Figure 7

Cytotoxicity of SWCNTs as a function of dose. At 24 hrs, the number of cells remaining attached in five fields of each treatment group in duplicate was determined and statistically analyzed. A significant reduction in viable cells expressed as the percent cell loss (panel A) was seen as a function of SWCNT treatment in a dose response fashion. In separate experiments, lactate dehydrogenase (LDH) was measured in the growth media from living DH82 cell cultures in the presence or absence of SWCNTs over a 24 hr period using a quantitative assay. DH82 cells (81,600) cultured alone released LDH over a 24 hr period equivalent to the death of 7,000 cells (~9%), estimated from the standard curve performed in parallel without SWCNTs. With treatments of 10 or 30 mg/ml SWCNTs added to the cultures, statistically significant increased amounts of LDH were detected in the supernatant indicating 17-18,000 cells had died, or 22% of the cells. This was statistically increased above baseline. After treatment with 100 μg/ml SWCNTs, 28,000 cells died or 34%. These results were compared to a pure LDH standard performed using the same assay in the presence and absence of SWCNTs. Values are mean ± SD with three doses of SWCNT. Statistically significant differences from control are indicated with **; p < 0.001.