Nanofibrous ε-polycaprolactone scaffolds containing Ag-doped magnetite nanoparticles: Physicochemical characterization and biological testing for wound dressing applications in vitro and in vivo

Skin wounds can lead to numerous complications with dangerous health consequences.In this work,magnetite nanoparticles were doped with different concentrations of antimicrobial silver(Ag)ions and incorporated into the electrospun nanofibrous ε-polycaprolactone(PCL)scaffolds.Nanoparticles and scaffolds with various Ag contents were characterized using a range of physicochemical techniques.Ag entered magnetite as cations and preferentially positioned at tetrahedral sites,introducing lattice distortions and topographic irregularities.Amorphization of the structure due to accommodation of Ag expanded the lattice in the bulk and contracted it on the surface,where broadened distribution of Fe-O coordinations was detected.Promoting spin canting and diminishing the double exchange interaction through altered distribution of ferric and ferrous ions,Ag softened the magnetism of magnetite.By making the nanoparticle structure more defective,Ag modified the interface with the polymer and promoted the protrusion of the nanoparticles from the surface of the polymeric nanofibers,thus increasing their roughness and hydrophilicity,with positive repercussions on cell adhesion and growth.Both the viability of human melanocytes and the antibacterial activity against E.coli and S.aureus increased with the concentration of Ag in the magnetite phase of the scaffolds.Skin wound healing rate in rats also increased in direct proportion with the concentration of Ag in the magnetite phase,and no abnormalities in the dermal and epidermal tissues were visible on day 10 in the treatment group.These results imply an excellent potential of these composite nanofibrous scaffolds for use as wound dressings and in other reconstructive skin therapies.

Hybridization between microstructure and magnetization improvement in lead and RE co-doped BiFeO_3

The crystal structure,magnetic and electrical properties of Bi（0.96）Pb（0.04） FeO3 and Bi（0.92）Pb（0.04）RE（0.04）FeO3（RE=La,Sm,Dy and Yb）polycrystalline samples were prepared by the flash autocombustion technique.X-ray diffraction（XRD）measurements show that the rare-earth doped compositions crystallized in rhombohedral symmetry of space group R3 c.The undoped sample consisted needle shape particles while rare earth substitution preferred platelet like particles as clarified from high resolution transmission electron microscopy（HRTEM）.Morphological features were examined using field emission scanning electron microscopy（FESEM）.Magnetization measurements showed that Yb^3＋ samples possessed the highest room temperature saturation magnetization while when Bi^3＋ ions were substituted by La^3＋ ions,a smaller MS（0.28 emu/g）was obtained.The coexistence of ferroelectric and magnetic transitions was detected using DSC and χM,indicating the multiferroic characteristics of Bi（0.92）Pb（0.04）RE（0.04）FeO3 crystallites.The Néel temperature shifted upwards with decreasing the ionic radius of rare earth ion.Nice correlation was established between microstructure,morphology and magnetic properties in view of the contribution of magnetocrystalline and shape anisotropy in the magnetic parameters values.