Green and Chemical Synthesis of Iron Oxide Nanoparticles: Comparative Study for antimicrobial activity and Toxicity Concerns

Infections caused by multidrug-resistant bacteria in healthcare settings highlight the critical need for robust infection control strategies and effective antimicrobial stewardship. This was further emphasized by the COVID-19 pandemic. This necessitates developing more effective antimicrobial agents. Iron oxide nanoparticles (IONPs) were reported to be biocompatible and possess a broad-spectrum antimicrobial activity with less susceptibilty of developing microbial resistance. Chemical synthesis is employed for industrial manufacture of IONPs. However, concerns about potential toxicity associated with chemical synthesis have led to a preference for green synthesis approaches, despite ongoing debates regarding their cytotoxicity. According to the authors' knowledge, the impact of synthesis methodology on the antimicrobial activity and cytotoxicity of IONPs has not been previously studied. Therefore, the current study is considered the first attempt to assess and compare the toxicity and antimicrobial effect of IONPs synthesized using different methodologies (green versus chemical synthesis) while correlating these effects to the physicochemical properties of IONPs. Additionally, this study addresses for the first time the disturbance of the microbial antioxidant defense system in multidrug-resistant bacteria after their exposure to IONPs. Both types of IONPs effectively eradicated SARS-CoV-2, and multidrug-resistant bacteria: S. aureus, and E. Coli, in addition, both disrupted the antioxidant bacterial defense mechanism, indicating that reactive oxygen species play a significant role in their antimicrobial activities. Chemically synthesized IONPs showed superior antimicrobial activity to those produced by green methods and in-vivo study demonstrated their greater compatibility with skin and eyes. Therefore, chemically synthesized IONPs might be used as a disinfectant in healthcare settings.