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Physico-chemical characteristics of nanoparticles have been shown to alter the uptake and toxicity of nanoparticles. This study investigated the uptake of six gold nanoparticles (AuNPs) into the human bronchial epithelial cell line BEAS-2B. The AuNPs studied included colloidal citrate-stabilised AuNPs of 14nm in diameter; and 14nm AuNPs conjugated to functional groups via polyethylene glycol (PEG), namely hydroxyl-PEG (POH), carboxyl-PEG (PCOOH), biotin-PEG (PBtn), nitrilotriacetic acid-PEG (PNTA), and azide-PEG (PAZ). Uptake was visualised by dark field microscopy using the CytoViva Hyperspectral Imaging system and after a 2hour incubation at 37°C, uptake was observed in cells treated with the citrate-stabilised and PCOOH AuNPs. However, no uptake was observed for the POH, PBtn, PNTA, or PAZ AuNPs, even after 24h of incubation. An investigation into the energy dependence of uptake of the citrate-stabilised and PCOOH AuNPs showed that uptake was an active process. Cells pre-treated with either chlorpromazine or genistein as endocytosis inhibitors for clathrin- and caveolae-mediated pathways respectively, prior to addition of AuNPs, suggested a caveolae-dependent mechanism of endocytosis. These results further support recent findings on the mechanism of intracellular uptake and localisation and the subsequent toxicity of nanoparticles.Uptake of gold nanoparticles in bronchial epithelial cells is energy dependent.End functional groups of PEG ligands on gold nanoparticles influences uptake.Uptake of citrate stabilised and COOH-PEG gold nanoparticles is caveolae-mediated.