Figure 1.

Schematic illustration of the BSA-Apt designed for colon cancer therapy. (A) Two-step reaction scheme for conjugating BSA with PD-L1 aptamer by a crosslinker (sulfo-SMCC). In this experiment, sulfo-SMCC first reacts with BSA to produce maleimide-activated protein. After removing non-reacted crosslinker, the maleimide-activated BSA reacts with the thiol-modified PD-L1 aptamers to form BSA-Apt. (B) PD-1/PD-L1 blockade scheme: BSA-Apt binds to PD-L1 expressed on the surface of tumor cells and blocks the PD-1/PD-L1 interaction.