Enhanced Photoacoustic Response by Synergistic Ag-Melanin Interplay at the Core of Ternary Biocompatible Hybrid Silica-Based Nanoparticles

Hybrid Se/melanin-like nanoparticles as ROS quenchers and inhibitors of amyloid aggregation

Hybrid selenium/melanin-like nanoparticles offer different therapeutic strategies against amyloid aggregation. In this study, novel Se-based nanostructures are synthesized, characterized, and preliminarily employed as modulators of amyloid aggregation. In detail, two types of Se NPs are tested: one containing only Se(0), named Se NPs, and the second hybrid Se/melanin structures, indicated as SeMel NPs. Advanced biophysical and spectroscopic analyses elucidate the structures of NPs and the mechanistic underpinnings of the inhibition of aggregation of two protein fragments employed as amyloid models, Aβ21-40 and NPM1264-277. Both NPs are investigated for their antioxidant and superoxide dismutase (SOD)-like activity, as well as for their colloidal stability through dynamic light scattering (DLS) and ζ-potential measurements. ThT and SEM experiments demonstrate their ability to suppress amyloid aggregation, while far-UV circular dichroism (CD) spectroscopy indicates secondary structure alterations upon nanoparticle interaction, revealing a shift from β-sheet-rich conformations towards α-helical intermediates. Finally, SeMel NPs demonstrate cytocompatibility with SH-SY5Y cells and an effective mitigation of the cytotoxic effects of the amyloid models. These findings position hybrid Se-melanin NPs as promising agents for targeted amyloid therapeutics.

Designing bioinspired multifunctional nanoplatforms to support wound healing and skin regeneration: Mg-hydroxyapatite meets melanins

Melanin is a multifunctional biological pigment that recently emerged as endowed with anti-inflammatory, antioxidant, and antimicrobial properties and with high potentialities in skin protection and regenerative medicine. Here, a biomimetic magnesium-doped nano-hydroxyapatite (MgHA) was synthesized and decorated with melanin molecules starting from two different monomeric precursors, i.e. 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and dopamine (DA), demonstrating to be able to polymerize on the surface of MgHA nanostructures, thus leading to a melanin coating. This functionalization was realized by a simple and green preparation method requiring mild conditions in an aqueous medium and room temperature. Complementary spectroscopy and electron imaging analyses were carried out to define the effective formation of a stable coating, the percentage of the organic compounds, and the structural properties of resulting melanin-coated nanostructures, which showed good antioxidant activity. The in vitro interaction with a cell model, i.e. mouse fibroblasts, was investigated. The excellent biocompatibility of all bioinspired nanostructures was confirmed from a suitable cell proliferation. Finally, the enhanced biological performances of the nanostructures coated with melanin from DHICA were confirmed by scratch assays. Jointly our findings indicated that low crystalline MgHA and melanin pigments can be efficiently combined, and the resulting nanostructures are promising candidates as multifunctional platforms for a more efficient approach for skin regeneration and protection.