Photo-alignment Property of Azobenzene-containing Polyimide Films Swollen by Alkyl-amine

Photo-alignment efficiency of polyimide containing azobenzene in the backbone structure (Azo-PI) is significantly enhanced by exposing the precursor (polyamic acid: Azo-PAA) film to alkyl-amine vapor prior to photo-alignment. In this study, we have investigated the relationships between the alkyl-amine vapor treatment time, the swelling ratio of Azo-PAA films, and the photo-induced in-plane anisotropy. We found that: the Azo-PAA film swells on exposure to alkyl-amine vapor, and the swelling finally saturates; and the photo-induced in-plane anisotropy is correlated very closely with the swelling ratio. In addition, we pointed out the importance of the process order of alkyl-amine vapor treatment and photo-alignment.     

Eventually positive solutions of first order nonlinear differential equations with a deviating argument

The following first order nonlinear differential equation with a deviating argument $ x'(t) + p(t)[x(\tau (t))]^\alpha = 0 $ is considered, where α > 0, α ≠ 1, p ∈ C[t ₀; ∞), p(t) > 0 for t ≧ t ₀, τ ∈ C[t ₀; ∞), lim _t→∞ τ(t) = ∞, τ(t) < t for t ≧ t ₀. Every eventually positive solution x(t) satisfying lim _t→∞ x(t) ≧ 0. The structure of solutions x(t) satisfying lim _t→∞ x(t) > 0 is well known. In this paper we study the existence, nonexistence and asymptotic behavior of eventually positive solutions x(t) satisfying lim _t→∞ x(t) = 0.     

Optimizing Charge Switching in Membrane Lytic Peptides for Endosomal Release of Biomacromolecules

Endocytic pathways are practical routes for the intracellular delivery of biomacromolecules. Along with this, effective strategies for endosomal cargo release into the cytosol are desired to achieve successful delivery. Focusing on compositional differences between the cell and endosomal membranes and the pH decrease within endosomes, we designed the lipid-sensitive and pH-responsive endosome-lytic peptide HAad. This peptide contains aminoadipic acid (Aad) residues, which serve as a safety catch for preferential permeabilization of endosomal membranes over cell membranes, and His-to-Ala substitutions enhance the endosomolytic activity. The ability of HAad to destabilize endosomal membranes was supported by model studies using large unilamellar vesicles (LUVs) and by increased intracellular delivery of biomacromolecules (including antibodies) into live cells. Cerebral ventricle injection of Cre recombinase with HAad led to Cre/loxP recombination in a mouse model, thus demonstrating potential applicability of HAad in vivo.     

An estimated quantitative lateral flow immunoassay for determination of artesunate using monoclonal antibody

There have been reports of fake artesunate (ART), which has led to deaths from untreated malaria in South East Asia. To rapidly screen for fake and adulterated ART products in the drug market, a lateral flow immunoassay (LFIA) based on a colloidal gold–monoclonal antibody probe for detection of ART within samples was developed. With this method, the calibration curve for ART was determined by the intensity ratio of the test and control bands at various ART concentrations. The linearity range was 12.5–200 μg/ml of ART. Samples were tested by the developed LFIA and can be calculated for ART contents. The levels of ART in the samples were also confirmed by enzyme-linked immunosorbent assay. The results of the two methods were in good conformance. The proposed LFIA was demonstrated to be a simple and rapid analytical method for detecting ART in the pharmaceutical formulation.     

Femtosecond laser-induced stimulation of a single neuron in a neuronal network

We demonstrated the stimulation of neurons at a single-cell level in cultured neuronal network by a focused femtosecond laser. When the femtosecond laser was focused on a neuron loaded with a fluorescent calcium indicator, the fluorescence intensity immediately increased at the laser spot, suggesting that intracellular Ca²⁺ increases in the neuronal cell due to the femtosecond laser irradiation. The probability of Ca²⁺ elevation at the laser spot depended on the average laser power, irradiation time, and position of the focal point along the optical axis, indicating that the femtosecond laser activates neurons because of multiphoton absorption. Moreover, after laser irradiation of a single neuron cultured on multielectrode arrays, the evoked electrical activity of the neurons was demonstrated by electrophysiological systems, which concluded that the focused femtosecond laser could achieve stimulating a single neuron in a neuronal network with high spatial and temporal resolution.     

Polarization-mode dispersion measurement by an optical time-domain reflectometer with polarimetry assuming backscattering by randomly oriented nonspherical particles

In previous work on polarization-mode dispersion (PMD) measurement with an optical time-domain reflectometer with polarimetry (p-OTDR), scatterers were assumed to be a cloud of small spherical particles in a fiber. We have found that the p-OTDR waveforms were fitted well by modified Mueller matrices, assuming scattering by a cloud of nonspherical particles. We realized a PMD measurement based on the p-OTDR Jones matrix eigenanalysis (JME) method. The measured PMD was consistent with that of JME standard measurement with transmission-type polarimetry.     

Photoinduced tandem three-component coupling of propanedinitrile, 2,5-dimethylhexa-2,4-diene, and cyanoarenes

A tandem three-component coupling photoreaction proceeds upon photoirradiation of MeCN/H2O solutions containing propanedinitrile (1, malononitrile), 2,5-dimethylhexa-2,4-diene (2), and polycyanoarenes in the presence of phenanthrene and carbonate, leading to selective alpha-monoalkylation of 1. The reaction proceeds via photo-NOCAS (Nucleophile-Olefin Combination, Aromatic Substitution) type mechanism: nucleophilic attack of the anion of 1 to photogenerated 2(*+) is followed by ipso-substitution on the radical anion of the polycyanoarene. It advances under mild, safe, and environmentally friendly conditions such as proceeding at ambient temperature without metals and halogens, and in the presence of weak base. The reaction also represents a novel and metal-free cross-coupling reaction that leads to ipso-substitution on polycyanoarene via aryl-cyano bond cleavage. In addition, the reaction is a rare example of introducing carbon nucleophile in the photoinduced electron transfer reaction, except that of cyanide ion.     

Preferential oxidation of carbon monoxide catalyzed by platinum nanoparticles in mesoporous silica

Preferential oxidation (PROX) of CO is an important practical process to purify H2 for use in polymer electrolyte fuel cells. Although many supported noble metal catalysts have been reported so far, their catalytic performances remain insufficient for operation at low temperature. We found that Pt nanoparticles in mesoporous silica give unprecedented activity, selectivity, and durability in the PROX reaction below 353 K. We also studied the promotional effect of mesoporous silica in the Pt-catalyzed PROX reaction by infrared spectroscopy using the isotopic tracer technique. Gas-phase O2 is not directly used for CO oxidation, but the oxygen of mesoporous silica is incorporated into CO2. These results suggest that CO oxidation is promoted by the attack of the surface OH groups to CO on Pt without forming water.     

Light exposure dependence of molecular orientation of glassy polyfluorene layers formed on photo-aligned polyimide films

We have investigated the molecular orientation of glassy poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) layers formed on photo-aligned polyimide films with different in-plane anisotropy. The polyimide contains azobenzene in the backbone structure (Azo-PI), allowing us to control the in-plane anisotropy of the film by varying linearly polarized light (LP-L) exposure. The glassy PFO layers (30 nm thick) were obtained by annealing the samples at the liquid crystalline phase of PFO and then quenching them to room temperature. The degree of alignment of PFO was assessed by the polarization ratio of photoluminescence (PL). The PL polarization ratio increased rapidly with the LP-L exposure, and it reached 10 at 2.8 J/cm². Beyond this LP-L exposure, it became almost constant around 10.4. This PL polarization ratio was much higher than the absorption dichroic ratio of the underlying Azo-PI film. This result suggests that the degree of alignment of PFO is determined by its liquid crystalline nature. The saturation dependence of the degree of alignment is very useful for fabricating alignment patterns by a simple photo-mask exposure method. We have succeeded in fabricating 3 μm line-and-space alignment patterns of PFO.