Synergistic effects of iron oxide nanoparticles and hydrogen peroxide in inhibiting Pseudomonas aeruginosa growth to combat bacterial contamination in water recovery systems

Abstract

Access to safe water is critical for public health. Pseudomonas aeruginosa is ranked as one of the most significant bacterial pathogens, threatening human health. Hydrogen peroxide and other biocides are often used to prevent the growth of bacteria, but the toxicity of these biocides is a major consideration when bacteria grow in water sources. This study explores the application of iron oxide nanoparticles (IONPs), both bare and polyacrylic acid-coated (PAA@IONPs), to enhance the effectiveness of hydrogen peroxide in eliminating P. aeruginosa, potentially reducing the required biocide concentrations and minimizing toxicity. X-ray diffraction crystallography (XRD) alongside X-ray photoelectron spectroscopy (XPS) showed that the synthesized IONPs were magnetite nanoparticles and Fourier-transform infrared (FTIR) spectroscopy proved that PAA coating was successfully functionalized to IONPs. The hydrodynamic size of the IONPs decreased from 106 ± 11 nm to 84 ± 3 nm when coated with PAA. Transmission electron microscopy (TEM) images confirmed a similar decrease in dry size from 16 ± 3 nm to 9 ± 2 nm post-coating. A week after storage, there was a decrease in the concentration of stored IONPs and PAA@IONPs due to settling by 56 ± 14% and 22.6 ± 0.6%, respectively, demonstrating that PAA coating increased colloidal stability of the IONPs. Coated nanoparticles exhibited a more negative zeta potential, which was also indicative of greater colloidal stability. In the presence of 3.65 mg ml⁻¹ IONPs and 182.25 mM of hydrogen peroxide, overnight bacterial growth was reduced by more than 63% compared to the sample with hydrogen peroxide alone. IONPs did not inhibit bacterial growth in the absence of hydrogen peroxide. The presence of 3.65 mg ml⁻¹ IONPs and 182.25 mM of hydrogen peroxide killed 90.2% of bacterial cells during one hour of exposure. These findings indicate the potential benefit of IONPs to combat bacterial growth, which could be applied in industrial settings to reduce the biocide concentration needed to curb bacterial development.