Figure 4.

Test for additive binding of BSA-cMWNTs and BSA-pMWNTs to cells. Equivalent numbers of RAW 264.7 cells were seeded in 6-well plates and incubated at 37 °C under standard cell culture conditions for 24 h prior to the experiment in preparation for the additive binding studies as described in Methods. Cells were exposed to serum- and sodium bicarbonate-free media containing either 100 µg/mL BSA-pMWNTs or BSA-cMWNTs (labelled pM and cM in the graph) followed by incubation at 4 °C for 90 min to establish the amount of each bound when separate. Additive binding was tested by exposing the cells simultaneously to both BSA-cMWNTs and BSA-pMWNTs for 90 min. In a slightly different experimental design, the cells incubated with either BSA-cMWNTs or BSA-pMWNTs at 4 °C for 45 min, washed, and incubated with BSA-pMWNTs or BSA-cMWNTs, respectively, at 4 °C for 45 min for a total incubation time of 90 minutes. Surface-bound MWNTs were extracted and quantified using the SDS-PAGE method. The numbers above the bars are the mean femtograms of MWNTs/cell, and each data point is the mean of ≥3 independent experiments ± SD.