selective and sensitive probe for detection of H₂O₂ both in vitro and in vivo. A rapid 430-fold enhancement of chemiluminescence was triggered directly by H₂O₂ without any laser excitation. Arsenic trioxide induced oxidative damage in leukemia was successfully detected. In particular, cerebral ischemia-reperfusion injury-induced H₂O₂ fluxes were visualized in rat brains using H₂O₂-CL-510 , providing a new chemical tool for real-time monitoring of H₂O₂ dynamics in living animals.