Objective: In recent decades, nanotechnology has been used for cancer diagnosis at early stages, and also designing drug delivery systems by targeting the nano-drug combination to cancer cells, and thus reducing the cytotoxicity to normal cells. Cobalt oxide is one of the most potent natural anticancer agents which has various applications in medicine, such as drug delivery systems, toxicity to cancer cells, and antibacterial properties. Cytotoxicity of cobalt oxide nanoparticles (Co3O4 NPs) can be studied on various cell lines. Methods: In this study, we first produced Co3O4 NPs using luminescence bacteria and then characterized their properties and investigated their anticancer activity on colorectal cancer cells. The nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform-infra red spectroscopy (FTIR) analysis. Results: The XRD and FTIR results illustrated the success in the synthesis of Co3O4 NPs. The result of SEM indicated that the biologically synthesized cobalt oxide nanoparticles are spherical in shape with about 70 nm diameter. The cytotoxicity study exhibited a time and dose dependent effect against CT26 colorectal cancer cells as shown by MTT assay. The half maximal inhibitory concentration (IC50) was found to be 60 μg/ml after 48 hours. The cytotoxic properties of Co3O4 NPs were also studied on mouse embryonic fibroblast cells (NIH/3T3) as a normal cell line, where the results indicated lower toxicity of the NPs compared to CT26 cancerous cells. Conclusion: Based on our results, the biologically synthesized Co3O4 NPs were found to specifically decrease the viability of CT26 cancerous cells in vitro and thus they exhibit multifunctional properties.

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