Novel electrochemical biosensors for investigating the interactions between atezolizumab and PD-1/PD-L1 and screening their small-molecular inhibitors

PD-1/PD-L1 pathway plays an important role in tumor immunotherapy. A novel immobilized overexpression cell electrochemical sensor was constructed using N-doped graphene-chitosan-Pt nanoparticles (NGR–CS–PtNPs) and polyaniline (PANI) to investigate the interaction between atezolizumab and HEK293 cells overexpressing PD-1 or PD-L1 proteins. The binding constant between atezolizumab and PD-L1-HEK293 cells was calculated to be 2.4 × 10 7 M −1 . Using this method to screen 18 main components from Aidi injection (ADI), it was found that the binding constant between ginsenoside Rg1 and PD-1-HEK293 cells was 9.9 × 10 4 M −1 . Then, a new electrochemical immunosensor was constructed using Au nanoparticles and 11-mercaptoundecanoic acid (11-MUA). The calculated binding constant between atezolizumab and purified PD-L1 protein was 6.11 × 10 9 M −1 , and IC 50 value was 2.73 ng/mL. Meanwhile, with the concentration of ginsenosides Rg1 increasing to 20 μM, the inhibition rate reached a maximum, which was about 50%. Electrochemical sensing technology was originally used to investigate the interactions between atezolizumab and PD-1/PD-L1. And using the above novel sensors, small molecule inhibitors targeting PD-1/PD-L1 could be screened and evaluated at different levels, leading to more accurate outcomes. Additionally, electrochemical sensors require simple equipment, low material costs, accompanying with the advantages of rapidity, sensitivity and high selectivity. • The interactions between atezolizumab and PD-1/PD-L1 proteins were studied on the protein and cell level. • PD-1/PD-L1 small-molecular inhibitors could be screened based on measuring binding constant and IC 50 . • The established methods have the advantages of low material costs, cheap equipment requirement, and easy processing steps. • Further applications could be carried out by replacing different kinds of overexpression cells and proteins.