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Antimicrobial activity of cobalt oxide nanoparticles against Fusobacterium nucleatum: an in vitro study
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Srilekha Jayakumar, Harishma S, Janani Karunakaran, Sreeram Rayar, Jwaalaa Rajkumar, Sreelakshmi PS
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J Korean Acad Conserv Dent ;Published online October 26, 2026
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DOI: https://doi.org/10.5395/rde.2026.51.e48
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 Abstract
- Objectives
Endodontic infections are biofilm-mediated diseases since biofilms are more resistant to antimicrobial agents. Nanoparticles have emerged as promising candidates for endodontic disinfection due to their ability to disrupt microbial growth and biofilm formation. The aim of this in vitro investigation is to analyze the antimicrobial, antibiofilm, and cytocompatibility potential of cobalt oxide nanoparticles (Co3O4).
Methods
Co3O4 nanoparticles were synthesized via the precipitation method and characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Antimicrobial activity against Fusobacterium nucleatum was assessed using the broth microdilution method to determine the minimum inhibitory concentration; an antibiofilm assay and time-kill curve were also carried out. Acridine orange/ethidium bromide fluorescence staining was employed to differentiate between live and dead microbial cells, while the MTT assay was done to evaluate the cytocompatibility of Co3O4 nanoparticles. The following groups were evaluated: Group 1, 3% sodium hypochlorite; Group 2, cobalt oxide nanoparticles; and Group 3, saline.
Results
Data were analyzed using one-way analysis of variance. Biofilm inhibition by Co3O4 nanoparticles exceeded 80% at concentrations of 500 and 250 µg/mL and showed moderate biofilm inhibition of more than 60% at concentrations of 62.5 µg/mL and 31.25 µg/mL. Time-kill analysis demonstrated rapid bacterial reduction within 15 minutes with Co3O4 nanoparticles. The MTT assay indicated acceptable cytocompatibility at concentrations ≤31.25 µg/mL, maintaining over 80% cell viability.
Conclusions
Co3O4 nanoparticles in this investigation revealed strong antimicrobial action with effective antibiofilm activity comparable to or higher than 3% NaOCl at certain concentrations (500, 250, and 125 µg/mL). Co3O4 nanoparticles showed ≥80% cytocompatibility at concentrations ≤31.25 µg/mL and demonstrated moderate antibiofilm activity.
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KACD
