Bactericidal effects of different silver-containing materials

The evaluation of the bactericidal effect of different silver-containing materials where silver is available as Ag+ (silver nitrate and different silver-exchanged zeolites), as metallic Ag0 (commercial silver nanoparticles) or as oxide (silver (I) oxide) was carried out in order to elucidate the importance of the bioavailability of silver (i.e., as free ions, metallic particles, combination of them, clusters, complexes, partially soluble or insoluble salts, etc.) on its bactericidal action.For the different materials tested, their bactericidal effect is ordered in the following sequence: AgNO3 > Ag-ZSM-5 > Ag2O > commercial silver-exchanged zeolite (granular) > commercial silver-exchanged zeolite (pellets) > Ag nanoparticles. In general, as the content of bioavailable ionic silver increases, the biocidal effectiveness of the corresponding silver-releasing material increases too.

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► For each material tested, the bactericidal activity increases with the silver content.
► The bactericidal effect is ordered in the following sequence: AgNO3 > Ag-ZSM-5 > Ag2O > commercial silver-exchanged zeolite (granular) > commercial silver-exchanged zeolite (pellets) > Ag nanoparticles.
► As the content of bioavailable ionic silver increases, the biocidal effectiveness increases too.
► Silver nanoparticles with sizes around 100 nm did not show bactericidal effects.
► For zeolites, there is a direct correlation between the biocidal effect and the oxidative stress.