The mouse colorectal cancer cells MC38 and the human embryonic kidney cells HEK-293T were seeded in 35-mm confocal dishes at a concentration of 1×10 5 mL -1 and cultured overnight for cell adherence. FITC-labeled EH (FITC-EH) was dissolved in cold PBS at a concentration of 0.5 mg mL -1 . The cells were then washed three times with cold PBS and incubated with Hoechst 33342 (10 µg mL -1 , 200 µL) at 4 ℃ for 15 min. Then, the cells were washed three times with cold PBS, and incubated with the prepared FITC-EH solution (0.5 mg mL -1 , 200 µL) at 4 ℃ for 15 min. Finally, the cells were washed three times with cold PBS. All the above operations were performed in the dark. Confocal fluorescence imaging was performed on confocal laser scanning microscope (CLSM).