Uptake of AgNPs by BEAS-2B cells. The cellular Ag dose was quantified by AAS (A). BEAS-2B cells were exposed to 10 μg/mL AgNPs for 4 h and the total cellular Ag content was analyzed by AAS. The Ag dose was expressed as pg per cell. Results are presented as mean ± standard deviation of 2 replicates. The uptake mechanisms were investigated using pharmacological inhibitors and 4°C exposure (B). BEAS-2B cells were pre-incubated with different pharmacological inhibitors at 37°C (clathrin-mediated endocytosis: amantadine 200 μM for 30 min, caveolin/lipid raft mediated endocytosis: nystatin 25 μM for 30 min, macropinocytosis: amiloride-HCl 100 μM for 30 min, general fluid-phase endocytosis: wortmannin 400 nM for 30 min, actin-dependent phagocytosis: cytochalasin D 1 μM for 1 h). For energy dependent inhibition of uptake the cells were pre-incubated at 4°C for 30 min. Following the pre-incubations, cells were exposed to 10 μg/mL 10 nm citrate coated or 75 nm citrate coated AgNPs for 2 h in the presence of the inhibitors or at 4°C. The total Ag content was determined using AAS. The results are expressed as % of the corresponding controls and presented as mean ± standard deviation of 2 replicates.