Enhanced mechanical properties and biocompatibility of hydroxyapatite scaffolds by magnesium and titanium oxides for bone tissue applications.

Significant attention has been devoted to bioactive implants for bone tissue applications, particularly composite scaffolds based on hydroxyapatite (HaP). This study explores the effects of Magnesium and Titanium oxides on the characteristics of HaP-based composite (HMT) scaffolds. The ceramic nanopowders were synthesized using in situ sol-gel, and then the scaffolds were fabricated by gel-casting technique, followed by heat treatment at 1200 °C. The thermal, microstructural, and structural properties of the samples were investigated by different characterization techniques. It was observed that the formation of the MgTiO3 phase in the composite scaffold was likely the key factor contributing to the improved mechanical properties. Finally, to evaluate bioactivity and biodegradability, scaffolds were immersed in simulated body fluid (SBF) buffer and analyzed by Field Emission Scanning Electron Microscopy (FESEM), and the viability of human fibroblast cells was assessed using the MTT assay. The composite scaffolds containing the MgTiO3 phase showed greater HaP layer formation on the scaffold surface, indicating enhanced biocompatibility.

Material extrusion additive manufacturing of poly(lactic acid)/Ti6Al4V@calcium phosphate core-shell nanocomposite scaffolds for bone tissue applications.

The use of porous scaffolds with appropriate mechanical and biological features for the host tissue is one of the challenges in repairing critical-size bone defects. With today's three-dimensional (3D) printing technology, scaffolds can be customized and personalized, thereby eliminating the problems associated with conventional methods. In this work, after preparing Ti6Al4V/Calcium phosphate (Ti64@CaP) core-shell nanocomposite via a solution-based process, by taking advantage of fused deposition modeling (FDM), porous poly(lactic acid) (PLA)-Ti64@CaP nanocomposite scaffolds were fabricated. Scanning electron microscope (SEM) showed that nanostructured calcium phosphate was distributed uniformly on the surface of Ti64 particles. Also, X-ray diffraction (XRD) indicated that calcium phosphate forms an octacalcium phosphate (OCP) phase. As a result of incorporating 6 wt% Ti64@CaP into the PLA, the compressive modulus and ultimate compressive strength values increased from 1.4 GPa and 29.5 MPa to 2.0 GPa and 53.5 MPa, respectively. Furthermore, the differential scanning calorimetry results revealed an increase in the glass transition temperature of PLA, rising from 57.0 to 62.4 °C, due to the addition of 6 wt% Ti64@CaP. However, it is worth noting that there was a moderate decrease in the crystallization and melting temperatures of the nanocomposite filament, which dropped from 97.0 to 89.5 °C and 167 to 162.9 °C, respectively. The scaffolds were seeded with human adipose tissue-derived mesenchymal stem cells (hADSCs) to investigate their biocompatibility and cell proliferation. Calcium deposition, ALP activity, and bone-related proteins and genes were also used to evaluate the bone differentiation potential of hADSCs. The obtained results showed that introducing Ti64@CaP considerably improved in vitro biocompatibility, facilitating the attachment, differentiation, and proliferation of hADSCs. Considering the findings of this study, the 3D-printed nanocomposite scaffold could be considered a promising candidate for bone tissue engineering applications.

Not Just Another Methanation Catalyst: Depleted Uranium Meets Nickel for a High-Performing Process Under Autothermal Regime.

Invited for this month's cover are collaborating teams from academia-the French ICPEES and IS2M of Centre national de la recherche scientifique (CNRS) and the Italian ICCOM of Consiglio Nazionale delle Ricerche (CNR)-and industry with the participation of the ORANO group. The cover picture shows a CO2 -to-CH4 process promoted by nickel nanoparticles supported on depleted uranium oxide under exceptionally low temperature values or autothermal conditions. The Research Article itself is available at 10.1002/cssc.202201859.

Not Just Another Methanation Catalyst: Depleted Uranium Meets Nickel for a High-Performing Process Under Autothermal Regime.

Ni-based catalysts prepared through impregnation of depleted uranium oxides (DU) have successfully been employed as highly efficient, selective, and durable systems for CO2 hydrogenation to substituted natural gas (SNG; CH4 ) under an autothermal regime. The thermo-physical properties of DU and the unique electronic structure of f-block metal-oxides combined with a nickel active phase, generated an ideal catalytic assembly for turning waste energy back into useful energy for catalysis. In particular, Ni/UOx stood out for the capacity of DU matrix to control the extra heat (hot-spots) generated at its surface by the highly exothermic methanation process. At odds with the benchmark Ni/γ-Al2 O3 catalyst, the double action played by DU as a "thermal mass" and "dopant" for the nickel active phase unveiled the unique performance of Ni/UOx composites as CO2 methanation catalysts. The ability of the weakly radioactive ceramic (UOx ) to harvest waste heat for more useful purposes was demonstrated in practice within a rare example of a highly effective and long-term methanation operated under autothermal regime (i. e., without any external heating source). This finding is an unprecedented example that allows a real step-forward in the intensification of "low-temperature" methanation with an effective reduction of energy wastes. At the same time, the proposed catalytic technology can be regarded as an original approach to recycle and bring to a second life a less-severe nuclear by-product (DU), providing a valuable alternative to its more costly long-term storage or controlled disposal.

Direct conversion of uranium dioxide UO2 to uranium tetrafluoride UF4 using the fluorinated ionic liquid [Bmim][PF6].

The industrial fluorination of UO2 to UF4 is based on a complex process involving the manipulation of a large amount of HF, a very toxic and corrosive gas. We present here a safer way to accomplish this reaction utilizing ionic liquid [Bmim][PF6] as a unique reaction medium and fluoride source.

Time resolved alteration process of oxide glasses.

Dissolution of oxide glasses by water has been studied by small angles X-ray scattering. It is shown that the altered residual surface layer due to dissolution and recondensation of Si atoms is a porous material with nanometer size pores. Based on five elements oxide glass (18NaO2-17B2O3-4CaO-yZrO2-(61-y)SiO2 with y=0, 1, 2, 4 and 8) the experiment highlights a strong influence of insoluble element on both the kinetic of alteration and the structure of the altered layer. It is shown that above 2% Zr content, the fraction of porous volume and the surface of exchange in the altered layer pass through a maximum value in the first hours of alteration corresponding to an overshoot of Si lixiviation without recondensation as the saturation limit is not reached. When the saturation limit is reached the porous volume fraction is just below the fraction of volume occupied primarily by the sodium and the boron.