Stability of transfected siRNA in C6/36 cells. A: C6/C36 cells were transfected with 1.0 μg FAM-labeled DenSi-1 and cultured for 7 days. FAM fluorescence in the cells was observed under fluorescence microscope(×200); B: C6/36 cells transfected with FAM-labeled siRNAs were harvested at different time points as indicated, washed and resuspended with PBS (pH7.4). FAM fluorescence was quantified by flow cytometry and the percentage of fluorescence positive cells was measured. The rates of C6/36 cells containing FAM-labeled siRNA at 6 hours, 1, 3, 5, and 7 dpi were 66.0%, 52.1%, 32.0%, 13.5% and 8.9%, respectively.