Influence of sulfated arabino- and glucuronoxylans charging-behavior regarding antithrombotic properties

Magnetic hydrogel based on xylan, poly (acrylic acid), and maghemite as adsorbent material for methylene blue adsorption: experimental design, kinetic, and isotherm

A magnetic hydrogel based on xylan (X), poly (acrylic acid), and maghemite (γ-Fe2O3) named HXA-Fe2O3 was synthesized, characterized, and applied as an alternative material to remove methylene blue (MB) from aqueous media by adsorption. Maghemite was synthesized by coprecipitation method and later incorporated in the hydrogel matrix synthesized by free radical polymerization. The characterization studies included FTIR, DSC, XRD, VSM, Zeta Potential, TGA, SEM, TEM, and N2 adsorption isotherms (BET). The physicochemical characterization results confirmed the intended synthesis and showed the compositional, thermal, structural, morphological, textural, and magnetic profile of the materials. The adsorption studies included experimental design, kinetic, and isotherm. A full factorial design was employed considering the factors adsorbent dosage (g L-1), pH, and ionic strength (mmol L-1 of NaCl) for adsorption capacity and removal percentage responses. As ionic strength was not significant, a Doehlert design was employed with adsorbent dosage and pH, indicating the optimal adsorption conditions. The kinetics was well described by the PSO model, while the isotherm obeyed the Sips model. Equilibrium was attained at 60 min, and the maximum experimental adsorption capacity was up to 250.26 mg g-1 at pH 8.5, adsorbent dosage of 0.2 g L-1, and 298 K. These findings show that the magnetic hydrogel produced has great potential to be applied in the adsorption of basic molecules, such as MB.

Molecular modification, structural characterization, and biological activity of xylans

The differences in the source and structure of xylans make them have various biological activities. However, due to their inherent structural limitations, the various biological activities of xylans are far lower than those of commercial drugs. Currently, several types of molecular modification methods have been developed to address these limitations, and many derivatives with specific biological activity have been obtained. Further research on structural characteristics, structure-activity relationship and mechanism of action is of great significance for the development of xylan derivatives. Therefore, the major molecular modification methods of xylans are introduced in this paper, and the primary structure and conformation characteristics of xylans and their derivatives are summarized. In addition, the biological activity and structure-activity relationship of the modified xylans are also discussed.

Insights into Adsorption Characterization of Sulfated Xylans onto Poly(ethylene terephthalate)

The main aim of this investigation was to study the interaction of sulfated xylans as antithrombotic substances with poly(ethylene terephthalate) (PET) model films as a model for blood contacting surfaces. The adsorption of sulfated xylans onto PET model films was studied as a function of pH and ionic strength using the quartz crystal microbalance with dissipation (QCM-D) technique. The application of positively charged polyethyleneimine (PEI) as an anchoring polymer was done to improve the adsorption. The hydrophilic/hydrophobic properties of functionalized PET surfaces were monitored by goniometry, whilst their elemental composition was determined by X-ray photoelectron spectroscopy. Sulfated xylans adsorbed favorably at pH 5 by physical interactions and by entropy gain driven adsorption. Higher ionic strengths of solutions improved adsorption, due to the reduction of electrostatic repulsive forces between PET surfaces and anionic xylans’ macromolecules. The intermediate PEI layer caused more extensive and stable adsorption due to Coulomb interactions. The surface modifications presented in this work provided important information regarding the adsorption/desorption phenomena between antithrombotic sulfated xylans and PET surfaces. The latter is of great interest when preparing advanced polymer composite material such as functional antithrombotic PET surfaces for blood-contacting medical devices and presents an extremely challenging research field.