HBMECs were plated on plastic to form monolayers and treated the following day with cut uncoated 3H-MWCNT, cut DSPE-PEG coated 3H-MWCNT, or vehicle for the specified times. (A) Cells were washed twice in ice cold PBS, harvested in lysis buffer, and 3H activity was assessed using a scintillation counter. Percent uptake was calculated based on input decays per minute. Three samples were used for each condition and the data are displayed as the mean ± standard error of each measurement. (B) Images taken after 24 h treatment show increased aggregation and sedimentation of uncoated MWCNTs on to HBMECs. By comparison, no aggregated or sedimented cut, DSPE-PEG coated MWCNTs are apparent. *p<0.05 (T-Test).