Sustainable Synthesis of Cobalt Oxide Nanoparticles (Co3O4-NPs) Using Extract of Nodosilinea nodulosa: Characterization and Potential Biological Applications

Cobalt oxide nanoparticles (Co3O4-NPs) were synthesized by an eco-friendly technique incorporating the cyanobacterial extract Nodosilinea nodulosa as a chelating agent, marking the first study to employ this species for such a purpose. This groundbreaking methodology introduces a unique biological element, thereby contributing to more sustainable nanotechnology practices. Co3O4-NPs synthesis was validated by UV-visible spectroscopy with a distinct peak at 453 nm, while the XRD analysis determined the particle size to be 41 nm. Several in vitro analyses were conducted to evaluate the potential therapeutic applications of the nanoparticles. The antimicrobial evaluations targeted two types of bacterial strains, i.e., Pseudomonas aeruginosa displayed the most susceptibility with the widest zone of inhibition (ZOI), while Bacillus safensis indicated the least susceptibility. Among the fungal varieties, Fusarium oxysporum exhibited increased vulnerability with a maximum ZOI of 3 +/- 0.04 mu g/mL, while Aspergillus flavus showed a lower (zone of inhibition) ZOI of 2 +/- 0.04 mu g/mL. The cytotoxicity was examined through a brine shrimp assay, resulting in an LC50 value of 498 mu g/mL. Significant hemolytic activity was observed at a higher concentration of 200 mu g/mL. The antioxidant assay indicated a 60% antioxidant activity at 200 mu g/mL concentration. Co3O4-NPs displayed ineffectiveness against insecticides: Tribolium castaneum, Sitophilus oryzae, and Rhyzopertha dominica. Phytotoxicity was found to be dose-dependent, with stronger effects at higher concentrations. This comprehensive study, by combining multiple biological assays, not only confirms the synthesis and attributes of Co3O4-NPs but also provides new insights into their biological effects, demonstrating significant biomedical potential and making them promising candidates for both in vitro and in vivo therapeutic applications.