Photokilling of waterborne-resistant pathogenic bacteria using cobalt-doped zinc oxide doped on reduced graphene oxide nanoparticles

This study is aimed at the chemical synthesis of light-activated cobalt-doped zinc oxide and its further doping on reduced graphene oxide(RGO)and assessment of its antibacterial activity on antibiotic-resistant waterborne pathogens including Enterococcus faecalis,Staphylococcus aureus,Klebsiella pneumonia,and Pseudomonas aeruginosa.The synthesized nanoparticles were characterized via UV–vis spectroscopy,scanning electron microscopy(SEM),and energy-dispersive X-ray spectroscopy(EDS).The minimal inhibitory concentration(MIC)of nanoparticles portrayed a significant killing of both Gram-positive and Gram-negative bacteria.The synthesized nanoparticles were further found as active killers of bacteria in drinking water.Further,these nanoparticles were found photothermally active alongside ROS generators.The photokilling activity makes them ideal replacement candidates for traditional water filters.

Photokilling of Escherichia coli Using Hybrid Titania Nanoparticles Suspended in an Aqueous Liquid

In this work, the photokilling of Escherichia coli using a “one-pot” synthesized suspension of anatase crystallized nanoparticles is evaluated. Preliminary to the biological tests concerning the antibacterial efficiency, the fabricated suspension, using a derived solgel process in soft chemistry condition, is characterized. Structural properties of the nanoparticles are investigated using Electronic Transmission Microscopy (TEM) equipped with Selected Area Electron Diffraction (SAED) probe and X-ray diffraction. The inorganic solid content was evaluated by Thermogravimetric Analysis (TGA). Photodegradation of Acid Orange 7 in aqueous solution was used a probe to assess the photocatalytic activity of the elaborated suspension under UV irradiation. The photokilling of Escherichia coli in presence of hybrid TiO2 nanoparticles suspended in aqueous liquid under UV irradiation is evaluated. Such TiO2 nanoparticles suspension shows a strong bactericidal activity with the total destruction of bacteria after only one hour.

Environmental Toxicity and Antimicrobial Efficiency of Titanium Dioxide Nanoparticles in Suspension

The aim of this work was to evaluate the photokilling efficiency of synthesized titanium dioxide nanoparticles in suspension. Two strains of Escherichia coli, Lactobacillus casei rhamnosus and Staphylococcus aureus were used as probes to test the photokilling activities of the nanoparticles. The toxicity effects of TiO2 nanoparticles on the environment were determined by a standard test using gram-negative bioluminescent bacteria Vibrio fischeri. The antimicrobial activity of these nanoparticles (NPs) was then investigated versus NPs concentration, UV irradiation time and micro- organism strains. We evaluated the LC50 values of the nanoparticles suspension by counting the Colony-Forming Units. Results highlighted the differences in bacteria sensitivity facing photokilling treatment induced by the irradiation of anatase TiO2 nanoparticles suspension. At the concentration of 1 g·L-1 TiO2, tested bacteria were killed after 30 minutes of photo-treatment. Using different TiO2 concentrations, the Staphylococcus aureus gram-positive/catalase-positive bacteria were more resistant than gram-negative/catalase-positive ones or gram-positive/catalase-negative bacteria. An effect of UV irradiation was evaluated by the quantification of hydrogen peroxide generated by the photolysis of water molecules in presence of the nanoparticles with or without the most resistant bacterium (S. aureus). After 30 minutes with UV irradiation in these two conditions, the concentration of hydrogen peroxide was 35 μM in presence of 1.2 g·L-1 TiO2 suspension. This result suggested that the resistance mechanism of S. aureus was not due to an extracelullar H2O2 enzymatic degradation.