3.2.2. Cellular Interaction after Exposure to Long and Shortened HNTs

We hypothesized that different sized HNTs would affect cellular behavior, including our bi-functionalized HNTs. Cell up taking efficiency for two different sized HNTs was analyzed. We monitored the fluorescent intensity changes of cells (cell number = 4.46 × 105 ± 0.063 × 105) in 24 h (Figure 5A). Cellular uptake efficiency for both sizes of HNTs exhibited similar changes along with time. In the end, higher amounts of shortened HNTs are detected in cells, indicating that the smaller size of HNTs is more easily absorbed by cells.

**Figure 5.** (**A**). Fluorescent intensity of FITC detected from CT26WT cells after 24 h incubation time (cell number for each test = 4.46 <sup>×</sup> 10<sup>5</sup> <sup>±</sup> 0.063 <sup>×</sup> 105, each group had 9 tests, error bar with standard deviation). (**B**). The summary of flow cytometry results for apoptosis and necrosis analysis. The detailed flow cytometry results showed in Supplementary Information Figure S1. (cell number for each test <sup>=</sup> <sup>3</sup> <sup>×</sup> <sup>10</sup>5, each group had 6 tests, error bar with standard deviation, \* represents *<sup>p</sup>* <sup>&</sup>lt; 0.05) (**C**). Fluorescent pictures for apoptosis & necrosis analysis, the green color represents apoptosis and the red color represents necrosis. The first column represents brightfield images (scale bar with 100 μm).
