Phosphate-dependent modulation of antibacterial strategy: a redox state-controlled toxicity of cerium oxide nanoparticles

• Published in: Bulletin of materials science Vol. 40; no. 6; pp. 1231 - 1240
• Main Authors: Sargia, Bhakti, Shah, Juhi, Singh, Ragini, Arya, Homica, Shah, Maitri, Karakoti, Ajay S, Singh, Sanjay
• Format: Journal Article
• Language: English
• Published: Bangalore, India Indian Academy of Sciences 01.10.2017; Springer Nature B.V
• Subjects: Antimicrobial agents; Antioxidants; Cerium oxides; Chemistry and Materials Science; E coli; Engineering; Enzymes; Hydrogen peroxide; Lanthanide phosphates; Materials Science; Microorganisms; Nanomaterials; Nanoparticles; Nitrates; Oxidation; Phosphates; Spectrum analysis; Superoxide dismutase; Surface chemistry; Toxicity; Mumbai India; India; cerium oxide nanoparticles; antibacterial; superoxide dismutase; catalase; Redox active nanomaterials
• ISSN: 0250-4707; 0973-7669
• DOI: 10.1007/s12034-017-1480-3

Specific reactivity of cerium oxide nanoparticles with phosphate ions was used to design a novel antibacterial system. The redox sensitivity of cerium oxide nanoparticles (CeNPs) was used to irreversibly scavenge phosphate ions from the microbial growth media resulting in nutrient starvation in microbes. Cerium oxide nanoparticles surface was engineered with different ratios of ( Ce ( + 3 ) / Ce ( + 4 ) ) cerium oxidation states and the effect of surface oxidation states was evaluated on the antibacterial activity. The nutrient depletion-based antibacterial activity is demonstrated selectively by CeNPs with higher Ce ( + 3 ) / Ce ( + 4 ) ratio on the surface. The surface chemistry of Ce ( + 3 ) is altered in the presence of phosphate, resulting in the irreversible formation of surface cerium phosphates leading to the loss of its intrinsic superoxide dismutase (SOD) activity. It is hypothesized that nutrient starvation by Ce ( + 3 ) leads to oxidative stress in microbes which is not neutralized by the altered surface chemistry of CeNPs with high ( Ce ( + 3 ) / Ce ( + 4 ) ) ratio. On the contrary, CeNPs with higher ( Ce ( + 4 ) / Ce ( + 3 ) ) ratio did not show any reactivity towards phosphate, thus depicted no antibacterial activity, confirming the hypothesis that surface chemistry, rather than size or morphology-dependent toxicity is the main reason for the observed antibacterial activity of CeNPs.