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.     

Three-dimensional effects on the linear adiabatic molecular wavefunctions in the H + H2 system

The adiabatic molecular wavefunctions in the H + H₂ system are obtained in one dimension by solving the double-well potential problem. In three dimensions, the corresponding linear adiabatic molecular wavefunctions are obtained. A comparison between these wavefunctions clearly suggests that the probability of reaction is smaller in three dimensions.     

Electrorheological characterization of polyaniline-coated poly(methyl methacrylate) suspensions

Surface-conductive particles consisting of a poly(methyl methacrylate) (PMMA) core and a polyaniline (PA)-coated shell were synthesized and adopted as suspended particles for electrorheological (ER) fluids. The PA-PMMA composite particles synthesized were monodisperse and spherical in shape. The PA-PMMA suspensions in silicone oil showed typical ER characteristics under an applied electric field. The PA-PMMA composite particles possess a higher dielectric constant and conductivity than the pure PA particle, within an acceptable conductivity range for ER fluids, but the PA-based ER fluid showed larger shear-stress enhancement than the PA-PMMA-based systems. This phenomena can be explained by the interfacial polarizability of PA-based ER fluids, which is the difference between the ER fluid's dielectric constant and loss factor - this polarizability was higher than that of PA-PMMA-based ER fluids, as shown by the dielectric spectrum of each fluid. The insulating PMMA core suppressed the interfacial polarization in ER fluids, resulting in reduced interaction among particles under an imposed electric field.     

Circular Dichroism Study of the Inclusion-Dissociation Behavior of Complexes between a Molecular Nanotube and Azobenzene Substituted Linear Polymers

We have investigated the inclusion properties of molecular nanotubes composed ofcrosslinked -cyclodextrin. Induced circular dichroism was used to probe theformation and dissociation of complexes between the nanotubes and azobenzenemodified linear polymers. The polymer was poly(ethylene glycol) (PEG), either withor without a hydrophobic alkyl chain.It was found that the inclusion complex betweenthe nanotubes and polymers formed at room temperature, and that the polymers dissociated from the nanotubes with increasing temperature. Further, the polymer with hydrophobic alkyl chain was bound inside the nanotube more strongly and dissociated more abruptly with increasing temperature than its hydrophilic counterpart as expected theoretically.     

Bystander CD4+ T cells: crossroads between innate and adaptive immunity

T cells are the central mediators of both humoral and cellular adaptive immune responses. Highly specific receptor-mediated clonal selection and expansion of T cells assure antigen-specific immunity. In addition, encounters with cognate antigens generate immunological memory, the capacity for long-term, antigen-specific immunity against previously encountered pathogens. However, T-cell receptor (TCR)-independent activation, termed “bystander activation”, has also been found. Bystander-activated T cells can respond rapidly and secrete effector cytokines even in the absence of antigen stimulation. Recent studies have rehighlighted the importance of antigen-independent bystander activation of CD4⁺ T cells in infection clearance and autoimmune pathogenesis, suggesting the existence of a distinct innate-like immunological function performed by conventional T cells. In this review, we discuss the inflammatory mediators that activate bystander CD4⁺ T cells and the potential physiological roles of these cells during infection, autoimmunity, and cancer.Subject terms: T cells, CD4-positive T cells     

Determination of estrone and 17 beta-estradiol in human hair by gas chromatography-mass spectrometry

An efficient procedure is described for the determination of estrone and 17 beta-estradiol in hair by gas chromatography-mass spectrometry (GC-MS). The method involves alkyloxycarbonylation with isobutyl chloroformate (isoBCF) of phenolic hydroxy groups after alkaline digestion of hair samples. The resulting isobutyloxycarbonyl derivatives of estrone and 17 beta-estradiol are extracted with hexane and subjected to chlorodifluoroacetyl derivatization in order to protect the remaining alcoholic hydroxy groups. When GC-MS with selected ion monitoring (SIM) was used, the quantitative ions were at m/z 270 and 384 in the electron ionization mass spectra for estrone and 17 beta-estradiol, respectively. The detection limits for SIM of the steroids were 1 and 2 pg, respectively, and the SIM responses were linear with correlation coefficients varying from 0.991 to 0.994 in the concentration range 0.2-4.0 ng g-1 for the estrogens studied. The detection of estrone and 17 beta-estradiol in hair samples was possible in the concentration range of 0.24-1.30 ng g-1. The concentrations of the two estrogens detected were different in male and female hair samples.     

Complexometric determination of magnesium oxide in flyash blended cement

A complexometric titration method is proposed to determine magnesium oxide in flyash blended cement. A 0.50 g of sample was heated with hydrochloric acid for 10 min. The solution was diluted to 500 ml, and 50 ml was pipetted and heated to boiling with 2.5 ml of 5% ammonium oxalate solution. The solution was then made alkaline by ammonium hydroxide. The suspension was cooled and filtered. The filtrate was titrated by standard 0.002M EDTA solution. The concentration of MgO in sample was calculated. The flyash content of the sample was determined by British Standard method and the recovery factor (f) was calculated by the equation of f = 100/(99 - 0.315 x %FA). Concentration of MgO in sample was corrected by multiplying the recovery factor with concentration initially found by EDTA titration. The precision of the method is better with more time saving than the official methods.     

A novel oxygen and/or carbon dioxide-sensitive optical transducer

A novel oxygen (O(2)) and/or carbon dioxide (CO(2))-sensitive transducer for the measurement of both gaseous O(2) and CO(2) over the concentration ranges of O(2), 0-100% and CO(2), 0-10% has been described employing a solution of 10.6 muM fluorescein (FL) and 190 muM potassium hydroxide in a solvent mixtures of 1:1 (v/v) N,N'-diethylaniline (DEA) and N,N-dimethylformamide. Increasing O(2) concentrations cause the absorbance of the solution at a wavelength of 400 nm to increase owing to a contact charge transfer reaction existing between O(2) and DEA molecules, and increasing CO(2) concentrations produce a non-linear fall in absorbance at 520 nm as the colour of FL changes from its orange dianion form to the colourless neutral, lactonic form. Both processes are independent of each other and reversible. The response to changes in O(2) concentrations is in good agreement with Beer-Lambert's law and the response to changes in CO(2) concentrations in non-linear. A fibre optic sensing system based on this solvent-dye solution has been set up for continuous and reversible determination of both gaseous O(2) and CO(2). Possible applications include environmental and physiological monitoring of O(2) over the ranges of 0-100% and CO(2), 0-10%.     

Dual effect of oxidative stress on NF-kappakB activation in HeLa cells

Reactive oxygen species (ROS) has been implicated as an inducer of NF-kappaB activity in numbers of cell types where exposure of cells to ROS such as H(2)O(2) leads to NF-kappaB activation. In contrast, exposure to oxidative stress in certain cell types induced reduction of tumor necrosis factor (TNF)- induced NF-kappaB activation. And various thiol-modifying agents including gold compounds and cyclopentenone prostaglandins inhibit NF-kappaB activation by blocking IkappaB kinase (IKK). To understand such conflicting effect of oxidative stress on NF- kappakB activation, HeLa cells were incubated with H(2)O(2) or diamide and TNF-induced expression of NF-kappaB reporter gene was measured. NF-kappaB activation was significantly blocked by these oxidizing agents, and the inhibition was accompanied with reduced nuclear NF-kappaB and inappropriate cytosolic IkappaB degradation. H(2)O(2) and diamide also inhibited IKK activation in HeLa and RAW 264.7 cells stimulated with TNF and lipopolysaccharide, respectively, and directly blocked IKK activity in vitro. In cells treated with H(2)O(2) alone, nuclear NF-kappaB was induced after 2 h without detectable degradation of cytosolic IkappaBalphaa or activation of IKK. Our results suggest that ROS has a dual effect on NF-kappaB activation in the same HeLa cells: it inhibits acute IKK-mediated NF-kappakB activation induced by inflammatory signals, while longer-term exposure to ROS induces NF-kappaB activity through an IKK-independent pathway.