The fate of silver nanoparticles in authentic human saliva

The physicochemical properties of silver nanoparticles (AgNPs) in human whole saliva are investigated herein. In authentic saliva samples, AgNPs exhibit a great stability with over 70% of the nanomaterial remaining intact after a 24-h incubation in the presence of ∼0.3 mM dissolved oxygen. The small loss of AgNPs from the saliva sample has been demonstrated to be a result of two processes: agglomeration/aggregation (not involving oxygen) and oxidative dissolution of AgNPs (assisted by oxygen). In authentic saliva, AgNPs are also shown to be more inert both chemically (silver oxidative dissolution) and electrochemically (electron transfer at an electrode) than in synthetic saliva or aqueous electrolytes. The results thus predict based on the chemical persistence (over a 24-h study) of AgNPs in saliva and hence the minimal release of hazardous Ag⁺ and reactive oxygen species that the AgNPs are less likely to cause serious harm to the oral cavity but this persistence may enable their transport to other environments.