Noble Nanoparticles
Noble nanoparticles (NPs), made of gold and silver, are attractive as antiviral agents for their surface functionalization versatility and their capacity to cleave disulfide bonds. Their use in disinfection has been extensively studied for different types of viruses. The morphology and the size of the NPs play a crucial role in their ability to efficiently interact with the capsids and in their toxicity for the organism. These nanomaterials are characterized by a very large specific surface area (inversely proportional to the particle diameter). As the particle size becomes smaller and smaller, the percentage of surface atoms increases, creating many unsaturated bonds due to lack of neighboring atoms. As a consequence, AgNPs and AuNPs have unstable atoms with high surface energy. This kind of structure provides a lot of contact adsorption sites and reaction points for further modifications. These chemical features allow to easily combine surface NP atoms with other atoms through chemical bonds.
Besides the composition of the metal core, several studies have pointed out the importance of the control of the surface chemistry. The surface groups can: (1) stabilize NPs in the biological media, (2) insert targeting agents, and (3) enhance the circulation time inside the body. Antiviral efficiency can be also enhanced by the multivalency effect, where highly branched ligands are used to locally augment the local concentration of the targeting molecules. In this section the main strategies and results for silver (AgNPs) and gold (AuNPs) nanoparticles in blocking viral entry will be critically discussed.