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Ultrasmall silver nanoclusters (Ag NCs) are one of the emerging and highly efficient antibacterial agents, owing to the unique features of sub-2 nm particle size and the high abundance of the active Ag+ species. However, practical applications of Ag NCs in biological environment are often hampered by silver oxidization, which results in particle aggregation and loss of antibacterial activity. In this study, for the first time, we develop a facile method to synthesize highly dispersed Ag NCs decorated mesoporous silica nanoparticles (Ag NC-MSNs) capable of long-term and efficient release of Ag+ ions. This novel Ag NC-MSNs nanocomposite was demonstrated as an effective antibacterial agent against both Gram-positive and Gram-negative pathogenic bacteria. Compared with the counterparts Ag NCs and silver nanoparticles decorated mesoporous silica nanoparticles (Ag NP-MSNs), Ag NC-MSNs exhibit 17-fold and 27-fold enhancement in antibacterial potency, respectively. The homogeneous distribution of ultrasmall Ag NCs in the mesoporous architecture of supporting MSNs matrix is crucial for the controlled release of Ag+ ions, leading to the superior broad-spectrum antimicrobial activity. Moreover, the cytotoxicity assay indicated that the effective antibacterial concentration of Ag NC-MSNs shows minimum toxicity on mammalian cells. This new Ag nanocomposite developed in this work is promising for practical applications against various microbial infections. [ABSTRACT FROM AUTHOR]

Development of new functional coatings in the field of health care, as antibacterial applications, deals with a straight control of the diffusive properties that rules the releasing of the active component. In this work, the development of a silver-rich nanocomposite thin coating, loaded with organically modified clay nanoparticles, is presented. The synthesis process included an environment-friendly silanization process of clay nanoparticles (Laponite® S482) with (3-glycidoxypropyl)trimethoxysilane (GPTMS) and the further hydrolytic condensation with tetraethoxysilane (TEOS). Silanization process and the obtained coatings were analysed by Fourier transformed infrared spectroscopy, UV–visible spectroscopy, X-ray diffraction, thermogravimetric curves and scanning electron microscopy. The silanization process of clay nanoparticles with the organically reactive alkyl alkoxysilane, allowed to stabilize and exfoliate the clay nanosheets within a hybrid organic-inorganic sol-gel material. Ring opening of grafted epoxy groups carried to an increasing of the basal spacing, of intercalated clay nanosheets, from 1.3 to 1.8 nm. Moreover, incorporation of organically modified clay nanosheets introduced a significant stabilization on the development of silver nanoparticles inside the structure of the nanocomposite coating, retaining the silver inside the coating material and restricting the growing of silver nanoparticles on the surface of the coating. Antibacterial behaviour, against E . coli cultures, performed through agar diffusion tests, provided promising results that allow assuming that the studied nanocomposite coating serves as a reservoir of ionic silver, permitting the antibacterial effect. [ABSTRACT FROM AUTHOR]

Abstract: Chitosan, associated with cellulose fibers, can be used for elaborating sponge-like structures (membranes, foams) for the binding of silver ions. The composite material has very promising antibacterial properties versus Pseudomonas aeruginosa (Gram−)≫ Escherichia coli (Gram−)> Staphylococcus hominis (Gram+)≫ Staphylococcus aureus (Gram+). The amount of silver required for bactericidal effect is quite low (below 0.1mg per disk, this means less than 6mgAgg−1) in antibiogram-type test but also for the treatment of water suspensions (in dynamic mode with water recycling). The presence of cellulose fibers improves the efficiency of metal binding, due to chitosan dispersion and enhancement of the availability and accessibility of amine groups. Silver nanoparticles (about 100nm) were observed by scanning electron microscopy. The photo-reduction (exposure to sun light or UV lamp) leaded to the partial aggregation of silver nanoparticles: metal ions that were released tended to aggregate at the surface of the material. [Copyright &y& Elsevier]