Synthesis, characterization and application of green seaweed mediated silver nanoparticles (AgNPs) as antibacterial agents for water disinfection.

A simple and eco-friendly method for the synthesis of hybrid bead silver nanoparticles (AgNPs) employing the aqueous extract derived from natural and renewable source namely tropical benthic green seaweed Ulva flexuosa was developed. This route involves the reduction of Ag+ ions anchored onto macro porous methacrylic acid copolymer beads to AgNPs for employing them as antibacterial agents for in vitro water disinfection. The seaweed extract itself acts as a reducing and stabilizing agent and requires no additional surfactant or capping agent for forming the AgNPs. The nanoparticles were analyzed using high-resolution transmission electron microscopy, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis and inductively coupled plasma optical emission spectroscopy. The study elucidates that such biologically synthesized AgNPs exhibit potential antibacterial activity against two Gram positive (Bacillus subtilis, Staphylococcus aureus) and two Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacterial strains tested. The bacterial count in treated water was reduced to zero for all the strains. Atomic force microscopy was performed to confirm the pre- and post-state of the bacteria with reference to their treatment with AgNPs. Attributes like facile environment-friendly procedure, stability and high antibacterial potency propel the consideration of these AgNPs as promising antibacterial entities.

Polymeric microspheres containing silver nanoparticles as a bactericidal agent for water disinfection.

A facile methodology has been developed by anchoring silver nanoparticles on to the macroporous methacrylic acid copolymer beads for disinfection of water in this study. Methacrylic acid copolymer beads are prepared by suspension polymerization technique. Silver nanoparticles formed on these copolymer beads by chemical reduction method are stable and are not washed away by water washing. Their stability is due to the interaction of nanoparticles with the carboxylic functional group on the copolymer beads. Copolymer beads containing silver nanoparticles are tested for their antibacterial activity against two gram positive and two gram negative bacteria. Antibacterial activity tested shows that they can be a potent biocidal material for water disinfection as they are highly effective against both gram positive and gram negative bacteria tested. The silver nanoparticles bound copolymer beads performed efficiently in bringing down the bacterial count to zero for all the strains tested except spore forming Bacillus subtilis which showed 99.9% reduction. There is no bacterial adsorption/adhesion on the copolymer beads containing silver nanoparticles proving them as effective water disinfectant.

Leukocyte-specific expression of the pp52 (LSP1) promoter is controlled by the cis-acting pp52 silencer and anti-silencer elements.

pp52 (LSP1) is a leukocyte-specific phosphoprotein that binds the cytoskeleton and has been implicated in affecting cytoskeletal remodeling in a variety of leukocyte functions, including cell motility and chemotaxis. The expression of pp52 is restricted to leukocytes by a 549 bp tissue-specific promoter. Here, we show that promoter fragments smaller than the 549 bp pp52 promoter have activity in fibroblasts where pp52 is not normally expressed. Specifically, a truncated construct (+1 to -99) functioned as a basal promoter active in leukocytes and fibroblasts. We identified two upstream regions within the 549 bp pp52 promoter responsible for restricting pp52 promoter activity in fibroblasts. These two regions contained a silencer (pp52 NRE) and an anti-silencer (pp52 anti-NRE) with opposing activities controlling pp52 gene expression. The pp52 NRE was active in both leukocytes and fibroblasts while the pp52 anti-NRE was only active in leukocytes, thereby allowing pp52 gene transcription in leukocytes but not in fibroblasts. The pp52 NRE was localized to an 89 bp DNA segment between -324 and -235 in the 549 bp pp52 promoter and functioned as an active silencer element in a position and orientation independent manner. The pp52 anti-NRE was localized to a 33 bp segment between -383 and -350 of the 549 bp pp52 promoter and acted as an anti-silencer element against the pp52 NRE, but lacked any intrinsic enhancing activity on its own. These findings indicate that the tissue specificity of the pp52 promoter is determined by the pp52 anti-NRE anti-silencer which over-rides the general inhibitory activity of the pp52 NRE silencer.