Biogenic synthesis of zinc oxide nanoparticles using cell-free extract of Spirogyra crassa (Kütz.) Kütz for sustainable biomedical and environmental applications

This study focuses on the biosynthesis of zinc oxide nanoparticles (ZnO NPs) utilizing the cell-free extract derived from the green alga Spirogyra crassa (Kütz.) Kütz. A suite of advanced analytical techniques, including FTIR, XRD, FESEM, EDS, HRTEM, XPS, and BET, were employed to confirm the formation and extensively characterize the biosynthesized ZnO nanoparticles. XRD analysis confirmed the formation of a highly crystalline nanomaterial with an average crystallite size of approximately 29 nm. FESEM and HRTEM analyses revealed that the biogenically synthesized ZnO nanoparticles predominantly exhibited a spherical morphology. The biogenically synthesized ZnO nanoparticles exhibit a well-defined crystalline structure, belonging to the hexagonal wurtzite phase with the space group P6₃mc (space group number: 186). BET analysis revealed that the biogenically synthesized ZnO nanoparticles have a total surface area of 14.97 m² g⁻¹, a pore volume of 0.0342 cm³ g⁻¹, and an average pore size of 3.07 nm. The ZnO NPs proved to exhibit significant antidiabetic potential as the sample showed the highest percentage (74.25% ± 2.7) of enzyme inhibition at 30 μg mL⁻¹ concentration with IC50 values of 18.69 μg mL⁻¹ for α-amylase and 19.06 μg mL⁻¹ for α-glucosidase, while in the antioxidant test, the highest percentage (85.15% ± 3.2) of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) scavenging activity was observed with an IC50 value of 17.90 μg mL⁻¹. In addition, the photocatalytic degradation of malachite green dye under sunlight irradiation demonstrated the environmental applicability of the synthesized nanoparticles, achieving a degradation efficiency of 95.7% within 150 minutes. These findings underscore the synergistic biomedical and environmental potential of algal-derived ZnO NPs for sustainable nanotechnology applications.