Colloidal Silver Research(Page 2)Colloidal Silver Research Study-3Interaction of silver nanoparticles with HIV-1 Jose Luis Elechiguerra1 email, Justin L Burt1 email, Jose R Morones1 email, Alejandra Camacho-Bragado2 email, Xiaoxia Gao2 email, Humberto H Lara3 email and Miguel Jose Yacaman1,2 email 1Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA 2Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA 3Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, Mexico author email corresponding author email Journal of Nanobiotechnology 2005, 3:6doi:10.1186/1477-3155-3-6Published: 29 June 2005Abstract The interaction of nanoparticles with biomolecules and microorganisms is an expanding field of research. Within this field, an area that has been largely unexplored is the interaction of metal nanoparticles with viruses. In this work, we demonstrate that silver nanoparticles undergo a size-dependent interaction with HIV-1, with nanoparticles exclusively in the range of 1–10 nm attached to the virus. The regular spatial arrangement of the attached nanoparticles, the center-to-center distance between nanoparticles, and the fact that the exposed sulfur-bearing residues of the glycoprotein knobs would be attractive sites for nanoparticle interaction suggest that silver nanoparticles interact with the HIV-1 virus via preferential binding to the gp120 glycoprotein knobs. Due to this interaction, silver nanoparticles inhibit the virus from binding to host cells, as demonstrated in vitro. Colloidal Silver Research Study-4Does the antibacterial activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the Gram-negative bacterium Escherichia coli. Pal S, Tak YK, Song JM. Research Institute of Pharmaceutical Sciences and College of Pharmacy, Seoul National University, Seoul 151-742, South Korea. In this work we investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-negative bacterium Escherichia coli, both in liquid systems and on agar plates. Energy-filtering transmission electron microscopy images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag(+) (in the form of AgNO(3)). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To our knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and our results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-negative organism E. coli. Colloidal Silver Research Study-5Nanocrystalline silver supported on activated carbon matrix from hydrosol: antibacterial mechanism under prolonged incubation conditions. Pal S, Tak YK, Joardar J, Kim W, Lee JE, Han MS, Song JM. Research Institute of Pharmaceutical Sciences and College of Pharmacy, Seoul National University, Seoul 151-742, South Korea. Nanocrystalline Silver-supported activated carbon (AC) was fabricated by directly loading silver nanoparticles into the porous AC matrix from a preformed nanosilver hydrosol. Silver-AC composites were also synthesized using a conventional thermal impregnation method. While XRD calculation indicated the presence of Ag crystallites in nanometer range, silver nanoparticle hydrosol-treated AC having the finest crystallite size CS (< 14.4 nm), SEM images clearly revealed that Ag crystals coalesced significantly with increasing temperature resulting in much larger particle size in thermally impregnated silver-AC composities. To clarify the antibacterial mechanism of silver nanoparticles impregnated into AC under prolonged incubation conditions the antibacterial activity was investigated against Gram-negative Escherichia coli. The kinetics of bacterial inactivation, in presence of hydroxyl radical (*OH) scavengers, and superoxide anion radical (*O2-) inducer suggest the contribution of the reactive oxygen species (ROS) to antibacterial effect. However, these ROS scavengers did not show any inhibition of bactericidal activity after approximately 1 h, suggesting that generated ROS are responsible for E. coli inactivation only during the initial 1 h of the incubation time. This study clearly indicates the plausible implication of eluted Ag+ as major lethal species responsible for the E. coli inactivation over extended process time. The antibacterial process was found to be highly promoted at higher temperature which was ascribed to the enhanced ROS formation and Ag+ elution at higher temperature. SEM images revealed considerable differences in the morphology of E. coli cells contacting with the virgin AC and that contacting with silver-supported AC. The strong antibacterial ability of formaldehyde-modified silver-supported AC further provided the indirect evidences for catalytic oxidation by ROS, and for the synergistic antibacterial effects of nanocrystalline silver and adsorbed formaldehyde. Comparison of the antibacterial activities of the silver-supported materials prepared by silver colloid deposition and by conventional thermal impregnation technique indicates that former is more efficient in controlling microorganism. Research Information RequestReturn to Colloidal Silver Research - Page 1
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