A simple technique based on doping polymers with in situ generated silver nanoparticles (Ag/PS films) has been developed. In particular, an antiseptic material has been prepared by dissolving silver 1,5-cyclooctadiene-hexafluoroacetylacetonate in amorphous polystyrene, and the obtained solid solution has been heated for ca. 10？s at a convenient temperature (180°C). Under such conditions the metal precursor decomposes producing silver atoms that diffuse into the polymer and clusterize. The antimicrobial characteristics of the resulting polystyrene-based material have been accurately evaluated toward Escherichia coli (E. coli) comparing the cytotoxicity effect of 10？wt.% and 30？wt.% (drastic and mild annealing) silver-doped polystyrene to the corresponding pure micrometric silver powder. Two different bacterial viability assays were performed in order to demonstrate the cytotoxic effect of Ag/PS films on cultured E. coli: (1) turbidimetric determination of optical density; (2) BacLight fluorescence-based test. Both methods have shown that silver-doped polystyrene (30？wt.%) provides higher antibacterial activity than pure Ag powder, under similar concentration and incubation conditions. 1. Introduction In recent years noble metal nanoparticles have been the subjects of many researches due to their unique electronic, optical, mechanical, magnetic, and chemical properties significantly different from those of bulk materials . These special and unique properties could be attributed to the small size and the large specific surface area characterizing these systems. For such reasons metallic nanoparticles have found applications in a variety of technological fields as catalysis, electronics, and photonics . Polymer-embedded metal nanoparticles represent a very simple and convenient way to use such nanostructures and some chemical and physical techniques are now available for preparing these materials, the most important approaches are usually based on the in situ thermolysis of metal precursors . Nanoparticles of silver have been found to exhibit interesting antibacterial activities [3, 4], and the investigation of this phenomenon has gained importance due to the increase of bacterial resistance to antibiotics, caused by their overuse. Recently, there have been developed materials (mainly textiles) containing silver nanoparticles, which exhibit very interesting antimicrobial activity. Antibacterial activity of the plastic-containing silver can be used, for example, in medicine to reduce infections as well as to prevent bacteria colonization on plastic
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