Effects of Engineered Cerium Oxide Nanoparticles on Bacterial Growth and Viability

Abstract

Interest in engineered nanostructures has risen in recent years due to their use in energy conservation strategies and biomedicine. To ensure prudent development and use of nanomaterials, the fate and effects of such engineered structures on the environment should be understood. Interactions of nanomaterials with environmental microorganisms are inevitable, but the general consequences of such interactions remain unclear, due to a lack of standard methods for assessing such interactions. Therefore, we have initiated a multianalytical approach to understand the interactions of synthesized nanoparticles with bacterial systems. These efforts are focused initially on cerium oxide nanoparticles and model bacteria in order to evaluate characterization procedures and the possible fate of such materials in the environment. The growth and viability of the Gram-negative species Escherichia coli and Shewanella oneidensis, a metal-reducing bacterium, and the Gram-positive species Bacillus subtilis were examined relative to cerium oxide particle size, growth media, pH, and dosage. A hydrothermal synthesis approach was used to prepare cerium oxide nanoparticles of defined sizes in order to eliminate complications originating from the use of organic solvents and surfactants. Bactericidal effects were determined from MIC and CFU measurements, disk diffusion tests, and live/dead assays. For E. coli and B. subtilis, clear strain-and size-dependent inhibition was observed, whereas S. oneidensis appeared to be unaffected by the particles. Transmission electron microscopy along with microarray-based transcriptional profiling was used to understand the response mechanism of the bacteria. Use of multiple analytical approaches adds confidence to toxicity assessments, while the use of different bacterial systems highlights the potential wide-ranging effects of nanomaterial interactions in the environment.

Soybean susceptibility to manufactured nanomaterials with evidence for food quality and soil fertility interruption

“…Soybean plants were grown through the seed production stage in soil amended with nano-CeO 2 (0, 0.1, 0.5, or 1 g·kg −1 ) or nano-ZnO (0, 0.05, 0.1, or 0.5 g·kg −1 ). Similar concentrations of these nanoparticles affect hydroponic plants (24,27) and microorganisms (25,28), but the effects on soilcultivated food crop plants are heretofore unknown. Plant growth was monitored by measuring stem length, leaf count, and leaf cover; the latter estimates total leaf area, can indicate plant health, and is affected by water stress (29) and metal exposure (30).…”

An investigation of the interactions between an E. coli bacterial quorum sensing biosensor and chitosan-based nanocapsules

“…On the other hand, conjugation of targeting ligands such as aptamers [8], peptides [9], or DNA [10], also confers nanomaterials with targeting capacity toward microorganisms [11][12][13]. Different types of microscopy (e.g., TEM, AFM, SEM) and molecular biology techniques offer powerful approaches to probe bacteria-nanomaterials interactions [14][15][16][17][18][19].…”

Cerium oxide and iron oxide nanoparticles abolish the antibacterial activity of ciprofloxacin against gram positive and gram negative biofilm bacteria

“…Studies on the antibacterial activity of CeO 2 nanoparticles have shown mixed results as well. While some studies have suggested antibacterial activity for CeO 2 nanoparticles (Shah et al 2012), others have indicated no toxic effect of CeO 2 nanoparticles on bacteria (Negahdary et al 2012;Pelletier et al 2010;Thill et al 2006).…”