In recent years, a great effort has been devoted to developing a new generation of materials for aeronautic applications. The driving force behind this effort is the reduction of costs, by extending the service life of aircraft parts (structural and engine components) and increasing fuel efficiency, load capacity and flight range. The present paper examines the most important classes of metallic materials including Al alloys, Ti alloys, Mg alloys, steels, Ni superalloys and metal matrix composites (MMC), with the scope to provide an overview of recent advancements and to highlight current problems and perspectives related to metals for aeronautics.

The concept of magnetic guidance is still challenging and has opened a wide range of perspectives in the field of tissue engineering. In this context, magnetic nanocomposites consisting of a poly(ε-caprolactone) (PCL) matrix and iron oxide (Fe₃O₄) nanoparticles were designed and manufactured for bone tissue engineering. The mechanical properties of PCL/Fe₃O₄ (80/20 w/w) nanocomposites were first assessed through small punch tests. The inclusion of Fe₃O₄ nanoparticles improved the punching properties as the values of peak load were higher than those obtained for the neat PCL without significantly affecting the work to failure. The effect of a time-dependent magnetic field on the adhesion, proliferation, and differentiation of human mesenchymal stem cells (hMSCs) was analyzed. The Alamar Blue assay, confocal laser scanning microscopy, and image analysis (i.e., shape factor) provided information on cell adhesion and viability over time, whereas the normalized alkaline phosphatase activity (ALP/DNA) demonstrated that the combination of a time-dependent field with magnetic nanocomposites (PCL/Fe₃O₄ Mag) influenced cell differentiation. Furthermore, in terms of extracellular signal-regulated kinase (ERK)1/2 phosphorylation, an insight into the role of the magnetic stimulation was reported, also demonstrating a strong effect due the combination of the magnetic field with PCL/Fe₃O₄ nanocomposites (PCL/Fe₃O₄ Mag).

Hydrogels currently represent a powerful solution to promote the regeneration of soft and hard tissues. Primarily, they assure efficient bio-molecular interactions with cells, also regulating their basic functions, guiding the spatially and temporally complex multi-cellular processes of tissue formation, and ultimately facilitating the restoration of structure and function of damaged or dysfunctional tissues. In order to overcome basic drawbacks of traditional synthesized hydrogels, many recent strategies have been implemented to realize multi-component hydrogels based on natural and/or synthetic materials with tailored chemistries and different degradation kinetics. Here, a critical review of main strategies has been proposed based on the use of hydrogels-based devices for the regeneration of complex tissues, i.e., osteo-chondral tissues and intervertebral disc.

A basic approach toward the design of three-dimensional (3D) rapid prototyped magnetic scaffolds for hard-tissue regeneration has been proposed. In particular, 3D scaffolds consisting of a poly(ε-caprolactone) (PCL) matrix and iron oxide (Fe₃O₄) or iron-doped hydroxyapatite (FeHA) nanoparticles were fabricated through a 3D fibre deposition technique. As a first approach, a polymer to nanoparticle weight ratio of 90/10 (wt/wt) was used. The effect of the inclusion of both kinds of nanoparticles on the mechanical, magnetic, and biological performances of the scaffolds was studied. The inclusion of Fe₃O₄ and FeHA nanoparticles generally improves the modulus and the yield stress of the fibres if compared to those of neat PCL, as well as the modulus of the scaffolds. Micro-computed tomography has confirmed the possibility to design morphologically-controlled structures with a fully interconnected pore network. Magnetisation analyses performed at 37°C have highlighted M-H curves that are not hysteretic; values of saturation magnetisation (M_s) of about 3.9 emu/g and 0.2 emu/g have been evaluated for PCL/Fe₃O₄ and PCL/FeHA scaffolds, respectively. Furthermore, results from confocal laser scanning microscopy (CLSM) carried out on cell-scaffold constructs have evidenced that human mesenchymal stem cells (hMSCs) better adhered and were well spread on the PCL/Fe₃O₄ and PCL/FeHA nanocomposite scaffolds in comparison with the PCL structures.