[en] PVA was dissolved in mixed solvent (DMSO and water) and followed by several freeze-thaw cycles in a mold to produce PVA membrane. Surface modification of PVA membranes by HA molecules was investigated to improve the hydrophilicity of the membrane surface thereby reducing adsorption of the proteins onto the membrane. The surface composition, water contact angle, optical and mechanical properties, surface morphology, cell compatibility and protein adhesion were systematically investigated. ATR-FTIR spectra, XPS, SEM and AFM indicated that PVA membranes were successfully modified by grafting of the HA. The modified membranes showed increased hydrophilicity and cytocompatibility, decreased surface roughness and mechanical properties, and suppressed cell and protein adhesion compared to the pristine membrane. In general, the achievement of the HA coating with anti-adhesive property can potentially be widely used on surface modification of artificial cornea and other biomedical implants. (paper)

[en] This report aimed to describe a novel type of core-shell-structured microcapsules suitable for spontaneous loading of anticoagulant heparin. Chitosan (CS) microspheres were fabricated by a sodium sulfate-based precipitation process. The microspheres were approximately 1 μm in size and applied as templates for microcapsules prepared by the layer-by-layer (LbL) self-assembly technique. Polyelectrolytes including polyanion poly(styrene sulfonate) and polycation CS were alternately deposited on CS microsphere templates, monitored by flow cytometry and zeta potential analysis. Scanning electron microscopy, confocal laser scanning microscopy, fluorescence microscopy, flow cytometry and laser particle size analysis were used to characterize the microcapsules. The resulted microcapsules were about 1 μm in average diameter, and allowed spontaneous loading of heparin through electrostatic interaction, with the encapsulation efficiency and loading capacity of 74.4% and 10.0%, respectively. Moreover, heparin could be released from the microcapsules in phosphate buffered saline at pH 7.4. It is suggested that the type of microcapsules may provide a new and effective system of heparin delivery for pharmaceutical use.

[en] Narrow-disperse poly(N,N′-methylenebisacryamide-co-methacrylic acid)/zirconium hydroxide (P(MBA-co-MAA)/Zr(OH)₄) core–shell composite microspheres were synthesized by the controlled sol–gel hydrolysis of inorganic zirconium n-butoxide (Zr(OBu)₄) precursor in ethanol and acetonitrile mixed solvent with P(MBA-co-MAA) microspheres as templates. The thickness of the outer inorganic Zr(OH)₄ shell-layer was well-controlled via altering the mass ratio of Zr(OBu)₄ to P(MBA-co-MAA) core particles as well as the water used for the hydrolysis. The corresponding hollow porous zirconium oxide (ZrO₂) microspheres were obtained after the selective removal of P(MBA-co-MAA) core via the calcination of P(MBA-co-MAA)/Zr(OH)₄ core–shell microspheres under 550 °C for 4 h in air. The structure and morphology of the resultant core–shell microspheres and the hollow porous ZrO₂ microspheres were characterized by transmission electron microscopy (TEM), STEM together with EDX spectrum, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, micromeritic analyzer, and thermogravimetric (TGA) analysis. -- Graphical abstract: Monodisperse P(MBA-co-MAA)/(ZrOH)₄ core–shell microspheres with amorphous zirconium hydroxide shell-layer were prepared by the controlled hydrolysis of Zr(OBu)₄ in acetonitrile/ethanol (4/1, V/V) mixed solvent. The mechanism of the encapsulation of zirconium hydroxide shell-layer over P(MBA-co-MAA) templates were performed via the efficient hydrogen-bonding interaction between the carboxylic acid groups as well as the amide groups on the surface of P(MBA-co-MAA) templates and the hydroxyl groups of the zirconium hydroxide molecules during the controlled hydrolysis. Highlights: ► Synthesis of P(MBA-co-MAA)/Zr(OH)₄ core-shell composite microspheres. ► Controlled thickness of Zr(OH)₄ shell-layer via altering loadings of Zr(OBu)₄. ► Preparation of hollow ZrO₂ microspheres with body-centered tetragonal phase.

[en] Highlights: •Electrochemical characteristics on nanoparticles and nanocomposites were compared. •The reasons for superior electrochemical activity of Fe₃O₄@Pt were discussed. •We report an excellent nitrite biosensor based on Fe₃O₄@Pt. •Electro-analytical parameters of nitrite at Fe₃O₄@Pt were evaluated in detail. -- Abstract: The electrochemical differences (such as charge transfer resistivity, electroactive surface, standard electron transfer rate constant, adsorption amount and analytical performance of nitrite sensor) between Fe₃O₄@Pt nanocomposites with two elements and core–shell structure and NPs (Fe₃O₄ nanoparticles and Pt nanoparticles) with single component and simple structure were investigated in detail. Above those investigations, it is believed that for the Fe₃O₄@Pt core–shell nanocomposites, Pt shell could provide more electro-catalytic activity while magnetic Fe₃O₄ core could provide larger surface area and facilitate the purification of nanocomposites. After that, Fe₃O₄@Pt nanocomposites modified GCE served as a nitrite sensor. Electrochemical parameters of nitrite at Fe₃O₄@Pt nanocomposites such as electron transfer number, electron transfer coefficient, standard heterogeneous rate constant and electron diffusion coefficient were evaluated. With the proposed electrochemical sensors, nitrite in tap water and orange juice could be detected. This investigation suggested that core–shell nanocomposites were superior for the fabrication of electrochemical sensors

[en] The volume phase transition of a hydrogel initiated by shrinking may result in complex patterns on its surface. Based on this unique property of hydrogel, we have developed a novel solvent precipitation method to prepare a kind of novel superabsorbent polymers with excellent hemostatic properties. A porous carboxymethyl chitosan grafted poly (acrylic acid) (CMCTS-g-PAA) superabsorbent polymer was prepared by precipitating CMCTS-g-PAA hydrogel with ethanol. Its potential application in hemostatic wound dressing was investigated. The results indicate that the modified superabsorbent polymer is non-cytotoxic. It showed a high swelling capacity and better hemostatic performance in the treatments of hemorrhage model of ear artery, arteria cruralis and spleen of the New Zealand white rabbit than the unmodified polymer and other commonly used clinic wound dressings. The hemostatic mechanism of the porous CMCTS-g-PAA polymer was also discussed. - Highlights: • The novel solvent precipitation method was developed to prepare the porous superabsorbent polymer. • The swelling rate was promoted and the harmful residual monomer was leached after modification. • The modified polymer showed good biological safety. • It showed good hemostasis to arterial hemorrhage model of the animal. • The hemostatic mechanism of the modified superabsorbent polymer was discussed.