Bouchra Benhniya, Fatima Zahra Karmil, Fatima Lakhdar, Badr-Ddine El Mouns, Noreddine Rezzoum, Samira Etahiri
The valorization of invasive marine macroalgae represents a sustainable strategy for developing eco-friendly bioactive materials. In this study, zinc oxide nanoparticles (ZnSm-NPs) were green-synthesized using an aqueous extract (AE-Sm) of the invasive brown seaweed Sargassum muticum collected from the Moroccan Atlantic coast. The synthesized nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), high-resolution transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED). The characterization analyses confirmed the successful formation of crystalline ZnO nanoparticles with a hexagonal wurtzite structure and predominantly spherical to rod-shaped morphology. The biological activities of ZnSm-NPs were then evaluated through anti-dermatophytic, antioxidant, and cytotoxicity assays. ZnSm-NPs exhibited potent anti-dermatophytic activity against Microsporum canis and Trichophyton rubrum, completely inhibiting mycelial growth under the tested conditions and showing minimum inhibitory concentrations (MICs) of 3.90 and 7.81 µg/mL, respectively. In addition, ZnSm-NPs displayed strong antioxidant activity, with IC50 values of 9.04 ± 0.45 µg/mL (DPPH) and 3.61 ± 0.03 µg/mL (ABTS), significantly outperforming the crude aqueous extract. Cytotoxicity assessment using Artemia salina nauplii revealed no significant acute toxicity under the tested conditions. Overall, this study demonstrates that S. muticum can be successfully valorized through green nanotechnology to produce ZnO nanoparticles with promising anti-dermatophytic and antioxidant properties. These findings highlight the potential of algal-mediated ZnO nanoparticles as sustainable bioactive nanomaterials while contributing to the valorization of invasive marine biomass.