Self-Assembled Monolayers of Silver Nanoparticles: From Intrinsic to Switchable Inorganic Antibacterial Surfaces

The layer-by-layer technique allows to graft molecular monolayers on bulk surfaces that, in turn, allow to graft monolayers of metal nanoparticles. This microreview focuses on the preparation of such materials featuring a monolayer of silver nanoparticles (AgNP) and their use as antimicrobial surfaces against both planktonic bacteria and biofilms. The role of Ag+ release and of direct cell/AgNP contact in the antibacterial action will be stressed as a function of the adhesive molecular layer, of the AgNP dimension and shape, of their surface density, and of the molecular overcoating. While these surfaces display an intrinsic antibacterial action, a further evolution will also be reviewed, in which additional photothermal antibacterial action can be switched on demand, using near-IR radiation and non-spherical AgNP or a combination of AgNP with non-spherical AuNP. The intrinsic and switchable photothermal action of these surfaces will be unraveled, and their synergistic effect stressed