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In this work, we designed a facile and label-free electrochemical biosensor based on intrinsic topological insulator (TI) Bi 2 Se 3 and peptide for the detection of immune checkpoint molecules. With topological protection, Bi 2 Se 3 could have robust surface states with low electronic noise, which was beneficial for the stable and sensitive electron transport between electrode and electrolyte interface. The peptides are easily synthesized and chemically modified, and have good biocompatibility and bioavailability, which is a suitable candidate as the recognition units for immune checkpoint molecules. Therefore, the peptide/Bi 2 Se 3 was developed as a suitable working electrode for the electrochemical biosensor. The basic performance of the designed peptide/Bi 2 Se 3 biosensor was investigated to determine the Anti-HA Tag Antibody and PD-L1 molecules. The linear detection range was from 3.6 × 10−10 mg mL−1 to 3.6 × 10−5 mg mL−1, and the detection limit was 1.07 × 10−11 mg mL−1. Moreover, the biosensor also displayed good selectivity and stability. [Display omitted] • Sensitive electrochemical biosensors combined with topological materials and peptides. • High-quality and large-scale topological crystal with few defects as electrodes. • Effective recognition units of peptides for the immune checkpoint. • A large detection range, good selectivity and stability with low detection limit of the sensing assay. • Excellent discernment in the complicated serum environment for clinical application. [ABSTRACT FROM AUTHOR]