Homogentisic acid induces morphological and mechanical aberration of ochronotic cartilage in alkaptonuria

Alkaptonuria (AKU) is a disease caused by a deficient homogentisate 1,2-dioxygenase activity leading to systemic accumulation of homogentisic acid (HGA), that forms a melanin-like polymer that progressively deposits onto connective tissues causing a pigmentation called “ochronosis” and tissue degeneration. The effects of AKU and ochronotic pigment on the biomechanical properties of articular cartilage need further investigation. To this aim, AKU cartilage was studied using thermal (thermogravimetry and differential scanning calorimetry) and rheological analysis. We found that AKU cartilage had a doubled mesopore radius compared to healthy cartilage. Since the mesoporous structure is the main responsible for maintaining a correct hydrostatic pressure and tissue homoeostasis, drastic changes of thermal and rheological parameters were found in AKU. In particular, AKU tissue lost its capability to enhance chondrocytes metabolism (decreased heat capacity) and hence the production of proteoglycans. A drastic increase in stiffness and decrease in dissipative and lubricant role ensued in AKU cartilage. Multiphoton and scanning electron microscopies revealed destruction of cell–matrix microstructure and disruption of the superficial layer. Such observations on AKU specimens were confirmed in HGA-treated healthy cartilage, indicating that HGA is the toxic responsible of morphological and mechanical alterations of cartilage in AKU.     

Ordered Network of Interconnected SnO2 Nanoparticles for Excellent Lithium‐Ion Storage

An ordered network of interconnected tin oxide (SnO₂) nanoparticles with a unique 3D architecture and an excellent lithium‐ion (Li‐ion) storage performance is derived for the first time through hydrolysis and thermal self‐assembly of the solid alkoxide precursor. Mesoporous anodes composed of these ≈9 nm‐sized SnO₂ particles exhibit substantially higher specific capacities, rate performance, coulombic efficiency, and cycling stabilities compared with disordered nanoparticles and commercial SnO₂. A discharge capacity of 778 mAh g^–1, which is very close to the theoretical limit of 781 mAh g^–1, is achieved at a current density of 0.1 C. Even at high rates of 2 C (1.5 A g^–1) and 6 C (4.7 A g^–1), these ordered SnO₂ nanoparticles retain stable specific capacities of 430 and 300 mAh g^–1, respectively, after 100 cycles. Interconnection between individual nanoparticles and structural integrity of the SnO₂ electrodes are preserved through numerous charge–discharge process cycles. The significantly better electrochemical performance of ordered SnO₂ nanoparticles with a tap density of 1.60 g cm^–3 is attributed to the superior electrode/electrolyte contact, Li‐ion diffusion, absence of particle agglomeration, and improved strain relaxation (due to tiny space available for the local expansion). This comprehensive study demonstrates the necessity of mesoporosity and interconnection between individual nanoparticles for improving the Li‐ion storage electrochemical performance of SnO₂ anodes.     

Mesoporous Decoration of Freestanding Palladium Nanotube Arrays Boosts the Electrocatalysis Capabilities toward Formic Acid and Formate Oxidation

Fabricating high‐performance electrocatalysts is the most critical step in commercializing direct formic acid or formate fuel cells. In this work, a dual‐template electrodeposition method is used to create freestanding mesoporosity decorated palladium nanotube arrays (P‐PdNTA) as a bifunctional electrocatalyst toward formic acid and formate oxidation (FAO/FOR). The phytantriol‐based soft template modifies the superficial chemistry of aluminum anodic oxide inner surfaces, thereby facilitating the regulated electrodeposition of highly stable palladium nanotubes. The sacrifice of the soft template generates substantial mesoporosity on the nanotubes, resulting in a 189% increase in the electrochemically active surface area with respect to the mesopore‐free PdNTA baseline. In addition, the soft template significantly increases the density of catalytically active sites per unit area via perturbation on routine nanotube growth, as evidenced by the doubled areal catalytic activity of P‐PdNTA versus PdNTA. Remarkably, the P‐PdNTA delivered gravimetric catalytic currents of 3.65 and 3.87 A mg^?1 for FAO and FOR, which are 8.5 and 6.5 times higher, respectively, than those of commercial Pt/C. These values are among the most favorable reported and benefit from the unique synergy of fast substance transport, large electrochemical active surface area and high areal population of catalytically active sites.