Antibacterial Activity of Plastics Coated with Silver-Doped Organic-Inorganic Hybrid Coatings Prepared by Sol-Gel Processes.

Silver-doped organic–inorganic hybrid coatings were prepared starting from tetraethoxysilane and α-triethoxysilane terminated poly(ethylene)–block–poly(ethyleneglycole) using the sol–gel process. They were applied as a thin layer (600-1000 nm) to PE and PVC films and the antibacterial activity of the coated films was tested against Gram-negative (Escherichia coli ATCC 25922) and Gram-positive (Staphylococcus aureus ATCC 6538) bacteria. The effect of several parameters (such as organic-inorganic ratio, type of catalyst, time of post-curing, Silver-ion concentration, etc.) was investigated. Measurements at different contact times showed a rapid decrease of the viable count for both the tested strains. The highest antibacterial activity (more than 6 log reduction within 6 hours starting from 106 CFU ml-1) was obtained for samples with an organic-inorganic ratio of 80:20 and a percentage of Silver salt of 5 wt% with respect to the coating. For the coatings prepared by an acid catalyzed process, a good antibacterial activity of the coated films was demonstrated through repeated washings in warm water or in physiological saline solution at room temperature.