Treatment with SWCNTs increases the endosomes per cell. (A) Cells were transfected with GFP-endo (Rho-GTPase), a marker for endocytosis, and treated with 100 μg/mL SWCNTs. Cells were then fixed at set timepoints after treatment and rapidly imaged by widefield microscopy. (B) The observable endosomes were segmented and counted using ImageJ. Errant points, such as those outside the cell, were identified and removed from the counts. The number of endosomes was determined by an average of n = 30 cells per treatment over 2 treatments at all time points. (C) After treatment with SWCNTs there was an apparent increase in endosomes per cell. After 20 min, this change became statistically significant from control (p < 0.001). Open circles are individual cells and black boxes are the average with an SEM error bar.