Unlocking the potential of self-healing and recyclable ionic elastomers for soft robotics applications.

In the field of soft robotics, current materials face challenges related to their load capacity, durability, and sustainability. Innovative solutions are required to address these problems beyond conventional strategies, which often lack long-term ecological viability. This study aims to overcome these limitations using mechanically robust, self-healing, and recyclable ionic elastomers based on carboxylated nitrile rubber (XNBR). The designed materials exhibited excellent mechanical properties, including tensile strengths (TS) exceeding 19 MPa and remarkable deformability, with maximum elongations (EB) over 650%. Moreover, these materials showed high self-healing capabilities, with 100% recovery efficiency of TS and EB at 110 °C after 3 to 5 h, and full recyclability, preserving their mechanical performance even after three recycling cycles. Furthermore, they were also moldable and readily scalable. Tendon-driven soft robotic grippers were successfully developed out of ionic elastomers, illustrating the potential of self-healing and recyclability in the field of soft robotics to reduce maintenance costs, increase material durability, and improve sustainability.

Epoxy Nanocomposites Filled with Carbon Nanoparticles.

Over the past decades, the development of high performance lightweight polymer nanocomposites and, in particular, of epoxy nanocomposites has become one the greatest challenges in material science. The ultimate goal of epoxy nanocomposites is to extrapolate the exceptional intrinsic properties of the nanoparticles to the bulk matrix. However, in spite of the efforts, this objective is still to be attained at commercially attractive scales. Key aspects to achieve this are ultimately the full understanding of network structure, the dispersion degree of the nanoparticles, the interfacial adhesion at the phase boundaries and the control of the localization and orientation of the nanoparticles in the epoxy system. In this Personal Account, we critically discuss the state of the art and evaluate the strategies to overcome these barriers.

Activating transcription factor 3 regulates chemokine expression in contracting C2C12 myotubes and in mouse skeletal muscle after eccentric exercise.

Activating transcription factor (ATF) 3 regulates chemokine expression in various cell types and tissues. Herein, we studied this regulation in contracting muscle cells in vitro, and in skeletal muscle after muscle-damaging exercise in vivo. C2C12 myotubes with normal or low ATF3 levels (atf3_siRNA) were electrically stimulated (EPS). Also, ATF3-knockout (ATF3-KO) and control mice ran downhill until exhaustion, and muscles were analyzed post-exercise. EPS increased ATF3 levels in myotubes (P < 0.01). Chemokine C-C motif ligand (ccl) 2 mRNA increased post-EPS, but atf3_siRNA attenuated the response (P < 0.05). Atf3_siRNA up-regulated ccl6 basal mRNA, and down-regulated ccl9 and chemokine C-X-C motif ligand (cxcl) 1 basal mRNAs. Post-exercise, ATF3-KO mice showed exacerbated mRNA levels of ccl6 and ccl9 in soleus (P < 0.05), and similar trends were observed for ccl2 and interleukin (il) 1ß (P < 0.09). In quadriceps, il6 mRNA level increased only in ATF3-KO (P < 0.05), and cxcl1 mRNA showed a similar trend (P = 0.082). Cluster of differentiation-68 (cd68) mRNA, a macrophage marker, increased in quadriceps and soleus independently of genotype (P < 0.001). Our data demonstrate that ATF3 regulates chemokine expression in muscle cells in vitro and skeletal muscle in vivo, but the regulation differs in each model. Cells other than myofibers may thus participate in the response observed in skeletal muscle. Our results also indicate that ATF3-independent mechanisms would regulate macrophage infiltration upon muscle-damaging exercise. The implications of chemokine regulation in skeletal muscle remain to be determined.

Exercise sensitizes skeletal muscle to extracellular ATP for IL-6 expression in mice.

Active skeletal muscle synthesizes and releases interleukin-6 (IL-6), which plays important roles in the organism's adaptation to exercise. Autocrine/paracrine ATP signaling has been shown to modulate IL-6 expression. The aim of this study was to determine whether a period of physical activity modifies the ATP-induced IL-6 expression. BalbC mice were either subject to 5 weeks voluntary wheel running (VA) or kept sedentary (SED). Flexor digitorum brevis muscles were dissected, stimulated with different ATP concentrations (0-100 µM) and IL-6 mRNA levels were measured using qPCR. ATP evoked a concentration-dependent rise in IL-6 mRNA in both SED and VA mice. VA mice however, had significantly higher ATP sensitivity (pD2 pharmacological values: VA=5.58±0.02 vs. SED=4.95±0.04, p<0.05). Interestingly, in VA mice we observed a positive correlation between the level of physical activity and the IL-6 mRNA increase following fiber stimulation with 10 µM ATP. In addition, there were lower P2Y2- and higher P2Y14-receptor mRNA levels in skeletal muscles of VA compared to SED mice, showing plasticity of nucleotide receptors with exercise. These results suggest that exercise increases skeletal muscle ATP sensitivity, a response dependent on the level of physical activity performed. This could have an important role in the mechanisms controlling skeletal muscle adaptation to exercise and training.

Heel-shoe interactions and the durability of EVA foam running-shoe midsoles.

A finite element analysis (FEA) was made of the stress distribution in the heelpad and a running shoe midsole, using heelpad properties deduced from published force-deflection data, and measured foam properties. The heelpad has a lower initial shear modulus than the foam (100 vs. 1050 kPa), but a higher bulk modulus. The heelpad is more non-linear, with a higher Ogden strain energy function exponent than the foam (30 vs. 4). Measurements of plantar pressure distribution in running shoes confirmed the FEA. The peak plantar pressure increased on average by 100% after 500 km run. Scanning electron microscopy shows that structural damage (wrinkling of faces and some holes) occurred in the foam after 750 km run. Fatigue of the foam reduces heelstrike cushioning, and is a possible cause of running injuries.

[Rheumatologic manifestations of chronic graft vs host disease. 4 case reports]. / Manifestaciones reumatológicas de la enfermedad injerto contra huésped crónica. A propósito de cuatro casos.

A description is given of four patients with the diagnosis of chronic graft-versus-host disease (cGVHD) who developed articular manifestations during the clinical course. One of the patients developed advanced lesions of scleroderma. The rheumatologic changes of the disease as well as other affections of organs, complications and prophylaxis are reviewed.