Biologically synthesized zinc oxide nanoparticles from <i>Turbinaria conoides</i> : characterization and biomedical efficacy

Abstract The present study focused on the green synthesis, comprehensive characterisation, and biological activity of zinc oxide nanoparticles (ZnO NPs) from brown seaweed Turbinaria conoides, which exhibited significant antibacterial, antioxidant, anti-inflammatory, and cytotoxic effects. The biosynthesised ZnO NPs mediated by T. conoides were systematically characterised through a suite of analytical techniques, including UV–visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and dynamic light scattering. The scanning electron microscopy confirmed the size range of 70–190 nm. The antibacterial efficacy of ZnO NPs mediated by T. conoides was evaluated against five different human bacterial pathogens. The highest zone of inhibition (19 mm) was observed against MRSA, while Mycobacterium smegmatis exhibited the lowest zone of inhibition (9.0 mm) at a concentration of 100 μg mL −1 . The ZnO NPs synthesised from T. conoides were evaluated using DPPH and ABTS assays, revealing a dose-dependent increase in scavenging activity. For anti-inflammatory assessment, the protein denaturation assay confirmed an inhibition range from 32.55 ± 0.2 (50 μg mL −1 ) to 54.9 ± 0.4 (250 μg mL −1 ). Similarly, in the anti-lipoxygenase assay, inhibition ranges from 41.96 ± 1.06 (50 μg mL −1 ) to 62.5 ± 1.02 (250 μg mL −1 ). Moreover, the MTT assay exposed cytotoxic effects of the A549 cell line with an IC 50 value of 84.00 μg mL −1 . The present study findings suggested that T. conoides mediated ZnO NPs hold significant potential for sustainable biomedical applications.