Scaffolds are three-dimensional porous structures that must have specific requirements to be applied in tissue engineering. Therefore, the study of factors affecting scaffold performance is of great importance. In this work, the optimal conditions for cross-linking preformed chitosan (CS) scaffolds by the tripolyphosphate polyanion (TPP) were investigated. The effect on scaffold physico-chemical properties of different concentrations of chitosan (1 and 2% w/v) and tripolyphosphate (1 and 2% w/v) as well as of cross-linking reaction times (2, 4, or 8 h) were studied. It was evidenced that a low CS concentration favored the formation of three-dimensional porous structures with a good pore interconnection while the use of more severe conditions in the cross-linking reaction (high TPP concentration and crosslinking reaction time) led to scaffolds with a suitable pore homogeneity, thermal stability, swelling behavior, and mechanical properties, but having a low pore interconnectivity. Preliminary biocompatibility tests showed a good osteoblasts’ viability when cultured on the scaffold obtained by CS 1%, TPP 1%, and an 8-h crosslinking time. These findings suggest how modulation of scaffold cross-linking conditions may permit to obtain chitosan scaffold with properly tuned morphological, mechanical and biological properties for application in the tissue regeneration field.

Wound healing is a dynamic process that can be seriously delayed by many factors including infectious complications. The development of dressings with intrinsic wound healing activity and/or releasing bioactive compounds may help with addressing such an issue. In this study, hyaluronic acid (HA) at different percentages (1–35%) was used to modify chitosan (CS) biological and physico-chemical properties in order to obtain 2D-matrices able to promote healing and protect from infection. HA incorporation in the CS matrix decreased film transparency and homogeneity, but improved film water uptake and surface wettability. The water vapor transmission rate (WVTR) increased up to a 5% HA content, where it reached the highest value (672 g/m² day), and decreased for higher HA contents. At all of the tested HA concentrations, HA affected mechanical properties providing matrices more flexible than pure CS with benefit for wound care. Pure CS films permitted S. epidermidis adhesion and biofilm formation. That was not true for CS/HA matrices, where HA at concentrations equal to or greater than 5% was able to avoid S. epidermidis adhesion. Fibroblasts adhesion also took benefit from the HA presence in the film, especially at 5% content, where the best adhesion and proliferation was found.

Despite advances in material sciences and clinical procedures for surgical hygiene, medical device implantation still exposes patients to the risk of developing local or systemic infections. The development of efficacious antimicrobial/antifouling materials may help with addressing such an issue. In this framework, polyethylene glycol (PEG)-grafted segmented polyurethanes were synthesized, physico-chemically characterized, and evaluated with respect to their bacterial fouling-resistance properties. PEG grafting significantly altered the polymer bulk and surface properties. Specifically, the PEG-grafted polyurethanes possessed a more pronounced hard/soft phase segregated microstructure, which contributed to improving the mechanical resistance of the polymers. The better flexibility of the soft phase in the PEG-functionalized polyurethanes compared to the pristine polyurethane (PU) was presumably also responsible for the higher ability of the polymer to uptake water. Additionally, dynamic contact angle measurements evidenced phenomena of surface reorganization of the PEG-functionalized polyurethanes, presumably involving the exposition of the polar PEG chains towards water. As a consequence, Staphylococcus epidermidis initial adhesion onto the surface of the PEG-functionalized PU was essentially inhibited. That was not true for the pristine PU. Biofilm formation was also strongly reduced.

Reducing the sample size can profoundly impact properties of bulk metallic glasses. Here, we systematically reduce the length scale of Au and Pt-based metallic glasses and study their vitrification behavior and atomic mobility. For this purpose, we exploit fast scanning calorimetry (FSC) allowing to study glassy dynamics in an exceptionally wide range of cooling rates and frequencies. We show that the main α relaxation process remains size independent and bulk-like. In contrast, we observe pronounced size dependent vitrification kinetics in micrometer-sized glasses, which is more evident for the smallest samples and at low cooling rates, resulting in more than 40 K decrease in fictive temperature, T_f, with respect to the bulk. We discuss the deep implications on how this outcome can be used to convey glasses to low energy states.

The description of kinetics of physical aging, namely the slow evolution of a glass thermodynamic state toward equilibrium, generally relies on the exclusive role of the main α relaxation. Here, we study the kinetics of physical aging over a wide temperature range in five small molecules interacting via van der Waals forces monitoring the time evolution of the glass enthalpic state. To this aim, we employ fast scanning calorimetry, which permits exploring a wide range of aging times. To challenge the role of the α relaxation in the description of physical aging, we employ a model-independent approach, based on the time to reach equilibrium, and a modified version of the single parameter aging model. The latter accounts for the non-linearity of aging making use of the so-called density scaling approach to describe the dependence of the α relaxation time on the glass thermodynamic state. We show that the α relaxation is generally adequate to describe aging at temperatures close to the glass transition and, for lower temperatures, the latest stages of equilibration. In contrast, at low aging temperatures, it fails to catch a wide portion of the time-dependent evolution of the glass thermodynamic state, which is found to be much faster than predicted considering only the α relaxation. Hence, our results and analysis provide compelling arguments that the description of glass equilibration under a wide range of aging conditions is conveyed by different molecular mechanisms, beyond the mere role of the α relaxation.

The composites based on basalt fibres and poly(lactic acid) (PLA) show promising applications in biomedical and automotive fields, but their mechanical performance is still largely hindered by poor interfacial properties. Zinc oxide nanorods have been successfully used to tune the PLA/basalt fibre interface by growing them on commercially available basalt fabrics. The hierarchical fibres significantly enhanced the mechanical properties of PLA-based composites, especially their flexural strength and stiffness. These values are 26% and 22% higher than those of unmodified basalt/PLA composites, and 24% and 34% higher than those of glass/PLA composites used as a baseline. The increase in tensile and flexural properties hinges on the mechanical interlocking action promoted by ZnO nanorods and on the creation of a compact transcrystallinity structure. A degradation of PLA matrix was detected but it was positively counteracted by the better interfacial stress transfer. This study offers a novel approach for modifying the fibre–matrix interface of biocomposites intended for high-performance applications.