Surface-modified AgNPs can also prevent viral infection by competitive adsorption on host cells. The process of infection of cells by herpes simplex virus type 1 (HSV-1) involves the interaction between viral envelope glycoproteins and heparan sulfate (HS) on cell surface. Therefore, researchers designed AgNPs capped with mercaptoethanesulfonate (Ag-MES) to compete with the cellular HS through the sulfonate end groups, thereby blocking the virus from entering the cells.30