Gür, Bahri; Gülhan, Barış; Akkaş, Önder; Akgöz, Melek; Vejselova Sezer, Canan; Cengiz, Mustafa; Kutlu, Hatice Mehtap; Alma, Mehmet Hakkı

The development of environmentally compatible nanomaterials with biomedical potential has garnered increasing interest. In this study, cobalt oxide nanoparticles (Co3O4-NPs) were synthesized by an eco-friendly method using Platanus orientalis L. leaf extract as a reducing and stabilizing agent. Structural and physicochemical characterizations confirmed the successful formation of spinel-type Co3O4-NPs with controlled size and morphology. Synthesis at pH 12 resulted in smaller (22.70 nm) and more stable nanoparticles which showed increased anticandidal activity. The minimum inhibitory concentrations (MIC: 3.91, 7.81, and 1.95 mg/mL) and the minimum fungicidal concentrations (MFC: 15.63, 62.50, and 7.81 mg/mL) indicated a strong antifungal effect against Candida albicans, Candida tropicalis , and Candida glabrata , respectively. In addition, Co3O4-NPs showed concentration-dependent cytotoxicity on MDA-MB-231 breast cancer cells with the inhibition concentration 50 value (IC50: 0.07 mg/mL 24-h) indicating potential anticancer effect. These results highlight the dual antifungal and cytotoxic capabilities of biogenically synthesized Co3O4-NPs, making them strong candidates for future biomedical applications.