Comprehensive in vitro and in vivo studies of novel melt-derived Nb-substituted 45S5 bioglass reveal its enhanced bioactive properties for bone healing

The present work presents and discusses the results of a comprehensive study on the bioactive properties of Nb-substituted silicate glass derived from 45S5 bioglass. In vitro and in vivo experiments were performed. We undertook three different types of in vitro analyses: (i) investigation of the kinetics of chemical reactivity and the bioactivity of Nb-substituted glass in simulated body fluid (SBF) by 31P MASNMR spectroscopy, (ii) determination of ionic leaching profiles in buffered solution by inductively coupled plasma optical emission spectrometry (ICP-OES), and (iii) assessment of the compatibility and osteogenic differentiation of human embryonic stem cells (hESCs) treated with dissolution products of different compositions of Nb-substituted glass. The results revealed that Nb-substituted glass is not toxic to hESCs. Moreover, adding up to 1.3 mol% of Nb2O5 to 45S5 bioglass significantly enhanced its osteogenic capacity. For the in vivo experiments, trial glass rods were implanted into circular defects in rat tibia in order to evaluate their biocompatibility and bioactivity. Results showed all Nb-containing glass was biocompatible and that the addition of 1.3 mol% of Nb2O5, replacing phosphorous, increases the osteostimulation of bioglass. Therefore, these results support the assertion that Nb-substituted glass is suitable for biomedical applications

Synthesis and Structural Properties of Niobium Pentoxide Powders: A Comparative Study of the Growth Process

Powders Nb2 O5 were prepared by two different synthesis method, Sol-Gel and polymeric precursors (Pechini). In the Pechini method before adding the citric acid in the process, four different solutions were used to get the samples. For Sol-gel method, two different processes were also used in obtaining powders. The precursor was completely solubilized in ethanol and then hydrolyzed with ammonia and water. The calcination of the samples was between 500 and 750°C. The resulting powders were characterized by Scanning Electron Microscopy (SEM), Brunauer, Emmett and Teller (BET) surface area measurements, UV-visible and Raman spectroscopy. The formation of T−Nb2 O5 orthorhombic took place upon calcination at 7500C. Crystallite sizes were determined using the Scherrer method which resulted in an uniformed size of about 25 − 65nm. Ultraviolet-Visible diffuse reflectance spectroscopy indicated a variation in the optical band gap values (3.32-3.40 eV) in crystal growth process. The Raman vibrational modes indicate the presence of the orthorhombic phase of the material

Preparation of Phase-Pure M1 MoVTeNb Oxide Catalysts by Hydrothermal Synthesis - Influence of Reaction Parameters

This work presents a detailed investigation of the preparation of MoVTeNbOx catalysts by hydrothermal synthesis. Phase-pure synthesis of M1 has been achieved applying the metals in a molar ratio Mo/V/Te/Nb=1/0.25/0.23/0.12. Raman, UV/Vis spectroscopy, and SEM/EDX analysis show that the elements are inhomogeneously distributed in the initial suspension that is formed after mixing the metal salts in an aqueous medium. Iso- and heteropoly anions of molybdenum, free telluric acid as well as supra-molecular polyoxometalate clusters are observed in the solution, whereas all metals have been found in the precipitate. Complete rearrangement of molecular building blocks under hydrothermal conditions is essential for formation of phase-pure materials. Optimized synthesis conditions with respect to temperature and time result in the formation a precursor consisting of nano-structured M1 characterized by an extended periodic organization in the [001] direction and a fairly homogeneous distribution of the elements. Residual ammonium containing supra-molecular species in the precursor result in the formation of phase mixtures during the subsequent crystallization by heat treatment in inert gas. Phase-pure M1 exhibits a distinct degree of flexibility with respect to the chemical composition that becomes obvious by incorporating Nb not exclusively into pentagonal bi-pyramidal units, but also into octahedral coordinated positions as shown by EXAFS. Anisotropic growth of the needle-like M1 crystals has been observed during the final heat treatment performed at 873-923 K in inert atmosphere disclosing a potential method to control the catalytic properties of MoVTeNbOx catalysts