Sol-Gel and Electrospinning Synthesis of Lithium Niobate-Silica Nanofibers

Lithium niobate-silica fibers were produced by the combination of the sol-gel method and the electrospinning technique. Two sol-gel solutions starting from niobium-lithium ethoxide and tetraethyl orthosilicate were prepared and then mixed with polyvinylpyrrolidone; the solutions were electrospun in a coaxial setup. The obtained lithium niobate-silica polymeric fibers were approximately 760 nm in diameter. Raman spectroscopy confirmed the composite composition by showing signals corresponding to lithium niobate and silica. Scanning electron microscopy showed coaxial fibers with a diameter of around 330 nm arranged as a fibrillar membrane at 800 °C. At 1000 °C the continuous shape of fibers was preserved; the structure is composed of silica and lithium niobate nanoparticles within the fibers. The formation of crystalline lithium niobate and amorphous SiO2 phase was also confirmed by XRD peaks

The oldest stratigraphic record of the Late Cretaceous shark Ptychodus mortoni Agassiz, from Vallecillo, Nuevo León, northeastern Mexico

In this paper we report the oldest geologic world record of Ptychodus mortoni, from the Vallecillo Member (Agua Nueva Formation), at Vallecillo, Nuevo León, northeastern Mexico. The presence of the ammonite Watinoceras coloradoense, allows the placement of the sediments of the Vallecillo member within the lower Turonian (Watinoceras coloradoense zone). With reference to this new data, the presence of Ptychodus mortoni in the Vallecillo member extend the temporal distribution of this species into the earliest Turonian. Also, this study suggests that the utility of this shark species as biostratigraphic control in late Cretaceous sediments should be revised in greater detailIn this paper we report the oldest geologic world record of Ptychodus mortoni, from the Vallecillo Member (Agua Nueva Formation), at Vallecillo, Nuevo León, northeastern Mexico. The presence of the ammonite Watinoceras coloradoense, allows the placement of the sediments of the Vallecillo member within the lower Turonian (Watinoceras coloradoense zone). With reference to this new data, the presence of Ptychodus mortoni in the Vallecillo member extend the temporal distribution of this species into the earliest Turonian. Also, this study suggests that the utility of this shark species as biostratigraphic control in late Cretaceous sediments should be revised in greater detai

FIBROUS SILICA-HYDROXYAPATITE COMPOSITE BY ELECTROSPINNING

New nanocomposite membrane was fabricated by electrospinning. The nanocomposite combines a glass and hydroxyapatite (HA). This research proposed the incorporation of glass to counteract the brittleness of HA in a composite formed by coaxial fibers which will be used for bone replacement. Calcium phosphate ceramics are used widely for dental and orthopedic reasons, because they can join tightly through chemical bonds and promote bone regeneration. Precursors HA and SiO2 were synthetized through the sol-gel method and then incorporated into a polymeric PVP matrix; later they were processed by coaxial electrospinning to obtain fibers with an average diameter of 538 nm which were characterized with techniques such as Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy, Differential Thermal Analysis and Scanning Electron Microscopy. Chemical and physical characterization of the membranes evidenced fibers in a coaxial disposition with a glass core and hydroxyapatite cover. The micro-porous fibers have many potential uses in the repair and treatment of bone defects, drug delivery and tissue engineering. Through ATR-FTIR and SEM-EDX analysis the presence of characteristic chemical groups, the fiber composition and microstructure were determined

In vitro evaluation of poly-ε-caprolactone-hydroxypatite-alumina electrospun fibers on the fibroblast’s proliferation

A biomaterial can replace the function of a real organ, conferring properties of support, regeneration or resistance. In the present investigation, a new composite was developed in the form of a polymeric membrane embedded with hydroxyapatite and alumina particles to be used as scaffolding and to allow cell viability. The support matrix is poly ε-caprolactone, which is a biodegradable polymer, hydroxyapatite is the ceramic that contributes to the improvement of osteoconductive and osteo-regenerative properties, while alumina provides the hardness to the composite for its viable application in the orthopedic industry. The morphology of the composite resulted in an interweaving of fibers with a diameter of 840 ​± ​230 ​nm. The composites were analyzed to the MTT cytotoxicity test, showing that none of the composites were toxic (p ​= ​0.0001); where the PCL/HA/α-Al2O3 composite showed greater cellular viability with 238%, demonstrating its possible usefulness as orthopedic material, in filling fractures, or bone imperfections caused by physical damage

Cell behavior on silica-hydroxyapatite coaxial composite.

Progress in the manufacture of scaffolds in tissue engineering lies in the successful combination of materials such as bioceramics having properties as porosity, biocompatibility, water retention, protein adsorption, mechanical strength and biomineralization. Hydroxyapatite (HA) is a ceramic material with lots of potential in tissue regeneration, however, its structural characteristics need to be improved for better performance. In this study, silica-hydroxyapatite (SiO2-HA) non-woven ceramic electrospunned membranes were prepared through the sol-gel method. Infrared spectra, scanning electron microscopy and XRD confirmed the structure and composition of composite. The obtained SiO2-HA polymeric fibers had approximately 230±20 nm in diameter and were then sintered at 800°C average diameter decreased to 110±17 nm. Three configurations of the membranes were obtained and tested in vitro, showing that the composite of SiO2-HA fibers showed a high percentage of viability on a fibroblast cell line. It is concluded that the fibers of SiO2-HA set in a coaxial configuration may be helpful to develop materials for bone regeneration