Fig. 9

The results of the PCA analysis: a Electric cell-substrate impedance sensing (ECSIS) in human lung epithelial A549 cells exposed to NMs for 24 h; b Alamar blue (AB) assay in human lung epithelial A549 cells exposed to NMs for 24 h; c Colony forming efficiency (CFE) in human lung epithelial A549 cells exposed to NMs for 9–12 days; d The plot of the normalized factor loadings. ZP: ζ-Potential; Size: crystalline size of the NMs measured by TEM; HDD: hydrodynamic diameter in stock (milliQ water) or DMEM (cell culture medium), at time point 0 h (T0) or 24 h (T24); PDI: polydispersity index