Identify aptamers binding human PD-L1 protein  by SELEX
we performed protein-based-SELEX using recombinant PD-L1 expressed with the C-terminal fused Fc region of human IgG1 (hPD-L1-hFc). Protein G magnetic beads coupled with hPD-L1-hFc (hPD-L1-hFc-beads) were used for positive selection, while the protein G magnetic beads and hFc-modified protein G magnetic beads (hFc-beads) were for negative selection. After 15 rounds of screening, the 5th, 10th, and 15th libraries were chosen for Next-Generation Sequencing.