Morphology-dependent bactericidal activities of Ag/CeO2 catalysts against Escherichia coli

Abstract

Silver-loaded CeO 2 nanomaterials (Ag/CeO 2 ) including Ag/CeO 2 nanorods, nanocubes, nanoparticles were prepared with hydrothermal and impregnation methods. Catalytic inactivation of Escherichia coli with Ag/CeO 2 catalysts through the formation of reactive oxygen species (ROS) was investigated. For comparison purposes, the bactericidal activities of CeO 2 nanorods, nanocubes and nanoparticles were also studied. There was a 3-4 log order improvement in the inactivation of E. coli with Ag/CeO 2 catalysts compared with CeO 2 catalysts. Temperature-programmed reduction of H 2 showed that Ag/CeO 2 catalysts had higher catalytic oxidation ability than CeO 2 catalysts, which was the reason for that Ag/CeO 2 catalysts exhibited stronger bactericidal activities than CeO 2 catalysts. Further, the bactericidal activities of CeO 2 and Ag/CeO 2 depend on their shapes. Results of 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping measurements by electron spin resonance and addition of catalase as a scavenger indicated the formation of •OH, •O 2 − , and H 2 O 2 , which caused the obvious bactericidal activity of catalysts. The stronger chemical bond between Ag and CeO 2 nanorods led to lower Ag + elution concentrations.The toxicity of Ag + eluted from the catalysts did not play an important role during the bactericidal process. Experimental results also indicated that Ag/CeO 2 induced the production of intracellular ROS and disruption of the cell wall and cell membrane. A possible production mechanism of ROS and bactericidal mechanism of catalytic oxidation were proposed.

Antimicrobial activity of silver loaded MnO2 nanomaterials with different crystal phases against Escherichia coli

“…5b) -formation on the surface of Ag/MnO 2 provided a strong indication that Ag/MnO 2 effectively activated the adsorbed oxygen to produce active oxygen species, which played important roles in the inactivation of E. coli. According to our results of U OH formation on the surface of Ag/CeO 2 (Wang et al, 2014) and Ag/MnO 2 in this study, it can be inferred that multivalent metal oxide supports are favorable to ROS formation.…”

“…Further, the interaction of Ag and the support can potentially promote the production of ROS and improve the bactericidal activity. Our previous studies showed that electron transfer between Ce 3+ /Ce , and the interaction of Ag and Ce was helpful for the production of ROS (Chang et al, 2008;Wang et al, 2014). In order to examine the universality of this concept, manganese oxides with variable valency were chosen for further research on bactericidal activity based on ROS.…”

Noble metal ion substituted CeO2 catalysts: Electronic interaction between noble metal ions and CeO2 lattice

“…Other metal ions are also in ionic state as can be found from their binding energies compiled in Table 3. Noble metal ions dispersed on CeO 2 support reported by several research groups confirming ionic nature of noble metal ions in CeO 2 are also given in the table [89,99,[127][128][129][130][131][132][133][134][135][136].…”

Intracellular mechanisms of solar water disinfection

“…According to the literature, cells incubation time at 37 °C in presence of DCFH-DA should range between 30 and 60 minutes, to permit the diffusion of probes inside cells and the hydrolysis by endogenous esterase3839. Nevertheless, these incubation times for samples containing solar irradiated E. coli may lead to modifications of physiological state of the cells, including ROS levels, due to metabolic activities during the incubation period.…”