Layered Al/CuO Thin Films for Tunable Ignition and Actuations.

Sputter-deposited Al/CuO multilayers are used to manufacture tunable igniters and actuators, with applications in various fields such as defense, space and infrastructure safety. This paper describes the technology of deposition and the characteristics of Al/CuO multilayers, followed by some examples of the applications of these energetic layers.

Fabrication of 3D scaffolds reproducing intestinal epithelium topography by high-resolution 3D stereolithography.

The small intestine is a complex tissue with a crypt/villus architecture and high tissue polarity. Maintenance of tissue integrity and function is supported by a constant renewal of the epithelium, with proliferative cells located in the crypts and differentiated cells migrating upward to the top of villi. So far, most in vitro studies have been limited to 2D surfaces or 3D organoid cultures that do not fully recapitulate the tissue 3D architecture, microenvironment and cell compartmentalization found in vivo. Here, we report the development of a 3D model that reproduces more faithfully the architecture of the intestinal epithelium in vitro. We developed a new fabrication process combining a photopolymerizable hydrogel that supports the growth of intestinal cell lines with high-resolution stereolithography 3D printing. This approach offers the possibility to create artificial 3D scaffolds matching the dimensions and architecture of mouse intestinal crypts and villi. We demonstrate that these 3D culture models support the growth and differentiation of Caco-2 cells for 3 weeks. These models may constitute a complementary approach to organoid cultures to study intestinal homeostasis by allowing guided self-organization and controlled differentiation, as well as for in vitro drug screening and testing.

Wet spinning and radial self-assembly of a carbohydrate low molecular weight gelator into well organized hydrogel filaments.

In this work, we describe how a simple single low molecular weight gelator (LMWG) molecule - N-heptyl-d-galactonamide, which is easy to produce at the gram scale - is spun into gel filaments by a wet spinning process based on solvent exchange. A solution of the gelator in DMSO is injected into water and the solvent diffusion triggers the supramolecular self-assembly of the N-heptyl-d-galactonamide molecules into nanometric fibers. These fibers entrap around 97% of water, thus forming a highly hydrated hydrogel filament, deposited in a well organized coil and locally aligned. This self-assembly mechanism also leads to a very narrow distribution of the supramolecular fiber width, around 150 nm. In addition, the self-assembled fibers are oriented radially inside the wet-spun filaments and at a high flow rate, fibers are organized in spirals. As a result, this process gives rise to a high control of the gelator self-assembly compared with the usual thermal sol-gel transition. This method also opens the way to the controlled extrusion at room temperature of these very simple, soft, biocompatible but delicate hydrogels. The gelator concentration and the flow rates leading to the formation of the gel filaments have been screened. The filament diameter, its internal morphology, the solvent exchange and the velocity of the jet have been investigated by video image analysis and electron microscopy. The stability of these delicate hydrogel ropes has been studied, revealing a polymorphic transformation into macroscopic crystals with time under some storage conditions. The cell viability of a neuronal cell line on the filaments has also been estimated.

Simple Synthetic Molecular Hydrogels from Self-Assembling Alkylgalactonamides as Scaffold for 3D Neuronal Cell Growth.

In this work, we demonstrated that the hydrogel obtained from a very simple and single synthetic molecule, N-heptyl-galactonamide was a suitable scaffold for the growth of neuronal cells in 3D. We evidenced by confocal microscopy the presence of the cells into the gel up to a depth of around 200 µm, demonstrating that the latter was permissive to cell growth and enabled a true 3D colonization and organization. It also supported successfully the differentiation of adult human neuronal stem cells (hNSCs) into both glial and neuronal cells and the development of a really dense neurofilament network. So the gel appears to be a good candidate for neural tissue regeneration. In contrast with other molecular gels described for cell culture, the molecule can be obtained at the gram scale by a one-step reaction. The resulting gel is very soft, a quality in accordance with the aim of growing neuronal cells, that requires low modulus substrates similar to the brain. But because of its fragility, specific procedures had to be implemented for its preparation and for cell labeling and confocal microscopy observations. Notably, the implementation of a controlled slow cooling of the gel solution was needed to get a very soft but nevertheless cohesive gel. In these conditions, very wide straight and long micrometric fibers were formed, held together by a second network of flexible narrower nanometric fibers. The two kinds of fibers guided the neurite and glial cell growth in a different way. We also underlined the importance of a tiny difference in the molecular structure on the gel performances: parent molecules, differing by a one-carbon increment in the alkyl chain length, N-hexyl-galactonamide and N-octyl-galactonamide, were not as good as N-heptyl-galactonamide. Their differences were analyzed in terms of gel fibers morphology, mechanical properties, solubility, chain parity, and cell growth.