64 research outputs found

    Tuneable drug-loading capability of chitosan hydrogels with varied network architectures

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    Advanced bioactive systems with defined macroscopic properties and spatio-temporal sequestration of extracellular biomacromolecules are highly desirable for next generation therapeutics. Here, chitosan (CT) hydrogels were prepared with neutral or negatively charged cross-linkers in order to promote selective electrostatic complexation with charged drugs. CT was functionalized with varied dicarboxylic acids, such as tartaric acid, poly(ethylene glycol) bis(carboxymethyl) ether, 1,4-phenylenediacetic acid and 5-sulfoisophthalic acid monosodium salt (PhS), whereby PhS was hypothesized to act as a simple mimetic of heparin. Attenuated total reflectance Fourier transform infrared spectroscopy showed the presence of Cdouble bond; length as m-dashO amide I, N–H amide II and Cdouble bond; length as m-dashO ester bands, providing evidence of covalent network formation. The cross-linker content was reversely quantified by proton nuclear magnetic resonance on partially degraded network oligomers, so that 18 mol.% PhS was exemplarily determined. Swellability (SR: 299 ± 65–1054 ± 121 wt.%), compressibility (E: 2.1 ± 0.9–9.2 ± 2.3 kPa), material morphology and drug-loading capability were successfully adjusted based on the selected network architecture. Here, hydrogel incubation with model drugs of varied electrostatic charge, i.e. allura red (AR, doubly negatively charged), methyl orange (MO, negatively charged) or methylene blue (MB, positively charged), resulted in direct hydrogel–dye electrostatic complexation. Importantly, the cationic compound, MB, showed different incorporation behaviours, depending on the electrostatic character of the selected cross-linker. In light of this tunable drug-loading capability, these CT hydrogels would be highly attractive as drug reservoirs towards e.g. the fabrication of tissue models in vitro

    Effects of Variations in Question-Phrasing on True-False Answers by Grade-School Children

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    A 72-item questionnaire was administered to 97 elementary school children in Grades 3 to 6. An attempt was made to assess the effect of asking the same basic type of question, when the following variations were independently introduced: (1) presence or absence of a negative in the statement of the question, (2) truth value of the statement to be answered, and (3) form of presentation of the material. All three variations produced some statistically significant results, such that number of errors was correlated with “mental steps” of decoding necessary for solution. Developmental differences with respect to the tasks were noted, such that certain discriminations were made earlier than others within the variations. </jats:p

    Child-Rearing Practices and Games of Strategy

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