Fig. 2. Biological studies of the modified human insulin analogues. (A) Bioactivity of human insulin and modified analogues. (B and C) Insulin uptake study. HEK293 cells were treated with fluorescein-modified insulin 12 (1 μg mL^–1) for 30 minutes in the absence (B) or presence (C) of human insulin (10 μg mL^–1). The cells were then washed three times using PBS to remove fluorescein-labeled insulin due to non-specific interactions.