Cytotoxicity of AgPURETM: Silver nanoparticles in the human intestinal cell line Caco-2

Purpose: Engineered nanomaterials may exhibit properties differing significantly from those observed in the bulk materials, because of their small dimensions and large surface-to-volume ratio. Due to their unique qualities silver nanoparticles are used in a wide range of consumer products. Even the use of nanoscaled silver hydrosol for nutritional purposes has been requested. Despite the wide applications of silver nanoparticles, there is still lack of information concerning the impact on human health after oral application. Methods: To investigate the effects of silver nanoparticles on human intestinal cells, we monitored the reaction of Caco-2 cells, as a model for the first intestinal barrier of the human body, and AgPure silver nanoparticles. AgPure has already been used in consumer products. The radius of gyration, hydrodynamic radius and size distribution were determined by SAXS and DLS. We studied the effects of AgPure on cell viability and proliferation by CellTiter-Blue assay, DAPI staining and xCELLigence impedance measurement. Additionally, we tested for membrane damage with LDH assay, for apoptotic effects with Annexin-V/7AAD staining and for reactive oxygen species with dichlorofluorescein assay.Results: AgPure are spherical with metal core radii of 7.4 nm and hydrodynamic radii of 22 nm with stabiliser. The size is Gaussian-distributed with a polydispersity of 17 %. When proliferating Caco-2 cells are exposed to AgPure, morphological abnormally adherence and particle dose- and time-dependant cytotoxicity was observed. However, apoptosis or membrane damage did not occur, but results of the dichlorofluorescein assay suggested the formation of reactive oxygen species as possible mechanism of cytotoxicity.