Physicochemical and biopharmaceutical characterization of novel Matrix-Liposomes.

Matrix-Liposomes (MLs) are a very promising solid oral drug delivery system; however, data on their interaction with biological membranes are not available. Here, we describe the quality of MLs manufactured by dual centrifugation. MLs were prepared with a Z-average range of 139 to 160 nm and a PDI of 0.18 to 0.25. To investigate the effect of MLs on intestinal tissue (with and without mucolytic treatment), we then established an ex vivo rat intestine model. The integrity of the epithelial membranes of rat intestine was not affected by the incubation with MLs without or with pre-mucolytic treatment. Tissue samples were also analysed for changes in P-glycoprotein (P-gp) expression and function. The net secretion of the P-gp substrate Rh123 across the rat duodenum was increased in the presence of MLs. To summarize, MLs do not affect intestinal epithelial integrity, although they impact Rh123 secretion. In future, these novel MLs have to be further evaluated for proficient intestinal drug delivery.

p-Channel organic semiconductors based on hybrid acene-thiophene molecules for thin-film transistor applications.

We report the structural and electrical characterization of two new p-channel organic semiconductors, 5,5'-bis(2-tetracenyl)-2,2'-bithiophene (1) and 5,5'-bis(2-anthracenyl)-2,2'-bithiophene (2). Both compounds exhibited a high degree of thermal stability with decomposition temperatures of 530 degrees C and 425 degrees C for 1 and 2, respectively. The thin-film structures of 1 and 2 were examined using wide-angle X-ray diffraction (XRD), grazing incidence X-ray diffraction (GIXD), and atomic force microscopy (AFM). Films of 1 and 2 pack in similar triclinic unit cells with the long axes of the molecules nearly perpendicular to the substrate. Thin-film transistors (TFTs) based on 1 and 2 exhibit contact-corrected linear regime hole mobility as high as 0.5 cm2/Vs and 0.1 cm2/Vs, respectively. The specific contact resistance at high gate voltages for gold top contacts was 2 x 10(4) Ohms cm and 3 x 10(4) Ohms cm for 35 nm thick films of 1 and 2, respectively. Long-term air stability tests revealed less degradation of the electrical properties of 1 and 2 in comparison to pentacene. Variable temperature measurements revealed activation energies as low as 22 and 27 meV for 1 and 2, respectively. The temperature and gate voltage dependence of the mobility are discussed in terms of a double exponential distribution of trap states and a model accounting for the layered structure of the organic films. The enhanced air and thermal stability over pentacene, combined with good electrical performance characteristics, make 2 a promising candidate for future organic TFT applications.

Effect of dielectric roughness on performance of pentacene TFTs and restoration of performance with a polymeric smoothing layer.

The morphology, structure, and transport properties of pentacene thin film transistors (TFTs) are reported showing the influence of the gate dielectric surface roughness. Upon roughening of the amorphous SiO2 gate dielectric prior to pentacene deposition, dramatic reductions in pentacene grain size and crystallinity were observed. The TFT performance of pentacene films deposited on roughened substrates showed reduced free carrier mobility, larger transport activation energies, and larger trap distribution widths. Spin coating roughened dielectrics with polystyrene produced surfaces with 2 A root-mean-square (rms) roughness. The pentacene films deposited on these coated surfaces had grain sizes, crystallinities, mobilities, and trap distributions that were comparable to the range of values observed for pentacene films deposited on thermally grown SiO2 (roughness also approximately 2 A rms).

Structural characterization of a pentacene monolayer on an amorphous SiO2 substrate with grazing incidence x-ray diffraction.

Grazing incidence X-ray diffraction reveals that a pentacene monolayer, grown on an amorphous SiO2 substrate that is commonly used as a dielectric layer in organic thin film transistors (OTFTs), is crystalline. A preliminary energy-minimized model of the monolayer, based on the GIXD data, reveals that the pentacene molecules adopt a herringbone arrangement with their long axes tilted slightly from the substrate normal. Although this arrangement resembles the general packing features of the (001) layer in single crystals of bulk pentacene, the monolayer lattice parameters and crystal structure differ from those of the bulk. Because carrier transport in pentacene OTFTs is presumed to occur in the semiconductor layers near the dielectric interface, the discovery of a crystalline monolayer structure on amorphous SiO2 has important implications for transport in OTFTs.