Silver impregnated on polymer-titania nanocomposite films exhibit excellent antibacterial properties with the added advantage of repeated use. The polyethylene glycol-polyurethane-titania designated as PEG-PU-TiO 2 polymer nanocomposite films were synthesized by simple solution casting technique. Silver has been incorporated into these films by photochemical reduction of silver nitrate solution. The TiO 2 facilitated the UV photoreduction of AgNO 3 to Ag, which is active as an antibacterial agent. Fourier Transformed Infrared Spectroscopy (FT-IR) confirms the formation of the polymer, polyurethane. X-ray Diffraction (XRD) determined the structure and scanning electron microscopy (SEM), the morphology of the films. XPS confirms the Ag to be in zero oxidation state and the amount of silver impregnated in the films as estimated by scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDAX), and atomic absorption spectroscopy (AAS) is about 2-4 at %. The antibacterial properties of these films were studied on Escherichia coli and Bacillus subtilis by the disk-diffusion method and this has been correlated with the percentage of Ag in the films. One very encouraging observation is that the antibacterial activity of the Ag in polymer-titania nanocomposite films showed reasonable activity even when tested in the microbial broth.
This Letter presents a detailed experimental and theoretical study to unravel the unique role of hydrogen peroxide in controlling phase and thereby shape and crystallinity of nanocrystalline titania. Analysis of all reaction parameters revealed that the H 2 O 2 /Ti ratio (r p ) is the predominant factor to obtain crystalline titania with different phase composition. Evolution of phase and crystallite size of the materials is determined from X-ray diffraction and Raman spectroscopy. Transmission electron microscopy images showed phase-related morphology, that is, truncated anatase and rod-like rutile. The solution Raman and Fourier transform infrared spectroscopy study confirmed different bonding pattern in the reaction medium. Complexation of titanium with -O-Oin bidentate manner with C 2v symmetry in the reaction mixture is confirmed by the strong Raman band at ∼630 cm -1 . Quantum mechanical calculations are performed using density functional theory with B3LYP/LANL2DZ to provide all possible intermediate structures and to predict the probable mechanism leading to the formation of different phases of titania under different experimental conditions. SECTION Nanoparticles and Nanostructures T
Co-doping with Cu and Mo is shown to have a synergistic effect on the photocatalytic activity of TiO 2 . The enhancement in activity is observed only if the synthesis route results in TiO 2 in which (Cu, Mo) co-dopants are forced into the TiO 2 lattice. Using x-ray photoelectron spectroscopy, Cu and Mo are shown to be present in the +2 and +6 oxidation states respectively. A systematic study of the ternary system shows that TiO 2 containing 6 mole % CuO and 1.5 mole % MoO 3 is the most active ternary composition. Ab-initio calculations show that co-doping of TiO 2 using (Mo, Cu) introduces levels above valence band, and below conduction band, resulting in a significant reduction in the band gap (~0.8 eV). However, co-doping also introduces deep defect states, which can have a deleterious impact on photoactivity. This helps rationalize the narrow compositional window over which the enhancement in photocatalytic activity is observed.
The bacterial toxin CcdB (Controller of Cell death or division B) targets DNA Gyrase, an essential bacterial topoisomerase, which is also the molecular target for fluoroquinolones. Here, we present a short cell‐penetrating 24‐mer peptide, CP1‐WT, derived from the Gyrase‐binding region of CcdB and examine its effect on growth of Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus and a carbapenem‐ and tigecycline‐resistant strain of Acinetobacter baumannii in both axenic cultures and mouse models of infection. The CP1‐WT peptide shows significant improvement over ciprofloxacin in terms of its in vivo therapeutic efficacy in treating established infections of S. Typhimurium, S. aureus and A. baumannii. The molecular mechanism likely involves inhibition of Gyrase or Topoisomerase IV, depending on the strain used. The study validates the CcdB binding site on bacterial DNA Gyrase as a viable and alternative target to the fluoroquinolone binding site.
Surface‐functionalized colloidal nanoparticles provide a versatile scaffold for protein surface recognition because of their size, the ability to tailor nanoparticle surfaces with a wide range of functionalities, and the ability to template the surface monolayer. Furthermore, the wide range of core materials such as TiO2 and Fe3O4 etc., enhance the utility of these particles. Owing to its high electron affinity for many proteins and enzymes, the dye Cibacron blue (CB) has been attached to various solid supports such as Sephadex, Sepharose, and polyacrylamide. The diversity shown by the blue dye in binding several unrelated classes of proteins makes it a potential candidate in terms of studies of the immobilized ligand. A facile method of synthesis and utility of a new, cheaper, and robust support material, TiO2 nanoparticles (NPs), functionalized with Cibacron blue dye for protein (lactic dehydrogenase) purification by affinity chromatography is described. The TiO2–CB nanoparticles do not lose their binding property even upon long storage, drying, and re‐suspending into buffer multiple times. Studies carried out with Fe3O4–CB nanoparticles have also shown that they bind lactic dehydrogenase similar to TiO2–CB nanoparticles.
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