Effect of Carbon Nanotubes on Erythrocytes Figure 6. Effect of AF-SWCNT’s on blood count of erythrocytes in mice. AF-SWCNT’s were administered to 6–8 weeks old Swiss mice by the indicated routes (panel A). Mice were administered vehicle (PBS alone) or AF-SWCNT’s (100 mg) intravenously, intratracheally, intraperitoneally, or the gavage route, and erythrocyte count was determined at different time intervals. Panel B shows effect of intravenously administered control and acid functionalised SWCNTs on hemoglobin content in blood. Results of a representative experiment have been shown. All data points represent mean 6 SEM of three observations. *p,0.01 as compared to PBS administered control groups. doi:10.1371/journal.pone.0022032.g006 Discussion Our first set of experiments indicated that the AF-SWCNTs had a marked toxic effect on erythrocytes in vitro. The effect was dose and time dependent and after one day of incubation with AF- SWCNT, 70–90% of the erythrocytes were lost at all the doses (10, 25 and 50 mg/ml) of AF-SWCNT. It was also interesting to observe that the damaging effect is seen earlier with the highest dose of 50 mg/ml leading to 70–90% decline in recovery after just 10–12 h while interaction ensures the similar damaging effect on erythrocytes treated with lower doses also (10 and 25 mg/ml) when kept for a longer duration (24 h). It should be noted that the Figure 7. Prolongation of anemia by a second dose of AF-SWCNTs. The experiment was performed as detailed in Figure 5 except that a second dose of SWCNTs and AF-SWCNTs was given 25 h after the first dose. Blood erythrocyte counts were monitored till three days. All data points represent mean 6 SEM of three observations. *p,0.01 as compared to PBS administered control groups. doi:10.1371/journal.pone.0022032.g007 PLoS ONE | www.plosone.org 6 July 2011 | Volume 6 | Issue 7 | e22032