Preparation and characterization of self-assembled nanoparticles based on glycol chitosan bearing adriamycin

An anthracycline drug, adriamycin, was chemically conjugated onto the backbone of glycol chitosan via an acid-labile cis-aconityl linkage. The physicochemical characteristics of the glycol chitosan–adriamycin (GC–ADR) conjugates were investigated by dynamic light scattering, atomic force microscopy, and fluorescence spectroscopy. The GC–ADR conjugates were capable of forming nano-sized self-aggregates in an aqueous medium, when the adriamycin content in the conjugate was in the range of 2.0–5.0 wt.%. The self-aggregates were spherical in shape, and had mean diameters of 238–304 nm, depending on the adriamycin content. The critical aggregation concentrations of the conjugates, estimated by the fluorescence quenching method, were as low as 1.0–2.5×10⁻² mg/ml. The size of self-aggregates was not affected by the polymer concentration in the range from 50 to 2,000 μg/ml, and was maintained up to 8 days in phosphate-buffered saline (pH 7.4), indicating high colloidal stability. The release of adriamycin from self-aggregates was significantly dependent on the pH of the medium due to the cis-aconityl linkage; e.g., the amount of adriamycin released for 4 days was 7.3±0.3% at pH 7, whereas it was 29.3±1.9% at pH 4. The cell viability results demonstrated that free adriamycin shows more potent cytotoxicity than the conjugates, primarily attributed to the sustained release of adriamycin from self-aggregates. In conclusion, the self-aggregates, formed by GC–ADR conjugates, might be useful for the site-specific delivery of adriamycin in a sustained manner.     

Preparation and characterization of functional group gradient surfaces

Functional group gradient surfaces where the density of functional groups changes gradually along the sample length were prepared. The functional group (? COOH, ? CONH₂, and ? OH group) gradient surfaces were produced by the treatment of low-density PE sheets using a corona with gradually increasing power, followed by the graft copolymerization of acrylic acid and subsequent substitution reaction of carboxylic acid groups to amide or hydroxyl groups. The prepared gradient surfaces were characterized by the measurement of water contact angle, FTIR-ATR, and ESCA. The gradient surfaces prepared can be used to systematically investigate the interactions of biological or other species in terms of the surface functional groups and their density of polymeric materials. © 1994 John Wiley & Sons, Inc.     

Selective oxidation of hydrogen sulfide to ammonium thiosulfate and sulfur over vanadium-bismuth oxide catalysts

The selective oxidation of hydrogen sulfide containing excess water and ammonia was studied over vanadium-bismuth mixed oxide catalysts. The investigation was focused on understanding the complex reaction steps and the roles of each metal oxide. Therefore, supported V₂O₅/TiO₂, V-Bi-O/TiO₂ catalysts and a mechanical mixture of V₂O₅ + Bi₂O₃ were tested in the reaction. Ammonia reacted either with H₂S or SO₂, produced from the oxidation of H₂S. Water vapor promoted the reaction of ammonia and SO₂. Strong synergistic phenomena in catalytic activity were observed for the mechanically mixed catalyst of V₂O₅ and Bi₂O₃. V-Bi-O/TiO₂ catalyst showed very high H₂S conversion without any considerable emission of SO₂. Temperature-programmed studies (TPR and TPO), XRD and Raman analyses revealed that the high catalytic performance of V-BiO/TiO₂ catalyst originated from the high redox capacity of the bismuth vanadate phase.     

Ruthenium‐catalyzed synthesis of quinolines via reductive heteroannulation of nitroarenes with 3‐amino‐1‐propanols

Nitroarenes are reductively cyclized with 3‐amino‐1‐propanols in dioxane/H₂O in the presence of a ruthenium catalyst and tin(II) chloride dihydrate together with isopropanol to afford the corresponding quinolines. A reaction pathway involving initial reduction of nitroarenes to anilines, propanol group transfer from 3‐amino‐1‐propanols to anilines, N‐alkylation of anilines by 3‐anilino‐1‐propanols and heteroannulation of 1,3‐dianilinopropanes is proposed.     

Quantitative analyses of shape-selective intercalation of isomeric mixtures of muconates into [LiAl2(OH)6]Cl.yH2O layered double hydroxide

Quantitative investigation of the shape selectivity for the competitive intercalation reaction of isomeric mixtures in the interlayer of LDH was achieved by analyzing the solid phases synthesized by the reaction of [LiAl(2)(OH)(6)]Cl.yH(2)O with various compositional mixtures of (E,E)- and (Z,Z)-muconates. The apparent partition constant K' for the anion-exchange reaction between (E,E)- and (Z,Z)-muconates was quite dependent on the mole fraction of muconates in solution. The only single phase saturated with [LiAl(2)(OH)(6)](2)[(E,E)-C(6)H(4)O(4)].zH(2)O could be obtained in the range of the initial mole fraction of (E,E)-muconate larger than 0.6 in the starting solution, while mixed phases intercalated with (E,E)- and (Z,Z)-muconates could be obtained at lower mole fractions of (E,E)-muconate. The shape selectivity for the competitive reaction of two muconates on the [LiAl(2)(OH)(6)](+) lattice could be ascribed to thermodynamic processes, and the conditions under which that pure (E,E)-muconate was efficiently separated from isomeric mixtures of two muconates were successfully evaluated.     

A novel oligothiophene derivative as a hole‐transport with emitting material for OLED

A novel oligothiophene derivative containing the triphenylamine moiety with high glass transition temperature (T_g; 135 °C), 5,5′‐{bis[4‐di(4‐thiophenyl)amino]phenyl}‐2,2′‐bithiophene (TTPA‐dimer) was synthesized by the dimerization of tris[4‐(2‐thienyl)phenyl]amine (TTPA) with a palladium catalysis. Some types of electroluminescent (EL) devices that use the amorphous material for a hole‐ and an electron‐transporting with an emitting layer were fabricated. These devices emitted a bright green‐yellowish light (λ_emi; around 510 nm) with a small full width at half maximum (FWHM) rather than that of Alq₃. The single layer EL device showed a maximum luminance of 221 cd/m² at 8 V (0.06 lm/W at 100 cd/m²). On the other hand, the double layer (TTPA‐dimer/Alq₃) EL device that used Alq₃ as the electron transport material was increased up to 10830 cd/m² at 12 V (0.89 lm/W at 300 cd/m²) and with a lower turn‐on voltage (3.2 V at 0.1 cd/m²) than other types of EL devices. Copyright © 2003 John Wiley & Sons, Ltd.     

Improved expression by cytomegalovirus promoter/enhancer and behavior of vascular endothelial growth factor gene after myocardial injection of naked DNA

Direct injection of the vascular endothelial growth factor (VEGF) gene plasmid DNA into the myocardium was shown to induce development of new blood vessels to increase the circulation in the heart of patients with coronary artery diseases. However, such angiogenic gene therapy (via naked DNA) was limited by low level of gene expression. Furthermore, the temporal and spatial characteristics of VEGF gene transfer in the heart are not known. In this study, we demonstrated that a plasmid vector, containing the human cytomegalovirus immediate early (HCMV IE) promoter and enhancer, induces greater expression of gene in the rat heart monitored by gene fused to the chloramphenicol acetyl transferase (CAT) reporter, than four different viral and cellular promoters. Interestingly, expression of VEGF121 protein showed an earlier peak, a shorter duration, and a wider distribution than that of CAT only. Therefore, a plasmid vector with an HCMV IE promoter/enhancer provides clear advantages over other previously developed plasmids. Furthermore, expression profile of VEGF121 gene may provide useful information in the design of angiogenic gene therapy in the heart.     

Reaction kinetics and critical phenomena: rates of some first order gas evolution reactions in binary solvents with a consolute point

We have measured the rate of carbon dioxide evolution in the aniline catalyzed decomposition of acetone dicarboxylic acid in a mixture of isobutyric acid + water near its consolute point. Within a temperature interval of 1 degrees C, which included the critical solution temperature, the first-order rate constant oscillated in magnitude by about 10% as it passed through three complete cycles of slowing down followed by speeding up. Whereas we can find no ready explanation for the speeding up, we suggest that, because the mixture contained no inert components, the slowing down should belong to the Griffiths-Wheeler class of strong critical effects [Phys. Rev. A 1970, 2, 1047]. As a check on this conclusion, we have measured the rate of the SN1 decomposition of benzene diazonium tetrafluoroborate in 2-butoxyethanol + water near the lower critical solution temperature and also the rate of the acid-catalyzed decomposition of ethyl diazoacetate in isobutyric acid + water near the upper critical solution temperature. Both of these reactions evolve nitrogen. In the first reaction, 2-butoxyethanol is inert, whereas in the second, isobutyric acid is inert. In both cases, because there was one inert component, we regarded the response of the rate constant to temperature in the critical region to be representative of the Griffiths-Wheeler class of weak critical effects. Within our accuracy of measurement of about 2% in the rate constant and about 1 mK in the temperature, we could detect no effect of the critical point on the rates of either of these reactions, suggesting that a weak effect may be too small to be seen with our experimental apparatus. The successful observation of a critical effect in the rate of decomposition of acetone dicarboxylic acid proves, however, that kinetic critical phenomena are observable in heterogeneous reactions.     

Modeling drop shape on contaminated surfaces or surfaces with physical structures

Surface contaminants are commonly found on films. They get transferred to the surface from incompletely cured silicone liners on the films or owing to migration of additives to the surface from within the film. During the process of ink jet printing (a noncontact printing process), surface contamination affects the shape of the drops (causing the formation of fingers and crescents) and hence image quality. This study uses modeling methods to examine how such surface contamination affects the drops shapes. Subsequently, it models the effect of surface structures (pits) on the drop shape. This study explores how image quality can be controlled in the presence of surface contamination and surface structures.     

Enantiomer separation of a novel aminothiazolecarboxamide fungicide using polysaccharide-derived chiral stationary phases

The direct enantioseparation of a novel aminothiazolecarboxamide fungicide, ethaboxam, on polysaccharide-derived chiral stationary phases (CSPs) is described. Good resolution is achieved with several polysaccharide-derived CSPs. Chiralcel OD (OD-H) and Chiralpak AS are excellent for direct enantiomer separation of ethaboxam. The elution behavior and the effects of eluent composition on the resolution of ethaboxam are also investigated. Furthermore, the mechanism for chiral recognition using molecular mechanics is discussed.