Toxicity of surface-coated gold NPs

Potential toxicity of surface-coated NPs was probed in human neuroblastoma SH-SY5Y cells (American Type Culture Collection, Manassus, VA). Cellular reduction of XTT was employed to evaluate cellular metabolic activity following NP exposure. Cells, sustained and prepared for experiments as described in Additional file 1, were incubated (24 h) with NPs (100 pM or 200 pM) diluted into medium, with medium alone (negative control), or with 2% Triton-X 100 in medium (positive control). Following incubation, cells were washed and treated (24 h) with 0.33 mg/mL XTT and 8.3 μmol/L phenozene methyl sulfate. Metabolically active cells reduce XTT to an orange formazan product, for which absorbance (450 nm) was measured using a BioTek Synergy 2 microplate reader (Winooski, VT). Results are reported as a percentage of the negative control following background (medium containing XTT) subtraction.