Supramolecular nanocarrier of siRNA from PEG-based block catiomer carrying diamine side chain with distinctive pKa directed to enhance intracellular gene silencing

An siRNA nanocarrier formed through self-assembly of PEG-based block catiomer possessing two distinct amino groups with different pKa values in a side chain was developed. This design provided the carrier with a sufficient siRNA complexation and an assumed buffering capacity in the endosomes, allowing it to exhibit remarkable gene knockdown abilities as well as sufficient serum tolerability.     

Wolfram

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Fabrication of combinatorial nm-planar electrode array for high throughput evaluation of organic semiconductors

We have fabricated a combinatorial nm-planar electrode array by using photolithography and chemical mechanical polishing processes for high throughput electrical evaluation of organic devices. Sub-nm precision was achieved with respect to the average level difference between each pair of electrodes and a dielectric layer. The insulating property between the electrodes is high enough to measure I-V characteristics of organic semiconductors. Bottom-contact field-effect-transistors (FETs) of pentacene were fabricated on this electrode array by use of molecular beam epitaxy. It was demonstrated that the array could be used as a pre-patterned device substrate for high throughput screening of the electrical properties of organic semiconductors.     

High-performance organic field-effect transistors based on pi-extended tetrathiafulvalene derivatives

Aromatic ring-condensed TTF derivatives exhibited excellent p-type FET performances in thin films. Introduction of fused benzene and pyrazine rings to the TTF skeleton was effective to enhance the intermolecular interactions and stability to oxygen. Ordered molecular alignment was confirmed by XRD studies. A pi-stacking structure was observed in the single crystal of diquinoxalinoTTF.     

High-speed evaluation of thermoelectric materials using multi-channel measurement system

We have developed a multi-channel measurement system for combinatorial investigation of thermoelectric materials. The measurement apparatus has ten series of pin-probe array which enables us to measure the Seebeck coefficient and electric conductivity of 10 samples simultaneously. A successful measurement on a composition-spread thin films library indicated that this measurement system is highly useful for the high-speed exploration of thermoelectric materials by combinatorial approach. This revised version was published online in August 2006 with corrections to the Cover Date.     

Combinatorial fabrication and magnetic properties of homoepitaxial Co and Li co-doped NiO thin-film nanostructures

Magnetic properties of nanostructured epitaxial thin layers of a series of Co and Li co-doped NiO on MgO(1 0 0) substrate with NiO buffer layer have been investigated. Thin films were synthesized by combinatorial laser molecular beam epitaxy (CLMBE) in the continuous binary composition spread approach. Large and linear variation of x was achieved in the growth of Co_xLi_0.2Ni_0.8−xO_, onto 9 mm of single substrate. Homoepitaxial growth with smooth surface morphology was confirmed by grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). Linear decrease in the band gap and optical transparency was observed with increasing cobalt concentration. The magneto-optical Kerr effect revealed a strong photon energy dependency with negative Kerr rotation for all the Co-concentrations in the film, suggesting intra-valence charge transfer (IVCT) between low spin state Co²⁺ with host Ni²⁺. Ferromagnetic (FM)-like ordering was observed at low temperatures, while antiferromagnetism predominates at room temperature in the Co and Li co-doped nickel oxide epitaxial films.     

pH-Responsive PEGylated nanogels as targetable and low invasive endosomolytic agents to induce the enhanced transfection efficiency of nonviral gene vectors

A pH-responsive PEGylated nanogel was successfully prepared by means of emulsion copolymerization of 2-(N,N-diethylamino)ethyl methacrylate (AMA) with heterobifunctional poly(ethylene glycol) (PEG) bearing a 4-vinylbenzyl group at the α-end and a lactose moiety at the ω-end in the presence of potassium persulfate and ethyleneglycol dimethacrylate as a cross-linker. Polyplex micelle composed of PEG-block-poly(l-lysine) copolymer and plasmid DNA (PEG-b-PLL/pDNA) exhibited a far more efficient transfection ability in the presence of lac-nanogel-8k-1.0% (PEG, M _n = 8000; cross-linking density, 1.0%) than the PEG-b-PLL/pDNA polyplex micelle alone (in the absence of lac-nanogel-8k-1.0%), suggesting that an appreciable fraction of lac-nanogel-8k-1.0% along with the PEG-b-PLL/pDNA polyplex micelle is taken up into the HuH-7 cells through the asialoglycoprotein receptor-mediated endocytosis process mediated by the cluster of a large number of lactose moieties on the surface of lac-nanogel-8k-1.0%, followed by the effective disruption of the endosome by the buffer effect of the unprotonated PAMA core in lac-nanogel-8k-1.0%. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

PEG-detachable polyplex micelles based on disulfide-linked block catiomers as bioresponsive nonviral gene vectors

PEG-based polyplex micelles, which can detach the surrounding PEG chains responsive to the intracellular reducing environment, were developed as nonviral gene vectors. A novel block catiomer, PEG-SS-P[Asp(DET)], was designed as follows: (i) insertion of biocleavable disulfide linkage between PEG and polycation segment to trigger PEG detachment and (ii) a cationic segment based on poly(aspartamide) with a flanking N-(2-aminoethyl)-2-aminoethyl group, P[Asp(DET)], in which the Asp(DET) unit acts as a buffering moiety inducing endosomal escape with minimal cytotoxicity. The polyplex micelles from PEG-SS-P[Asp(DET)] and plasmid DNA (pDNA) stably dispersed in an aqueous medium with a narrowly distributed size range of approximately 80 nm due to the formation of hydrophilic PEG palisades while undergoing aggregation by the addition of 10 mM dithiothreitol (DTT) at the stoichiometric charge ratio, indicating the PEG detachment from the micelles through the disulfide cleavage. The PEG-SS-P[Asp(DET)] micelles showed both a 1-3 orders of magnitude higher gene transfection efficiency and a more rapid onset of gene expression than PEG-P[Asp(DET)] micelles without disulfide linkages, due to much more effective endosomal escape based on the PEG detachment in endosome. These findings suggest that the PEG-SS-P[Asp(DET)] micelle may have promising potential as a nonviral gene vector exerting high transfection with regulated timing and minimal cytotoxicity.