University of Trento

The acetabular labrum is a fibrocartilaginous ring that surrounds the acetabular rim, anchoring to bone and ensuring hip joint stability and sealing. It is mainly composed of fibrochondrocytes and type I collagen fibers, providing resistance to mechanical stress during daily activities. Femoroacetabular impingement can compromise these properties, leading to labral degeneration, hip pain, reduced quality of life, and early osteoarthritis. To address this, biomaterials that mimic the native labral and support regeneration are under investigation. This study developed composite hydrogels combining, for the first time, Bombyx mori-derived silk fibroin methacrylate (SilMA) and wool-derived keratin microfibers (KI) to create a bioartificial labrum prototype. Two KI concentrations (12.5% and 25% w/w), mixed with SilMA, were tested and compared to SilMA alone. KI powder was dispersed into SilMA, and ultraviolet (UV) exposure time was optimized for hydrogel crosslinking. Morphological and mechanical characterization of the hydrogels was performed, along with the evaluation of cell biocompatibility and cell behavior with human chondrocytes (C28/I2) using a lactate dehydrogenase assay, transmission electron microscopy, and histology. Increasing KI concentration enhanced viscosity, shear stiffness, and elastic modulus under dry and wet conditions. Biocompatibility assays confirmed cell viability up to 14days. Overall, SilMA-KI hydrogels demonstrated favorable mechanical performance and cytocompatibility, highlighting their potential as scaffolds for acetabular labrum regeneration.

• PA12 fatigue life characterization with Average Strain Energy Density (ASED) method. • An algorithm is developed for lattice structure fatigue predictions. • Fatigue predictions are conducted on as-designed lattice geometries. • The critical radius for the ASED method is identified for MJF PA12 material. The industrial sector continues to explore innovative strategies to exploit the full potential of Additive Manufacturing (AM). Among its many advantages, AM enables the fabrication of lattice structures; these are lightweight metamaterials with tunable mechanical properties and excellent energy absorption capabilities. Despite their promise, the widespread industrial use of such structures is limited by the difficulty in accurately assessing their fatigue behavior. This study presents a methodology aimed at predicting the fatigue life of polymer-based lattice components, with a specific focus on PA12 manufactured using the Multi Jet Fusion (MJF) process. This is an industrially relevant technology offering large production volumes, high printing quality and low production costs. The approach begins with fatigue testing of bulk PA12 specimens to establish baseline material behavior. Based on these results, a predictive algorithm is developed to estimate the fatigue performance of lattice structures. The model adopts an energy-based framework inspired by the Average Strain Energy Density (ASED) method, previously used for metallic materials, and adapts it to the characteristics of polymer lattices. The proposed methodology contributes to the development of efficient fatigue assessment tools, supporting the broader adoption of lattice structures in cost-sensitive industrial applications where polymer-based materials are effective.

• Pore–notch competition quantified using energy-based stressed volume and strain energy. • Pearlitic and high-silicon ferritic irons show fatigue reversal with notch severity. • Computed tomography and extreme-value statistics inform defect-sensitive fatigue. • High-silicon ferritic iron shows greater pore tolerance in blunt, large stressed volumes. • Simplified strain-energy method enables fatigue design without tomography or FE. Heavy-section castings of ductile cast iron (DCI) unavoidably contain micro shrinkage porosity due to non-uniform, slow cooling, and service components also feature geometric stress raisers. This study quantifies how these two realities—intrinsic defects and notches—jointly control fatigue resistance and formalizes a design approach that accounts for their interaction. We compare a pearlitic EN-GJS-600–3 (GJS-600–3) and a high-silicon solid solution strengthened ferritic (HSi) DCI, which exhibit different matrix ductility and distinct pore populations. Pore size distributions are characterized (via X-ray computed tomography, CT), and extreme-value statistics are used to estimate the most critical defect expected in the highly stressed region of notched specimens. This defect measure is then coupled to a strain energy density (SED) criterion to predict fatigue limits. Fatigue tests on plain and V-notched specimens with varying notch severity reveal a systematic transition from pore-dominated initiation (plain and mildly notched) to notch-dominated initiation (severe notches). The proposed CT–statistics–SED framework reproduces both the fatigue limits and the observed switch in the governing initiation site. Compared with GJS-600–3, the HSi grade shows lower intrinsic fatigue strength but greater tolerance to distributed microporosity, leading to improved reliability in geometries with large highly stressed volumes. The approach provides a practical route to defect-aware fatigue design of DCI components, suggesting material-and-geometry selection: pearlitic grades for smaller, sharper features where notch control prevails; high-silicon ferritic grades for large, blunt features where defect tolerance is paramount. Overall, the method supports lighter, more reliable cast designs without resorting to overly conservative safety factors.

The 5,6,7,8-tetrahydrobiopterin (H 4 B) cofactor is essential for several enzymatic functions, including phenylalanine-4-hydroxylase (PAH, EC 1.14.16.1). However, H 4 B is highly unstable and spontaneously oxidizes in aqueous solution at room temperature, which complicates its measurement in clinical and research settings and has led to its exclusion from many routine analytical protocols. This study addresses the need for a quantitative description of H 4 B autoxidation and for practical strategies to mitigate analytical artefacts in solution and in urine. A kinetic study using flow injection analysis–tandem mass spectrometry (FIA–MS/MS) was carried out to monitor H 4 B signal decay under different media and antioxidant compositions, and the data were interpreted within a pseudo-first-order kinetic framework. Autoxidation was fastest in aqueous solvent and slower in urine, with rate constants further modulated by the presence of ascorbic acid (H 2 A) and glutathione (GSH). Equimolar H 2 A and GSH, and excess GSH, significantly slowed H 4 B decay but did not fully suppress oxidation, indicating partial stabilization rather than complete protection. Cyclic voltammetry and thermodynamic analysis provided complementary information on redox potentials, intermediates and thermodynamic affinity, linking changes in reaction rate to the underlying redox equilibria. The combined kinetic, electrochemical and thermodynamic results show that matrix composition and antioxidant content critically influence H 4 B stability in solution and in urine. While antioxidants such as H 2 A and GSH attenuate spontaneous oxidation, careful control of sample handling, timing and storage remains essential. The mechanistic insight obtained her e supports the rational design of stabilization and preparation protocols for future LC–MS/MS assays targeting H 4 B in bioanalytical and diagnostic applications. • H4B autoxidation kinetics were mapped in solution and urine. • FIA-MS/MS, voltammetry and modelling give a unified redox picture. • Antioxidants GSH and ascorbate slow H4B decay without full stabilisation. • Urine matrix partially stabilises H4B and modulates antioxidant effects. • Practical guidelines are proposed for handling H4B in bioanalytical assays.