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

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

Early Christian Rhetoric(s)<i>In Situ</i>

ABSTRACTIn the nineteenth and twentieth centuries, an unprecedented number of Gnostic manuscripts were unearthed at sites across Egypt. Discovered on the Cairo antiquities market, in ancient trash heaps, and in buried jars, these papyri have radically refigured the landscape of early Christian history. Rhetoric, however, has overlooked the Gnostics. Long denigrated as heretical, Gnostic texts invite historians of rhetoric to (re)consider the role of gender in the early Church, the interplay between gnōsis and contemporary rhetorical concepts, and the&amp;#x2028;development of early Christian rhetorical practice(s) within diverse historical contexts, including the Second Sophistic. In response to recent calls for rhetorical archaeology, this essay returns to Cairo, Oxyrhynchus, and Nag Hammadi. These three locations refigure early Christian rhetoric(s) in situ.</jats:p