Particle uptake efficiency is significantly affected by type of capping agent and cell line

Surface-functionalized silver nanoparticles (AgNPs) are the most deployed engineered nanomaterials in consumer products because of their optical, antibacterial and electrical properties. Almost all engineered nanoparticles are coated with application-specific capping agents (i.e. organic/inorganic ligands on particle surface) to enhance their stability in suspension or increase their biocompatibility for biomedicine. The aim of this study was to investigate the contribution of the selected capping agents to their observed health impacts using realistic dose ranges. AgNPs capped with citrate, polyvinylpyrrolidone (PVP) and tannic acid were studied with human bronchoalveolar carcinoma (A549) and human colon adenocarcinoma (Caco-2) cell lines and compared against exposures to Ag ions. Cellular uptake and cytotoxicity were evaluated up to 24 h. Tannic acid capped AgNPs induced higher cellular uptake and rate in both cell lines. Citrate-capped and PVP-capped AgNPs behaved similarly over 24 h. All three of the capped AgNPs penetrated more into the A549 cells than Caco-2 cells. In contrast, the uptake rate of Ag ions in Caco-2 cells (0.11 ± 0.0001 µg h(-1) ) was higher than A549 cells (0.025 ± 0.00004 µg h(-1) ). The exposure concentration of 3 mg l(-1) is below the EC50 value for all of the AgNPs; therefore, little cytotoxicity was observed in any experiment conducted herein. Exposure of Ag ions, however, interrupted cell membrane integrity and cell proliferation (up to 70% lysed after 24 h). These findings indicate cellular uptake is dependent on capping agent, and when controlled to realistic exposure concentrations, cellular function is not significantly affected by AgNP exposure.