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Dal Lago V.,Brazilian Synchrotron Light Laboratory (LNLS) | Dal Lago V.,National University of Cordoba | Frana De Oliveira L.,Brazilian Synchrotron Light Laboratory (LNLS) | De Almeida Gonalves K.,Lnbio Laboratorio Nacional Of Biociencias | And 2 more authors.
Journal of Materials Chemistry | Year: 2011

Silver nanoparticles (AgNPs) are attracting attention due to their bactericidal activity and consequent possible biomedical applications. The key to their broad-acting and potent biocidal property seems to be based on the size-related mechanism by which AgNPs act on different bacteria strains. Here, we report the synthesis and successful size-selective fractionation of AgNPs obtained through chemical reduction of silver nitrate in ethylene glycol using polyvinylpyrrolidone as a protective agent. A combination of characterization techniques (UV-vis spectroscopy, transmission electron microscopy and small-angle X-ray scattering) is employed to differentiate the two size-fractionated samples. From the analyses, it is evidenced that AgNPs are mainly spherical and have their radius centered at ∼8.5 and ∼11.0 nm. The nanoparticles bactericidal efficacy is investigated using the disk diffusion test against Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and Micrococcus lysodeikticus. Although both fractionated samples present bactericidal activity against all four tested bacteria (one Gram negative and three Gram positives), those presenting smaller size own enhanced antibacterial properties. © 2011 The Royal Society of Chemistry. Source


De Oliveira L.F.,Brazilian Synchrotron Light Laboratory (LNLS) | De Almeida Goncalves K.,Lnbio Laboratorio Nacional Of Biociencias | Boreli F.H.,Brazilian Synchrotron Light Laboratory (LNLS) | Kobarg J.,Lnbio Laboratorio Nacional Of Biociencias | Cardoso M.B.,Brazilian Synchrotron Light Laboratory (LNLS)
Journal of Materials Chemistry | Year: 2012

The ever increasing antibiotic resistance levels in pathogenic and non-pathogenic bacteria have boosted the search for effective controlling methods of bacterial infections. In this context, we prepared colloidal silica-lysozyme composites to evaluate the interaction between these structures and bacteria. Lysozyme was chosen since it is a protein that holds bactericidal properties and that, in the reaction process, acts as a catalyst which favors silica hydrolysis and condensation. The high entrapment yield of lysozyme in the silica cage (approximately 95%) does not change the secondary structure of the protein resulting in a material with superior bactericidal properties. The antimicrobial differences when silica-lysozyme composites are tested against Escherichia coli and Staphylococcus aureus are used to propose an interaction mechanism between colloids and bacteria. Bactericidal properties of the composites are attributed to the ultra-structural organization of the composite which, due to the positive surface charge, is attracted by the negative bacterial cell wall while lysozyme is delivered. © 2012 The Royal Society of Chemistry. Source


De Oliveira L.F.,Brazilian Synchrotron Light Laboratory (LNLS) | De Oliveira Goncalves J.,Brazilian Synchrotron Light Laboratory (LNLS) | De Almeida Goncalves K.,Lnbio Laboratorio Nacional Of Biociencias | Kobarg J.,Lnbio Laboratorio Nacional Of Biociencias | Cardoso M.B.,Brazilian Synchrotron Light Laboratory (LNLS)
Journal of Biomedical Nanotechnology | Year: 2013

Silver nanoparticles are widely used due to their biomedical-antibacterial applications. At the same time, the stabilization of these nanoparticles is challenging and may be made using polymeric carbohydrates, based on the practice of avoiding toxic chemicals and undesirable residues. In this study, we synthesized silver nanoparticles (AgNPs) which were stabilized by carbohydrates (potato starch and chitosan) and characterized by UV-Vis spectroscopy, zeta potential and transmission electron microscopy techniques. Bactericidal efficiency of AgNPs capped with different carbohydrates was tested demonstrating that the synthesized materials were able to inhibit the growth of two clinical/medical relevant bacteria strains (Escherichia coli and Staphylococcus aureus). AgNPs stabilized by chitosan presented enhanced bactericidal activity if compared to the ones synthesized in presence of potato starch. This difference is mainly attributed to the known antibacterial properties of chitosan associated to overall positive charge of the nanoparticles capped by this polymer. Those nanoparticles obtained in presence of starch presented minor bactericidal effects since the starch-capping agent is not able to contribute to the avoidance of bacteria growth and confers a quasi-neutral charge to the nanoparticle. Source

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