Fig. 8
Apparent permeability coefficient (Papp) of CuO NMs and CuSO4. The Caco-2/Raji B (a) and Caco-2/HT29-MTX (b) co-cultures were exposed to CuO NMs or CuSO4 at concentrations of 3.17, 6.34 or 12.68 Cu µg/cm2 for 24 and 48 h. The concentration of Cu in the AP and BL compartment was determined by ICP-OES and Papp was calculated. Data are expressed as mean Papp ×10−7 cm/s ± SEM (n = 3). Significance at p < 0.05 is indicted by * for comparison of CuO NMs at a concentration of 3.17 Cu µg/cm2 at 24 h to other treatment concentrations within each time point or # for comparison of equivalent concentrations between the 24 and 48 h time points